534b5c2be0b5ba802a52d031bbc1f9c651dff5ffcba9d23cd6c11cf26b8f6df9

ensimple/1886.html.txt

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+An organism is an individual living thing. It is easy to recognize a living thing, but not so easy to define it. Animals and plants are organisms, obviously. Organisms are a biotic, or living, part of the environment. Rocks and sunshine are parts of the non-living environment.
+
+Organisms usually have five basic needs, to continue their metabolism. They need air, water, nutrient (food), energy, and a place to live. However, not all living things need all these at the same time. Many organisms do not need access to air at all.
+
+A little thought is needed about viruses. There is no agreement as to whether they should be regarded as living. They are made of protein and nucleic acid, and they evolve, which is a really important fact. However, they exist in two quite different phases. One phase is dormant, not active. The other is inside a living cell of some other organism. Then the virus is very active reproducing itself. Consider the parallel with a computer program. When in use it is active; when it is not, it is completely inactive. It is still a program all the same.
+
+Another example from biology is the spore, which is a distribution phase of a bacteria, fungus or some plants. They are not active until they get to the right situation. They have all the working parts to build a complete organism, but for the moment it is switched off.
+
+Some organisms are made up of millions of cells. They are multicellular organisms. Many can be seen without using a microscope.
+
+Most organisms are so small that they cannot be seen with the naked eye. You need a microscope to see them. They are called microorganisms. Organisms can be made up of just one cell. They are called unicellular organisms or single celled organisms. Examples include bacteria, and protozoa such as the Amoeba and Paramecium.
+
+The Tree of Life project works on the relationships between living things. Identifying a LUCA (last universal common ancestor) is one of its main aims. The LUCA is estimated to have lived some 3.8 billion years ago (sometime in the Palaeoarchaean era).[1][2]
+
+The idea came from Charles Darwin's On the Origin of Species, "Therefore... probably all the organic beings which have ever lived on this earth have descended from some one primordial form..."

ensimple/1887.html.txt

@@ -0,0 +1,15 @@
+An organism is an individual living thing. It is easy to recognize a living thing, but not so easy to define it. Animals and plants are organisms, obviously. Organisms are a biotic, or living, part of the environment. Rocks and sunshine are parts of the non-living environment.
+
+Organisms usually have five basic needs, to continue their metabolism. They need air, water, nutrient (food), energy, and a place to live. However, not all living things need all these at the same time. Many organisms do not need access to air at all.
+
+A little thought is needed about viruses. There is no agreement as to whether they should be regarded as living. They are made of protein and nucleic acid, and they evolve, which is a really important fact. However, they exist in two quite different phases. One phase is dormant, not active. The other is inside a living cell of some other organism. Then the virus is very active reproducing itself. Consider the parallel with a computer program. When in use it is active; when it is not, it is completely inactive. It is still a program all the same.
+
+Another example from biology is the spore, which is a distribution phase of a bacteria, fungus or some plants. They are not active until they get to the right situation. They have all the working parts to build a complete organism, but for the moment it is switched off.
+
+Some organisms are made up of millions of cells. They are multicellular organisms. Many can be seen without using a microscope.
+
+Most organisms are so small that they cannot be seen with the naked eye. You need a microscope to see them. They are called microorganisms. Organisms can be made up of just one cell. They are called unicellular organisms or single celled organisms. Examples include bacteria, and protozoa such as the Amoeba and Paramecium.
+
+The Tree of Life project works on the relationships between living things. Identifying a LUCA (last universal common ancestor) is one of its main aims. The LUCA is estimated to have lived some 3.8 billion years ago (sometime in the Palaeoarchaean era).[1][2]
+
+The idea came from Charles Darwin's On the Origin of Species, "Therefore... probably all the organic beings which have ever lived on this earth have descended from some one primordial form..."

ensimple/1888.html.txt

@@ -0,0 +1,15 @@
+An organism is an individual living thing. It is easy to recognize a living thing, but not so easy to define it. Animals and plants are organisms, obviously. Organisms are a biotic, or living, part of the environment. Rocks and sunshine are parts of the non-living environment.
+
+Organisms usually have five basic needs, to continue their metabolism. They need air, water, nutrient (food), energy, and a place to live. However, not all living things need all these at the same time. Many organisms do not need access to air at all.
+
+A little thought is needed about viruses. There is no agreement as to whether they should be regarded as living. They are made of protein and nucleic acid, and they evolve, which is a really important fact. However, they exist in two quite different phases. One phase is dormant, not active. The other is inside a living cell of some other organism. Then the virus is very active reproducing itself. Consider the parallel with a computer program. When in use it is active; when it is not, it is completely inactive. It is still a program all the same.
+
+Another example from biology is the spore, which is a distribution phase of a bacteria, fungus or some plants. They are not active until they get to the right situation. They have all the working parts to build a complete organism, but for the moment it is switched off.
+
+Some organisms are made up of millions of cells. They are multicellular organisms. Many can be seen without using a microscope.
+
+Most organisms are so small that they cannot be seen with the naked eye. You need a microscope to see them. They are called microorganisms. Organisms can be made up of just one cell. They are called unicellular organisms or single celled organisms. Examples include bacteria, and protozoa such as the Amoeba and Paramecium.
+
+The Tree of Life project works on the relationships between living things. Identifying a LUCA (last universal common ancestor) is one of its main aims. The LUCA is estimated to have lived some 3.8 billion years ago (sometime in the Palaeoarchaean era).[1][2]
+
+The idea came from Charles Darwin's On the Origin of Species, "Therefore... probably all the organic beings which have ever lived on this earth have descended from some one primordial form..."

ensimple/1889.html.txt

@@ -0,0 +1,15 @@
+An organism is an individual living thing. It is easy to recognize a living thing, but not so easy to define it. Animals and plants are organisms, obviously. Organisms are a biotic, or living, part of the environment. Rocks and sunshine are parts of the non-living environment.
+
+Organisms usually have five basic needs, to continue their metabolism. They need air, water, nutrient (food), energy, and a place to live. However, not all living things need all these at the same time. Many organisms do not need access to air at all.
+
+A little thought is needed about viruses. There is no agreement as to whether they should be regarded as living. They are made of protein and nucleic acid, and they evolve, which is a really important fact. However, they exist in two quite different phases. One phase is dormant, not active. The other is inside a living cell of some other organism. Then the virus is very active reproducing itself. Consider the parallel with a computer program. When in use it is active; when it is not, it is completely inactive. It is still a program all the same.
+
+Another example from biology is the spore, which is a distribution phase of a bacteria, fungus or some plants. They are not active until they get to the right situation. They have all the working parts to build a complete organism, but for the moment it is switched off.
+
+Some organisms are made up of millions of cells. They are multicellular organisms. Many can be seen without using a microscope.
+
+Most organisms are so small that they cannot be seen with the naked eye. You need a microscope to see them. They are called microorganisms. Organisms can be made up of just one cell. They are called unicellular organisms or single celled organisms. Examples include bacteria, and protozoa such as the Amoeba and Paramecium.
+
+The Tree of Life project works on the relationships between living things. Identifying a LUCA (last universal common ancestor) is one of its main aims. The LUCA is estimated to have lived some 3.8 billion years ago (sometime in the Palaeoarchaean era).[1][2]
+
+The idea came from Charles Darwin's On the Origin of Species, "Therefore... probably all the organic beings which have ever lived on this earth have descended from some one primordial form..."

ensimple/189.html.txt

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+Native Americans (also called Aboriginal Americans, American Indians, Amerindians or indigenous peoples of America) are the people and their descendants, who were in the Americas when Europeans arrived.  There are many different tribes of Native American people, with many different languages.  There are more than three million Native Americans in Canada and the U.S. combined.  About 51 million Native Americans live in Latin America.
+
+Sometimes these people are called Indians, but this may be confusing, because it is the same word used for people from India. When Christopher Columbus explored, he did not know about the Americas. He was in the Caribbean but thought he was in the East Indies, so he called the people Indians.
+
+Many Native Americans died after the Europeans came to the Americas. There were diseases that came with the Europeans but were new to the Native Americans. There were battles with the Europeans. Many native people were hurt or killed by settlers who took their lands.
+
+The ancestors of Native Americans came to the Americas from Asia. Some of them may have come to America 15,000 years ago when Alaska was connected to Siberia by the Bering land bridge.
+
+The earliest peoples in the Americas came from Siberia when there was an ice bridge across the Bering Strait. The cold but mainly grassy plain which connected Siberia with Canada is called Beringia.  It is reckoned that a few thousand people arrived in  Beringia from eastern Siberia during the Last Glacial Maximum before moving into the Americas sometime after 16,500 years before the present (BP).[1] This would have occurred as the American glaciers blocking the way southward melted,[2][3][4][5][6] but before the bridge was covered by the sea about 11,000 years BP.
+
+Before European colonization, Beringia was inhabited by the Yupik peoples on both sides of the straits. This culture remains in the region today, with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia.[7]
+
+Native Americans are divided into many small nations, called First Nations in Canada and tribes elsewhere.
+
+According to the 2010 United States census, 0.9% of Americans say they are Native American, 2.9 million people, and 1.7% of Americans say they are both Native American and something else.  They are not evenly spread out through the United States.  About a third of the people in Alaska are Native Alaskan and about a sixth of the people in Oklahoma are Native American.[8]
+
+In the United States, most Native Americans live in cities.  About 28% of Native Americans live on reservations.  Many Native Americans are poor, and 24% are extremely poor.  They tend to be the targets of violence more than white people are.[9]

ensimple/1890.html.txt

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+The Etruscan civilization lasted from about 900 BC to 27 BC and was a culture in ancient Italy. The Romans called the people Etrusci or Tusci. The Ancient Greeks called them Tyrrhenoi or Tyrrsenoi. The Etruscans called themselves Rasenna.
+
+The Etruscan civilization began in pre-history. When it was most powerful, it had three confederacies (like modern states): Etruria, Latinum and the Po Valley and Campania. The Etruscans ruled Rome until 396 BC.
+
+Not much is known about the Etruscan language. Not much of its writing survives. Most what survives is from engravings on tombstones. The Etruscans used an alphabet similar to those in Phoenicia and Greece.[1]
+
+The language is related to the Tyrrhenian language family and is not clearly related to other languages. Some Etruscan letters were used by the Romans in the Latin alphabet, which many languages use such as English. Some Romans, such as Cicero, were fluent readers of Etruscan, but few of thire writings survive.
+
+The lack of texts makes knowledge of their society and culture depend on much later Roman sources. Politics was based on the small city and probably the family unit. In their heyday, the Etruscan elite became rich by trade with the Celtic world to the north and the Greeks to the south, and filled their large family tombs with imported luxuries. Ancient Greece had a huge influence on their art and architecture, and Greek mythology was evidently very familiar to them.
+
+Etruscan, the third great ancient language of culture in Italy, does not survive in any great literary works, unlike Greek and Latin. An Etruscan religious literature existed, and evidence suggests that there was a body of historical literature and drama as well. For example, the name of a playwright, Volnius, of obscure date, is known who wrote "Tuscan tragedies". Although there is no evidence of notation, it is possible that Etruscan music was in a written form.
+
+The Etruscans mined metals like copper and iron. They became rich and powerful and travelled around the Mediterranean Sea. The Etruscans began to lose power in the 5th century BC. The Romans began conquering parts of Etruscan land. By the beginning of the 1st century BC, the Etruscans had been entirely defeated.
+
+Etruscan art included wall paintings, metalwork and sculpture in terracotta. Sculpture in cast bronze was famous and widely exported, but few large examples have survived because bronze was valuable and so was often recycled.[2]
+

ensimple/1891.html.txt

@@ -0,0 +1,16 @@
+The Etruscan civilization lasted from about 900 BC to 27 BC and was a culture in ancient Italy. The Romans called the people Etrusci or Tusci. The Ancient Greeks called them Tyrrhenoi or Tyrrsenoi. The Etruscans called themselves Rasenna.
+
+The Etruscan civilization began in pre-history. When it was most powerful, it had three confederacies (like modern states): Etruria, Latinum and the Po Valley and Campania. The Etruscans ruled Rome until 396 BC.
+
+Not much is known about the Etruscan language. Not much of its writing survives. Most what survives is from engravings on tombstones. The Etruscans used an alphabet similar to those in Phoenicia and Greece.[1]
+
+The language is related to the Tyrrhenian language family and is not clearly related to other languages. Some Etruscan letters were used by the Romans in the Latin alphabet, which many languages use such as English. Some Romans, such as Cicero, were fluent readers of Etruscan, but few of thire writings survive.
+
+The lack of texts makes knowledge of their society and culture depend on much later Roman sources. Politics was based on the small city and probably the family unit. In their heyday, the Etruscan elite became rich by trade with the Celtic world to the north and the Greeks to the south, and filled their large family tombs with imported luxuries. Ancient Greece had a huge influence on their art and architecture, and Greek mythology was evidently very familiar to them.
+
+Etruscan, the third great ancient language of culture in Italy, does not survive in any great literary works, unlike Greek and Latin. An Etruscan religious literature existed, and evidence suggests that there was a body of historical literature and drama as well. For example, the name of a playwright, Volnius, of obscure date, is known who wrote "Tuscan tragedies". Although there is no evidence of notation, it is possible that Etruscan music was in a written form.
+
+The Etruscans mined metals like copper and iron. They became rich and powerful and travelled around the Mediterranean Sea. The Etruscans began to lose power in the 5th century BC. The Romans began conquering parts of Etruscan land. By the beginning of the 1st century BC, the Etruscans had been entirely defeated.
+
+Etruscan art included wall paintings, metalwork and sculpture in terracotta. Sculpture in cast bronze was famous and widely exported, but few large examples have survived because bronze was valuable and so was often recycled.[2]
+

ensimple/1892.html.txt

@@ -0,0 +1,16 @@
+The Etruscan civilization lasted from about 900 BC to 27 BC and was a culture in ancient Italy. The Romans called the people Etrusci or Tusci. The Ancient Greeks called them Tyrrhenoi or Tyrrsenoi. The Etruscans called themselves Rasenna.
+
+The Etruscan civilization began in pre-history. When it was most powerful, it had three confederacies (like modern states): Etruria, Latinum and the Po Valley and Campania. The Etruscans ruled Rome until 396 BC.
+
+Not much is known about the Etruscan language. Not much of its writing survives. Most what survives is from engravings on tombstones. The Etruscans used an alphabet similar to those in Phoenicia and Greece.[1]
+
+The language is related to the Tyrrhenian language family and is not clearly related to other languages. Some Etruscan letters were used by the Romans in the Latin alphabet, which many languages use such as English. Some Romans, such as Cicero, were fluent readers of Etruscan, but few of thire writings survive.
+
+The lack of texts makes knowledge of their society and culture depend on much later Roman sources. Politics was based on the small city and probably the family unit. In their heyday, the Etruscan elite became rich by trade with the Celtic world to the north and the Greeks to the south, and filled their large family tombs with imported luxuries. Ancient Greece had a huge influence on their art and architecture, and Greek mythology was evidently very familiar to them.
+
+Etruscan, the third great ancient language of culture in Italy, does not survive in any great literary works, unlike Greek and Latin. An Etruscan religious literature existed, and evidence suggests that there was a body of historical literature and drama as well. For example, the name of a playwright, Volnius, of obscure date, is known who wrote "Tuscan tragedies". Although there is no evidence of notation, it is possible that Etruscan music was in a written form.
+
+The Etruscans mined metals like copper and iron. They became rich and powerful and travelled around the Mediterranean Sea. The Etruscans began to lose power in the 5th century BC. The Romans began conquering parts of Etruscan land. By the beginning of the 1st century BC, the Etruscans had been entirely defeated.
+
+Etruscan art included wall paintings, metalwork and sculpture in terracotta. Sculpture in cast bronze was famous and widely exported, but few large examples have survived because bronze was valuable and so was often recycled.[2]
+

ensimple/1893.html.txt

@@ -0,0 +1,16 @@
+The Etruscan civilization lasted from about 900 BC to 27 BC and was a culture in ancient Italy. The Romans called the people Etrusci or Tusci. The Ancient Greeks called them Tyrrhenoi or Tyrrsenoi. The Etruscans called themselves Rasenna.
+
+The Etruscan civilization began in pre-history. When it was most powerful, it had three confederacies (like modern states): Etruria, Latinum and the Po Valley and Campania. The Etruscans ruled Rome until 396 BC.
+
+Not much is known about the Etruscan language. Not much of its writing survives. Most what survives is from engravings on tombstones. The Etruscans used an alphabet similar to those in Phoenicia and Greece.[1]
+
+The language is related to the Tyrrhenian language family and is not clearly related to other languages. Some Etruscan letters were used by the Romans in the Latin alphabet, which many languages use such as English. Some Romans, such as Cicero, were fluent readers of Etruscan, but few of thire writings survive.
+
+The lack of texts makes knowledge of their society and culture depend on much later Roman sources. Politics was based on the small city and probably the family unit. In their heyday, the Etruscan elite became rich by trade with the Celtic world to the north and the Greeks to the south, and filled their large family tombs with imported luxuries. Ancient Greece had a huge influence on their art and architecture, and Greek mythology was evidently very familiar to them.
+
+Etruscan, the third great ancient language of culture in Italy, does not survive in any great literary works, unlike Greek and Latin. An Etruscan religious literature existed, and evidence suggests that there was a body of historical literature and drama as well. For example, the name of a playwright, Volnius, of obscure date, is known who wrote "Tuscan tragedies". Although there is no evidence of notation, it is possible that Etruscan music was in a written form.
+
+The Etruscans mined metals like copper and iron. They became rich and powerful and travelled around the Mediterranean Sea. The Etruscans began to lose power in the 5th century BC. The Romans began conquering parts of Etruscan land. By the beginning of the 1st century BC, the Etruscans had been entirely defeated.
+
+Etruscan art included wall paintings, metalwork and sculpture in terracotta. Sculpture in cast bronze was famous and widely exported, but few large examples have survived because bronze was valuable and so was often recycled.[2]
+

ensimple/1894.html.txt

@@ -0,0 +1,16 @@
+The Etruscan civilization lasted from about 900 BC to 27 BC and was a culture in ancient Italy. The Romans called the people Etrusci or Tusci. The Ancient Greeks called them Tyrrhenoi or Tyrrsenoi. The Etruscans called themselves Rasenna.
+
+The Etruscan civilization began in pre-history. When it was most powerful, it had three confederacies (like modern states): Etruria, Latinum and the Po Valley and Campania. The Etruscans ruled Rome until 396 BC.
+
+Not much is known about the Etruscan language. Not much of its writing survives. Most what survives is from engravings on tombstones. The Etruscans used an alphabet similar to those in Phoenicia and Greece.[1]
+
+The language is related to the Tyrrhenian language family and is not clearly related to other languages. Some Etruscan letters were used by the Romans in the Latin alphabet, which many languages use such as English. Some Romans, such as Cicero, were fluent readers of Etruscan, but few of thire writings survive.
+
+The lack of texts makes knowledge of their society and culture depend on much later Roman sources. Politics was based on the small city and probably the family unit. In their heyday, the Etruscan elite became rich by trade with the Celtic world to the north and the Greeks to the south, and filled their large family tombs with imported luxuries. Ancient Greece had a huge influence on their art and architecture, and Greek mythology was evidently very familiar to them.
+
+Etruscan, the third great ancient language of culture in Italy, does not survive in any great literary works, unlike Greek and Latin. An Etruscan religious literature existed, and evidence suggests that there was a body of historical literature and drama as well. For example, the name of a playwright, Volnius, of obscure date, is known who wrote "Tuscan tragedies". Although there is no evidence of notation, it is possible that Etruscan music was in a written form.
+
+The Etruscans mined metals like copper and iron. They became rich and powerful and travelled around the Mediterranean Sea. The Etruscans began to lose power in the 5th century BC. The Romans began conquering parts of Etruscan land. By the beginning of the 1st century BC, the Etruscans had been entirely defeated.
+
+Etruscan art included wall paintings, metalwork and sculpture in terracotta. Sculpture in cast bronze was famous and widely exported, but few large examples have survived because bronze was valuable and so was often recycled.[2]
+

ensimple/1895.html.txt

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+
+
+Actinobacteria (high-G+C)
+Firmicutes (low-G+C)
+Tenericutes (no wall)
+
+Aquificae
+Bacteroidetes/Fibrobacteres–Chlorobi (FCB group)
+Chlamydiae
+Deinococcus-Thermus
+Fusobacteria
+Gemmatimonadetes
+Nitrospirae
+Planctomycetes–Verrucomicrobia/Chlamydiae (PVC group)
+Proteobacteria
+Spirochaetes
+Synergistetes
+
+Acidobacteria
+Chloroflexi
+Chrysiogenetes
+Cyanobacteria
+Deferribacteres
+Dictyoglomi
+Thermodesulfobacteria
+Thermotogae
+
+Eubacteria Woese & Fox, 1977
+
+Bacteria (sing. bacterium) are very small organisms. They are prokaryotic microorganisms. Bacterial cells do not have a nucleus, and most have no organelles with membranes around them. Most have a cell wall. They do have DNA, and their biochemistry is basically the same as other living things. They are amongst the simplest and the oldest organisms.   They function as independent organisms.
+
+Almost all bacteria are so tiny they can only be seen through a microscope. Bacteria are made up of one cell, so they are a kind of unicellular organism. They are among the simplest single-celled organisms on Earth, and were one of the earliest forms of life. They include a number of extremophiles which live in extreme habitats.
+
+There are probably more individual bacteria than any other sort of organism on the planet.[1] Most bacteria live in the ground or in water, but many live inside or on the skin of other organisms, including humans. There are about 1:1 bacterial cells as human cells in each of our bodies[2][3]. Some bacteria can cause diseases, but others help us in everyday activities like digesting food (gut flora). Some even work for us in factories, producing cheese and yogurt.
+
+The founder of bacteriology was a German biologist called Ferdinand Cohn (1828–1898). He published the first biological classification of bacteria, based on their appearance.[4]
+
+A bacterium reproduces (creates more bacteria) by dividing in half and creating two "daughter" cells. Each daughter is identical in shape to the parent, but is smaller.
+
+Bacteria do not have sexes, but they do transmit DNA by several kinds of horizontal gene transfer. This is how they share resistance to antibiotics from one strain to another. The complete DNA sequence is known for many bacterial strains.
+
+Bacteria have one bacterial chromosome.[5]
+
+Bacteria vary widely in size and shape, but in general they are at least ten times larger than viruses. A typical bacterium is about 1 µm (one micrometer) in diameter, so a thousand bacteria lined up would be one millimeter long. There are about five nonillion (5×1030) bacteria on Earth.[1]
+
+Bacteria are identified and grouped by their shapes. Bacilli are rod-shaped, cocci are ball-shaped, spirilla are spiral-shaped, and vibrio are shaped like a comma or a boomerang.
+
+Pathogenic bacteria, the harmful kind, enter the human body from the air, water or food. Once inside, these bacteria attach themselves to or invade specific cells in our respiratory system, digestive tract or in any open wound. There they begin to reproduce and spread while using your body's food and nutrients to give them energy to help them reproduce.
+
+Some bacteria are extremophiles. Some microbes thrive inside rocks up to 580 meters below the sea floor under 2.6 kilometers of ocean off the Pacific Northwest of the United States.[6][7] According to one of the researchers, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are."[6]
+
+All modern ideas start with the sequence analysis of DNA and RNA. In 1987, Carl Woese, the forerunner of the molecular phylogeny revolution, divided bacteria into 11 divisions based on 16S ribosomal RNA (SSU) sequences:[8][9]

ensimple/1896.html.txt

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+Ferdinand Victor Eugène Delacroix (26 April 1798 – 13 August 1863) was a French Romantic artist regarded from the outset of his career as the leader of the French Romantic school.[1] Delacroix's use of expressive brushstrokes and his study of the optical effects of colour profoundly shaped the work of the Impressionists, while his passion for the exotic inspired the artists of the Symbolist movement. A fine lithographer, Delacroix illustrated various works of William Shakespeare, the Scottish writer Sir Walter Scott, and the German writer Johann Wolfgang von Goethe.
+
+In contrast to the Neoclassical perfectionism of his chief rival Ingres, Delacroix took for his inspiration the art of Rubens and painters of the Venetian Renaissance, with an attendant emphasis on color and movement rather than clarity of outline and carefully modeled form. Dramatic and romantic content characterized the central themes of his maturity, and led him not to the classical models of Greek and Roman art, but to travel in North Africa, in search of the exotic.[2] Friend and spiritual heir to Théodore Géricault, Delacroix was also inspired by Byron, with whom he shared a strong identification with the "forces of the sublime", of nature in often violent action.[3]
+
+However, Delacroix was given neither to sentimentality nor bombast, and his Romanticism was that of an individualist. In the words of Baudelaire, "Delacroix was passionately in love with passion, but coldly determined to express passion as clearly as possible."[4]
+
+Delacroix was a member of the Club des Hashischins, or Hashish Club. This group of French writers experimented with hashish to get ideas.[5]

ensimple/1897.html.txt

@@ -0,0 +1,7 @@
+Ferdinand Victor Eugène Delacroix (26 April 1798 – 13 August 1863) was a French Romantic artist regarded from the outset of his career as the leader of the French Romantic school.[1] Delacroix's use of expressive brushstrokes and his study of the optical effects of colour profoundly shaped the work of the Impressionists, while his passion for the exotic inspired the artists of the Symbolist movement. A fine lithographer, Delacroix illustrated various works of William Shakespeare, the Scottish writer Sir Walter Scott, and the German writer Johann Wolfgang von Goethe.
+
+In contrast to the Neoclassical perfectionism of his chief rival Ingres, Delacroix took for his inspiration the art of Rubens and painters of the Venetian Renaissance, with an attendant emphasis on color and movement rather than clarity of outline and carefully modeled form. Dramatic and romantic content characterized the central themes of his maturity, and led him not to the classical models of Greek and Roman art, but to travel in North Africa, in search of the exotic.[2] Friend and spiritual heir to Théodore Géricault, Delacroix was also inspired by Byron, with whom he shared a strong identification with the "forces of the sublime", of nature in often violent action.[3]
+
+However, Delacroix was given neither to sentimentality nor bombast, and his Romanticism was that of an individualist. In the words of Baudelaire, "Delacroix was passionately in love with passion, but coldly determined to express passion as clearly as possible."[4]
+
+Delacroix was a member of the Club des Hashischins, or Hashish Club. This group of French writers experimented with hashish to get ideas.[5]

ensimple/1898.html.txt

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+Pope Pius XII (Latin: Pius PP. XII; Italian: Pio XII), born Eugenio Maria Giuseppe Giovanni Pacelli (March 2, 1876 – October 9, 1958), was an Italian priest of the Roman Catholic Church and the 261st Pope from 1939 to 1958.[1]
+
+Pacelli was born on 2 March 1876 in Rome, Italy. He studied at the Capranica Seminary and the Pontifical Gregorian University. In 1895, he earned a degree in Theology.[2]
+
+Pacelli was ordained as a priest on 2 April 1899. In 1904, he was raised to the rank of Monsignor.  He worked at the Office of the Congregation of Extraordinary Ecclesiastical Affairs.[2]
+
+In 1917, Pope Benedict XV appointed him an archbishop and nuncio to Bavaria, Germany.[2]
+
+Pope Pius XI raised Pacelli to the rank of Cardinal in December 1929.[3]
+
+In February 1930, Cardinal Pacelli became the Vatican Secretary of State.[3]
+
+Cardinal Pacelli was elected Pope on 2 March 1939,[2] which was his 63th birthday.
+
+Pius  XII wrote forty-one official papal letters (encylicals).
+
+Pius XII named forty-two new cardinals.
+
+Media related to Pius XII at Wikimedia Commons
+
+Peter Linus Anacletus (Cletus) Clement I Evaristus Alexander I Sixtus I Telesphorus Hyginus Pius I Anicetus Soter Eleuterus Victor I Zephyrinus Callixtus I Urban I Pontian Anterus Fabian Cornelius Lucius I Stephen I Sixtus II Dionysius Felix I Eutychian Caius Marcellinus Marcellus I Eusebius Miltiades Sylvester I Mark
+
+Julius I Liberius Damasus I Siricius Anastasius I Innocent I Zosimus Boniface I Celestine I Sixtus IIILeo I Hilarius Simplicius Felix III Gelasius I Anastasius II Symmachus Hormisdas  John I Felix IV Boniface II John II Agapetus I Silverius Vigilius Pelagius IJohn III Benedict I Pelagius II Gregory I Sabinian Boniface III Boniface IV Adeodatus I
+
+Boniface V Honorius I Severinus John IV Theodore I Martin I Eugene IVitalian Adeodatus II Donus Agatho Leo II Benedict II John V Conon Sergius I John VI John VII Sisinnius Constantine Gregory II Gregory IIIZachary Stephen II Paul I Stephen III Adrian I Leo III Stephen IV Paschal I Eugene II Valentine Gregory IV
+
+Sergius II Leo IV Benedict III Nicholas I Adrian II John VIII Marinus I Adrian III Stephen V Formosus Boniface VI Stephen VI Romanus Theodore II John IX Benedict IV Leo V Sergius III Anastasius III Lando John X Leo VI Stephen VII John XI Leo VII Stephen VIII Marinus II Agapetus II John XII Benedict V Leo VIII John XIII Benedict VI
+
+Benedict VII John XIV John XV Gregory V Sylvester II John XVII John XVIII Sergius IV  Benedict VIII John XIX Benedict IXa Sylvester III Benedict IXa Gregory VI Clement II Benedict IXa Damasus II Leo IX Victor II Stephen IX Nicholas II Alexander II Gregory VII Victor III Urban II Paschal II Gelasius II Callixtus II Honorius II Innocent II Celestine II Lucius II Eugene III
+
+Anastasius IV Adrian IV Alexander III Lucius III Urban III Gregory VIII Clement III Celestine III Innocent III Honorius III Gregory IX Celestine IV Innocent IV Alexander IV Urban IV Clement IV Gregory X Innocent V Adrian V John XXIb Nicholas III Martin IV Honorius IV Nicholas IV Celestine V Boniface VIII Benedict XIb Clement V John XXII Benedict XII Clement VI Innocent VI Urban V
+
+Gregory XI Urban VI Boniface IX Innocent VII Gregory XII Martin V Eugene IV Nicholas V Callixtus III Pius II Paul II Sixtus IV Innocent VIII Alexander VI Pius III Julius II Leo X Adrian VI Clement VII Paul III Julius III Marcellus II Paul IV Pius IV Pius V Gregory XIII Sixtus V Urban VII Gregory XIV Innocent IX Clement VIII Leo XI Paul V
+
+Gregory XV Urban VIII Innocent X Alexander VII Clement IX Clement X Innocent XI Alexander VIII Innocent XII Clement XI Innocent XIII Benedict XIII Clement XII Benedict XIV Clement XIII Clement XIV Pius VI Pius VII Leo XII Pius VIII Gregory XVI Pius IX Leo XIII Pius X Benedict XV Pius XI Pius XII John XXIII Paul VI John Paul I John Paul IIBenedict XVIFrancis

ensimple/1899.html.txt

@@ -0,0 +1,34 @@
+Eurasia is the combined landmass of the continent of Europe and Asia in the northern part of the Earth. Eurasia is made of Europe and Asia, which are on the same tectonic plate and do not have a sea between them.  The word is made by adding "Eur" (from Europe) to "Asia" to make "Eurasia".
+
+Some geographers say it's all one continent, because unlike the Americas or Africa, Europe and Asia are not divided by sea. The Ancient Greeks divided the world they knew into Europe, Asia and Africa. Knowing little of the land north of the Black Sea, they took that and the Sea of Marmara as dividing Europe from Asia. Since then, people have been talking about Asia and Europe as two continents so it is now a tradition.
+
+The OECD’s Eurasia activities involve 13 countries extending from the borders of the European Union to the Far East:
+
+Some other continents are not completely divided by sea and are joined together and by a thin strip of land (called an isthmus) like North America and South America. However, Europe and Asia are not divided by sea.
+
+Sometimes Eurasia is divided into West Eurasia and East Eurasia. West Eurasia is Europe and the Middle East. Historians sometimes add North Africa to West Eurasia because the Sahara Desert divides North Africa from the other parts of Africa and it is as difficult to cross as a sea. It is the largest continent, and some people like to combine it with Africa as "Afro-Eurasia".
+
+
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/19.html.txt

@@ -0,0 +1,11 @@
+The Space Shuttle Challenger disaster occurred on January 28, 1986, when the NASA's Space Shuttle Challenger broke up 73 seconds after liftoff. All seven crew members were killed. It was the 25th flight of a Space Shuttle. The cause of the explosion was a part called an O-ring that broke in the right solid rocket booster. During the flight, hot gases escaped from the O-ring and made it break apart. Shuttles stopped flying for two and a half years.
+
+It was unusually cold on the morning of the Space shuttle's launch. The engineers argued that the Challenger should not take off because the temperature was 31 °F (−1 °C; 273 K) and the O-Rings could not seal right if the temperature was under 53 °F (12 °C; 285 K). The NASA commanders did not agree and said that the backup O-ring would work. They were later proved wrong. The temperature was so low that icicles were hanging from some parts of the launch pad.[1]
+
+At a little more than a minute after liftoff, the engines increased power to produce the highest thrust possible (known as throttling up). The flight controllers informed the shuttle crew that their flight status was "go" at the throttle-up stage. The flight commander Dick Scobee responded with "Roger, go at throttle up." However, at 72 seconds after liftoff, the right booster pulled away from one of the parts attaching to the external tank. Right then, the Challenger suddenly went off its intended path, which may have been felt by the crew.  Half a second later, Smith said the last words picked up by the recorder designed to record all interactions in the crew area of the shuttle during flight: "Uh oh...".  Smith may have been responding to the shuttle's computer telling him that the engines were moving quickly to compensate for the now loose booster in a useless attempt to get the shuttle back on the planned path.
+
+Little is known of what happened in the minutes after the breakup. The crew cabin was still intact as it started falling. The official report into the disaster says that the crew survived the first breakup and that at least three people were still alive. They were able to move switches which required a cover to be pulled off before they could be moved, probably when they tried to regain control of the craft. The crew cabin did not have any kind of parachute, and it smashed into the ocean after falling for 2 minutes and 45 seconds at roughly 207 miles per hour (333 kilometres per hour). Any crew that might have survived the first break up died instantly with more than 200 times the force of normal gravity. This is like going from 0 to over 4,400 miles per hour (7,100 kilometres per hour) and then slowing back down to 0 all within a second.
+
+Many people wanted to know why the Challenger exploded. President Ronald Reagan asked for a report about the disaster. It was called the Rogers Commission Report and it was written by a group of astronauts, scientists and engineers. They worked out what had happened and why the Challenger exploded. The report said that the people in charge at NASA did not listen to the engineers who said the O-rings were not safe; and that sometimes the people in charge thought that parts of the shuttle were well made when they were not. They also wrote that NASA sometimes did unsafe things because people would get angry if the shuttle launches were delayed.
+
+There were no shuttle flights while the report was written. After the report was written, NASA had to be more careful in many different ways.

ensimple/190.html.txt

@@ -0,0 +1,17 @@
+Native Americans (also called Aboriginal Americans, American Indians, Amerindians or indigenous peoples of America) are the people and their descendants, who were in the Americas when Europeans arrived.  There are many different tribes of Native American people, with many different languages.  There are more than three million Native Americans in Canada and the U.S. combined.  About 51 million Native Americans live in Latin America.
+
+Sometimes these people are called Indians, but this may be confusing, because it is the same word used for people from India. When Christopher Columbus explored, he did not know about the Americas. He was in the Caribbean but thought he was in the East Indies, so he called the people Indians.
+
+Many Native Americans died after the Europeans came to the Americas. There were diseases that came with the Europeans but were new to the Native Americans. There were battles with the Europeans. Many native people were hurt or killed by settlers who took their lands.
+
+The ancestors of Native Americans came to the Americas from Asia. Some of them may have come to America 15,000 years ago when Alaska was connected to Siberia by the Bering land bridge.
+
+The earliest peoples in the Americas came from Siberia when there was an ice bridge across the Bering Strait. The cold but mainly grassy plain which connected Siberia with Canada is called Beringia.  It is reckoned that a few thousand people arrived in  Beringia from eastern Siberia during the Last Glacial Maximum before moving into the Americas sometime after 16,500 years before the present (BP).[1] This would have occurred as the American glaciers blocking the way southward melted,[2][3][4][5][6] but before the bridge was covered by the sea about 11,000 years BP.
+
+Before European colonization, Beringia was inhabited by the Yupik peoples on both sides of the straits. This culture remains in the region today, with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia.[7]
+
+Native Americans are divided into many small nations, called First Nations in Canada and tribes elsewhere.
+
+According to the 2010 United States census, 0.9% of Americans say they are Native American, 2.9 million people, and 1.7% of Americans say they are both Native American and something else.  They are not evenly spread out through the United States.  About a third of the people in Alaska are Native Alaskan and about a sixth of the people in Oklahoma are Native American.[8]
+
+In the United States, most Native Americans live in cities.  About 28% of Native Americans live on reservations.  Many Native Americans are poor, and 24% are extremely poor.  They tend to be the targets of violence more than white people are.[9]

ensimple/1900.html.txt

@@ -0,0 +1,9 @@
+In physics, buoyancy (pronounced /ˈbɔɪ.ənsi/) is a force on an object making that object rise or move upward. It comes from the Spanish word for "float", boyar. Buoyancy is made by the difference in pressure put on the object by the Fluid or air that the object is in.
+
+The net upward buoyancy force is equal to the magnitude of the weight of fluid that is displaced by the body. This force enables the object to float or at least to seem lighter. Buoyancy is important for many vehicles such as boats, ships, balloons, and blimps.
+
+If the object has exactly the same density as the liquid, then its buoyancy is the same as its weight. It will not sink or float.
+
+If the object has a higher average density than the liquid, then its buoyancy is less than its weight. It will sink. That is why pebbles do not float.
+
+If the object has a lower average density than the liquid, then its buoyancy is greater than its weight. That is why, although a ship may be made of steel which is more dense than water, it floats because it encloses a volume of air and the resulting shape has an average density less than that of the water.

ensimple/1901.html.txt

@@ -0,0 +1,34 @@
+Eurasia is the combined landmass of the continent of Europe and Asia in the northern part of the Earth. Eurasia is made of Europe and Asia, which are on the same tectonic plate and do not have a sea between them.  The word is made by adding "Eur" (from Europe) to "Asia" to make "Eurasia".
+
+Some geographers say it's all one continent, because unlike the Americas or Africa, Europe and Asia are not divided by sea. The Ancient Greeks divided the world they knew into Europe, Asia and Africa. Knowing little of the land north of the Black Sea, they took that and the Sea of Marmara as dividing Europe from Asia. Since then, people have been talking about Asia and Europe as two continents so it is now a tradition.
+
+The OECD’s Eurasia activities involve 13 countries extending from the borders of the European Union to the Far East:
+
+Some other continents are not completely divided by sea and are joined together and by a thin strip of land (called an isthmus) like North America and South America. However, Europe and Asia are not divided by sea.
+
+Sometimes Eurasia is divided into West Eurasia and East Eurasia. West Eurasia is Europe and the Middle East. Historians sometimes add North Africa to West Eurasia because the Sahara Desert divides North Africa from the other parts of Africa and it is as difficult to cross as a sea. It is the largest continent, and some people like to combine it with Africa as "Afro-Eurasia".
+
+
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1902.html.txt

@@ -0,0 +1,29 @@
+Euro is the currency (money) of the countries in the eurozone. One euro is divided into 100 cent (officially)[1] (singular) or "cents" (unofficially).[2]
+
+Because of the number of different languages in the European Union, there are different, unofficial, names for this unit (the French call them "centimes" and the Spanish "céntimos", for example).
+
+It was created in 1999, but until 1 January 2002 it was used only for electronic payments. In 2002, 12 countries of the European Union (EU) got rid of their national currencies completely and adopted euro notes and coins as their only money. There was a change-over period, called the "transition period", when both the old national money and the euro were accepted, but by 28 February 2002, all 12 countries were using just euros.
+
+In 2006, Slovenia became the 13th country to use the euro. In 2008 Cyprus and Malta became the 14th and 15th countries to use the euro. In 2009, Slovakia became the 16th country to use the euro. In 2011, Estonia became the 17th country to use the euro. In 2014, Latvia became the 18th country and in 2015, Lithuania became the 19th country to use the euro.
+
+There are seven different banknotes, each one with a different colour, size and face value: €5 (grey), €10 (red), €20 (blue), €50 (orange), €100 (green), €200 (yellow), €500 (purple).
+
+Coins are of eight different amounts: €0.01, €0.02, €0.05, €0.1, €0.2, €0.5, €1, €2.
+
+On every banknote, there is a picture of a different European building style. All banknotes are the same throughout the entire eurozone; there are no different designs for different countries, unlike the euro coins. One side of each coin is the same in all euro countries. The other side is different since each country who mints the coins inserts a symbol relating to that country. Today there are many different sets of coins. Any of the coins can be used everywhere throughout the eurozone despite the country-specific symbol on the back.
+
+The ten new European countries that entered the European Union in May 2004 are planning to adopt the Euro also. First they must meet some conditions to show that they have stable economies.
+
+The symbol for the euro is the Greek letter epsilon (E) with two horizontal lines: €.
+
+Some people see it as the Latin capital letter C with an equal sign (=).
+
+It is also legal to simply write euro. This is especially useful when the symbol cannot be produced, or the result is not satisfactory.
+
+Members of the eurozone are:
+
+These countries form the Economic and Monetary Union (EMU).
+
+Even though they are not part of the EU, the euro is also the currency used in:
+
+Many other countries' currencies are "pegged" (tied) to, although not exactly equal to, the euro:

ensimple/1903.html.txt

@@ -0,0 +1,62 @@
+Europe is the western part of the continent of Eurasia, sometimes thought of as its own continent. It is separated from Asia by the Ural Mountains in Russia and the Bosporus strait in Turkey.
+
+Europe is bordered by water on three sides. On the west is the Atlantic Ocean. To the north is the Arctic Ocean. The Mediterranean Sea separates Southeastern Europe from Africa. On the eastern border of Europe are the Ural River and Ural Mountains.
+
+There are at least 43 countries in Europe (the European identity of Cyprus, Georgia, Turkey and Russia are disputed). Most of these countries are members of the European Union.
+
+Europe covers about 10,180,000 square kilometers (3,930,000 square miles). This is 2% of the Earth's surface (6.8% of its land area).
+
+As of 2017, about 510 million people lived in Europe.[1]
+
+Europe makes 44% of the world's wine.
+
+Europe contains the world's second most-active volcano, which is Mount Etna that is currently the most-active volcano in the continent.
+
+Europe is a major tourist attraction. People come from all over the world to see its many World Heritage Sites and other attractions.
+
+Europe is named after a princess in Greek mythology called "Europa." The myth says that Zeus kidnapped Europa and took her to Crete, where she became the mother of King Minos (from whom Europe’s first civilization gets its name, the Minoans).
+
+The name "Europa" was later used to describe Greece. Then, as the rest of modern-day Europe started to have cities and empires, the entire area West of the Ural Mountains came to be called "Europa".
+
+The history of Europe is long and has many turns. Many great countries originated from Europe. Greek mythology and the beginning of western civilization came from European nations.
+
+Some of the major periods in European history have been:
+
+Andreas M. Kaplan describes modern Europe as a continent where many different cultures live closely together, "embracing maximum cultural diversity at minimal geographical distances".[2]
+
+There are several major regions of Europe:
+
+Within these regions, there are up to 47 independent European countries (with the identities of 4 transcontinental countries being disputed). The largest is the Russian Federation, which covers 39% of Europe.
+
+The European city with the largest population is Istanbul. The country with the largest population is the Russian Federation. About 15% of Europeans live in Russia.
+
+Two European countries, the United Kingdom and the Republic of Ireland, are on islands called the British Isles.
+
+Most of Europe lies in temperate climate zones.
+
+However, there are many different climates throughout Europe. For example, during the winter, it may be snowing and -30 degrees Celsius for 4–5 months in Finland. Yet it may be much warmer, with no snow at all except on high mountains, in Spain.
+
+The European Union is a confederation of 27 European countries. These countries agree to follow common laws so that their citizens can move and trade in EU countries almost the same as they do in their own. Nineteen of these countries also share the same type of money: the euro.
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1904.html.txt

@@ -0,0 +1,62 @@
+Europe is the western part of the continent of Eurasia, sometimes thought of as its own continent. It is separated from Asia by the Ural Mountains in Russia and the Bosporus strait in Turkey.
+
+Europe is bordered by water on three sides. On the west is the Atlantic Ocean. To the north is the Arctic Ocean. The Mediterranean Sea separates Southeastern Europe from Africa. On the eastern border of Europe are the Ural River and Ural Mountains.
+
+There are at least 43 countries in Europe (the European identity of Cyprus, Georgia, Turkey and Russia are disputed). Most of these countries are members of the European Union.
+
+Europe covers about 10,180,000 square kilometers (3,930,000 square miles). This is 2% of the Earth's surface (6.8% of its land area).
+
+As of 2017, about 510 million people lived in Europe.[1]
+
+Europe makes 44% of the world's wine.
+
+Europe contains the world's second most-active volcano, which is Mount Etna that is currently the most-active volcano in the continent.
+
+Europe is a major tourist attraction. People come from all over the world to see its many World Heritage Sites and other attractions.
+
+Europe is named after a princess in Greek mythology called "Europa." The myth says that Zeus kidnapped Europa and took her to Crete, where she became the mother of King Minos (from whom Europe’s first civilization gets its name, the Minoans).
+
+The name "Europa" was later used to describe Greece. Then, as the rest of modern-day Europe started to have cities and empires, the entire area West of the Ural Mountains came to be called "Europa".
+
+The history of Europe is long and has many turns. Many great countries originated from Europe. Greek mythology and the beginning of western civilization came from European nations.
+
+Some of the major periods in European history have been:
+
+Andreas M. Kaplan describes modern Europe as a continent where many different cultures live closely together, "embracing maximum cultural diversity at minimal geographical distances".[2]
+
+There are several major regions of Europe:
+
+Within these regions, there are up to 47 independent European countries (with the identities of 4 transcontinental countries being disputed). The largest is the Russian Federation, which covers 39% of Europe.
+
+The European city with the largest population is Istanbul. The country with the largest population is the Russian Federation. About 15% of Europeans live in Russia.
+
+Two European countries, the United Kingdom and the Republic of Ireland, are on islands called the British Isles.
+
+Most of Europe lies in temperate climate zones.
+
+However, there are many different climates throughout Europe. For example, during the winter, it may be snowing and -30 degrees Celsius for 4–5 months in Finland. Yet it may be much warmer, with no snow at all except on high mountains, in Spain.
+
+The European Union is a confederation of 27 European countries. These countries agree to follow common laws so that their citizens can move and trade in EU countries almost the same as they do in their own. Nineteen of these countries also share the same type of money: the euro.
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1905.html.txt

@@ -0,0 +1,62 @@
+Europe is the western part of the continent of Eurasia, sometimes thought of as its own continent. It is separated from Asia by the Ural Mountains in Russia and the Bosporus strait in Turkey.
+
+Europe is bordered by water on three sides. On the west is the Atlantic Ocean. To the north is the Arctic Ocean. The Mediterranean Sea separates Southeastern Europe from Africa. On the eastern border of Europe are the Ural River and Ural Mountains.
+
+There are at least 43 countries in Europe (the European identity of Cyprus, Georgia, Turkey and Russia are disputed). Most of these countries are members of the European Union.
+
+Europe covers about 10,180,000 square kilometers (3,930,000 square miles). This is 2% of the Earth's surface (6.8% of its land area).
+
+As of 2017, about 510 million people lived in Europe.[1]
+
+Europe makes 44% of the world's wine.
+
+Europe contains the world's second most-active volcano, which is Mount Etna that is currently the most-active volcano in the continent.
+
+Europe is a major tourist attraction. People come from all over the world to see its many World Heritage Sites and other attractions.
+
+Europe is named after a princess in Greek mythology called "Europa." The myth says that Zeus kidnapped Europa and took her to Crete, where she became the mother of King Minos (from whom Europe’s first civilization gets its name, the Minoans).
+
+The name "Europa" was later used to describe Greece. Then, as the rest of modern-day Europe started to have cities and empires, the entire area West of the Ural Mountains came to be called "Europa".
+
+The history of Europe is long and has many turns. Many great countries originated from Europe. Greek mythology and the beginning of western civilization came from European nations.
+
+Some of the major periods in European history have been:
+
+Andreas M. Kaplan describes modern Europe as a continent where many different cultures live closely together, "embracing maximum cultural diversity at minimal geographical distances".[2]
+
+There are several major regions of Europe:
+
+Within these regions, there are up to 47 independent European countries (with the identities of 4 transcontinental countries being disputed). The largest is the Russian Federation, which covers 39% of Europe.
+
+The European city with the largest population is Istanbul. The country with the largest population is the Russian Federation. About 15% of Europeans live in Russia.
+
+Two European countries, the United Kingdom and the Republic of Ireland, are on islands called the British Isles.
+
+Most of Europe lies in temperate climate zones.
+
+However, there are many different climates throughout Europe. For example, during the winter, it may be snowing and -30 degrees Celsius for 4–5 months in Finland. Yet it may be much warmer, with no snow at all except on high mountains, in Spain.
+
+The European Union is a confederation of 27 European countries. These countries agree to follow common laws so that their citizens can move and trade in EU countries almost the same as they do in their own. Nineteen of these countries also share the same type of money: the euro.
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1906.html.txt

@@ -0,0 +1 @@
+Europa may refer to:

ensimple/1907.html.txt

@@ -0,0 +1,62 @@
+Europe is the western part of the continent of Eurasia, sometimes thought of as its own continent. It is separated from Asia by the Ural Mountains in Russia and the Bosporus strait in Turkey.
+
+Europe is bordered by water on three sides. On the west is the Atlantic Ocean. To the north is the Arctic Ocean. The Mediterranean Sea separates Southeastern Europe from Africa. On the eastern border of Europe are the Ural River and Ural Mountains.
+
+There are at least 43 countries in Europe (the European identity of Cyprus, Georgia, Turkey and Russia are disputed). Most of these countries are members of the European Union.
+
+Europe covers about 10,180,000 square kilometers (3,930,000 square miles). This is 2% of the Earth's surface (6.8% of its land area).
+
+As of 2017, about 510 million people lived in Europe.[1]
+
+Europe makes 44% of the world's wine.
+
+Europe contains the world's second most-active volcano, which is Mount Etna that is currently the most-active volcano in the continent.
+
+Europe is a major tourist attraction. People come from all over the world to see its many World Heritage Sites and other attractions.
+
+Europe is named after a princess in Greek mythology called "Europa." The myth says that Zeus kidnapped Europa and took her to Crete, where she became the mother of King Minos (from whom Europe’s first civilization gets its name, the Minoans).
+
+The name "Europa" was later used to describe Greece. Then, as the rest of modern-day Europe started to have cities and empires, the entire area West of the Ural Mountains came to be called "Europa".
+
+The history of Europe is long and has many turns. Many great countries originated from Europe. Greek mythology and the beginning of western civilization came from European nations.
+
+Some of the major periods in European history have been:
+
+Andreas M. Kaplan describes modern Europe as a continent where many different cultures live closely together, "embracing maximum cultural diversity at minimal geographical distances".[2]
+
+There are several major regions of Europe:
+
+Within these regions, there are up to 47 independent European countries (with the identities of 4 transcontinental countries being disputed). The largest is the Russian Federation, which covers 39% of Europe.
+
+The European city with the largest population is Istanbul. The country with the largest population is the Russian Federation. About 15% of Europeans live in Russia.
+
+Two European countries, the United Kingdom and the Republic of Ireland, are on islands called the British Isles.
+
+Most of Europe lies in temperate climate zones.
+
+However, there are many different climates throughout Europe. For example, during the winter, it may be snowing and -30 degrees Celsius for 4–5 months in Finland. Yet it may be much warmer, with no snow at all except on high mountains, in Spain.
+
+The European Union is a confederation of 27 European countries. These countries agree to follow common laws so that their citizens can move and trade in EU countries almost the same as they do in their own. Nineteen of these countries also share the same type of money: the euro.
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1908.html.txt

@@ -0,0 +1,9 @@
+Europa is a large moon of the planet Jupiter. It is a little smaller than Earth's Moon and it is the sixth largest moon in the solar system.
+
+Europa's diameter is about 3000 kilometers. It probably has an iron core, and an atmosphere that's mostly oxygen. The surface is icy and very smooth. There are not a lot of craters, but there are some cracks and lines. Because the surface is so young and smooth, scientists believe that there is a liquid ocean under the surface, a so-called subsurface ocean, and that it is kept warm by tidal heating.[7] In other words, Jupiter's strong gravitational pull on Europa makes it warm.
+
+The moon Europa was found by Simon Marius in December 1609. Galileo Galilei first saw the moon in January 1610 (he did not know Marius had found it). Simon Marius was the one who had the idea of the name 'Europa'.
+
+The moon Europa is named after a princess from Greek mythology who became the first queen of Crete. However, people usually called Europa 'Jupiter II' until the middle of the 20th century.
+
+Notes

ensimple/1909.html.txt

@@ -0,0 +1,14 @@
+Europa is a figure from Greek mythology. She is the daughter of Phoenician king Agenor and of Telephassa. Zeus falls in love with her. Because of his wife Hera, he has to take the shape of a bull. Hermes makes the herd of cattle with the bull Zeus graze near the beach near Sidon, where Europa is playing. That way, Zeus is able to abduct Europa on his back. He swims to Matala on Crete where he shows himself. The children of Europa and Zeus are Minos, Rhadamanthys and Sarpedon. Because of a prophecy of Aphrodite, the new continent Europe is named after Europa.
+
+The oldest telling of the story can be found in the Illiad by Homer. There, she is the daughter of Phoinix.[1] Other ancient tellings include "Europa" by Moschos, and the Metamorphoses by Ovid.[2]
+
+Agenor sent his sons to search for Europa, but they could not find her. Cadmus asks the Oracle at Delphi and is told to give up the search, and found Thebes in Boetia instead.
+
+According to other sources, Europa remained on Crete, were she married Asterion, and became queen. Asterion did not have any children, so he adopted her sons.[3]
+
+The oldest known paintings which clearly show Europa date from the 7th century BC.
+
+
+
+
+

ensimple/191.html.txt

@@ -0,0 +1,17 @@
+Native Americans (also called Aboriginal Americans, American Indians, Amerindians or indigenous peoples of America) are the people and their descendants, who were in the Americas when Europeans arrived.  There are many different tribes of Native American people, with many different languages.  There are more than three million Native Americans in Canada and the U.S. combined.  About 51 million Native Americans live in Latin America.
+
+Sometimes these people are called Indians, but this may be confusing, because it is the same word used for people from India. When Christopher Columbus explored, he did not know about the Americas. He was in the Caribbean but thought he was in the East Indies, so he called the people Indians.
+
+Many Native Americans died after the Europeans came to the Americas. There were diseases that came with the Europeans but were new to the Native Americans. There were battles with the Europeans. Many native people were hurt or killed by settlers who took their lands.
+
+The ancestors of Native Americans came to the Americas from Asia. Some of them may have come to America 15,000 years ago when Alaska was connected to Siberia by the Bering land bridge.
+
+The earliest peoples in the Americas came from Siberia when there was an ice bridge across the Bering Strait. The cold but mainly grassy plain which connected Siberia with Canada is called Beringia.  It is reckoned that a few thousand people arrived in  Beringia from eastern Siberia during the Last Glacial Maximum before moving into the Americas sometime after 16,500 years before the present (BP).[1] This would have occurred as the American glaciers blocking the way southward melted,[2][3][4][5][6] but before the bridge was covered by the sea about 11,000 years BP.
+
+Before European colonization, Beringia was inhabited by the Yupik peoples on both sides of the straits. This culture remains in the region today, with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia.[7]
+
+Native Americans are divided into many small nations, called First Nations in Canada and tribes elsewhere.
+
+According to the 2010 United States census, 0.9% of Americans say they are Native American, 2.9 million people, and 1.7% of Americans say they are both Native American and something else.  They are not evenly spread out through the United States.  About a third of the people in Alaska are Native Alaskan and about a sixth of the people in Oklahoma are Native American.[8]
+
+In the United States, most Native Americans live in cities.  About 28% of Native Americans live on reservations.  Many Native Americans are poor, and 24% are extremely poor.  They tend to be the targets of violence more than white people are.[9]

ensimple/1910.html.txt

@@ -0,0 +1,14 @@
+Europa is a figure from Greek mythology. She is the daughter of Phoenician king Agenor and of Telephassa. Zeus falls in love with her. Because of his wife Hera, he has to take the shape of a bull. Hermes makes the herd of cattle with the bull Zeus graze near the beach near Sidon, where Europa is playing. That way, Zeus is able to abduct Europa on his back. He swims to Matala on Crete where he shows himself. The children of Europa and Zeus are Minos, Rhadamanthys and Sarpedon. Because of a prophecy of Aphrodite, the new continent Europe is named after Europa.
+
+The oldest telling of the story can be found in the Illiad by Homer. There, she is the daughter of Phoinix.[1] Other ancient tellings include "Europa" by Moschos, and the Metamorphoses by Ovid.[2]
+
+Agenor sent his sons to search for Europa, but they could not find her. Cadmus asks the Oracle at Delphi and is told to give up the search, and found Thebes in Boetia instead.
+
+According to other sources, Europa remained on Crete, were she married Asterion, and became queen. Asterion did not have any children, so he adopted her sons.[3]
+
+The oldest known paintings which clearly show Europa date from the 7th century BC.
+
+
+
+
+

ensimple/1911.html.txt

@@ -0,0 +1,9 @@
+Europa is a large moon of the planet Jupiter. It is a little smaller than Earth's Moon and it is the sixth largest moon in the solar system.
+
+Europa's diameter is about 3000 kilometers. It probably has an iron core, and an atmosphere that's mostly oxygen. The surface is icy and very smooth. There are not a lot of craters, but there are some cracks and lines. Because the surface is so young and smooth, scientists believe that there is a liquid ocean under the surface, a so-called subsurface ocean, and that it is kept warm by tidal heating.[7] In other words, Jupiter's strong gravitational pull on Europa makes it warm.
+
+The moon Europa was found by Simon Marius in December 1609. Galileo Galilei first saw the moon in January 1610 (he did not know Marius had found it). Simon Marius was the one who had the idea of the name 'Europa'.
+
+The moon Europa is named after a princess from Greek mythology who became the first queen of Crete. However, people usually called Europa 'Jupiter II' until the middle of the 20th century.
+
+Notes

ensimple/1912.html.txt

@@ -0,0 +1,29 @@
+Euro is the currency (money) of the countries in the eurozone. One euro is divided into 100 cent (officially)[1] (singular) or "cents" (unofficially).[2]
+
+Because of the number of different languages in the European Union, there are different, unofficial, names for this unit (the French call them "centimes" and the Spanish "céntimos", for example).
+
+It was created in 1999, but until 1 January 2002 it was used only for electronic payments. In 2002, 12 countries of the European Union (EU) got rid of their national currencies completely and adopted euro notes and coins as their only money. There was a change-over period, called the "transition period", when both the old national money and the euro were accepted, but by 28 February 2002, all 12 countries were using just euros.
+
+In 2006, Slovenia became the 13th country to use the euro. In 2008 Cyprus and Malta became the 14th and 15th countries to use the euro. In 2009, Slovakia became the 16th country to use the euro. In 2011, Estonia became the 17th country to use the euro. In 2014, Latvia became the 18th country and in 2015, Lithuania became the 19th country to use the euro.
+
+There are seven different banknotes, each one with a different colour, size and face value: €5 (grey), €10 (red), €20 (blue), €50 (orange), €100 (green), €200 (yellow), €500 (purple).
+
+Coins are of eight different amounts: €0.01, €0.02, €0.05, €0.1, €0.2, €0.5, €1, €2.
+
+On every banknote, there is a picture of a different European building style. All banknotes are the same throughout the entire eurozone; there are no different designs for different countries, unlike the euro coins. One side of each coin is the same in all euro countries. The other side is different since each country who mints the coins inserts a symbol relating to that country. Today there are many different sets of coins. Any of the coins can be used everywhere throughout the eurozone despite the country-specific symbol on the back.
+
+The ten new European countries that entered the European Union in May 2004 are planning to adopt the Euro also. First they must meet some conditions to show that they have stable economies.
+
+The symbol for the euro is the Greek letter epsilon (E) with two horizontal lines: €.
+
+Some people see it as the Latin capital letter C with an equal sign (=).
+
+It is also legal to simply write euro. This is especially useful when the symbol cannot be produced, or the result is not satisfactory.
+
+Members of the eurozone are:
+
+These countries form the Economic and Monetary Union (EMU).
+
+Even though they are not part of the EU, the euro is also the currency used in:
+
+Many other countries' currencies are "pegged" (tied) to, although not exactly equal to, the euro:

ensimple/1913.html.txt

@@ -0,0 +1,9 @@
+
+
+The eurypterids, related to arachnids, were the largest known arthropods. They are members of the extinct order Eurypterida. It is a most diverse Chelicerate order.[1]
+
+The largest, such as Jaekelopterus, reached 2½ metres in length, but most species were less than 20 cm (8 inches). They were the largest arthropods of all time. They were predators which thrived in the warm, shallow seas and lakes of the Ordovician to the Permian periods, around 460 to 248 million years ago. Recent research suggsts their eyesight was not very good.[2]
+
+The move from the sea to fresh water probably occurred by the Pennsylvanian period. Eurypterids went extinct during the Permian–Triassic extinction event 251 million years ago, and their fossils have a near global distribution.
+
+The typical eurypterid had a large, flat, semicircular carapace, followed by a jointed section, and finally a tapering, flexible tail, most ending with a long spine at the end (Pterygotus, though, had a large flat tail, possibly with a smaller spine). Behind the head of the eurypterids were twelve body segments. These segments are formed by a dorsal plate, called a tergite, and a ventral plate, called a sternite. The tail, known as the telson, is spiked in most eurypterids.[3]

ensimple/1914.html.txt

@@ -0,0 +1,2 @@
+Eva Anna Paula Braun (6 February 1912 – 30 April 1945) was the longtime girlfriend of Adolf Hitler. She met him in Munich when she was 17 years old. They married the day before they committed suicide (killed themselves), Braun killed herself by using cyanide. Hitler used cyanide and at the same time shot himself. When she was married, she was known as Eva Anna Paula Hitler. She was born in Munich, Germany and died in Berlin, Germany at the age of 33. Her body was burned as well as Adolf Hitler.
+

ensimple/1915.html.txt

@@ -0,0 +1,19 @@
+Evaporation is when a liquid becomes a gas without forming bubbles inside the liquid volume. If bubbles are formed we are talking instead about "boiling".
+
+For example, water left in a bowl will slowly disappear. The water evaporates into water vapor, the gas phase of water. The water vapor mixes with the air.
+
+The opposite of evaporation is condensation.
+
+When the molecules in a liquid are heated, they move faster. This makes them full of energy and so the particles collide with each other, and eventually they become so far apart that they become a gas.
+
+During evaporation only the molecules near the liquid surface are changing from liquid to vapor. During boiling the molecules inside the volume of the liquid are also changing to vapor. For this reason during evaporation no bubbles are formed, instead they are formed during boiling.
+
+Evaporation can happen at any temperature, while boiling happens only at a specified temperature called the "boiling point". Evaporation happens slowly, but boiling happens quickly.
+
+Some liquids evaporate more quickly than others. There are many factors that affect the evaporation rate.
+
+The rate of evaporation depends on the liquid's exposed surface area (faster when increased), the humidity of surroundings (slower when increased), the presence of wind (faster when increased) and the temperature (faster when increased).
+
+Liquid with high boiling points (those that boil at very high temperatures) tend to evaporate more slowly than those with lower boiling temperatures.[1]
+
+Evaporation is a very essential part of the water cycle.

ensimple/1916.html.txt

@@ -0,0 +1,9 @@
+Bishop is the title of a rank in the clergy of a Christian Church. The diocese which a bishop governs is called a bishopric. A Bishop may be given the rank of Archbishop in an Archdiocese.[1]
+
+Usually, there are priests, then there are bishops. However, some Protestant churches have no bishops or archbishops. The Presbyterian church is an example.[2] The Church of Scotland is headed by a Moderator, who is elected by the General Assembly each year.[3] Other Christian movements have neither bishops nor priests: Quakers are a good example.
+
+In the Catholic church, the Pope is chosen by all the cardinals from amongst their number.[4] According to church law, this does not have to be the case: any male, unmarried, baptized Christian who is judged fit for the office can become pope. However, the last pope who was not a bishop was Urban VI (elected in 1378).
+
+The pope is also 'the Bishop of Rome'.  In fact he rules an independent state within Rome, called the Vatican.  All Roman Catholic bishops answer to the pope (or to patriarchs in some orthodox churches).  In the Anglican church, bishops are governed by Archbishops.
+
+Usually a bishop can be identified by a special hat, called a mitre.

ensimple/1917.html.txt

@@ -0,0 +1,9 @@
+Bishop is the title of a rank in the clergy of a Christian Church. The diocese which a bishop governs is called a bishopric. A Bishop may be given the rank of Archbishop in an Archdiocese.[1]
+
+Usually, there are priests, then there are bishops. However, some Protestant churches have no bishops or archbishops. The Presbyterian church is an example.[2] The Church of Scotland is headed by a Moderator, who is elected by the General Assembly each year.[3] Other Christian movements have neither bishops nor priests: Quakers are a good example.
+
+In the Catholic church, the Pope is chosen by all the cardinals from amongst their number.[4] According to church law, this does not have to be the case: any male, unmarried, baptized Christian who is judged fit for the office can become pope. However, the last pope who was not a bishop was Urban VI (elected in 1378).
+
+The pope is also 'the Bishop of Rome'.  In fact he rules an independent state within Rome, called the Vatican.  All Roman Catholic bishops answer to the pope (or to patriarchs in some orthodox churches).  In the Anglican church, bishops are governed by Archbishops.
+
+Usually a bishop can be identified by a special hat, called a mitre.

ensimple/1918.html.txt

@@ -0,0 +1,26 @@
+[5]Mount Everest [a] is the highest mountain on Earth. Mount Everest is in the Himalayas, the highest mountain range in the world. It is about 8,848.00 metres (29,028.87 ft) high.[6]
+
+Its peak is on the border of Nepal and China. It is above the Death Zone where the air is too thin for a human being to live, so usually compressed gas tanks with different gas mixes for different altitudes are used when climbing. The Death Zone refers to the parts of Mount Everest that are above 7,600 metres (24,900 ft) above sea level.
+
+Two other mountains also can be named as the "highest" mountains - the Hawaiian volcano Mauna Loa on Hawaii island is the highest mountain measured from the base underwater to the summit (more than 11 kilometres), and the summit of Mount Chimborazo is the fixed point on Earth which is the greatest distance from the center. This is because of the shape of the Earth: the circumference around the Equator is greater than around the poles.
+
+"Everest Base Camp" is used to mean the two base camps on opposite sides of Mount Everest. South Base Camp is in Nepal at an altitude of 5,364 metres (17,598 ft) (28°0′26″N 86°51′34″E / 28.00722°N 86.85944°E / 28.00722; 86.85944). North Base Camp is in Tibet at 5,150.00 meters (16,896.33 ft)[7][8][9]  (28°8′29″N 86°51′5″E / 28.14139°N 86.85139°E / 28.14139; 86.85139 (North Base Camp)).  These camps are simple campsite shelters at the bottom (or base) of the mountain. They are used by mountain climbers during their journey up or down the mountain. Supplies are provided there and climbers rest, heal and make trip preparations.
+
+South Base Camp is used when climbing up the southeast ridge. North Base Camp is used when climbing up the northeast ridge.[10]
+
+Supplies are shipped to the South Base Camp by Sherpas or porters, and with the help of animals, usually yaks. The North Base Camp has vehicle access (at least in the summer months).  Climbers usually rest at base camp for several days for their bodies to get used to the thin air of high altitudes.
+
+This reduces the risks and severity of altitude sickness.
+
+Mount Everest has a very cold and snowy climate. Winds can speed up to 177 mph (285 km/h). The coldest month is January with a high of −74 °F (−59 °C) and the warmest month in mount everest is July with a high of −10 °F (−23 °C).
+Because of climate change, the glaciers around Mount Everest may disappear over the next few decades.[11]
+
+A survey of India in 1856 recorded Everest. It was called Peak XV. This first published height was 8,840 m (29,000 ft). Everest was given its official English name in 1865 by the Royal Geographical Society.
+
+British people began exploring the area around Mount Everest in 1921. The first expedition to try to climb to the top of Everest was in 1922. On June 8th, 1924, George Leigh Mallory and climbing partner Andrew Irvine tried to climb to the summit of Mount Everest. They disappeared into the fog and were not seen again until Mallory's dead body was found by Conrad Anker in 1999.
+
+The top of Mount Everest was first reached in May 1953 by the Sherpa Tenzing Norgay and the New Zealander Sir Edmund Hillary.
+
+In March 2020, Nepal closed the mountain to climbing. This was part of the effort to stop the 2019–20 coronavirus pandemic.[13][14]
+
+Sherpas are the local people who live near the foot of Mount Everest. For the Sherpas, Mount Everest is a sacred mountain and before they climb Mount Everest they always do a sacrificial offering.[5]

ensimple/1919.html.txt

@@ -0,0 +1,26 @@
+[5]Mount Everest [a] is the highest mountain on Earth. Mount Everest is in the Himalayas, the highest mountain range in the world. It is about 8,848.00 metres (29,028.87 ft) high.[6]
+
+Its peak is on the border of Nepal and China. It is above the Death Zone where the air is too thin for a human being to live, so usually compressed gas tanks with different gas mixes for different altitudes are used when climbing. The Death Zone refers to the parts of Mount Everest that are above 7,600 metres (24,900 ft) above sea level.
+
+Two other mountains also can be named as the "highest" mountains - the Hawaiian volcano Mauna Loa on Hawaii island is the highest mountain measured from the base underwater to the summit (more than 11 kilometres), and the summit of Mount Chimborazo is the fixed point on Earth which is the greatest distance from the center. This is because of the shape of the Earth: the circumference around the Equator is greater than around the poles.
+
+"Everest Base Camp" is used to mean the two base camps on opposite sides of Mount Everest. South Base Camp is in Nepal at an altitude of 5,364 metres (17,598 ft) (28°0′26″N 86°51′34″E / 28.00722°N 86.85944°E / 28.00722; 86.85944). North Base Camp is in Tibet at 5,150.00 meters (16,896.33 ft)[7][8][9]  (28°8′29″N 86°51′5″E / 28.14139°N 86.85139°E / 28.14139; 86.85139 (North Base Camp)).  These camps are simple campsite shelters at the bottom (or base) of the mountain. They are used by mountain climbers during their journey up or down the mountain. Supplies are provided there and climbers rest, heal and make trip preparations.
+
+South Base Camp is used when climbing up the southeast ridge. North Base Camp is used when climbing up the northeast ridge.[10]
+
+Supplies are shipped to the South Base Camp by Sherpas or porters, and with the help of animals, usually yaks. The North Base Camp has vehicle access (at least in the summer months).  Climbers usually rest at base camp for several days for their bodies to get used to the thin air of high altitudes.
+
+This reduces the risks and severity of altitude sickness.
+
+Mount Everest has a very cold and snowy climate. Winds can speed up to 177 mph (285 km/h). The coldest month is January with a high of −74 °F (−59 °C) and the warmest month in mount everest is July with a high of −10 °F (−23 °C).
+Because of climate change, the glaciers around Mount Everest may disappear over the next few decades.[11]
+
+A survey of India in 1856 recorded Everest. It was called Peak XV. This first published height was 8,840 m (29,000 ft). Everest was given its official English name in 1865 by the Royal Geographical Society.
+
+British people began exploring the area around Mount Everest in 1921. The first expedition to try to climb to the top of Everest was in 1922. On June 8th, 1924, George Leigh Mallory and climbing partner Andrew Irvine tried to climb to the summit of Mount Everest. They disappeared into the fog and were not seen again until Mallory's dead body was found by Conrad Anker in 1999.
+
+The top of Mount Everest was first reached in May 1953 by the Sherpa Tenzing Norgay and the New Zealander Sir Edmund Hillary.
+
+In March 2020, Nepal closed the mountain to climbing. This was part of the effort to stop the 2019–20 coronavirus pandemic.[13][14]
+
+Sherpas are the local people who live near the foot of Mount Everest. For the Sherpas, Mount Everest is a sacred mountain and before they climb Mount Everest they always do a sacrificial offering.[5]

ensimple/192.html.txt

@@ -0,0 +1,50 @@
+Central America ([América Central or Centroamérica] error: {{lang-xx}}: text has italic markup (help)) is the central geographic region of the Americas and specifically part of the continent known as North America. It goes from Guatemala and Belize in the north-west, to Panama in the south-east. It is the area of land that sits south-east of Mexico and north-west of Colombia. It is between the Pacific Ocean and the Caribbean Sea.
+
+Central America has an area of 524,000 square kilometers (202,000 sq mi). It is almost 0.1% of the Earth's surface. This is a list of the countries in Central America, from the largest to the smallest:
+
+While Nicaragua is the largest country in area, of Central America, Guatemala has the largest population by country in Central America, with more than 14 million people and they also have the most populated city in Central America, being Guatemala City.
+
+Six of the seven countries have Spanish as their official language, with Belize being the non-Spanish speaking country, as their official language is English, although there are now at least 195,597 (62.8%) of people in Belize who speak Spanish.[2]
+
+Some people also speak indigenous or creole languages like the Maya languages.
+
+Central America has a density of 77 people per square kilometer.
+
+Central America has an area of 524,000 square kilometers (202,000 sq mi). It is almost 0.1% of the Earth's total surface. In 2009 the population was estimated at 41,739,000. It has a density of 77 people per square kilometer or 206 people per square mile.
+
+Central America has many unique features that go from the north-western borders of Belize and Guatemala to the Isthmus of Panama. There it connects to the Colombian Pacific Lowlands in South America.
+
+Central America is an area of some 524,000 square kilometres. The Pacific Ocean is on the southwest, the Caribbean Sea to the northeast, and the Gulf of Mexico to the north. Most of Central America rests on the Caribbean Plate.
+
+The region is geologically active. It has volcanic eruptions and earthquakes from time to time.
+
+The 1976 Guatemala earthquake  killed 23,001 people. Managua, the capital of Nicaragua, was devastated by earthquakes in 1931 and 1972. The last one killed about 5,001 people. Three earthquakes hit El Salvador. The first one in 1986 and two in 2001. An earthquake devastated northern and central Costa Rica in 2009. It killed at least 35 people. In Honduras a powerful earthquake happened in 2009.
+
+Volcanic eruptions are common. In 1968 the Arenal Volcano in Costa Rica erupted. This killed at least 87 people. The 3 villages of Tabacon, Pueblo Nuevo, and San Luis were buried under ash.
+
+Central America has many mountain ranges; the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia and the Cordillera de Talamanca. Most of the population of Honduras, Costa Rica and Guatemala live in valleys, between mountains. Valleys are also suitable for the production of coffee, beans and other crops.
+
+Central America is part of the Mesoamerican Biodiversity hotspot, boasting 7% of the world's biodiversity.[3] As a bridge between North and South America, Central America has many species from the Nearctic and the Neotropic ecozones. However the southern countries (Costa Rica and Panama) of the region have more biodiversity than the northern countries (Guatemala and Belize), meanwhile the central countries (Honduras, Nicaragua and El Salvador) have least biodiversity.[3] The table shows current statistics for the seven countries:
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+

ensimple/1920.html.txt

@@ -0,0 +1,255 @@
+Evolution is a biological process that makes living things change over a long time. The explanation of how this process works and how living beings have come to be the way they are is called the theory of evolution.[1]
+
+Earth is very old.[2][3] By studying the layers of rock that make up Earth's crust, scientists can find out about its past. This kind of research is called historical geology.
+
+It is known that living things have changed over time, because their remains can be seen in the rocks. These remains are called 'fossils'. This proves that the animals and plants of today are different from those of long ago.  The older the fossils, the bigger the differences from modern forms.[4]  This has happened because evolution has taken place. That evolution has taken place is a fact, because it is overwhelmingly supported by many lines of evidence.[5][6][7] At the same time, evolutionary questions are still being actively researched by biologists.
+
+Comparison of DNA sequences allows organisms to be grouped by how similar their sequences are. In 2010 an analysis compared sequences to phylogenetic trees, and supported the idea of common descent. There is now "strong quantitative support, by a formal test",[8] for the unity of life.[9]
+
+The theory of evolution is the basis of modern biology. Theodosius Dobzhansky, a well-known evolutionary biologist, has said: "Nothing in biology makes sense except in the light of evolution".[10]
+
+The evidence for evolution is given in a number of books.[11][12][13][14] Some of this evidence is discussed here.
+
+The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:
+
+The most convincing evidence for the occurrence of evolution is the discovery of extinct organisms in older geological strata... The older the strata are...the more different the fossil will be from living representatives... that is to be expected if the fauna and flora of the earlier strata had gradually evolved into their descendants.
+
+The evolution of the horse family (Equidae) is a good example of the way that evolution works. The oldest fossil of a horse is about 52 million years old. It was a small animal with five toes on the front feet and four on the hind feet. At that time, there were more forests in the world than today. This horse lived in woodland, eating leaves, nuts and fruit with its simple teeth. It was only about as big as a fox.[19]
+
+About 30 million years ago the world started to become cooler and drier. Forests shrank; grassland expanded, and horses changed. They ate grass, they grew larger, and they ran faster because they had to escape faster predators. Because grass wears teeth out, horses with longer-lasting teeth had an advantage.
+
+For most of this long period of time, there were a number of horse types (genera). Now, however, only one genus exists: the modern horse, Equus. It has teeth which grow all its life, hooves on single toes, great long legs for running, and the animal is big and strong enough to survive in the open plain.[19] Horses lived in western Canada until 12,000 years ago,[20] but all horses in North America became extinct about 11,000 years ago. The causes of this extinction are not yet clear. Climate change and over-hunting by humans are suggested.
+
+So, scientists can see that changes have happened. They have happened slowly over a long time. How these changes have come about is explained by the theory of evolution.
+
+This is a topic which fascinated both Charles Darwin and Alfred Russel Wallace.[21][22][23] When new species occur, usually by the splitting of older species, this takes place in one place in the world. Once it is established, a new species may spread to some places and not others.
+
+Australasia has been separated from other continents for many millions of years. In the main part of the continent, Australia, 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians are endemic.[24] Its native mammals are mostly marsupials like kangaroos, bandicoots, and quolls.[25] By contrast, marsupials are today totally absent from Africa and form a small portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del monte occur (see the Great American Interchange).
+
+The only living representatives of primitive egg-laying mammals (monotremes) are the echidnas and the platypus. They are only found in Australasia, which includes Tasmania, New Guinea, and Kangaroo Island. These monotremes are totally absent in the rest of the world.[26] On the other hand, Australia is missing many groups of placental mammals that are common on other continents (carnivora, artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and rodents, which arrived later.[27]
+
+The evolutionary story is that placental mammals evolved in Eurasia, and wiped out the marsupials and monotremes wherever they spread. They did not reach Australasia until more recently. That is the simple reason why Australia has most of the world's marsupials and all the world's monotremes.
+
+In about 6,500 sq mi (17,000 km2), the Hawaiian Islands have the most diverse collection of Drosophila flies in the world, living from rainforests to mountain meadows. About 800 Hawaiian fruit fly species are known.
+
+Genetic evidence shows that all the native fruit fly species in Hawaiʻi have descended from a single ancestral species that came to the islands, about 20 million years ago. Later adaptive radiation was caused by a lack of competition and a wide variety of vacant niches. Although it would be possible for a single pregnant female to colonise an island, it is more likely to have been a group from the same species.[28][29][30][31]
+
+The combination of continental drift and evolution can explain what is found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian period on the ancient supercontinent of Gondwana.[32]
+
+Glossopteris fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.
+
+During the Permian, these continents were connected as Gondwana. This is known from magnetic striping in the rocks, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian.[13]p103[33]
+
+When biologists look at living things, they see that animals and plants belong to groups which have something in common. Charles Darwin explained that this followed naturally if "we admit the common parentage of allied forms, together with their modification through variation and natural selection".[21]p402[11]p456
+
+For example, all insects are related. They share a basic body plan, whose development is controlled by master regulatory genes.[34] They have six legs; they have hard parts on the outside of the body (an exoskeleton); they have eyes formed of many separate chambers, and so on. Biologists explain this with evolution. All insects are the descendants of a group of animals who lived a long time ago. They still keep the basic plan (six legs and so on) but the details change. They look different now because they changed in different ways: this is evolution.[35]
+
+It was Darwin who first suggested that all life on Earth had a single origin, and from that beginning "endless forms most beautiful and most wonderful have been, and are being, evolved".[11]p490[21] Evidence from molecular biology in recent years has supported the idea that all life is related by common descent.[36]
+
+Strong evidence for common descent comes from vestigial structures.[21]p397 The useless wings of flightless beetles are sealed under fused wing covers. This can be simply explained by their descent from ancestral beetles which had wings that worked.[14]p49
+
+Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in ancestral species, are called vestigial organs. Those organs are functional in the ancestral species but are now either nonfunctional or re-adapted to a new function. Examples are the pelvic girdles of whales, halteres (hind wings) of flies, wings of flightless birds, and the leaves of some xerophytes (e.g. cactus) and parasitic plants (e.g. dodder).
+
+However, vestigial structures may have their original function replaced with another. For example, the halteres in flies help balance the insect while in flight, and the wings of ostriches are used in mating rituals, and in aggressive display. The ear ossicles in mammals are former bones of the lower jaw.
+
+In 1893, Robert Wiedersheim published a book on human anatomy and its relevance to man's evolutionary history. This book contained a list of 86 human organs that he considered vestigial.[37] This list included examples such as the appendix and the 3rd molar teeth (wisdom teeth).
+
+The strong grip of a baby is another example.[38] It is a vestigial reflex, a remnant of the past when pre-human babies clung to their mothers' hair as the mothers swung through the trees. This is borne out by the babies' feet, which curl up when it is sitting down (primate babies grip with the feet as well). All primates except modern man have thick body hair to which an infant can cling, unlike modern humans. The grasp reflex allows the mother to escape danger by climbing a tree using both hands and feet.[13][39]
+
+Vestigial organs often have some selection against them. The original organs took resources, sometimes huge resources. If they no longer have a function, reducing their size improves fitness. And there is direct evidence of selection. Some cave crustacea reproduce more successfully with smaller eyes than do those with larger eyes. This may be because the nervous tissue dealing with sight now becomes available to handle other sensory input.[40]p310
+
+From the eighteenth century it was known that embryos of different species were much more similar than the adults. In particular, some parts of embryos reflect their evolutionary past. For example, the embryos of land vertebrates develop gill slits like fish embryos. Of course, this is only a temporary stage, which gives rise to many structures in the neck of reptiles, birds and mammals. The proto-gill slits are part of a complicated system of development: that is why they persisted.[34]
+
+Another example are the embryonic teeth of baleen whales.[41] They are later lost. The baleen filter is developed from different tissue, called keratin. Early fossil baleen whales did actually have teeth as well as the baleen.[42]
+
+A good example is the barnacle. It took many centuries before natural historians discovered that barnacles were crustacea. Their adults look so unlike other crustacea, but their larvae are very similar to those of other crustacea.[43]
+
+Charles Darwin lived in a world where animal husbandry and domesticated crops were vitally important. In both cases farmers selected for breeding individuals with special properties, and prevented the breeding of individuals with less desirable characteristics. The eighteenth and early nineteenth century saw a growth in scientific agriculture, and artificial breeding was part of this.
+
+Darwin discussed artificial selection as a model for natural selection in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural selection:
+
+Nikolai Vavilov showed that rye, originally a weed, came to be a crop plant by unintentional selection. Rye is a tougher plant than wheat: it survives in harsher conditions. Having become a crop like the wheat, rye was able to become a crop plant in harsh areas, such as hills and mountains.[45][46]
+
+There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection. There are practical differences. Experimental studies of artificial selection show that "the rate of evolution in selection experiments is at least two orders of magnitude (that is 100 times) greater than any rate seen in nature or the fossil record".[47]p157
+
+Some have thought that artificial selection could not produce new species. It now seems that it can.
+
+New species have been created by domesticated animal husbandry, but the details are not known or not clear. For example, domestic sheep were created by hybridisation, and no longer produce viable offspring with Ovis orientalis, one species from which they are descended.[48] Domestic cattle, on the other hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce fertile offspring with them.[49]
+
+The best-documented new species came from laboratory experiments in the late 1980s. William Rice and G.W. Salt bred fruit flies, Drosophila melanogaster, using a maze with three different choices of habitat such as light/dark and wet/dry. Each generation was put into the maze, and the groups of flies that came out of two of the eight exits were set apart to breed with each other in their respective groups.
+
+After thirty-five generations, the two groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only within the areas they preferred, and so did not mate with flies that preferred the other areas.[50][51]
+
+Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in Drosophila pseudoobscura fruit flies after only eight generations using different food types, starch and maltose.[52]
+
+
+
+Dodd's experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.[53]
+
+Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms.[54] Others call it evolution when new species appear.
+
+Changes can happen quickly in the smaller, simpler organisms. For example, many bacteria that cause disease can no longer be killed with some of the antibiotic medicines. These medicines have only been in use about eighty years, and at first worked extremely well. The bacteria have evolved so that they are no longer affected by antibiotics anymore.[55] The drugs killed off all the bacteria except a few which had some resistance. These few resistant bacteria produced the next generation.
+
+The Colorado beetle is famous for its ability to resist pesticides. Over the last 50 years it has become resistant to 52 chemical compounds used in insecticides, including cyanide.[56] This is natural selection speeded up by the artificial conditions. However, not every population is resistant to every chemical.[57] The populations only become resistant to chemicals used in their area.
+
+Although there were a number of natural historians in the 18th century who had some idea of evolution, the first well-formed ideas came in the 19th century. Three biologists are most important.
+
+Jean-Baptiste de Lamarck (1744–1829), a French biologist, claimed that animals changed according to natural laws. He said that animals could pass on traits they had acquired during their lifetime to their offspring, using inheritance. Today, his theory is known as Lamarckism. Its main purpose is to explain adaptations by natural means.[58] He proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus use and disuse.
+
+Lamarck's idea was that a giraffe's neck grew longer because it tried to reach higher up. This idea failed because it conflicts with heredity (Mendel's work). Mendel made his discoveries about half a century after Lamarck's work.
+
+Charles Darwin (1809–1882) wrote his On the Origin of Species in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place. But Darwin did not understand about genetics and how traits were actually passed on. He could not accurately explain what made children look like their parents.
+
+Nevertheless, Darwin's explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin's idea was that the giraffe's neck became longer because those with longer necks survived better.[21]p177/9 These survivors passed their genes on, and in time the whole species got longer necks.
+
+An Austrian monk called Gregor Mendel (1822–1884) bred plants. In the mid-19th century, he discovered how traits were passed on from one generation to the next.
+
+He used peas for his experiments: some peas have white flowers and others have red ones. Some peas have green seeds and others have yellow seeds. Mendel used artificial pollination to breed the peas. His results are discussed further in Mendelian inheritance. Darwin thought that the inheritance from both parents blended together. Mendel proved that the genes from the two parents stay separate, and may be passed on unchanged to later generations.
+
+Mendel published his results in a journal that was not well-known, and his discoveries were overlooked. Around 1900, his work was rediscovered.[59][60] Genes are bits of information made of DNA which work like a set of instructions. A set of genes are in every living cell. Together, genes organise the way an egg develops into an adult. With mammals, and many other living things, a copy of each gene comes from the father and another copy from the mother. Some living organisms, including some plants, only have one parent, so get all their genes from them. These genes produce the genetic differences which evolution acts on.
+
+Darwin's On the Origin of Species has two themes: the evidence for evolution, and his ideas on how evolution took place. This section deals with the second issue.
+
+The first two chapters of the Origin deal with variation in domesticated plants and animals, and variation in nature.
+
+All living things show variation. Every population which has been studied shows that animal and plants vary as much as humans do.[61][62]p90 This is a great fact of nature, and without it evolution would not occur. Darwin said that, just as man selects what he wants in his farm animals, so in nature the variations allow natural selection to work.[63]
+
+The features of an individual are influenced by two things, heredity and environment. First, development is controlled by genes inherited from the parents. Second, living brings its own influences. Some things are entirely inherited, others partly, and some not inherited at all.
+
+The colour of eyes is entirely inherited; they are a genetic trait. Height or weight is only partly inherited, and the language is not at all inherited. Just to be clear: the fact that humans can speak is inherited, but what language is spoken depends on where a person lives and what they are taught. Another example: a person inherits a brain of somewhat variable capacity. What happens after birth depends on many things such as home environment, education and other experiences. When a person is adult, their brain is what their inheritance and life experience have made it.
+
+Evolution only concerns the traits which can be inherited, wholly or partly. The hereditary traits are passed on from one generation to the next through the genes. A person's genes contain all the traits which they inherit from their parents. The accidents of life are not passed on. Also, of course, each person lives a somewhat different life: that increases the differences.
+
+Organisms in any population vary in reproductive success.[64]p81 From the point of view of evolution, 'reproductive success' means the total number of offspring which live to breed and leave offspring themselves.
+
+Variation can only affect future generations if it is inherited. Because of the work of Gregor Mendel, we know that much variation is inherited. Mendel's 'factors' are now called genes. Research has shown that almost every individual in a sexually reproducing species is genetically unique.[65]p204
+
+Genetic variation is increased by gene mutations. DNA does not always reproduce exactly. Rare changes occur, and these changes can be inherited. Many changes in DNA cause faults; some are neutral or even advantageous. This gives rise to genetic variation, which is the seed-corn of evolution. Sexual reproduction, by the crossing over of chromosomes during meiosis, spreads variation through the population. Other events, like natural selection and drift, reduce variation. So a population in the wild always has variation, but the details are always changing.[62]p90
+
+Evolution mainly works by natural selection. What does this mean? Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence. Those who survive will produce the next generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes a population and causes evolution.
+
+Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:
+
+There are now many cases where natural selection has been proved to occur in wild populations.[5][67][68] Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.[69]
+
+The force of selection can be much stronger than was thought by the early population geneticists. The resistance to pesticides has grown quickly. Resistance to warfarin in Norway rats (Rattus norvegicus) grew rapidly because those that survived made up more and more of the population. Research showed that, in the absence of warfarin, the resistant homozygote was at a 54% disadvantage to the normal wild type homozygote.[62]p182[70] This great disadvantage was quickly overcome by the selection for warfarin resistance.
+
+Mammals normally cannot drink milk as adults, but humans are an exception. Milk is digested by the enzyme lactase, which switches off as mammals stop taking milk from their mothers. The human ability to drink milk during adult life is supported by a lactase mutation which prevents this switch-off. Human populations have a high proportion of this mutation wherever milk is important in the diet. The spread of this 'milk tolerance' is promoted by natural selection, because it helps people survive where milk is available. Genetic studies suggest that the oldest mutations causing lactase persistence only reached high levels in human populations in the last ten thousand years.[71][72] Therefore, lactase persistence is often cited as an example of recent human evolution.[73][74] As lactase persistence is genetic, but animal husbandry a cultural trait, this is gene–culture coevolution.[75]
+
+Adaptation is one of the basic phenomena of biology.[76] Through the process of adaptation, an organism becomes better suited to its habitat.[77]
+
+Adaptation is one of the two main processes that explain the diverse species we see in biology.  The other is speciation (species-splitting or cladogenesis).[78][79] A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.[80][81]
+
+When people speak about adaptation they often mean something which helps an animal or plant survive. One of the most widespread adaptations in animals is the evolution of the eye. Another example is the adaptation of horses' teeth to grinding grass. Camouflage is another adaptation; so is mimicry. The better adapted animals are the most likely to survive, and to reproduce successfully (natural selection).
+
+An internal parasite (such as a fluke) is a good example: it has a very simple bodily structure, but still the organism is highly adapted to its particular environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life cycle, which is often quite complex.[82]
+
+Not all features of an organism are adaptations.[62]p251 Adaptations tend to reflect the past life of a species. If a species has recently changed its life style, a once valuable adaptation may become useless, and eventually become a dwindling vestige.
+
+Adaptations are never perfect. There are always tradeoffs between the various functions and structures in a body. It is the organism as a whole which lives and reproduces, therefore it is the complete set of adaptations which gets passed on to future generations.
+
+In populations, there are forces which add variation to the population (such as mutation), and forces which remove it. Genetic drift is the name given to random changes which remove variation from a population. Genetic drift gets rid of variation at the rate of 1/(2N) where N = population size.[47]p29 It is therefore "a very weak evolutionary force in large populations".[47]p55
+
+Genetic drift explains how random chance can affect evolution in surprisingly big ways, but only when populations are quite small.  Overall, its action is to make the individuals more similar to each other, and hence more vulnerable to disease or to chance events in their environment.
+
+How species form is a major part of evolutionary biology. Darwin interpreted 'evolution' (a word he did not use at first) as being about speciation. That is why he called his famous book On the Origin of Species.
+
+Darwin thought most species arose directly from pre-existing species. This is called anagenesis: new species by older species changing. Now we think most species arise by previous species splitting: cladogenesis.[87][88]
+
+Two groups that start the same can also become very different if they live in different places. When a species gets split into two geographical regions, a process starts. Each adapts to its own situation. After a while, individuals from one group can no longer reproduce with the other group. Two good species have evolved from one.
+
+A German explorer, Moritz Wagner, during his three years in Algeria in the 1830s, studied flightless beetles. Each species is confined to a stretch of the north coast between rivers which descend from the Atlas mountains to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.[89] He wrote later:
+
+This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.[91]
+
+One example of natural speciation is the three-spined stickleback, a sea fish that, after the last ice age, invaded freshwater, and set up colonies in isolated lakes and streams. Over about 10,000 generations, the sticklebacks show great differences, including variations in fins, changes in the number or size of their bony plates, variable jaw structure, and color differences.[92]
+
+The wombats of Australia fall into two main groups, common wombats and hairy-nosed wombats. The two types look very similar, apart from the hairiness of their noses. However, they are adapted to different environments. Common wombats live in forested areas and eat mostly green food with lots of moisture. They often feed in the daytime. Hairy-nosed wombats live on hot dry plains where they eat dry grass with very little water or nutrition it. Their metabolic rate is slow and they sleep most of the day underground.
+
+When two groups that started the same become different enough, then they become two different species. Part of the theory of evolution is that all living things started the same, but then split into different groups over billions of years.[93]
+
+This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s.[94][95] It has been updated regularly ever since.
+The synthesis explains how the ideas of Charles Darwin fit with the discoveries of Gregor Mendel, who found out how we inherit our genes. The modern synthesis brought Darwin's idea up to date. It bridged the gap between different types of biologists: geneticists, naturalists, and palaeontologists.
+
+When the theory of evolution was developed, it was not clear that natural selection and genetics worked together. But Ronald Fisher showed that natural selection would work to change species.[96] Sewall Wright explained genetic drift in 1931.[97]
+
+Co-evolution is where the existence of one species is tightly bound up with the life of one or more other species.
+
+New or 'improved' adaptations which occur in one species are often followed by the appearance and spread of related features in the other species. The life and death of living things is intimately connected, not just with the physical environment, but with the life of other species.
+
+These relationships may continue for millions of years, as it has in the pollination of flowering plants by insects.[102][103] The gut contents, wing structures, and mouthparts of fossilized beetles and flies suggest that they acted as early pollinators. The association between beetles and angiosperms during the Lower Cretaceous period led to parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in Upper Cretaceous flowers signals the beginning of the mutualism between hymenoptera and angiosperms.[104]
+
+Charles Darwin was the first to use this metaphor in biology. The evolutionary tree shows the relationships among various biological groups. It includes data from DNA, RNA and protein analysis. Tree of life work is a product of traditional comparative anatomy, and modern molecular evolution and molecular clock research.
+
+The major figure in this work is Carl Woese, who defined the Archaea, the third domain (or kingdom) of life.[105] Below is a simplified version of present-day understanding.[106]
+
+Macroevolution: the study of changes above the species level, and how they take place. The basic data for such a study are fossils (palaeontology) and the reconstruction of ancient environments. Some subjects whose study falls within the realm of macroevolution:
+
+It is a term of convenience: for most biologists it does not suggest any change in the process of evolution.[5][107][108]p87 For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis.[109] They are in the minority.
+
+Altruism – the willingness of some to sacrifice themselves for others – is widespread in social animals. As explained above, the next generation can only come from those who survive and reproduce. Some biologists have thought that this meant altruism could not evolve by the normal process of selection. Instead a process called "group selection" was proposed.[110][111] Group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group.
+
+For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution.[112][113][114][115]
+
+In simple cases it can be seen at once that traditional selection suffices. For example, if one sibling sacrifices itself for three siblings, the genetic disposition for the act will be increased. This is because siblings share on average 50% of their genetic inheritance, and the sacrificial act has led to greater representation of the genes in the next generation.
+
+Altruism is now generally seen as emerging from standard selection.[116][117][118][119][120] The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.[121][122]
+
+Hamilton's equation describes whether or not a gene for altruistic behaviour will spread in a population. The gene will spread if rxb is greater than c:
+
+where:
+
+At first, sexual reproduction might seem to be at a disadvantage compared with asexual reproduction. In order to be advantageous, sexual reproduction (cross-fertilisation) has to overcome a two-fold disadvantage (takes two to reproduce) plus the difficulty of finding a mate. Why, then, is sex so nearly universal among eukaryotes? This is one of the oldest questions in biology.[123]
+
+The answer has been given since Darwin's time: because the sexual populations adapt better to changing circumstances. A recent laboratory experiment suggests this is indeed the correct explanation.[124][125]
+
+In the main experiment, nematode worms were divided into two groups. One group was entirely outcrossing, the other was entirely selfing. The groups were subjected to a rugged terrain and repeatedly subjected to a mutagen.[128] After 50 generations, the selfing population showed a substantial decline in fitness (= survival), whereas the outcrossing population showed no decline. This is one of a number of studies that show sexuality to have real advantages over non-sexual types of reproduction.[129]
+
+An important activity is artificial selection for domestication. This is when people choose which animals to breed from, based on their traits. Humans have used this for thousands of years to domesticate plants and animals.[130]
+
+More recently, it has become possible to use genetic engineering. New techniques such as 'gene targeting' are now available. The purpose of this is to insert new genes or knock out old genes from the genome of a plant or animal. A number of Nobel Prizes have already been awarded for this work.
+
+However, the real purpose of studying evolution is to explain and help our understanding of biology. After all, it is the first good explanation of how living things came to be the way they are. That is a big achievement. The practical things come mostly from genetics, the science started by Gregor Mendel, and from molecular and cell biology.
+
+In 2010 the journal Nature selected 15 topics as 'Evolution gems'. These were:
+
+The idea that all life evolved had been proposed before Charles Darwin published On the Origin of species. Even today, some people still discuss the concept of evolution and what it means to them, their philosophy, and their religion. Evolution does explain some things about our human nature.[133] People also talk about the social implications of evolution, for example in sociobiology.
+
+Some people have the religious belief that life on Earth was created by a god. In order to fit in the idea of evolution with that belief, people have used ideas like guided evolution or theistic evolution. They say that evolution is real, but is being guided in some way.[17][134][135][136]
+
+There are many different concepts of theistic evolution. Many creationists believe that the creation myth found in their religion goes against the idea of evolution.[137] As Darwin realised, the most controversial part of the evolutionary thought is what it means for human origins.
+
+In some countries, especially in the United States, there is tension between people who accept the idea of evolution and those who do not accept it. The debate is mostly about whether evolution should be taught in schools, and in what way this should be done.[138]
+
+Other fields, like cosmology[139] and earth science[140] also do not match with the original writings of many religious texts. These ideas were once also fiercely opposed. Death for heresy was threatened to those who wrote against the idea that Earth was the center of the universe.
+
+Evolutionary biology is a more recent idea. Certain religious groups oppose the idea of evolution more than other religious groups do. For instance, the Roman Catholic Church now has the following position on evolution: Pope Pius XII said in his encyclical Humani Generis published in the 1950s:
+
+Pope John Paul II updated this position in 1996. He said that Evolution was "more than a hypothesis":
+
+The Anglican Communion also does not oppose the scientific account of evolution.
+
+Many of those who accepted evolution were not much interested in biology. They were interested in using the theory to support their own ideas on society.
+
+Some people have tried to use evolution to support racism. People wanting to justify racism claimed that certain groups, such as black people, were inferior. In nature, some animals do survive better than others, and it does lead to animals better adapted to their circumstances. With humans groups from different parts of the world, all evolution can say is that each group is probably well suited to its original situation. Evolution makes no judgements about better or worse. It does not say that any human group is superior to any other.[143]
+
+This amazing idea of eugenics was rather different. Two things had been noticed as far back as the 18th century. One was the great success of farmers in breeding cattle and crop plants. They did this by selecting which animals or plants would produce the next generation (artificial selection). The other observation was that lower class people had more children than upper-class people. If (and it's a big if) the higher classes were there on merit, then their lack of children was the exact reverse of what should be happening. Faster breeding in the lower classes would lead to the society getting worse.
+
+The idea to improve the human species by selective breeding is called eugenics. The name was proposed by Francis Galton, a bright scientist who meant to do good.[144]  He said that the human stock (gene pool) should be improved by selective breeding policies. This would mean that those who were considered "good stock" would receive a reward if they reproduced. However, other people suggested that those considered "bad stock" would need to undergo compulsory sterilization, prenatal testing and birth control. The German Nazi government (1933–1945) used eugenics as a cover for their extreme racial policies, with dreadful results.[145]
+
+The problem with Galton's idea is how to decide which features to select. There are so many different skills people could have, you could not agree who was "good stock" and who was "bad stock". There was rather more agreement on who should not be breeding. Several countries passed laws for the compulsory sterilisation of unwelcome groups.[146] Most of these laws were passed between 1900 and 1940. After World War II, disgust at what the Nazis had done squashed any more attempts at eugenics.
+
+Some equations can be solved using algorithms that simulate evolution. Evolutionary algorithms work like that.
+
+Another example of using ideas about evolution to support social action is Social Darwinism. Social Darwinism is a term given to the ideas of the 19th century social philosopher Herbert Spencer. Spencer believed the survival of the fittest could and should be applied to commerce and human societies as a whole.
+
+Again, some people used these ideas to claim that racism, and ruthless economic policies were justified.[147] Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.[148][149]
+
+Some people disagree with the idea of evolution. They disagree with it for a number of reasons. Most often these reasons are influenced by or based on their religious beliefs. People who do not agree with evolution usually believe in creationism or intelligent design.
+
+Despite this, evolution is one of the most successful theories in science. People have discovered it to be useful for different kinds of research. None of the other suggestions explain things, such as fossil records, as well. So, for almost all scientists, evolution is not in doubt.[150][151][152][153]
+
+These books are mostly about the evidence for evolution.
+
+These books cover most evolutionary topics.
+

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+Evolution is a biological process that makes living things change over a long time. The explanation of how this process works and how living beings have come to be the way they are is called the theory of evolution.[1]
+
+Earth is very old.[2][3] By studying the layers of rock that make up Earth's crust, scientists can find out about its past. This kind of research is called historical geology.
+
+It is known that living things have changed over time, because their remains can be seen in the rocks. These remains are called 'fossils'. This proves that the animals and plants of today are different from those of long ago.  The older the fossils, the bigger the differences from modern forms.[4]  This has happened because evolution has taken place. That evolution has taken place is a fact, because it is overwhelmingly supported by many lines of evidence.[5][6][7] At the same time, evolutionary questions are still being actively researched by biologists.
+
+Comparison of DNA sequences allows organisms to be grouped by how similar their sequences are. In 2010 an analysis compared sequences to phylogenetic trees, and supported the idea of common descent. There is now "strong quantitative support, by a formal test",[8] for the unity of life.[9]
+
+The theory of evolution is the basis of modern biology. Theodosius Dobzhansky, a well-known evolutionary biologist, has said: "Nothing in biology makes sense except in the light of evolution".[10]
+
+The evidence for evolution is given in a number of books.[11][12][13][14] Some of this evidence is discussed here.
+
+The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:
+
+The most convincing evidence for the occurrence of evolution is the discovery of extinct organisms in older geological strata... The older the strata are...the more different the fossil will be from living representatives... that is to be expected if the fauna and flora of the earlier strata had gradually evolved into their descendants.
+
+The evolution of the horse family (Equidae) is a good example of the way that evolution works. The oldest fossil of a horse is about 52 million years old. It was a small animal with five toes on the front feet and four on the hind feet. At that time, there were more forests in the world than today. This horse lived in woodland, eating leaves, nuts and fruit with its simple teeth. It was only about as big as a fox.[19]
+
+About 30 million years ago the world started to become cooler and drier. Forests shrank; grassland expanded, and horses changed. They ate grass, they grew larger, and they ran faster because they had to escape faster predators. Because grass wears teeth out, horses with longer-lasting teeth had an advantage.
+
+For most of this long period of time, there were a number of horse types (genera). Now, however, only one genus exists: the modern horse, Equus. It has teeth which grow all its life, hooves on single toes, great long legs for running, and the animal is big and strong enough to survive in the open plain.[19] Horses lived in western Canada until 12,000 years ago,[20] but all horses in North America became extinct about 11,000 years ago. The causes of this extinction are not yet clear. Climate change and over-hunting by humans are suggested.
+
+So, scientists can see that changes have happened. They have happened slowly over a long time. How these changes have come about is explained by the theory of evolution.
+
+This is a topic which fascinated both Charles Darwin and Alfred Russel Wallace.[21][22][23] When new species occur, usually by the splitting of older species, this takes place in one place in the world. Once it is established, a new species may spread to some places and not others.
+
+Australasia has been separated from other continents for many millions of years. In the main part of the continent, Australia, 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians are endemic.[24] Its native mammals are mostly marsupials like kangaroos, bandicoots, and quolls.[25] By contrast, marsupials are today totally absent from Africa and form a small portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del monte occur (see the Great American Interchange).
+
+The only living representatives of primitive egg-laying mammals (monotremes) are the echidnas and the platypus. They are only found in Australasia, which includes Tasmania, New Guinea, and Kangaroo Island. These monotremes are totally absent in the rest of the world.[26] On the other hand, Australia is missing many groups of placental mammals that are common on other continents (carnivora, artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and rodents, which arrived later.[27]
+
+The evolutionary story is that placental mammals evolved in Eurasia, and wiped out the marsupials and monotremes wherever they spread. They did not reach Australasia until more recently. That is the simple reason why Australia has most of the world's marsupials and all the world's monotremes.
+
+In about 6,500 sq mi (17,000 km2), the Hawaiian Islands have the most diverse collection of Drosophila flies in the world, living from rainforests to mountain meadows. About 800 Hawaiian fruit fly species are known.
+
+Genetic evidence shows that all the native fruit fly species in Hawaiʻi have descended from a single ancestral species that came to the islands, about 20 million years ago. Later adaptive radiation was caused by a lack of competition and a wide variety of vacant niches. Although it would be possible for a single pregnant female to colonise an island, it is more likely to have been a group from the same species.[28][29][30][31]
+
+The combination of continental drift and evolution can explain what is found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian period on the ancient supercontinent of Gondwana.[32]
+
+Glossopteris fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.
+
+During the Permian, these continents were connected as Gondwana. This is known from magnetic striping in the rocks, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian.[13]p103[33]
+
+When biologists look at living things, they see that animals and plants belong to groups which have something in common. Charles Darwin explained that this followed naturally if "we admit the common parentage of allied forms, together with their modification through variation and natural selection".[21]p402[11]p456
+
+For example, all insects are related. They share a basic body plan, whose development is controlled by master regulatory genes.[34] They have six legs; they have hard parts on the outside of the body (an exoskeleton); they have eyes formed of many separate chambers, and so on. Biologists explain this with evolution. All insects are the descendants of a group of animals who lived a long time ago. They still keep the basic plan (six legs and so on) but the details change. They look different now because they changed in different ways: this is evolution.[35]
+
+It was Darwin who first suggested that all life on Earth had a single origin, and from that beginning "endless forms most beautiful and most wonderful have been, and are being, evolved".[11]p490[21] Evidence from molecular biology in recent years has supported the idea that all life is related by common descent.[36]
+
+Strong evidence for common descent comes from vestigial structures.[21]p397 The useless wings of flightless beetles are sealed under fused wing covers. This can be simply explained by their descent from ancestral beetles which had wings that worked.[14]p49
+
+Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in ancestral species, are called vestigial organs. Those organs are functional in the ancestral species but are now either nonfunctional or re-adapted to a new function. Examples are the pelvic girdles of whales, halteres (hind wings) of flies, wings of flightless birds, and the leaves of some xerophytes (e.g. cactus) and parasitic plants (e.g. dodder).
+
+However, vestigial structures may have their original function replaced with another. For example, the halteres in flies help balance the insect while in flight, and the wings of ostriches are used in mating rituals, and in aggressive display. The ear ossicles in mammals are former bones of the lower jaw.
+
+In 1893, Robert Wiedersheim published a book on human anatomy and its relevance to man's evolutionary history. This book contained a list of 86 human organs that he considered vestigial.[37] This list included examples such as the appendix and the 3rd molar teeth (wisdom teeth).
+
+The strong grip of a baby is another example.[38] It is a vestigial reflex, a remnant of the past when pre-human babies clung to their mothers' hair as the mothers swung through the trees. This is borne out by the babies' feet, which curl up when it is sitting down (primate babies grip with the feet as well). All primates except modern man have thick body hair to which an infant can cling, unlike modern humans. The grasp reflex allows the mother to escape danger by climbing a tree using both hands and feet.[13][39]
+
+Vestigial organs often have some selection against them. The original organs took resources, sometimes huge resources. If they no longer have a function, reducing their size improves fitness. And there is direct evidence of selection. Some cave crustacea reproduce more successfully with smaller eyes than do those with larger eyes. This may be because the nervous tissue dealing with sight now becomes available to handle other sensory input.[40]p310
+
+From the eighteenth century it was known that embryos of different species were much more similar than the adults. In particular, some parts of embryos reflect their evolutionary past. For example, the embryos of land vertebrates develop gill slits like fish embryos. Of course, this is only a temporary stage, which gives rise to many structures in the neck of reptiles, birds and mammals. The proto-gill slits are part of a complicated system of development: that is why they persisted.[34]
+
+Another example are the embryonic teeth of baleen whales.[41] They are later lost. The baleen filter is developed from different tissue, called keratin. Early fossil baleen whales did actually have teeth as well as the baleen.[42]
+
+A good example is the barnacle. It took many centuries before natural historians discovered that barnacles were crustacea. Their adults look so unlike other crustacea, but their larvae are very similar to those of other crustacea.[43]
+
+Charles Darwin lived in a world where animal husbandry and domesticated crops were vitally important. In both cases farmers selected for breeding individuals with special properties, and prevented the breeding of individuals with less desirable characteristics. The eighteenth and early nineteenth century saw a growth in scientific agriculture, and artificial breeding was part of this.
+
+Darwin discussed artificial selection as a model for natural selection in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural selection:
+
+Nikolai Vavilov showed that rye, originally a weed, came to be a crop plant by unintentional selection. Rye is a tougher plant than wheat: it survives in harsher conditions. Having become a crop like the wheat, rye was able to become a crop plant in harsh areas, such as hills and mountains.[45][46]
+
+There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection. There are practical differences. Experimental studies of artificial selection show that "the rate of evolution in selection experiments is at least two orders of magnitude (that is 100 times) greater than any rate seen in nature or the fossil record".[47]p157
+
+Some have thought that artificial selection could not produce new species. It now seems that it can.
+
+New species have been created by domesticated animal husbandry, but the details are not known or not clear. For example, domestic sheep were created by hybridisation, and no longer produce viable offspring with Ovis orientalis, one species from which they are descended.[48] Domestic cattle, on the other hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce fertile offspring with them.[49]
+
+The best-documented new species came from laboratory experiments in the late 1980s. William Rice and G.W. Salt bred fruit flies, Drosophila melanogaster, using a maze with three different choices of habitat such as light/dark and wet/dry. Each generation was put into the maze, and the groups of flies that came out of two of the eight exits were set apart to breed with each other in their respective groups.
+
+After thirty-five generations, the two groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only within the areas they preferred, and so did not mate with flies that preferred the other areas.[50][51]
+
+Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in Drosophila pseudoobscura fruit flies after only eight generations using different food types, starch and maltose.[52]
+
+
+
+Dodd's experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.[53]
+
+Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms.[54] Others call it evolution when new species appear.
+
+Changes can happen quickly in the smaller, simpler organisms. For example, many bacteria that cause disease can no longer be killed with some of the antibiotic medicines. These medicines have only been in use about eighty years, and at first worked extremely well. The bacteria have evolved so that they are no longer affected by antibiotics anymore.[55] The drugs killed off all the bacteria except a few which had some resistance. These few resistant bacteria produced the next generation.
+
+The Colorado beetle is famous for its ability to resist pesticides. Over the last 50 years it has become resistant to 52 chemical compounds used in insecticides, including cyanide.[56] This is natural selection speeded up by the artificial conditions. However, not every population is resistant to every chemical.[57] The populations only become resistant to chemicals used in their area.
+
+Although there were a number of natural historians in the 18th century who had some idea of evolution, the first well-formed ideas came in the 19th century. Three biologists are most important.
+
+Jean-Baptiste de Lamarck (1744–1829), a French biologist, claimed that animals changed according to natural laws. He said that animals could pass on traits they had acquired during their lifetime to their offspring, using inheritance. Today, his theory is known as Lamarckism. Its main purpose is to explain adaptations by natural means.[58] He proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus use and disuse.
+
+Lamarck's idea was that a giraffe's neck grew longer because it tried to reach higher up. This idea failed because it conflicts with heredity (Mendel's work). Mendel made his discoveries about half a century after Lamarck's work.
+
+Charles Darwin (1809–1882) wrote his On the Origin of Species in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place. But Darwin did not understand about genetics and how traits were actually passed on. He could not accurately explain what made children look like their parents.
+
+Nevertheless, Darwin's explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin's idea was that the giraffe's neck became longer because those with longer necks survived better.[21]p177/9 These survivors passed their genes on, and in time the whole species got longer necks.
+
+An Austrian monk called Gregor Mendel (1822–1884) bred plants. In the mid-19th century, he discovered how traits were passed on from one generation to the next.
+
+He used peas for his experiments: some peas have white flowers and others have red ones. Some peas have green seeds and others have yellow seeds. Mendel used artificial pollination to breed the peas. His results are discussed further in Mendelian inheritance. Darwin thought that the inheritance from both parents blended together. Mendel proved that the genes from the two parents stay separate, and may be passed on unchanged to later generations.
+
+Mendel published his results in a journal that was not well-known, and his discoveries were overlooked. Around 1900, his work was rediscovered.[59][60] Genes are bits of information made of DNA which work like a set of instructions. A set of genes are in every living cell. Together, genes organise the way an egg develops into an adult. With mammals, and many other living things, a copy of each gene comes from the father and another copy from the mother. Some living organisms, including some plants, only have one parent, so get all their genes from them. These genes produce the genetic differences which evolution acts on.
+
+Darwin's On the Origin of Species has two themes: the evidence for evolution, and his ideas on how evolution took place. This section deals with the second issue.
+
+The first two chapters of the Origin deal with variation in domesticated plants and animals, and variation in nature.
+
+All living things show variation. Every population which has been studied shows that animal and plants vary as much as humans do.[61][62]p90 This is a great fact of nature, and without it evolution would not occur. Darwin said that, just as man selects what he wants in his farm animals, so in nature the variations allow natural selection to work.[63]
+
+The features of an individual are influenced by two things, heredity and environment. First, development is controlled by genes inherited from the parents. Second, living brings its own influences. Some things are entirely inherited, others partly, and some not inherited at all.
+
+The colour of eyes is entirely inherited; they are a genetic trait. Height or weight is only partly inherited, and the language is not at all inherited. Just to be clear: the fact that humans can speak is inherited, but what language is spoken depends on where a person lives and what they are taught. Another example: a person inherits a brain of somewhat variable capacity. What happens after birth depends on many things such as home environment, education and other experiences. When a person is adult, their brain is what their inheritance and life experience have made it.
+
+Evolution only concerns the traits which can be inherited, wholly or partly. The hereditary traits are passed on from one generation to the next through the genes. A person's genes contain all the traits which they inherit from their parents. The accidents of life are not passed on. Also, of course, each person lives a somewhat different life: that increases the differences.
+
+Organisms in any population vary in reproductive success.[64]p81 From the point of view of evolution, 'reproductive success' means the total number of offspring which live to breed and leave offspring themselves.
+
+Variation can only affect future generations if it is inherited. Because of the work of Gregor Mendel, we know that much variation is inherited. Mendel's 'factors' are now called genes. Research has shown that almost every individual in a sexually reproducing species is genetically unique.[65]p204
+
+Genetic variation is increased by gene mutations. DNA does not always reproduce exactly. Rare changes occur, and these changes can be inherited. Many changes in DNA cause faults; some are neutral or even advantageous. This gives rise to genetic variation, which is the seed-corn of evolution. Sexual reproduction, by the crossing over of chromosomes during meiosis, spreads variation through the population. Other events, like natural selection and drift, reduce variation. So a population in the wild always has variation, but the details are always changing.[62]p90
+
+Evolution mainly works by natural selection. What does this mean? Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence. Those who survive will produce the next generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes a population and causes evolution.
+
+Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:
+
+There are now many cases where natural selection has been proved to occur in wild populations.[5][67][68] Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.[69]
+
+The force of selection can be much stronger than was thought by the early population geneticists. The resistance to pesticides has grown quickly. Resistance to warfarin in Norway rats (Rattus norvegicus) grew rapidly because those that survived made up more and more of the population. Research showed that, in the absence of warfarin, the resistant homozygote was at a 54% disadvantage to the normal wild type homozygote.[62]p182[70] This great disadvantage was quickly overcome by the selection for warfarin resistance.
+
+Mammals normally cannot drink milk as adults, but humans are an exception. Milk is digested by the enzyme lactase, which switches off as mammals stop taking milk from their mothers. The human ability to drink milk during adult life is supported by a lactase mutation which prevents this switch-off. Human populations have a high proportion of this mutation wherever milk is important in the diet. The spread of this 'milk tolerance' is promoted by natural selection, because it helps people survive where milk is available. Genetic studies suggest that the oldest mutations causing lactase persistence only reached high levels in human populations in the last ten thousand years.[71][72] Therefore, lactase persistence is often cited as an example of recent human evolution.[73][74] As lactase persistence is genetic, but animal husbandry a cultural trait, this is gene–culture coevolution.[75]
+
+Adaptation is one of the basic phenomena of biology.[76] Through the process of adaptation, an organism becomes better suited to its habitat.[77]
+
+Adaptation is one of the two main processes that explain the diverse species we see in biology.  The other is speciation (species-splitting or cladogenesis).[78][79] A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.[80][81]
+
+When people speak about adaptation they often mean something which helps an animal or plant survive. One of the most widespread adaptations in animals is the evolution of the eye. Another example is the adaptation of horses' teeth to grinding grass. Camouflage is another adaptation; so is mimicry. The better adapted animals are the most likely to survive, and to reproduce successfully (natural selection).
+
+An internal parasite (such as a fluke) is a good example: it has a very simple bodily structure, but still the organism is highly adapted to its particular environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life cycle, which is often quite complex.[82]
+
+Not all features of an organism are adaptations.[62]p251 Adaptations tend to reflect the past life of a species. If a species has recently changed its life style, a once valuable adaptation may become useless, and eventually become a dwindling vestige.
+
+Adaptations are never perfect. There are always tradeoffs between the various functions and structures in a body. It is the organism as a whole which lives and reproduces, therefore it is the complete set of adaptations which gets passed on to future generations.
+
+In populations, there are forces which add variation to the population (such as mutation), and forces which remove it. Genetic drift is the name given to random changes which remove variation from a population. Genetic drift gets rid of variation at the rate of 1/(2N) where N = population size.[47]p29 It is therefore "a very weak evolutionary force in large populations".[47]p55
+
+Genetic drift explains how random chance can affect evolution in surprisingly big ways, but only when populations are quite small.  Overall, its action is to make the individuals more similar to each other, and hence more vulnerable to disease or to chance events in their environment.
+
+How species form is a major part of evolutionary biology. Darwin interpreted 'evolution' (a word he did not use at first) as being about speciation. That is why he called his famous book On the Origin of Species.
+
+Darwin thought most species arose directly from pre-existing species. This is called anagenesis: new species by older species changing. Now we think most species arise by previous species splitting: cladogenesis.[87][88]
+
+Two groups that start the same can also become very different if they live in different places. When a species gets split into two geographical regions, a process starts. Each adapts to its own situation. After a while, individuals from one group can no longer reproduce with the other group. Two good species have evolved from one.
+
+A German explorer, Moritz Wagner, during his three years in Algeria in the 1830s, studied flightless beetles. Each species is confined to a stretch of the north coast between rivers which descend from the Atlas mountains to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.[89] He wrote later:
+
+This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.[91]
+
+One example of natural speciation is the three-spined stickleback, a sea fish that, after the last ice age, invaded freshwater, and set up colonies in isolated lakes and streams. Over about 10,000 generations, the sticklebacks show great differences, including variations in fins, changes in the number or size of their bony plates, variable jaw structure, and color differences.[92]
+
+The wombats of Australia fall into two main groups, common wombats and hairy-nosed wombats. The two types look very similar, apart from the hairiness of their noses. However, they are adapted to different environments. Common wombats live in forested areas and eat mostly green food with lots of moisture. They often feed in the daytime. Hairy-nosed wombats live on hot dry plains where they eat dry grass with very little water or nutrition it. Their metabolic rate is slow and they sleep most of the day underground.
+
+When two groups that started the same become different enough, then they become two different species. Part of the theory of evolution is that all living things started the same, but then split into different groups over billions of years.[93]
+
+This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s.[94][95] It has been updated regularly ever since.
+The synthesis explains how the ideas of Charles Darwin fit with the discoveries of Gregor Mendel, who found out how we inherit our genes. The modern synthesis brought Darwin's idea up to date. It bridged the gap between different types of biologists: geneticists, naturalists, and palaeontologists.
+
+When the theory of evolution was developed, it was not clear that natural selection and genetics worked together. But Ronald Fisher showed that natural selection would work to change species.[96] Sewall Wright explained genetic drift in 1931.[97]
+
+Co-evolution is where the existence of one species is tightly bound up with the life of one or more other species.
+
+New or 'improved' adaptations which occur in one species are often followed by the appearance and spread of related features in the other species. The life and death of living things is intimately connected, not just with the physical environment, but with the life of other species.
+
+These relationships may continue for millions of years, as it has in the pollination of flowering plants by insects.[102][103] The gut contents, wing structures, and mouthparts of fossilized beetles and flies suggest that they acted as early pollinators. The association between beetles and angiosperms during the Lower Cretaceous period led to parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in Upper Cretaceous flowers signals the beginning of the mutualism between hymenoptera and angiosperms.[104]
+
+Charles Darwin was the first to use this metaphor in biology. The evolutionary tree shows the relationships among various biological groups. It includes data from DNA, RNA and protein analysis. Tree of life work is a product of traditional comparative anatomy, and modern molecular evolution and molecular clock research.
+
+The major figure in this work is Carl Woese, who defined the Archaea, the third domain (or kingdom) of life.[105] Below is a simplified version of present-day understanding.[106]
+
+Macroevolution: the study of changes above the species level, and how they take place. The basic data for such a study are fossils (palaeontology) and the reconstruction of ancient environments. Some subjects whose study falls within the realm of macroevolution:
+
+It is a term of convenience: for most biologists it does not suggest any change in the process of evolution.[5][107][108]p87 For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis.[109] They are in the minority.
+
+Altruism – the willingness of some to sacrifice themselves for others – is widespread in social animals. As explained above, the next generation can only come from those who survive and reproduce. Some biologists have thought that this meant altruism could not evolve by the normal process of selection. Instead a process called "group selection" was proposed.[110][111] Group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group.
+
+For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution.[112][113][114][115]
+
+In simple cases it can be seen at once that traditional selection suffices. For example, if one sibling sacrifices itself for three siblings, the genetic disposition for the act will be increased. This is because siblings share on average 50% of their genetic inheritance, and the sacrificial act has led to greater representation of the genes in the next generation.
+
+Altruism is now generally seen as emerging from standard selection.[116][117][118][119][120] The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.[121][122]
+
+Hamilton's equation describes whether or not a gene for altruistic behaviour will spread in a population. The gene will spread if rxb is greater than c:
+
+where:
+
+At first, sexual reproduction might seem to be at a disadvantage compared with asexual reproduction. In order to be advantageous, sexual reproduction (cross-fertilisation) has to overcome a two-fold disadvantage (takes two to reproduce) plus the difficulty of finding a mate. Why, then, is sex so nearly universal among eukaryotes? This is one of the oldest questions in biology.[123]
+
+The answer has been given since Darwin's time: because the sexual populations adapt better to changing circumstances. A recent laboratory experiment suggests this is indeed the correct explanation.[124][125]
+
+In the main experiment, nematode worms were divided into two groups. One group was entirely outcrossing, the other was entirely selfing. The groups were subjected to a rugged terrain and repeatedly subjected to a mutagen.[128] After 50 generations, the selfing population showed a substantial decline in fitness (= survival), whereas the outcrossing population showed no decline. This is one of a number of studies that show sexuality to have real advantages over non-sexual types of reproduction.[129]
+
+An important activity is artificial selection for domestication. This is when people choose which animals to breed from, based on their traits. Humans have used this for thousands of years to domesticate plants and animals.[130]
+
+More recently, it has become possible to use genetic engineering. New techniques such as 'gene targeting' are now available. The purpose of this is to insert new genes or knock out old genes from the genome of a plant or animal. A number of Nobel Prizes have already been awarded for this work.
+
+However, the real purpose of studying evolution is to explain and help our understanding of biology. After all, it is the first good explanation of how living things came to be the way they are. That is a big achievement. The practical things come mostly from genetics, the science started by Gregor Mendel, and from molecular and cell biology.
+
+In 2010 the journal Nature selected 15 topics as 'Evolution gems'. These were:
+
+The idea that all life evolved had been proposed before Charles Darwin published On the Origin of species. Even today, some people still discuss the concept of evolution and what it means to them, their philosophy, and their religion. Evolution does explain some things about our human nature.[133] People also talk about the social implications of evolution, for example in sociobiology.
+
+Some people have the religious belief that life on Earth was created by a god. In order to fit in the idea of evolution with that belief, people have used ideas like guided evolution or theistic evolution. They say that evolution is real, but is being guided in some way.[17][134][135][136]
+
+There are many different concepts of theistic evolution. Many creationists believe that the creation myth found in their religion goes against the idea of evolution.[137] As Darwin realised, the most controversial part of the evolutionary thought is what it means for human origins.
+
+In some countries, especially in the United States, there is tension between people who accept the idea of evolution and those who do not accept it. The debate is mostly about whether evolution should be taught in schools, and in what way this should be done.[138]
+
+Other fields, like cosmology[139] and earth science[140] also do not match with the original writings of many religious texts. These ideas were once also fiercely opposed. Death for heresy was threatened to those who wrote against the idea that Earth was the center of the universe.
+
+Evolutionary biology is a more recent idea. Certain religious groups oppose the idea of evolution more than other religious groups do. For instance, the Roman Catholic Church now has the following position on evolution: Pope Pius XII said in his encyclical Humani Generis published in the 1950s:
+
+Pope John Paul II updated this position in 1996. He said that Evolution was "more than a hypothesis":
+
+The Anglican Communion also does not oppose the scientific account of evolution.
+
+Many of those who accepted evolution were not much interested in biology. They were interested in using the theory to support their own ideas on society.
+
+Some people have tried to use evolution to support racism. People wanting to justify racism claimed that certain groups, such as black people, were inferior. In nature, some animals do survive better than others, and it does lead to animals better adapted to their circumstances. With humans groups from different parts of the world, all evolution can say is that each group is probably well suited to its original situation. Evolution makes no judgements about better or worse. It does not say that any human group is superior to any other.[143]
+
+This amazing idea of eugenics was rather different. Two things had been noticed as far back as the 18th century. One was the great success of farmers in breeding cattle and crop plants. They did this by selecting which animals or plants would produce the next generation (artificial selection). The other observation was that lower class people had more children than upper-class people. If (and it's a big if) the higher classes were there on merit, then their lack of children was the exact reverse of what should be happening. Faster breeding in the lower classes would lead to the society getting worse.
+
+The idea to improve the human species by selective breeding is called eugenics. The name was proposed by Francis Galton, a bright scientist who meant to do good.[144]  He said that the human stock (gene pool) should be improved by selective breeding policies. This would mean that those who were considered "good stock" would receive a reward if they reproduced. However, other people suggested that those considered "bad stock" would need to undergo compulsory sterilization, prenatal testing and birth control. The German Nazi government (1933–1945) used eugenics as a cover for their extreme racial policies, with dreadful results.[145]
+
+The problem with Galton's idea is how to decide which features to select. There are so many different skills people could have, you could not agree who was "good stock" and who was "bad stock". There was rather more agreement on who should not be breeding. Several countries passed laws for the compulsory sterilisation of unwelcome groups.[146] Most of these laws were passed between 1900 and 1940. After World War II, disgust at what the Nazis had done squashed any more attempts at eugenics.
+
+Some equations can be solved using algorithms that simulate evolution. Evolutionary algorithms work like that.
+
+Another example of using ideas about evolution to support social action is Social Darwinism. Social Darwinism is a term given to the ideas of the 19th century social philosopher Herbert Spencer. Spencer believed the survival of the fittest could and should be applied to commerce and human societies as a whole.
+
+Again, some people used these ideas to claim that racism, and ruthless economic policies were justified.[147] Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.[148][149]
+
+Some people disagree with the idea of evolution. They disagree with it for a number of reasons. Most often these reasons are influenced by or based on their religious beliefs. People who do not agree with evolution usually believe in creationism or intelligent design.
+
+Despite this, evolution is one of the most successful theories in science. People have discovered it to be useful for different kinds of research. None of the other suggestions explain things, such as fossil records, as well. So, for almost all scientists, evolution is not in doubt.[150][151][152][153]
+
+These books are mostly about the evidence for evolution.
+
+These books cover most evolutionary topics.
+

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+Evolution is a biological process that makes living things change over a long time. The explanation of how this process works and how living beings have come to be the way they are is called the theory of evolution.[1]
+
+Earth is very old.[2][3] By studying the layers of rock that make up Earth's crust, scientists can find out about its past. This kind of research is called historical geology.
+
+It is known that living things have changed over time, because their remains can be seen in the rocks. These remains are called 'fossils'. This proves that the animals and plants of today are different from those of long ago.  The older the fossils, the bigger the differences from modern forms.[4]  This has happened because evolution has taken place. That evolution has taken place is a fact, because it is overwhelmingly supported by many lines of evidence.[5][6][7] At the same time, evolutionary questions are still being actively researched by biologists.
+
+Comparison of DNA sequences allows organisms to be grouped by how similar their sequences are. In 2010 an analysis compared sequences to phylogenetic trees, and supported the idea of common descent. There is now "strong quantitative support, by a formal test",[8] for the unity of life.[9]
+
+The theory of evolution is the basis of modern biology. Theodosius Dobzhansky, a well-known evolutionary biologist, has said: "Nothing in biology makes sense except in the light of evolution".[10]
+
+The evidence for evolution is given in a number of books.[11][12][13][14] Some of this evidence is discussed here.
+
+The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:
+
+The most convincing evidence for the occurrence of evolution is the discovery of extinct organisms in older geological strata... The older the strata are...the more different the fossil will be from living representatives... that is to be expected if the fauna and flora of the earlier strata had gradually evolved into their descendants.
+
+The evolution of the horse family (Equidae) is a good example of the way that evolution works. The oldest fossil of a horse is about 52 million years old. It was a small animal with five toes on the front feet and four on the hind feet. At that time, there were more forests in the world than today. This horse lived in woodland, eating leaves, nuts and fruit with its simple teeth. It was only about as big as a fox.[19]
+
+About 30 million years ago the world started to become cooler and drier. Forests shrank; grassland expanded, and horses changed. They ate grass, they grew larger, and they ran faster because they had to escape faster predators. Because grass wears teeth out, horses with longer-lasting teeth had an advantage.
+
+For most of this long period of time, there were a number of horse types (genera). Now, however, only one genus exists: the modern horse, Equus. It has teeth which grow all its life, hooves on single toes, great long legs for running, and the animal is big and strong enough to survive in the open plain.[19] Horses lived in western Canada until 12,000 years ago,[20] but all horses in North America became extinct about 11,000 years ago. The causes of this extinction are not yet clear. Climate change and over-hunting by humans are suggested.
+
+So, scientists can see that changes have happened. They have happened slowly over a long time. How these changes have come about is explained by the theory of evolution.
+
+This is a topic which fascinated both Charles Darwin and Alfred Russel Wallace.[21][22][23] When new species occur, usually by the splitting of older species, this takes place in one place in the world. Once it is established, a new species may spread to some places and not others.
+
+Australasia has been separated from other continents for many millions of years. In the main part of the continent, Australia, 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians are endemic.[24] Its native mammals are mostly marsupials like kangaroos, bandicoots, and quolls.[25] By contrast, marsupials are today totally absent from Africa and form a small portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del monte occur (see the Great American Interchange).
+
+The only living representatives of primitive egg-laying mammals (monotremes) are the echidnas and the platypus. They are only found in Australasia, which includes Tasmania, New Guinea, and Kangaroo Island. These monotremes are totally absent in the rest of the world.[26] On the other hand, Australia is missing many groups of placental mammals that are common on other continents (carnivora, artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and rodents, which arrived later.[27]
+
+The evolutionary story is that placental mammals evolved in Eurasia, and wiped out the marsupials and monotremes wherever they spread. They did not reach Australasia until more recently. That is the simple reason why Australia has most of the world's marsupials and all the world's monotremes.
+
+In about 6,500 sq mi (17,000 km2), the Hawaiian Islands have the most diverse collection of Drosophila flies in the world, living from rainforests to mountain meadows. About 800 Hawaiian fruit fly species are known.
+
+Genetic evidence shows that all the native fruit fly species in Hawaiʻi have descended from a single ancestral species that came to the islands, about 20 million years ago. Later adaptive radiation was caused by a lack of competition and a wide variety of vacant niches. Although it would be possible for a single pregnant female to colonise an island, it is more likely to have been a group from the same species.[28][29][30][31]
+
+The combination of continental drift and evolution can explain what is found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian period on the ancient supercontinent of Gondwana.[32]
+
+Glossopteris fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.
+
+During the Permian, these continents were connected as Gondwana. This is known from magnetic striping in the rocks, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian.[13]p103[33]
+
+When biologists look at living things, they see that animals and plants belong to groups which have something in common. Charles Darwin explained that this followed naturally if "we admit the common parentage of allied forms, together with their modification through variation and natural selection".[21]p402[11]p456
+
+For example, all insects are related. They share a basic body plan, whose development is controlled by master regulatory genes.[34] They have six legs; they have hard parts on the outside of the body (an exoskeleton); they have eyes formed of many separate chambers, and so on. Biologists explain this with evolution. All insects are the descendants of a group of animals who lived a long time ago. They still keep the basic plan (six legs and so on) but the details change. They look different now because they changed in different ways: this is evolution.[35]
+
+It was Darwin who first suggested that all life on Earth had a single origin, and from that beginning "endless forms most beautiful and most wonderful have been, and are being, evolved".[11]p490[21] Evidence from molecular biology in recent years has supported the idea that all life is related by common descent.[36]
+
+Strong evidence for common descent comes from vestigial structures.[21]p397 The useless wings of flightless beetles are sealed under fused wing covers. This can be simply explained by their descent from ancestral beetles which had wings that worked.[14]p49
+
+Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in ancestral species, are called vestigial organs. Those organs are functional in the ancestral species but are now either nonfunctional or re-adapted to a new function. Examples are the pelvic girdles of whales, halteres (hind wings) of flies, wings of flightless birds, and the leaves of some xerophytes (e.g. cactus) and parasitic plants (e.g. dodder).
+
+However, vestigial structures may have their original function replaced with another. For example, the halteres in flies help balance the insect while in flight, and the wings of ostriches are used in mating rituals, and in aggressive display. The ear ossicles in mammals are former bones of the lower jaw.
+
+In 1893, Robert Wiedersheim published a book on human anatomy and its relevance to man's evolutionary history. This book contained a list of 86 human organs that he considered vestigial.[37] This list included examples such as the appendix and the 3rd molar teeth (wisdom teeth).
+
+The strong grip of a baby is another example.[38] It is a vestigial reflex, a remnant of the past when pre-human babies clung to their mothers' hair as the mothers swung through the trees. This is borne out by the babies' feet, which curl up when it is sitting down (primate babies grip with the feet as well). All primates except modern man have thick body hair to which an infant can cling, unlike modern humans. The grasp reflex allows the mother to escape danger by climbing a tree using both hands and feet.[13][39]
+
+Vestigial organs often have some selection against them. The original organs took resources, sometimes huge resources. If they no longer have a function, reducing their size improves fitness. And there is direct evidence of selection. Some cave crustacea reproduce more successfully with smaller eyes than do those with larger eyes. This may be because the nervous tissue dealing with sight now becomes available to handle other sensory input.[40]p310
+
+From the eighteenth century it was known that embryos of different species were much more similar than the adults. In particular, some parts of embryos reflect their evolutionary past. For example, the embryos of land vertebrates develop gill slits like fish embryos. Of course, this is only a temporary stage, which gives rise to many structures in the neck of reptiles, birds and mammals. The proto-gill slits are part of a complicated system of development: that is why they persisted.[34]
+
+Another example are the embryonic teeth of baleen whales.[41] They are later lost. The baleen filter is developed from different tissue, called keratin. Early fossil baleen whales did actually have teeth as well as the baleen.[42]
+
+A good example is the barnacle. It took many centuries before natural historians discovered that barnacles were crustacea. Their adults look so unlike other crustacea, but their larvae are very similar to those of other crustacea.[43]
+
+Charles Darwin lived in a world where animal husbandry and domesticated crops were vitally important. In both cases farmers selected for breeding individuals with special properties, and prevented the breeding of individuals with less desirable characteristics. The eighteenth and early nineteenth century saw a growth in scientific agriculture, and artificial breeding was part of this.
+
+Darwin discussed artificial selection as a model for natural selection in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural selection:
+
+Nikolai Vavilov showed that rye, originally a weed, came to be a crop plant by unintentional selection. Rye is a tougher plant than wheat: it survives in harsher conditions. Having become a crop like the wheat, rye was able to become a crop plant in harsh areas, such as hills and mountains.[45][46]
+
+There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection. There are practical differences. Experimental studies of artificial selection show that "the rate of evolution in selection experiments is at least two orders of magnitude (that is 100 times) greater than any rate seen in nature or the fossil record".[47]p157
+
+Some have thought that artificial selection could not produce new species. It now seems that it can.
+
+New species have been created by domesticated animal husbandry, but the details are not known or not clear. For example, domestic sheep were created by hybridisation, and no longer produce viable offspring with Ovis orientalis, one species from which they are descended.[48] Domestic cattle, on the other hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce fertile offspring with them.[49]
+
+The best-documented new species came from laboratory experiments in the late 1980s. William Rice and G.W. Salt bred fruit flies, Drosophila melanogaster, using a maze with three different choices of habitat such as light/dark and wet/dry. Each generation was put into the maze, and the groups of flies that came out of two of the eight exits were set apart to breed with each other in their respective groups.
+
+After thirty-five generations, the two groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only within the areas they preferred, and so did not mate with flies that preferred the other areas.[50][51]
+
+Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in Drosophila pseudoobscura fruit flies after only eight generations using different food types, starch and maltose.[52]
+
+
+
+Dodd's experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.[53]
+
+Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms.[54] Others call it evolution when new species appear.
+
+Changes can happen quickly in the smaller, simpler organisms. For example, many bacteria that cause disease can no longer be killed with some of the antibiotic medicines. These medicines have only been in use about eighty years, and at first worked extremely well. The bacteria have evolved so that they are no longer affected by antibiotics anymore.[55] The drugs killed off all the bacteria except a few which had some resistance. These few resistant bacteria produced the next generation.
+
+The Colorado beetle is famous for its ability to resist pesticides. Over the last 50 years it has become resistant to 52 chemical compounds used in insecticides, including cyanide.[56] This is natural selection speeded up by the artificial conditions. However, not every population is resistant to every chemical.[57] The populations only become resistant to chemicals used in their area.
+
+Although there were a number of natural historians in the 18th century who had some idea of evolution, the first well-formed ideas came in the 19th century. Three biologists are most important.
+
+Jean-Baptiste de Lamarck (1744–1829), a French biologist, claimed that animals changed according to natural laws. He said that animals could pass on traits they had acquired during their lifetime to their offspring, using inheritance. Today, his theory is known as Lamarckism. Its main purpose is to explain adaptations by natural means.[58] He proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus use and disuse.
+
+Lamarck's idea was that a giraffe's neck grew longer because it tried to reach higher up. This idea failed because it conflicts with heredity (Mendel's work). Mendel made his discoveries about half a century after Lamarck's work.
+
+Charles Darwin (1809–1882) wrote his On the Origin of Species in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place. But Darwin did not understand about genetics and how traits were actually passed on. He could not accurately explain what made children look like their parents.
+
+Nevertheless, Darwin's explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin's idea was that the giraffe's neck became longer because those with longer necks survived better.[21]p177/9 These survivors passed their genes on, and in time the whole species got longer necks.
+
+An Austrian monk called Gregor Mendel (1822–1884) bred plants. In the mid-19th century, he discovered how traits were passed on from one generation to the next.
+
+He used peas for his experiments: some peas have white flowers and others have red ones. Some peas have green seeds and others have yellow seeds. Mendel used artificial pollination to breed the peas. His results are discussed further in Mendelian inheritance. Darwin thought that the inheritance from both parents blended together. Mendel proved that the genes from the two parents stay separate, and may be passed on unchanged to later generations.
+
+Mendel published his results in a journal that was not well-known, and his discoveries were overlooked. Around 1900, his work was rediscovered.[59][60] Genes are bits of information made of DNA which work like a set of instructions. A set of genes are in every living cell. Together, genes organise the way an egg develops into an adult. With mammals, and many other living things, a copy of each gene comes from the father and another copy from the mother. Some living organisms, including some plants, only have one parent, so get all their genes from them. These genes produce the genetic differences which evolution acts on.
+
+Darwin's On the Origin of Species has two themes: the evidence for evolution, and his ideas on how evolution took place. This section deals with the second issue.
+
+The first two chapters of the Origin deal with variation in domesticated plants and animals, and variation in nature.
+
+All living things show variation. Every population which has been studied shows that animal and plants vary as much as humans do.[61][62]p90 This is a great fact of nature, and without it evolution would not occur. Darwin said that, just as man selects what he wants in his farm animals, so in nature the variations allow natural selection to work.[63]
+
+The features of an individual are influenced by two things, heredity and environment. First, development is controlled by genes inherited from the parents. Second, living brings its own influences. Some things are entirely inherited, others partly, and some not inherited at all.
+
+The colour of eyes is entirely inherited; they are a genetic trait. Height or weight is only partly inherited, and the language is not at all inherited. Just to be clear: the fact that humans can speak is inherited, but what language is spoken depends on where a person lives and what they are taught. Another example: a person inherits a brain of somewhat variable capacity. What happens after birth depends on many things such as home environment, education and other experiences. When a person is adult, their brain is what their inheritance and life experience have made it.
+
+Evolution only concerns the traits which can be inherited, wholly or partly. The hereditary traits are passed on from one generation to the next through the genes. A person's genes contain all the traits which they inherit from their parents. The accidents of life are not passed on. Also, of course, each person lives a somewhat different life: that increases the differences.
+
+Organisms in any population vary in reproductive success.[64]p81 From the point of view of evolution, 'reproductive success' means the total number of offspring which live to breed and leave offspring themselves.
+
+Variation can only affect future generations if it is inherited. Because of the work of Gregor Mendel, we know that much variation is inherited. Mendel's 'factors' are now called genes. Research has shown that almost every individual in a sexually reproducing species is genetically unique.[65]p204
+
+Genetic variation is increased by gene mutations. DNA does not always reproduce exactly. Rare changes occur, and these changes can be inherited. Many changes in DNA cause faults; some are neutral or even advantageous. This gives rise to genetic variation, which is the seed-corn of evolution. Sexual reproduction, by the crossing over of chromosomes during meiosis, spreads variation through the population. Other events, like natural selection and drift, reduce variation. So a population in the wild always has variation, but the details are always changing.[62]p90
+
+Evolution mainly works by natural selection. What does this mean? Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence. Those who survive will produce the next generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes a population and causes evolution.
+
+Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:
+
+There are now many cases where natural selection has been proved to occur in wild populations.[5][67][68] Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.[69]
+
+The force of selection can be much stronger than was thought by the early population geneticists. The resistance to pesticides has grown quickly. Resistance to warfarin in Norway rats (Rattus norvegicus) grew rapidly because those that survived made up more and more of the population. Research showed that, in the absence of warfarin, the resistant homozygote was at a 54% disadvantage to the normal wild type homozygote.[62]p182[70] This great disadvantage was quickly overcome by the selection for warfarin resistance.
+
+Mammals normally cannot drink milk as adults, but humans are an exception. Milk is digested by the enzyme lactase, which switches off as mammals stop taking milk from their mothers. The human ability to drink milk during adult life is supported by a lactase mutation which prevents this switch-off. Human populations have a high proportion of this mutation wherever milk is important in the diet. The spread of this 'milk tolerance' is promoted by natural selection, because it helps people survive where milk is available. Genetic studies suggest that the oldest mutations causing lactase persistence only reached high levels in human populations in the last ten thousand years.[71][72] Therefore, lactase persistence is often cited as an example of recent human evolution.[73][74] As lactase persistence is genetic, but animal husbandry a cultural trait, this is gene–culture coevolution.[75]
+
+Adaptation is one of the basic phenomena of biology.[76] Through the process of adaptation, an organism becomes better suited to its habitat.[77]
+
+Adaptation is one of the two main processes that explain the diverse species we see in biology.  The other is speciation (species-splitting or cladogenesis).[78][79] A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.[80][81]
+
+When people speak about adaptation they often mean something which helps an animal or plant survive. One of the most widespread adaptations in animals is the evolution of the eye. Another example is the adaptation of horses' teeth to grinding grass. Camouflage is another adaptation; so is mimicry. The better adapted animals are the most likely to survive, and to reproduce successfully (natural selection).
+
+An internal parasite (such as a fluke) is a good example: it has a very simple bodily structure, but still the organism is highly adapted to its particular environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life cycle, which is often quite complex.[82]
+
+Not all features of an organism are adaptations.[62]p251 Adaptations tend to reflect the past life of a species. If a species has recently changed its life style, a once valuable adaptation may become useless, and eventually become a dwindling vestige.
+
+Adaptations are never perfect. There are always tradeoffs between the various functions and structures in a body. It is the organism as a whole which lives and reproduces, therefore it is the complete set of adaptations which gets passed on to future generations.
+
+In populations, there are forces which add variation to the population (such as mutation), and forces which remove it. Genetic drift is the name given to random changes which remove variation from a population. Genetic drift gets rid of variation at the rate of 1/(2N) where N = population size.[47]p29 It is therefore "a very weak evolutionary force in large populations".[47]p55
+
+Genetic drift explains how random chance can affect evolution in surprisingly big ways, but only when populations are quite small.  Overall, its action is to make the individuals more similar to each other, and hence more vulnerable to disease or to chance events in their environment.
+
+How species form is a major part of evolutionary biology. Darwin interpreted 'evolution' (a word he did not use at first) as being about speciation. That is why he called his famous book On the Origin of Species.
+
+Darwin thought most species arose directly from pre-existing species. This is called anagenesis: new species by older species changing. Now we think most species arise by previous species splitting: cladogenesis.[87][88]
+
+Two groups that start the same can also become very different if they live in different places. When a species gets split into two geographical regions, a process starts. Each adapts to its own situation. After a while, individuals from one group can no longer reproduce with the other group. Two good species have evolved from one.
+
+A German explorer, Moritz Wagner, during his three years in Algeria in the 1830s, studied flightless beetles. Each species is confined to a stretch of the north coast between rivers which descend from the Atlas mountains to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.[89] He wrote later:
+
+This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.[91]
+
+One example of natural speciation is the three-spined stickleback, a sea fish that, after the last ice age, invaded freshwater, and set up colonies in isolated lakes and streams. Over about 10,000 generations, the sticklebacks show great differences, including variations in fins, changes in the number or size of their bony plates, variable jaw structure, and color differences.[92]
+
+The wombats of Australia fall into two main groups, common wombats and hairy-nosed wombats. The two types look very similar, apart from the hairiness of their noses. However, they are adapted to different environments. Common wombats live in forested areas and eat mostly green food with lots of moisture. They often feed in the daytime. Hairy-nosed wombats live on hot dry plains where they eat dry grass with very little water or nutrition it. Their metabolic rate is slow and they sleep most of the day underground.
+
+When two groups that started the same become different enough, then they become two different species. Part of the theory of evolution is that all living things started the same, but then split into different groups over billions of years.[93]
+
+This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s.[94][95] It has been updated regularly ever since.
+The synthesis explains how the ideas of Charles Darwin fit with the discoveries of Gregor Mendel, who found out how we inherit our genes. The modern synthesis brought Darwin's idea up to date. It bridged the gap between different types of biologists: geneticists, naturalists, and palaeontologists.
+
+When the theory of evolution was developed, it was not clear that natural selection and genetics worked together. But Ronald Fisher showed that natural selection would work to change species.[96] Sewall Wright explained genetic drift in 1931.[97]
+
+Co-evolution is where the existence of one species is tightly bound up with the life of one or more other species.
+
+New or 'improved' adaptations which occur in one species are often followed by the appearance and spread of related features in the other species. The life and death of living things is intimately connected, not just with the physical environment, but with the life of other species.
+
+These relationships may continue for millions of years, as it has in the pollination of flowering plants by insects.[102][103] The gut contents, wing structures, and mouthparts of fossilized beetles and flies suggest that they acted as early pollinators. The association between beetles and angiosperms during the Lower Cretaceous period led to parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in Upper Cretaceous flowers signals the beginning of the mutualism between hymenoptera and angiosperms.[104]
+
+Charles Darwin was the first to use this metaphor in biology. The evolutionary tree shows the relationships among various biological groups. It includes data from DNA, RNA and protein analysis. Tree of life work is a product of traditional comparative anatomy, and modern molecular evolution and molecular clock research.
+
+The major figure in this work is Carl Woese, who defined the Archaea, the third domain (or kingdom) of life.[105] Below is a simplified version of present-day understanding.[106]
+
+Macroevolution: the study of changes above the species level, and how they take place. The basic data for such a study are fossils (palaeontology) and the reconstruction of ancient environments. Some subjects whose study falls within the realm of macroevolution:
+
+It is a term of convenience: for most biologists it does not suggest any change in the process of evolution.[5][107][108]p87 For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis.[109] They are in the minority.
+
+Altruism – the willingness of some to sacrifice themselves for others – is widespread in social animals. As explained above, the next generation can only come from those who survive and reproduce. Some biologists have thought that this meant altruism could not evolve by the normal process of selection. Instead a process called "group selection" was proposed.[110][111] Group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group.
+
+For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution.[112][113][114][115]
+
+In simple cases it can be seen at once that traditional selection suffices. For example, if one sibling sacrifices itself for three siblings, the genetic disposition for the act will be increased. This is because siblings share on average 50% of their genetic inheritance, and the sacrificial act has led to greater representation of the genes in the next generation.
+
+Altruism is now generally seen as emerging from standard selection.[116][117][118][119][120] The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.[121][122]
+
+Hamilton's equation describes whether or not a gene for altruistic behaviour will spread in a population. The gene will spread if rxb is greater than c:
+
+where:
+
+At first, sexual reproduction might seem to be at a disadvantage compared with asexual reproduction. In order to be advantageous, sexual reproduction (cross-fertilisation) has to overcome a two-fold disadvantage (takes two to reproduce) plus the difficulty of finding a mate. Why, then, is sex so nearly universal among eukaryotes? This is one of the oldest questions in biology.[123]
+
+The answer has been given since Darwin's time: because the sexual populations adapt better to changing circumstances. A recent laboratory experiment suggests this is indeed the correct explanation.[124][125]
+
+In the main experiment, nematode worms were divided into two groups. One group was entirely outcrossing, the other was entirely selfing. The groups were subjected to a rugged terrain and repeatedly subjected to a mutagen.[128] After 50 generations, the selfing population showed a substantial decline in fitness (= survival), whereas the outcrossing population showed no decline. This is one of a number of studies that show sexuality to have real advantages over non-sexual types of reproduction.[129]
+
+An important activity is artificial selection for domestication. This is when people choose which animals to breed from, based on their traits. Humans have used this for thousands of years to domesticate plants and animals.[130]
+
+More recently, it has become possible to use genetic engineering. New techniques such as 'gene targeting' are now available. The purpose of this is to insert new genes or knock out old genes from the genome of a plant or animal. A number of Nobel Prizes have already been awarded for this work.
+
+However, the real purpose of studying evolution is to explain and help our understanding of biology. After all, it is the first good explanation of how living things came to be the way they are. That is a big achievement. The practical things come mostly from genetics, the science started by Gregor Mendel, and from molecular and cell biology.
+
+In 2010 the journal Nature selected 15 topics as 'Evolution gems'. These were:
+
+The idea that all life evolved had been proposed before Charles Darwin published On the Origin of species. Even today, some people still discuss the concept of evolution and what it means to them, their philosophy, and their religion. Evolution does explain some things about our human nature.[133] People also talk about the social implications of evolution, for example in sociobiology.
+
+Some people have the religious belief that life on Earth was created by a god. In order to fit in the idea of evolution with that belief, people have used ideas like guided evolution or theistic evolution. They say that evolution is real, but is being guided in some way.[17][134][135][136]
+
+There are many different concepts of theistic evolution. Many creationists believe that the creation myth found in their religion goes against the idea of evolution.[137] As Darwin realised, the most controversial part of the evolutionary thought is what it means for human origins.
+
+In some countries, especially in the United States, there is tension between people who accept the idea of evolution and those who do not accept it. The debate is mostly about whether evolution should be taught in schools, and in what way this should be done.[138]
+
+Other fields, like cosmology[139] and earth science[140] also do not match with the original writings of many religious texts. These ideas were once also fiercely opposed. Death for heresy was threatened to those who wrote against the idea that Earth was the center of the universe.
+
+Evolutionary biology is a more recent idea. Certain religious groups oppose the idea of evolution more than other religious groups do. For instance, the Roman Catholic Church now has the following position on evolution: Pope Pius XII said in his encyclical Humani Generis published in the 1950s:
+
+Pope John Paul II updated this position in 1996. He said that Evolution was "more than a hypothesis":
+
+The Anglican Communion also does not oppose the scientific account of evolution.
+
+Many of those who accepted evolution were not much interested in biology. They were interested in using the theory to support their own ideas on society.
+
+Some people have tried to use evolution to support racism. People wanting to justify racism claimed that certain groups, such as black people, were inferior. In nature, some animals do survive better than others, and it does lead to animals better adapted to their circumstances. With humans groups from different parts of the world, all evolution can say is that each group is probably well suited to its original situation. Evolution makes no judgements about better or worse. It does not say that any human group is superior to any other.[143]
+
+This amazing idea of eugenics was rather different. Two things had been noticed as far back as the 18th century. One was the great success of farmers in breeding cattle and crop plants. They did this by selecting which animals or plants would produce the next generation (artificial selection). The other observation was that lower class people had more children than upper-class people. If (and it's a big if) the higher classes were there on merit, then their lack of children was the exact reverse of what should be happening. Faster breeding in the lower classes would lead to the society getting worse.
+
+The idea to improve the human species by selective breeding is called eugenics. The name was proposed by Francis Galton, a bright scientist who meant to do good.[144]  He said that the human stock (gene pool) should be improved by selective breeding policies. This would mean that those who were considered "good stock" would receive a reward if they reproduced. However, other people suggested that those considered "bad stock" would need to undergo compulsory sterilization, prenatal testing and birth control. The German Nazi government (1933–1945) used eugenics as a cover for their extreme racial policies, with dreadful results.[145]
+
+The problem with Galton's idea is how to decide which features to select. There are so many different skills people could have, you could not agree who was "good stock" and who was "bad stock". There was rather more agreement on who should not be breeding. Several countries passed laws for the compulsory sterilisation of unwelcome groups.[146] Most of these laws were passed between 1900 and 1940. After World War II, disgust at what the Nazis had done squashed any more attempts at eugenics.
+
+Some equations can be solved using algorithms that simulate evolution. Evolutionary algorithms work like that.
+
+Another example of using ideas about evolution to support social action is Social Darwinism. Social Darwinism is a term given to the ideas of the 19th century social philosopher Herbert Spencer. Spencer believed the survival of the fittest could and should be applied to commerce and human societies as a whole.
+
+Again, some people used these ideas to claim that racism, and ruthless economic policies were justified.[147] Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.[148][149]
+
+Some people disagree with the idea of evolution. They disagree with it for a number of reasons. Most often these reasons are influenced by or based on their religious beliefs. People who do not agree with evolution usually believe in creationism or intelligent design.
+
+Despite this, evolution is one of the most successful theories in science. People have discovered it to be useful for different kinds of research. None of the other suggestions explain things, such as fossil records, as well. So, for almost all scientists, evolution is not in doubt.[150][151][152][153]
+
+These books are mostly about the evidence for evolution.
+
+These books cover most evolutionary topics.
+

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+Existence usually means "the state or fact of being", but there are many different views on the meaning of the word existence, and what it means to exist.
+
+In English, existence is usually connected with the verb "to be".
+
+The first sentence can be understood to say "I exist as a human", and simply speaking, this is probably true. The fourth sentence is more difficult to understand, because it can be understood to say "seven exists as the sum of four and three", but "seven" is not something that we can see or touch like a pen or a human.
+
+The question "What is existence?" is a very important one for philosophers, and many people think Aristotle is the first human being to have thought seriously about the question.

ensimple/1924.html.txt

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+Existence usually means "the state or fact of being", but there are many different views on the meaning of the word existence, and what it means to exist.
+
+In English, existence is usually connected with the verb "to be".
+
+The first sentence can be understood to say "I exist as a human", and simply speaking, this is probably true. The fourth sentence is more difficult to understand, because it can be understood to say "seven exists as the sum of four and three", but "seven" is not something that we can see or touch like a pen or a human.
+
+The question "What is existence?" is a very important one for philosophers, and many people think Aristotle is the first human being to have thought seriously about the question.

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+An extrasolar planet (or exoplanet) is a natural planet in a planetary system outside our own solar system.
+
+In 2013, estimates of the number of terrestrial planets in the Milky Way ranged from at least 17 billion[1] to at least 144 billion.[2] The smaller estimate studied planet candidates gathered by the Kepler space observatory.[3] Among them are 461 Earth-size planets, at least four of which are in the "habitable zone" where liquid water can exist. One of the four, dubbed Kepler-69c, is a mere 1.5 times the size of the Earth and around a star like our own Sun – about as near as the current data allow to finding an "Earth 2.0".[4]
+
+Earlier work suggested that there are at least 100 billion planets of all types in our galaxy, an average of at least one per star. There are also planets that orbit brown dwarfs, and free-floating planets that orbit the galaxy directly just as the stars do. It is unclear whether either type should be called a "planet".[5][6][7]
+
+In the sixteenth century, the Italian philosopher Giordano Bruno, an early supporter of the Copernican theory that the Earth and other planets orbit the Sun, put forward the view that the fixed stars are similar to the Sun and are likewise accompanied by planets. Bruno was burnt at the stake by the Holy Inquisition.[8]
+
+In the eighteenth century, the same possibility was mentioned by Isaac Newton in his Principia. Making a comparison to the Sun's planets, he wrote "And if the fixed stars are the centres of similar systems, they will all be constructed according to a similar design and subject to the dominion of One".[9]
+
+The first published and confirmed discovery was made in 1988.[10] It was finally confirmed in 1992.
+
+In 1992, radio astronomers announced the discovery of planets around another pulsar.[11] These pulsar planets are believed to have formed from the unusual remnants of the supernova that produced the pulsar, in a second round of planet formation. Otherwise they may be the remaining rocky cores of gas giants that survived the supernova and then decayed into their current orbits.
+
+On October 6, 1995, Michel Mayor and Didier Queloz of the University of Geneva announced the first definitive detection of an exoplanet orbiting an ordinary main-sequence star (51 Pegasi).[12] This discovery, made at the Observatoire de Haute-Provence, started the modern era of exoplanetary discovery. Technological advances, most notably in high-resolution spectroscopy, led to the quick detection of many new exoplanets. These advances allowed astronomers to detect exoplanets indirectly by measuring their gravitational influence on the motion of their parent stars. Additional extrasolar planets were eventually detected by watching occultations when a star becomes dimmer as an orbiting planet passed in front of it.
+
+In May 2016 NASA announced the discovery of 1,284 exoplanets which brought the total number of exoplanets to over 3,000.[13]
+
+Extrasolar planets can have many different forms.
+
+
+
+The nearest star with planets is Alpha Centauri. It is 4.3 light years away. Using standard rockets, it would take tens of thousands of years to get there.[14]  The nearest star similar to our Sun is Tau Ceti. It has five planets, one of which in the habitable zone, where liquid water may exist.[15][16]
+
+Some extrasolar planets might be Earth-like. This means that they have conditions very similar to that of the Earth. Planets are ranked by a formula called the Earth similarity index or ESI for short. The ESI goes from one (most Earth-like) to zero (least Earth-like). For a planet to be habitable it should have an ESI of at least 0.8.[17] For comparison, the four solar terrestrial planets are included in this list.

ensimple/1926.html.txt

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+Mining is the process of digging things out of the ground.  Any material that cannot be grown must be mined.  Mining things from the ground is called extraction.  Mining can include extraction of metals and minerals, like coal, diamond, gold, silver, platinum, copper, tin and iron.  Mining can also include other things like oil and natural gas.
+
+Some mining is done by scraping away the soil (dirt) from the top of the ground.  This is called surface mining.  Some mining is done by going deep underground into a mine shaft. This is called underground mining.  Some mining, such as gold mining, is done in other ways.  Gold can be mined by searching in the bed of a river or other stream of water to remove the flakes of gold.  This is called panning or placer mining.
+
+A worker in a mine is called a miner. Underground mining is a dangerous job.  Many mines have accidents. Hundreds of miners die every year from accidents, mostly in poor countries. Safety rules and special safety equipment is used to try and protect miners from accidents.  Underground coal mining is especially dangerous because coal can give off poisonous and explosive gases.
+
+Some towns are mining towns.  People live there because they can make money as miners or by doing things for miners.  When mining stops the town may become a ghost town.

ensimple/1927.html.txt

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+Space exploration is a term which describes searching outer space. There are many reasons for space exploration. The most important reasons are for scientific research and the interest of humans to learn more about outer space. For centuries, humans had dreamt of reaching outer space. Better rockets made it possible in the 20th century. On October 4, 1957, the former Soviet Union launched the Sputnik 1, which was the first artificial satellite. This started the Space Race and people later went into orbit and Americans visited the Moon in Project Apollo.
+
+Many space probes have gone to various planets and other places in the solar system to send back information about them. When people first went to space they didn't know how the effects of microgravity would have on humans so they sent animals instead. But in 1961 the soviets launched the first human into space, Yuri Gagarin.
+
+The first telescope was probably invented in 1608 by Hans Lippershey.  The Orbiting Astronomical Observatory 2 was the first space telescope launched on December 7, 1968.[1] As of February 2, 2019, about 3,891 exoplanets are discovered. The Milky Way galaxy has more than 100–400 billion stars[2] and more than 100 billion planets.[3] There are about 2 trillion galaxies in the observable universe.[4][5]
+

ensimple/1928.html.txt

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+An explosion is a fast increase in volume and increase in energy made available.  It normally makes high temperatures and makes gases. Many natural events can make explosions, such as lightning, volcanic eruptions, meteors, and supernovae. People make explosions mostly by using chemical explosive materials.
+
+A chemical explosion starts pressure waves in the medium where it happens.  Explosions are categorized as deflagrations if the pressure waves are subsonic and detonations if they are supersonic.  When a detonation happens, the resulting pressure waves are named shock waves.
+
+Unintentional explosions can be caused when chemicals are mixed together, or when pressurized containers or flammable materials are heated or exposed to flames. To cause an explosion, pressure does not have to be present but is always a result of an explosion.
+
+Several safety measures are used to prevent unintentional explosions.  Many countries require that chemicals, fuels, and pressurized containers that may explode be labelled with warning labels.  As well, many countries have regulations restricting the possession and use of potentially explosive materials so they will only go to appropriate industrial and research uses.  Transportation regulations require potentially explosive chemicals, fuels, and pressurized containers to be transported safely.
+
+Intentional explosions are caused when armies fire artillery or when air forces drop bombs on enemies.  Military engineers handle explosives and arrange intentional explosions during wartime.  Intentional explosions are also used by civilians in demolition.  They break up old and obsolete buildings and bridges, and break rock and stone for construction.  Explosions are made for activities such as mining, construction, and large-scale civil engineering projects such as building tunnels, roads, railways, and dams.
+

ensimple/1929.html.txt

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+The Holocaust, sometimes called The Shoah (Hebrew: השואה‎), was a genocide in which Nazi Germany systematically killed people during World War II. About six million Jews were killed,[a][13][14] as well as five million others that the Nazis claimed were inferior (mostly Slavs, communists, Romani/Roma people, people with disabilities, homosexuals, and Jehovah's Witnesses). These people were rounded up, put in ghettos, forced to work in concentration camps, and then killed in gas chambers.[15]  Jews were forced to wear the yellow Star of David, a symbol of their religion.
+
+There was hatred and persecution of Jews (anti-Semitism) in Europe for hundreds of years. Many people wrongly thought that all Jews became rich by stealing money from other people, such as Christians; that they did not like people other than their fellow Jews; and that they harmed children to use their blood for religious rituals (blood libel). These beliefs were not true, and were based on stereotypes and prejudices.
+
+However these beliefs were popular in the German-speaking world and elsewhere in the late 1800s.
+
+Adolf Hitler was born in Austria during this time, when many people disliked Jews. He may have been jealous of Jewish success in Austria. However, in a book he wrote called Mein Kampf ("My Struggle"), he said it was the Jews' fault that Germany and Austria lost World War I. He also wrote that Germany's economic problems were the Jews' fault. Many people agreed with Hitler’s ideas and supported him as the leader of the Nazi Party.[16][17]
+
+Not all deaths were written down, so the exact numbers are not known. However various sources approximate:
+
+Led by Hitler, the Nazis killed millions of Jews. They forced Jews to wear the golden Star of David on their upper bodies. Jews were rounded up by the thousands and crammed into trains that took them to concentration camps like Auschwitz as well as death camps. Most of the Jews killed in the Holocaust were not German. They were from Poland or the Soviet Union.
+
+The Nazis killed millions of people, hundreds at a time, with poison gas in special rooms called gas chambers. They forced others to dig giant holes in the ground where, after days of hard work, Jews and other prisoners were shot, buried, and burned in a mass grave. The Nazis executed many others by shooting, stabbing, or beating them to death. Still others died in forced marches from one camp to another.  Many other people died of starvation, diseases, and freezing to death because of the terrible conditions in the concentration camps.
+
+On the other hand, there were people who saved Jews from the Holocaust, because they thought it was the right thing to do. Some of them were later given "Righteous Among the Nations" awards by Yad Vashem.
+
+Some people say the Holocaust did not happen at all,[20] or was not as bad as historians say it was. This is called Holocaust denial. However, almost all historians agree that the Holocaust did happen and has been described correctly.[21] Many Holocaust deniers profess that the Nazis did not kill as many people as historians say. Instead, they claim many of these people died from disease or lack of food, usually in order to shift blame from the Nazis. These ideas have been disproven by historical accounts, eyewitness evidence, and documentary evidence from the Nazis themselves. Also many Jews were killed because Hitler ordered it. In some countries in Europe, including Germany,[22] it is against the law to say that the Holocaust never happened.[23]
+
+Yad Vashem (2019): "The Holocaust was the murder by Nazi Germany of six million Jews."[12]

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+Central America ([América Central or Centroamérica] error: {{lang-xx}}: text has italic markup (help)) is the central geographic region of the Americas and specifically part of the continent known as North America. It goes from Guatemala and Belize in the north-west, to Panama in the south-east. It is the area of land that sits south-east of Mexico and north-west of Colombia. It is between the Pacific Ocean and the Caribbean Sea.
+
+Central America has an area of 524,000 square kilometers (202,000 sq mi). It is almost 0.1% of the Earth's surface. This is a list of the countries in Central America, from the largest to the smallest:
+
+While Nicaragua is the largest country in area, of Central America, Guatemala has the largest population by country in Central America, with more than 14 million people and they also have the most populated city in Central America, being Guatemala City.
+
+Six of the seven countries have Spanish as their official language, with Belize being the non-Spanish speaking country, as their official language is English, although there are now at least 195,597 (62.8%) of people in Belize who speak Spanish.[2]
+
+Some people also speak indigenous or creole languages like the Maya languages.
+
+Central America has a density of 77 people per square kilometer.
+
+Central America has an area of 524,000 square kilometers (202,000 sq mi). It is almost 0.1% of the Earth's total surface. In 2009 the population was estimated at 41,739,000. It has a density of 77 people per square kilometer or 206 people per square mile.
+
+Central America has many unique features that go from the north-western borders of Belize and Guatemala to the Isthmus of Panama. There it connects to the Colombian Pacific Lowlands in South America.
+
+Central America is an area of some 524,000 square kilometres. The Pacific Ocean is on the southwest, the Caribbean Sea to the northeast, and the Gulf of Mexico to the north. Most of Central America rests on the Caribbean Plate.
+
+The region is geologically active. It has volcanic eruptions and earthquakes from time to time.
+
+The 1976 Guatemala earthquake  killed 23,001 people. Managua, the capital of Nicaragua, was devastated by earthquakes in 1931 and 1972. The last one killed about 5,001 people. Three earthquakes hit El Salvador. The first one in 1986 and two in 2001. An earthquake devastated northern and central Costa Rica in 2009. It killed at least 35 people. In Honduras a powerful earthquake happened in 2009.
+
+Volcanic eruptions are common. In 1968 the Arenal Volcano in Costa Rica erupted. This killed at least 87 people. The 3 villages of Tabacon, Pueblo Nuevo, and San Luis were buried under ash.
+
+Central America has many mountain ranges; the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia and the Cordillera de Talamanca. Most of the population of Honduras, Costa Rica and Guatemala live in valleys, between mountains. Valleys are also suitable for the production of coffee, beans and other crops.
+
+Central America is part of the Mesoamerican Biodiversity hotspot, boasting 7% of the world's biodiversity.[3] As a bridge between North and South America, Central America has many species from the Nearctic and the Neotropic ecozones. However the southern countries (Costa Rica and Panama) of the region have more biodiversity than the northern countries (Guatemala and Belize), meanwhile the central countries (Honduras, Nicaragua and El Salvador) have least biodiversity.[3] The table shows current statistics for the seven countries:
+
+Africa
+
+Antarctica
+
+Asia
+
+Australia
+
+Europe
+
+North America
+
+South America
+
+Afro-Eurasia
+
+Americas
+
+Eurasia
+
+Oceania
+