# Wikijunior:Biology/Introduction



## Introduction

**Biology** is the study of life. It helps us understand many things,
such as how our body works, how our body keeps warm, and what we are
made of. Biology is very important to know. Some things we can learn
about in biology are *genetics* (the study of human traits), *zoology*
(the study of animals), *botany* (the study of plants), and *ecology*
(the study of relationships between all living things).

Someone who studies biology is called a *biologist*.

Image:Human female metaphase chromosomes.tif\|thumb\|genetics
Image:Begegnung-01.jpg\|thumb\|zoology Image: Pachycereus pringlei
forest.jpg \|thumb\|botany
Image:Sunrise_over_Veterans_Park_2420.jpg\|thumb\|ecology

## What is life?

Living things are different from things that are not alive. It is
usually easy to tell what is living and what is not, but it is sometimes
hard to tell, like with very small organisms.

Here are some properties of living things. You might notice that some
non-living things can also have some of these properties.

-   **Living things can change and grow.** However, volcanoes can also
    change and grow when they erupt.
-   **Living things can move.** However, the wind is moving air, and
    water always moves downhill.
    -   Just like animals, even plants can move. They can grow, and
        sometimes move more rapidly than that, in response to things
        such as the sun or water. One example is that sunflowers will
        naturally turn during the course of the day so that they are
        always facing the sun. Similarly, another example is that if a
        plant gets tipped over, it will want to turn upwards to face the
        sun.
-   **Living things can reproduce,** which means that they can produce
    copies of themselves, over and over. This is the most important
    difference between living and non-living things.
    -   In order to reproduce, living things need nutrition, which are
        nutrients and energy sources in order to assemble the materials
        needed to reproduce themselves. In this process, living things
        must excrete waste. Waste is material which is of no use to
        living things, or in some cases, material that can be harmful.

Animals, bacteria, and plants are examples of living things. Rivers,
mountains, oceans, and soil are examples of non-living things, but they
are often homes for living things.

Cars and tables are also not living things, because they cannot
reproduce themselves.

Image:The_freshwater_alga_Spirogyra.jpg\|thumb\|Freshwater Alga
Image:Viburnum_opulus_fruits_close-up\_-\_Keila.jpg\|thumb\|Berry
Image:Anax imperator 2015 11 23 6807.jpg\|thumb\|Dragon-fly
Image:Uitrollend blad van een Polystichum setiferum. 19-04-2023. (d.j.b)
01.jpg\|thumb\|Fern Image:Hellenic pond turtle (Emys orbicularis
hellenica) Butrint.jpg\|thumb\|Turtle Image:Iceland Poppy Papaver
nudicaule \'Champagne Bubbles\' Orange Center.jpg\|thumb\|Bloom

## Levels of life

Living things can be of many different sizes. Size is very important in
biology, since biologists organize the structures and groupings of
living creatures according to size. A living creature is called an
organism. Organisms can consist of single cells or multiple different
types of cells grouped into tissues and organs.

From smallest to largest, these are how living things are grouped:

Cells
:   Most cells are only a few microns wide, and are so small that they
    can only be seen with a microscope. A micron is one thousandth of a
    millimeter.

Tissues
:   Tissues are groups of similar cells that are all doing similar
    things, like a muscle, which pulls things together.

Organs
:   Organs are made of lots of tissues. They all have a special
    function, like the heart, which pumps blood.

Organ systems
:   Organ systems are groups of organs which work together to do
    something. For example, all the organs which digest your food make
    up the digestive system.

Organisms
:   An organism is a whole living thing, like you, or a tree.

Populations
:   A population is a group of organisms which are all the same species
    and live together.

Communities
:   A community is a group of populations of different species, which
    live together; for example, all the fish in a lake.

Ecosystems
:   All the communities of organisms in an area, and the way they
    interact with non-living things like rivers or the weather in that
    area, form an ecosystem.

Biomes
:   A biome is a large region of Earth that has a certain climate and
    certain types of living things. Major biomes include tundra,
    forests, grasslands, and deserts.

Biosphere
:   The biosphere is the whole network of living things on planet Earth
    --- eight thousand miles in diameter, twenty five thousand miles
    around the equator.

Everything in this list is made up of the things above it. For example,
communities are made of many populations and populations are made up of
many organisms.

  ----------------------------------------------------------------------------------------------
   ! {width="400"}
                            The earth, our home, our biotope in space.
  ----------------------------------------------------------------------------------------------



