Biological Evolution Lecture Notes

Introduction to Evolution Misconceptions

• General Misconception: Evolution often portrayed incorrectly in games and cartoons.
• Reality: Individuals don't evolve during their lifetime; evolution occurs over generations in populations.
• Term Misunderstandings:
  • Theory: Different meaning in science vs casual use.
  • Fitness: In biology, relates to the number of offspring and genes passed down, not physical strength.
  • Evolution: Not always about increased complexity in biology.

Biological Evolution Defined

• Definition: Change in a population's inherited traits over generations.
• Population: Group of the same species with genetic variety.
• Gene Pool: Variety in genes among a population.

Mechanisms of Evolution

• Gene Flow: Movement of genes between populations, often through migration.
• Mutations: Genetic changes which can be harmful, beneficial, or neutral.
• Genetic Drift: Changes in genetic makeup due to random events (e.g., lawn mower affecting grasshopper population gene pool).
• Natural Selection: Traits that improve survival and reproduction (e.g., green grasshoppers being better camouflaged).

Lines of Evidence for Evolution

Homologies

• Definition: Similarities due to shared ancestry.

Molecular Homologies

• DNA Comparisons: Indicates relatedness between species (e.g., turkey and emu more closely related than turkey and termite).
• Proteins and Amino Acids: Similar characteristics support evolutionary relationships.

Anatomical Homologies

• Homologous Structures: Similar structures due to common ancestry, different functions (e.g., human arm and dog forelimb).
• Analogous Structures: Similar functions but not from common ancestry (e.g., bird wing vs insect wing).
• Vestigial Structures: Inherited but lost most/all function (e.g., claw on chicken wings).

Developmental Homology

• Embryology: Similar developmental stages (e.g., notochord, pharyngeal slits in vertebrates) support common ancestry.

Fossil Record

• Fossils: Remains or traces of organisms used to study past life.
• Information Gained: Changes in characteristics, ancestral organism traits.
• Radiometric Dating: Determines fossil age using radioactive decay.

Biogeography

• Definition: Study of species distribution across the geographic landscape.
• Island Populations: Unique but closely related to nearby mainland due to isolated evolution.
• Continental Drift: Marsupials in Australia and South America share ancestry due to past continental connections (Pangea).

Conclusion

• Continued Evolution: Evolution is ongoing (e.g., antibiotic resistance in bacteria).
• Encouragement: Stay curious about biological processes.