# Wikijunior:Biology/Organs



## Organs

! A heart\|thumb Many living things have
**organs**. Your heart, brain, lungs, liver, and kidneys are all
examples of organs.

Organs are made up of two or more
tissues.

All organs have something that they do to keep you healthy. For example,
the heart pumps blood, and the lungs give you air.

Organs work together in groups called organ
systems.

## Cambrian explosion and organ formation

The earth formed about 4.5 billion years ago. One billion years later,
at the latest, there will be unicellular organisms. Complex
single-celled organisms, called eukaryotes, arose until about 2 billion
years ago. The first multicellular organisms, such as filamentous algae,
jellyfish and worms, arose 1-2 billion years ago. Around 540 million
years ago, animals with complex organs such as hearts and eyes emerged.
Just as the economy and way of life of people fundamentally changed in
the industrial revolution in a short historical time, all animal tribes
that exist today have developed in a geologically short time. Biologists
speak of the Cambrian explosion. The industrial was triggered by basic
innovations such as the steam engine. The Cambrian explosion was also
probably triggered by basic innovations that made organ formation
possible. The prerequisite is that cells specialize and then migrate to
the right place.

<File:Medusina> asteroides.jpg <File:Life> in the Ediacaran sea.jpg
<File:DickinsoniaCostata.jpg> <File:20191020> Yohoia tenuis.png
<File:Opabinia> smithsonian.JPG <File:Figure> 27 04 03.jpg

