Expert-level evolutionary biology covering natural selection, genetic drift, molecular evolution, phylogenetics, speciation, macroevolution, and the modern synthesis.
Requirements: variation, heritability, differential fitness. Types: directional, stabilizing, disruptive, sexual, kin, group. Adaptation: trait increasing fitness in current environment. Fitness: reproductive success relative to population mean. Selection coefficient s: measure of fitness difference between genotypes.
Random change in allele frequencies due to sampling in finite populations. Effective population size Ne: determines rate of drift. Bottleneck: severe reduction reduces genetic diversity. Founder effect: small founding population carries limited diversity. Genetic drift vs selection: drift dominates when Nes much less than 1.
Neutral theory: most molecular variation is selectively neutral (Kimura). Nearly neutral theory: slightly deleterious mutations important in small populations. Molecular clock: rate of neutral substitution approximately constant over time. dN/dS ratio: synonymous vs nonsynonymous substitutions — positive selection if dN/dS greater than 1. Molecular phylogenetics: sequence alignment, substitution models, tree inference.
Parsimony: minimize evolutionary changes required to explain data. Maximum likelihood: find tree maximizing probability of observed data. Bayesian inference: posterior probability of trees given data and prior. Substitution models: JC69, HKY85, GTR — nucleotide substitution rates. Bootstrap support: resampling to assess node confidence.
Allopatric: geographic isolation leads to reproductive isolation. Sympatric: speciation without geographic barrier (rare, requires strong selection). Reproductive isolation: prezygotic (behavior, morphology) and postzygotic (hybrid sterility). Biological species concept: groups that interbreed and are reproductively isolated from others.
| Pitfall | Fix |
|---|---|
| Adaptationist storytelling | Test adaptive hypotheses with quantitative predictions |
| Ignoring drift | Selection is not the only evolutionary force |
| Long branch attraction | Use better substitution models, add taxa |
| Confusing gene trees and species trees | Use coalescent-based methods for species trees |