AP BIO Evolution

• Genetic Drift – Random changes in allele frequencies in a population.

• Founder Effect – When a small group starts a new population, leading to reduced genetic diversity.

• Adaptive Radiation – A single species evolves into many different forms to fill various niches.

• Evolution – The change in species over time due to genetic variation and selection.

• Natural Selection – Organisms with beneficial traits survive and reproduce more.

• Disruptive Selection – Extreme traits are favored over the average trait.

• Directional Selection – One extreme trait is favored over others.

• Stabilizing Selection – The average trait is favored, while extremes are selected against.

• Convergent Evolution – Unrelated species develop similar traits due to similar environments.

• Divergent Evolution – A common ancestor leads to species that become more different over time.

• Homologous Structures – Similar structures in different species due to a common ancestor.

• Analogous Structures – Different structures with similar functions, not due to a common ancestor.

• Vestigial Structures – Body parts that have lost their original function.

• Fossils – Preserved remains of ancient organisms.

• Biogeography – The study of where species live and how they evolved.

• Embryology – The study of embryos to understand evolutionary relationships.

• Gene Flow – The movement of genes between populations.

• Fitness – How well an organism survives and reproduces.

• Allopatric Speciation – New species form due to geographic separation.

• Sympatric Speciation – New species form without geographic separation.

• Reproductive Isolation – When species can’t mate due to barriers like behavior or genetics.

• Punctuated Equilibrium – Evolution happens in quick bursts, not gradually.

• Gradualism – Evolution happens slowly over time.

• Heterozygous Advantage – When being heterozygous for a gene gives a survival advantage.

Stickleback Evolution Summary

Stickleback fish originally had spines and armor for protection, but when some populations moved to freshwater, they lost these traits because there were fewer predators. Over generations, genetic changes led to populations with smaller or no spines, showing natural selection at work.

Hardy-Weinberg Problems

1. 36% of the population is homozygous recessive (aa).

   • a. Frequency of aa genotype = 0.36

   • b. Frequency of a allele (q) = √0.36 = 0.6

   • c. Frequency of A allele (p) = 1 - 0.6 = 0.4

   • d. Frequency of AA = (0.4)² = 0.16, Frequency of Aa = 2(0.4)(0.6) = 0.48

   • e. Dominant phenotype (AA + Aa) = 0.16 + 0.48 = 0.64, Recessive phenotype (aa) = 0.36

2. 4% (0.04) of students have the recessive trait (aa).

   • a. q (recessive allele frequency) = √0.04 = 0.2

   • b. p (dominant allele frequency) = 1 - 0.2 = 0.8

   • c. Heterozygous frequency (2pq) = 2(0.8)(0.2) = 0.32 (32%)

3. 40% of butterflies are white (bb, q² = 0.40).

   • a. Heterozygous frequency = 2pq = 2(0.37)(0.63) ≈ 0.47 (47%)

   • b. Homozygous dominant (BB) frequency = p² = (0.63)² ≈ 0.40 (40%)

4. 20 people start a population, 2 are heterozygous (carriers of cystic fibrosis).

   • a. Chance of cystic fibrosis (q²) on the island = (1/20)² = 0.0025 (0.25%)

   • b. Cystic fibrosis births are 0.25% ÷ 0.059% ≈ 4.24 times higher than the mainland.

Bird and Mammal Traits

• Five bird traits – Feathers, beaks, hollow bones, laying eggs, warm-blooded.

• Four mammal traits – Hair, mammary glands, live birth (mostly), warm-blooded.

Comparisons

• Amniote eggs came before hair.

• Keratinized skin came before bipedalism.

• Jawless animal – Hagfish or lamprey.

• Animals with lungs – Amphibians, reptiles, birds, mammals.

• Most common ancestor of pigeon, mouse, and chimp – A reptile-like ancestor.

• Outgroup organism – The species that shares the least traits with the rest in a cladogram.