AP Biology Unit 7

natural selection

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals

directional selection

a single phenotype is favored, causing the allele frequency to continuously shift in one direction

diversifying / disruptive selection

extreme values for a trait are favored over intermediate values

stabilizing selection

genetic diversity decreases as the population stabilizes on a particular trait value

artificial selection

Selectively breeding organisms with specific traits in order to produce offspring with desirable traits.

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

bottleneck effect

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

gene flow

Movement of alleles into or out of a population due to the migration of individuals

polygenic traits

traits controlled by two or more genes

fitness

measure of relative reproductive success

Microevolution

Change in allele frequencies in a population over generations.

Macroevolution

large-scale evolutionary changes that take place over long periods of time

mutation

a random error in gene replication that leads to a change

adaptation

A characteristic that improves an individual's ability to survive and reproduce in a particular environment

evolution

The change in the genetic makeup of a population over time is supported by multiple lines of evidence

genetic variation

Genotypic and phenotypic differences in a population

Selective pressures

Any biotic or abiotic factors influencing survivability

analogous structures

Structures evolved independently in different species due to similar environment/selective pressures

homologous structures

Structures in different species that are similar because of common ancestry

vestigial structures

remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species

Endosymbiosis

A process by which the mitochondria and chloroplasts of eukaryotic cells probably evolved from symbiotic associations between small prokaryotic cells living inside larger cells

Hardy-Weinberg equilibrium

A model for describing and predicting allele frequencies in a non evolving population

5 requirements to use Hardy-Weinberg

-Large population (no genetic drift)
-Absence of migration (no gene flow)
-No net mutation (no modified gene flow)
-Random mating (no sexual selection)
-Absence of selection (no natural selection)

What is the H-W equation to calculate genotype/phenotype?

p2 + 2pq + q2 = 1

What is the H-W equation to calculate alleles?

p + q = 1

p in H-W equation

dominant allele

q in H-W equation

recessive allele

Speciation

process by which new species form. - occurs when groups in a species become reproductively isolated and diverge

allopatric speciation

groups from an ancestral population evolve into separate species due to a period of geographical separation

sympatric speciation

groups from the same ancestral population evolve into separate species without any geographical separation

gene pool

collection of gene variants

prezygotic barriers

prevent members of different species from mating to produce a zygote, a single-celled embryo

habitat isolation

Two species might prefer different habitats and thus be unlikely to encounter one another (prezygotic)

temporal isolation

Two species might reproduce at different times of the day or year and thus be unlikely to meet up when seeking mates (prezygotic)

behavioral isolation

Two species might have different courtship behaviors or mate preferences and thus find each other "unattractive" (prezygotic)

gametic isolation

Two species might produce egg and sperm cells that can't combine in fertilization, even if they meet up through mating (prezygotic)

mechanical isolation

Two species might have bodies or reproductive structures that simply don't fit together (prezygotic)

postzygotic barriers

keep hybrid zygotes—one-celled embryos with parents of two different species—from developing into healthy, fertile adults

Polyploidy

condition of having more than two full sets of chromosomes

Gradualism

When evolution occurs slowly over hundreds of thousands or millions of years.

punctuated equilibrium

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change