evolution

## What I do - Study mechanisms of evolutionary change - Analyze natural selection and adaptation - Research speciation and biodiversity - Construct phylogenetic trees - Investigate molecular evolution - Study population genetics ## When to use me - When studying evolutionary relationships - When analyzing adaptation mechanisms - When constructing phylogenies - When studying speciation - When researching molecular evolution - When analyzing population genetics ## Key Concepts ### Mechanisms of Evolution - **Natural selection**: Differential reproductive success - **Genetic drift**: Random allele frequency change - **Gene flow**: Migration between populations - **Mutation**: Source of genetic variation - **Non-random mating**: Assortative/disassortative ### Natural Selection ```python # Example: Selection coefficient calculation def selection_coefficient(w1, w2): """ Calculate selection coefficient. w1, w2: Fitness values of genotypes """ return 1 - (w2 / w1) def allele_frequency(p, q, s, t): """ Calculate allele frequency change under selection. p: Frequency of dominant allele q: Frequency of recessive allele s: Selection coefficient against dominant t: Selection coefficient against recessive """ delta_p = (p * q * (p*s - q*t)) / (1 - s*p**2 - t*q**2) return delta_p ``` ### Phylogenetics **Tree Construction Methods** - Maximum parsimony - Maximum likelihood - Neighbor-joining - UPGMA **Molecular Evolution** - dN/dS ratio: Nonsynonymous vs synonymous substitutions - Molecular clock: Constant mutation rate - Positive selection: Adaptive evolution ### Evidence for Evolution - Fossil record - Comparative anatomy - Molecular biology - Biogeography - Direct observation