Evolution Test Notes

1. Historical Background & Modern Evolutionary Views

• Evolutionary theory developed through fossil evidence, comparative anatomy, and genetics.

• Charles Darwin and Alfred Wallace proposed evolution by natural selection.

• Influences from Lyell (geological changes) and Malthus (population growth limits).

• Lamarck’s Theory of Acquired Characteristics (disproven).

2. Evidence for Evolution

• Fossil record: Shows transitional forms and extinction events.

• Comparative anatomy:

  • Homologous structures (same structure, different function – common ancestry).

  • Analogous structures (same function, different structure – convergent evolution).

  • Vestigial structures (remnants of ancestral features).

• Embryological evidence: Similar embryonic development across species.

• Biochemical & genetic evidence: DNA similarities, shared proteins.

3. Evolution by Natural Selection

• Key concepts:

  • Fitness = Ability to survive and reproduce.

  • Survival of the Fittest = Those best adapted to the environment reproduce more.

  • Niche & Competition = Organisms compete for resources.

• Speciation:

  • Allopatric speciation: Physical barriers separate populations.

  • Sympatric speciation: New species evolve without physical separation.

• Examples: Peppered moths, antibiotic resistance.

4. Agents of Evolution

• DNA: Stores genetic information, undergoes mutations.

• Mutations:

  • Beneficial (advantageous traits).

  • Neutral (no effect).

  • Harmful (reduce fitness).

  • Caused by mutagens (radiation, chemicals).

• Genetic concepts:

  • Genotype vs. Phenotype: Genetic makeup vs. physical traits.

  • Alleles, gene pool, and variation: Diversity in populations.

• Types of Natural Selection:

  • Directional: Favors one extreme trait.

  • Stabilizing: Favors average traits.

  • Disruptive: Favors extreme traits, not the average.

• Artificial Selection: Humans selectively breed traits (e.g., dog breeds).

• Accidental Selection: Industrial melanism (e.g., dark moths in polluted areas).

• Genetic Drift:

  • Bottleneck Effect: Drastic reduction in population size.

  • Founder Effect: New population from a few individuals.

• Gene Flow: Migration introduces new alleles.

5. Models of Evolution

• Gradualism: Evolution is slow and steady.

• Punctuated Equilibrium: Long stability with sudden bursts of change.

• Mass Extinctions: Drastic reductions in biodiversity, leading to evolutionary shifts.

6. Patterns of Evolution

• Divergent Evolution: Common ancestor, species evolve differently (e.g., Darwin’s finches).

• Convergent Evolution: Different ancestors, species develop similar traits (e.g., wings in bats and birds).

• Co-evolution: Two species evolve in response to each other (e.g., predators and prey, flowers and pollinators).