Key Concepts in Astronomy and Evolutionary Biology

The Origin of the Moon

• Sister. The Moon formed while the Earth did, but the Moon is 100 million years younger, and their densities are different.
• Adopted. Both formed, but the Moon formed in an area farthest from the Sun and would have been attracted to the Earth. This does not explain the difference in age.
• Daughter. A planet similar to Mars collided with the Earth. Part of the star that crashed formed a debris cloud that orbited around the Earth. The union of these materials created the Moon.

Prebiotic Synthesis

Hypotheses in which life would have originated on Earth as a result of a process:

• Formation of simple organic molecules. Radiation caused molecules to react, forming simple organic molecules.
• Formation of complex organic molecules. Simple organic molecules combined to form more complex ones, leading to the primordial soup.
• Formation of coacervates. The compounds of the primordial soup joined, causing coacervates.

Saltationism

Saltationism is a theory that species have periods of stability interrupted by short periods of change.

Stars

A star's life depends on its mass. Stars transform hydrogen into helium. When a star consumes all its hydrogen, it becomes a red giant. When it exhausts the helium, it becomes a white dwarf.

Nebulae

Nebulae are masses of dust and gas.

Synthetic Theory of Evolution

• The evolutionary unit is not the individual but the population.
• Natural selection acts on the gene pool of the population or the set of genes with their variants.
• The origin of variability is in mutations.
• Mutations are heritable and occur randomly. They can be detrimental or advantageous.

Evidence for Evolution

• Fossil record. Fossils allow us to verify that species have appeared and become extinct.
• Comparative anatomy. The anatomy of the forelimb skeleton of a person, bat, dolphin, or bird responds to the same model and is formed by the same pieces.
• Embryology. The embryos of a fish, reptile, bird, or mammal are similar in their early stages but later follow a process of progressive differentiation.
• Molecular biology. All living things are made of the same chemicals.

Bipedalism

One criterion is used to differentiate between the lineage of hominids and anthropomorphic apes.

• Foramen magnum. The foramen magnum is the hole in the skull through which the spinal cord passes. In hominids, it is oriented downward, and in apes, it is oriented backward.
• Hip arrangement. In hominids, the femora are directed obliquely from the hips to converge at the knees. In apes, they are vertical.
• Changes in the foot. Adaptation to standing assumed that the foot was lengthened, and the thumb aligned with the other toes.