Prokaryotic Cell
![Picture](http://www.editmysite.com/editor/images/na.png)
Prokaryotic cells first developed 3.5 BYA (billion years ago). Prokaryotic are so simple that they don't even have nucleus. For at least a billion years these were only living things on Earth.
Jellyfish-Like Animals
![Picture](http://www.editmysite.com/editor/images/na.png)
600 MYA (million years ago) Jellyfish were formed. Jellyfish are invertabrates they have been drifting ocean currents for million of years. More complex then unicellular organisms can be longer different functions.
Arthropods
![Picture](http://www.editmysite.com/editor/images/na.png)
Arthropods were formed 570 MYA. Examples of Arthropods are insects, spiders, crabs, and lobsters.
First Mass Extinction
![Picture](http://www.editmysite.com/editor/images/na.png)
First Mass Extinction was 544 MYA. Global ice age caused this extinction and was the reason it happened.