AP Bio Unit 7 Essential Terms

Convergent evolution

Species that live in similar environments that evolve similar adaptations but do not have a common ancestor

Differential reproductive success

When individuals with phenotypes that give them a survival advantage are more likely to survive and reproduce.

Directional Selection

One end of the range of phenotypes is favored by natural selection, causing the frequency of that phenotype to increase over time

Stabilizing selection

The intermediate phenotype is favored and extreme phenotypes are selected against.

Disruptive selection

Individuals on both ends of the phenotypic ranges are likelier to survive and reproduce than individuals with an intermediate phenotype.

Artificial selection

Selectively breeding domesticated plants or animals to produce populations with desired traits.

sexual selection

When individuals with certain characteristics are more likely to attract mates than other individuals

gene flow

transfer of alleles from one population to another, caused by the migration of individuals into a population.

genetic drift

random loss of alleles in a population, more likely to occur in smaller populations

bottleneck effect

When the size of the population is greatly reduced for one or more generations, reducing number of different alleles.

founder effect

When members of a larger population start a new population, decreasing genetic diversity

speciation

evolution of new species

adaptive radiation

The evolution of organisms into separate species that occupy different ecological niches.

Gradualism

The slow and constant pace of speciation is due to a stable environment and less selective pressure on populations.

Punctuated equilibrium

Long periods of stability in species are interrupted by periods of rapid evolution.

Allopatric speciation

Larger populations become geographically separated, and the smaller subgroups diverge and become separate species.

Sympatric speciation

Speciation occurs in the same geographic area and is due to prezygotic and postzygotic reproductive barriers.

Habitat isolation

When organisms live in different habitats and do not come in contact with each other, resulting in no mating/formation of a zygote

Temporal isolation

When organisms live in the same habitat but have different times for being active or different breeding seasons.

Behavioral isolation

Some species will interbreed only with others who perform compatible mating behaviors, such as mating calls or dances.

Mechanical isolation

If the sexual organs of the organisms are incompatible and prevent the transfer of gametes

Gametic isolation

If two organisms can successfully copulate ,but have incompatible gametes

Reduced hybrid viability

When two organisms that can form a zygote but the zygote does not survive till adulthood or age of reproduction

Reduced hybrid fertility

When the zygote survives till adulthood but is infertile

Hybrid breakdown

When the zygote is viable and fertile, future generations of the hybrid become weaker and less robust and eventually die out.