bio unit 7 test

evolution

the change in characteristics of a species or population over time

how do organisms develop resistances?

developing mutations via natural selection

genetic drift

random events cause changes to alleles

bottleneck effect

a large population is non-selectively reduced, ex. natural disasters

founder effect

a small group splits off from a population and creates a smaller gene pool, affecting the frequency of certain alleles

what four random occurrences drive evolution?

mutations, genetic drift, gene flow, and non-random mating

darwin’s two main observations on natural selection

#1. traits are heritable

#2. more offspring are produced than survive

divergent evolution

two species with a recent common ancestor evolve different traits and diverge

convergent evolution

two species with different common ancestors evolve similar traits

homologous structures

similar structure, different function

analogous structures

similar function, different structures

prezygotic barriers

prevent mating/hinder fertilization

postzygotic barriers

prevent viability of hybrids

five types of prezygotic barriers

habitat, temporal, behavioral, mechanical, genetic isolation

three types of postzygotic barriers

reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

allopatric speciation

population separated, prevents gene flow

sympatric speciation

new species evolves in population, exploitation of new niche

gradualism

evolution occurs slowly over many years

punctuated equilibrium

evolution occurs quickly after many years of stasis

directional selection

the average skews to one extreme

stabilizing selection

the center is the most common, and the extremes are uncommon

disruptive selection

the center is uncommon, and the extremes are more common

support the endosymbiotic theory

mitochondria have membranes, their own dna, and reproduce via mitosis

evidence of evolution

fossil record, molecular biology, biogeography