The Origin of Life!!

How did life begin?! There are tons of different theories.. but the one I'm about to explain is according to Scientists. You may believe this, or your own theory, or some sort of hybrid of the two, and that's okay!!

According to scientists, when Earth was first formed, there was NO life. This Earth was really hot, and full of ammonium, some Carbon Dioxide, water, and some other gases all mixed up in a "soup". Take a look at the video below to understand better..

http://www.youtube.com/watch?v=jTCoKlB0s4Y

1. The first "cells" that evolved were called protocells (above). These LOOKED like real cells- they had a cell membrane and DNA inside- but they weren't alive! These protocells started replicating and eventually the first prokaryotic cells evolved.

2. The first REAL cells that appeared were PROKARYOTIC cells. These cells are very simple, only containing a DNA strand, ribosomes, a cytoplasm, and cell wall (and sometimes flagella for moving around- locomotion!). 


**These first prokaryotic cells were HETEROTROPHS (like the chicken below)... meaning that they DON'T make their own food, and need to eat other organisms for food.
-Because these heterotrophs were going through the process of fermentation (a type of cellular respiration) they were releasing Carbon Dioxide (CO2). Now, the atmosphere is full of too much Carbon Dioxide!

 3. Because there was too much Carbon Dioxide in the atmosphere, autotrophs evolved. Autotrophs are organisms that make their own food (such as through photosynthesis with plants). To do so, they take in Carbon Dioxide and release Oxygen.
-Now, the atmosphere is full of Oxygen, and has less Carbon Dioxide (just like today!).

                                                   This diagram is autotrophic bacteria (prokaryote)

 

Plants are another example of autotrophs (above)

4. Finally, these prokarytoic (simple) cells began to "eat" small bacteria. These bacteria turned into organelles of the new eukarytoic cells. Eukaryotic cells are COMPLEX cells containing specialized organelles with their own functions. Plants and animals (such as humans) have eukaryotic cells! (See diagram of eukaryote below!!).

*For prokaryotes to turn into eukaryotes, they go through a process called endosymbiosis (where they eat small organelles).