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evolution
cumulative change in the genetic composition of a population or species over time
Darwin’s 3 major propositions
species aren’t immutable - pops show phenotypic variation and species change over time. e.g. different coloured snapdragons or different beak sizes in finches. No variation = no evolution
descent with modification - related species share common ancestor and diverged over time. Inheritance of traits happen with mods through many genes. evidence = homologous structures
natural selection - differences in phenotype of individuals makes some survive and reproduce more effectively then others = outcompete. Phenotype most suited (fittest) for enviro = more likely to produce offspring. Driver of evolution
homologous structures
similar anatomical features in different species, indicating common ancestry and evolutionary relationships.
speciation
formation of new and distinct species in course of evolution. Evolutionary consequence of reproductive isolation
what would happen if a population showed no phenotypic variation
No natural selection. If enviro changed, population would be unable to adapt = won’t evolve over time. Possible extinction