Fundamental Theories of Cosmic and Biological Change

Theories of Lunar Formation

The Capture Theory (Adopted)

This theory suggests the Moon was formed simultaneously with the Earth, but in a remote area. It was later captured by the Sun's gravitational field and then transformed into our terrestrial satellite.

The Giant Impact Hypothesis (Daughter)

This theory holds that a terrestrial body, similar in size to Mars (often called Theia), collided with the Earth. Part of the material constituted a cloud of impact residues that remained orbiting the Earth. The accretion of these materials originated the Moon. Terrestrial materials participated in this formation, contributing to the Moon's crust and mantle, but not its core.

Lamarckism: The Theory of Acquired Characters

Jean-Baptiste Lamarck considered living beings had a natural tendency toward progress and complexity. His theory is called Lamarckism. The basic ideas are:

• Organisms change over time.
• Changing environmental conditions modify species by altering their habits and needs.
• Use and Disuse: The use and disuse of organs determine changes. If an organ develops through heavy use, it will atrophy if not used. The need may even cause a new organ to develop.
• Changes thus acquired are transmitted to the offspring. The accumulation of these changes creates different species.

Evolutionary Theories: Darwin and Modern Synthesis

Basic Ideas of Darwin's Theory of Evolution

More individuals are born than can survive in any species. Resources are limited, meaning not all survive. Key tenets include:

• Between individuals of any kind, there are heritable variations or differences.
• Natural Selection occurs: those who are fittest and have advantages survive and reproduce.
• Populations change gradually. Surviving individuals transmit the advantageous variation to their offspring.

The Synthetic Theory of Evolution (Modern Synthesis)

In the mid-twentieth century, Darwin's theory was enriched and updated with new scientific knowledge. The result was the Synthetic Theory of Evolution. Its most important contributions are:

• The evolutionary unit is the population, not the individual. Natural selection acts on the gene pool (the set of genes and all its variants within a population).
• The origin of variability lies in mutations. A mutation is a sudden change that occurs in the DNA. These changes show different characteristics. Since they affect genetic material, they are heritable.
• Mutations occur randomly and are generally harmful to their carriers, meaning they will be deleted by natural selection.