Evolutionary Theory & Natural Selection

Study Notes

Evolutionary theory is a scientific theory explaining the diversity of life through descent with modification
Pre-Darwinian views of species were static and unchanging
Darwin's ideas aligned with current views, demonstrating that species change over time.
Natural selection is the process where individuals better adapted to their environment are more likely to survive and reproduce, passing on advantageous traits.
Natural selection explains both the unity and diversity of life.
Adaptations are traits that improve an organism's survival and reproductive success in a specific environment.
Artificial selection is the selective breeding of organisms by humans for desirable traits, demonstrating that evolution occurs through selective pressure.
Evidence for evolution includes direct observations, homology (anatomical, developmental, and molecular), fossils, and biogeography.

Direct observations show how organisms adapt and change over relatively short periods.
Example: antibiotic resistance in bacteria evolves quickly due to selection for traits that confer immunity to the drugs.

Homologous structures show common ancestry.
Similar structures in different organisms with a shared evolutionary history.
Homologous structures support evolution because of the presence of shared characteristics.
Vestigial structures are remnants of features that served important functions in ancestral organisms but no longer have a clear function.
Vestigial structures provide examples of evolutionary relationships.
Analogous structures show convergent evolution.
Convergent evolution occurs when different species independently develop similar traits due to similar environmental pressures.
Developmental homologies: similarities in embryonic development provide evidence of common ancestry.
Molecular homologies show common ancestry through the similarities in DNA or protein sequences.

Fossils show the history of life on Earth and how species have evolved over time.
Gaps in the fossil record are explained by incomplete fossil preservation and the difficulty of finding complete and representative specimens.
Gaps do not disprove evolution, rather highlight the incomplete nature of the fossil record.
Biogeography studies the geographic distribution of organisms.
Distribution patterns support evolution, with present species reflecting events in their evolutionary history.

Skin color is an example of natural selection.
UV light levels, skin color, and human migration have a relationship, relating skin color to UV levels in different geographical areas.
Skin color is a trait that has adapted to different environmental conditions.