Unit 3 ALL - Bio

Evolution

any change in relative frequencies of alleles in a population’s gene pool

Selection pressure

an external force which drives changes in the frequency of traits within a population (disease, predation, etc)

Inheritance

the process by which genetic information is passed from parent to offspring

Fitness

how well an organism can survive and reproduce

Homologous structures

common ancestry, different functions

Analogous structures

different ancestry, same function

Speciation

the evolutionary process by which new, distinct species arise from an ancestral population, caused by reproductive isolation

Geographic Isolation

when two populations are separated geographically

Behavioral Isolation

when two populations that were once able to interbreed evolve in courtship rituals/behavior

Cladogram

a diagram that shows how different groups of organisms diverged from common ancestors

Natural selection

the process by which organisms with variations most suited to their environment survive and reproduce

Variation

the differences in characteristics within a population or species

Adaptation

any heritable characteristic that increases an organisms ability to survive and reproduce

Coevolution

when two or more species reciprocally affect each other's evolution

Divergent evolution

two or more related species evolve in different directions from a common ancestor, leading to new species

Convergent evolution

when two unrelated organisms independently evolve similarities when adapting to similar environments

Reproductive isolation

when a species’ gene pool gets split because members stop breeding with other members

Temporal isolation

when two or more species reproduce at different times

Trait

a specific, heritable characteristic or feature of an organism

Vestigial Structures

structures that have lost all/most of their original function through evolution

arms race

organisms develop ways to resist “weapons“, a result of evolution in response to natural selection

directional selection

occurs when individuals at one end of curve have greater fitness than anywhere else

stabilizing selection

occurs when individuals near center of curve have greater fitness than either end

disruptive selection

occurs when phenotypes at both upper and lower ends of curve have greater fitness than the middle

genetic drift

random change in allele frequency, can cause allele to become more/less common in a population

genetic bottlenecks

a change in allele frequency following dramatic reduction in the size of a population

founder effect

allele frequencies change because of a migration of a small subgroup of a pre

genetic equilibrium

when a population is not evolving, allele frequencies in its gene pool are not changing

Hardy-Weinberg Principle

allele frequencies in a population should remain constant unless one or more factors cause these frequencies to change

Nonrandom mating

a factor where genes for traits selected for/against are not in equilibrium

sexual selection

when females select mates based on size, strength, coloration, etc.

small population size

a factor where genetic drift mainly effects small populations and evolution happens more easily

gene flow

the movement of genes into or out of a population

mutations

can introduce new alleles in a gene pool, causing evolution