Evolution - Honors Bio

Evolution

the change in the allele frequency of a population over time.

Populations evolve, not individuals.

Fossil Record

shows changes in species over time and transitional forms.

Homologous structures

similar structure, different function (common ancestry).

Analogous structures

different structure, similar function (convergent evolution).

Vestigial structures

remnants of once-useful organs.

Embryology

similar early development indicates common ancestry.

Biochemistry

similar DNA and proteins suggest evolutionary relationships.

Biogeography

distribution of species supports descent with modification.

Natural Selection

individuals with favorable traits survive and reproduce more. Requires variation, heritability, overproduction, and differential survival.

Genetic Drift

random changes in allele frequencies, especially in small populations. Bottleneck effect and founder effect are key examples.

Gene Flow

movement of alleles between populations (migration).

Mutation

introduces new genetic variation.

Non-random Mating

certain traits increase reproductive success (sexual selection).

Directional Selection

occurs when natural selection favors one of the extreme variations of a trait

Stabilizing Selection

favors average traits.

Disruptive Selection

favors both extremes over the average.

speciation

the formation of new and distinct species in the course of evolution.

Allopatric speciation

the process of speciation that occurs with geographic isolation

Sympatric speciation

Speciation without a divided population.

Reproductive isolation

prevents gene flow.

Prezygotic barriers

before fertilization (temporal, behavioral, mechanics).

Postzygotic barriers

after fertilization (nonviable,sterile offspring).

Convergent Evolution

unrelated species evolve similar traits.

Divergent Evolution

related species evolve different traits.

Coevolution

species evolve in response to one another.

Adaptive Radiation

many new species evolve from a common ancestor.

Gradualism

slow, steady change.

Punctuated Equilibrium

rapid change followed by stability.