Evolution of Species

Drew Bernard

BIOL 1407

2-17-2016

Major Milestones in Evolutionary History

In the beginning, when earth was formed about 4.6 billion years ago (recent findings convey a figure a bit older than this), the earth was lifeless, just as any other planet in our solar system currently. The earth was struck by many meteorites, many of them carrying extraterrestrial molecules such as amino acids. The atmosphere consisted of many molecules that are essential in the creation of important biological molecules. As atoms and molecules tend to arrange themselves in the lowest possible energy arrangement, some of these arrangements created organic molecular order with a spark, such as lightening. Such molecules became the building block of a self-replicating macromolecule, now theorized to be RNA. Other organic molecules such as lipids, due to molecular structure, created an ordered phospholipid bilayer in water. If this self-replicating RNA molecule were to be surrounded by a phospholipid bilayer, you now have a self-replicating cell. This serious of events is theorized or have occurred to create life.

Around 3.5 billion years ago is when unicellular life evolved. These unicellular lifeforms include oxygen producing bacteria which start using the CO2 in the air and producing oxygen gas through a process called photosynthesis. This radically changed the atmosphere composition. About 0.6 billion years ago is when the first eukaryotic cells are thought to have been formed. The theory of endosymbiosis states that there were two separate cells, one was a mitochondrion bacterium, the other was a larger bacterium. The larger bacterium is thought to have engulfed the smaller mitochondrion bacterium, and keep the cell living inside of it because of the beneficial aspect of energy creation that the mitochondrion could provide. This cell would then reproduce and pass down this advantage through binary fission.

After this, natural selection would further evolution and eventually create...