Origins of Life and Biological Evidence for Evolution

Oparin’s Theory of the Origin of Life

1. The primitive atmosphere was made up of gases: ammonia, water vapor, methane, and hydrogen.
2. The energy for the first chemical reactions to occur came from volcanic eruptions, radiation from the sun, and storms.
3. The temperature of the Earth fell, so the water vapor condensed and formed seas.
4. Organic molecules, synthesized by the reactions, accumulated in the water and joined together to form bigger molecules.
5. Coacervates were structures formed by organic molecules insulated from the water.
6. The first cell appeared when the coacervates started to reproduce.

The Endosymbiotic Theory

The Endosymbiotic Theory of Margulis explains the appearance of the first eukaryotic living things from the symbiotic relationships between prokaryotic organisms. The theory states that mitochondria appeared when energy-producing bacteria were phagocytosed by bigger bacteria and became symbionts. In the same way, chloroplasts were formed from photosynthetic bacteria that were engulfed by bigger prokaryotes.

Anatomical Evidence of Evolution

Comparative anatomy involves studying and comparing the structure of different organs. Two organisms are related if their organs have a similar internal structure, even if they are shaped differently. There are three types of anatomical evidence:

Homologous Organs

Homologous organs are similar in structure and share a common origin but may be adapted to perform different functions. Divergent evolution refers to the changes from a common ancestor caused by habits and/or the environment.

Analogous Organs

Analogous organs are those that have evolved separately but look alike because they are adapted to perform the same function. Convergent evolution refers to the changes that create similar structures in groups of living things that are not related at all.

Vestigial Organs

Vestigial organs are those organs, found in some living things, that do not perform any functions. They simply show an evolutionary relationship with other living things. One example of a vestigial organ is the coccyx (or tailbone) in humans. The coccyx is the remnant of a lost tail. Other organs are the appendix and the wisdom teeth.

Lamarckism and Darwinism

Lamarckism, or the theory of acquired characteristics, suggests that organisms develop structures that they need to adapt to the environment. The acquired characteristics were transmitted to the descendants, and that way, new species appear. Darwinism