Unit Checkpoint

Answer: Observations: 1) Variation exists in populations, 2) Some variation is heritable, 3) More offspring are produced than survive, 4) Survival and reproduction are not random. Inferences: 1) Individuals with favorable traits survive and reproduce more, 2) Favorable traits become more common over generations.

Answer: 1) Fossil record - shows change over time; 2) Comparative anatomy - homologous/vestigial structures show common ancestry; 3) Molecular biology - DNA/protein similarities reflect relationships; 4) Biogeography - species distribution reflects evolutionary history. Each provides independent support; together they create overwhelming evidence.

Answer: Directional: selects for one extreme (e.g., larger beaks during drought). Stabilizing: selects against extremes, favoring average (e.g., human birth weight). Disruptive: selects for both extremes against the middle (e.g., beak sizes in birds with two seed sizes).

Answer: 1) Genetic drift - random changes, especially in small populations; 2) Gene flow - movement of alleles between populations; 3) Mutation - creates new variation; 4) Sexual selection - mating preferences affect traits. Natural selection is most important, but all contribute to evolution.

Answer: Allopatric: populations geographically separated (island, mountain range) evolve independently. Sympatric: speciation without geographic separation (through polyploidy, habitat differentiation, or temporal isolation). Allopatric is more common.

Answer: q2 = 160/1000 = 0.16, so q = 0.4, and p = 0.6. Genotypes: AA (p2) = 0.36, Aa (2pq) = 0.48, aa (q2) = 0.16. Expected numbers: 360 AA, 480 Aa, 160 aa.

Answer: Branch points show common ancestors. Tips are living or extinct species. Closer branch points = more recent common ancestor = more closely related. The tree shows hypothesized evolutionary history based on shared traits and molecular data.

Answer: Coevolution: two species evolve in response to each other. Example: Predator-prey (cheetah speed and gazelle speed increase together), or mutualism (flower shapes and pollinator tongue lengths match). Each species is a selective pressure on the other.

Answer: Evolution has no foresight or end goal. Mutations occur randomly. Selection only favors what works now, not what might be useful later. "More evolved" is meaningless - all living species are equally evolved for current conditions. Evolution is change, not progress.

Sample CER: Claim: Homologous structures in different species provide evidence for common ancestry. Evidence: The forelimbs of humans, whales, bats, and cats all contain the same bones (humerus, radius, ulna, carpals, metacarpals, phalanges) in the same relative positions, despite serving different functions (grasping, swimming, flying, walking). Reasoning: If these species were created independently, there's no reason they would share the same bone structure for such different purposes. However, if they share a common ancestor with this bone pattern, then each lineage modified the inherited structure for its specific needs. The underlying similarity indicates shared ancestry; the differences show adaptation to different environments.