AP Biology Unit 7 Evolution

abiotic factors

Nonliving components of environment.

adaptation

inherited characteristic that increases an organism's chance of survival

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

allele frequency

a measure of how common a certain allele is in the population

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

analogous structures

structures that do not have a common evolutionary origin but are similar in function

artificial selection

Breeding organisms with specific traits in order to produce offspring with identical traits.

background extinction

extinction caused by slow and steady process of natural selection

balancing selection

natural selection that maintains two or more phenotypic forms in a population

binomial nomenclature

A system for giving each organism a two-word scientific name that consists of the genus name followed by the species name

Biodiversity

the variety of life in the world or in a particular habitat or ecosystem.

Biogeography

Study of past and present distribution of organisms

biological species concept

Species is a group of populations whose members have the potential to produce fertile offspring.

biotic factors

All the living organisms that inhabit an environment

bottleneck effect

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

Carbon-14

a long-lived naturally occurring radioactive carbon isotope of mass 14, used in carbon dating and as a tracer in biochemistry.

Clade

A group of species that includes an ancestral species and all its descendants.

Cladistics

A phylogenetic classification system that uses shared derived characters and ancestry as the sole criterion for grouping taxa.

Coevolution

Process by which two species evolve in response to changes in each other

common ancestor

The shared ancestor of new, different species that arose from one population

convergent evolution

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

derived characteristics

characteristics that appear in recent parts of a lineage but not in its older members

descent with modification

each living species has descended, with changes, from other species over time

directional selection

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

disruptive selection

favors individuals at both extremes of the phenotypic range

divergent evolution

when two or more species sharing a common ancestor become more different over time

Embryology

study of embryos and their development

Endosymbiosis

A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.

evolutionary fitness

a measurement of the degree to which an organism can successfully adapt to its environment and can reproduce fertile offspring

mass extinction

A large extinction of species in a relatively short period of time

fossil record

information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived

founder effect

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

gene flow

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

genetic drift

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

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

genotype frequency

The proportion of a genotype among individuals in a population.

Gradualism

A proposed explanation in evolutionary biology stating that new species arise from the result of slight modifications (mutations and resulting phenotypic changes) over many generations.

Hardy-Weinberg equilibrium

condition in which a population's allele frequencies for a given trait do not change from generation to generation

heterozygote advantage

Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.

homologous structures

similar structures that related species have inherited from a common ancestor - may have a different function

Lamark's theory

acquired characteristics- organisms will obtain or lose characteristics based on use or disuse

Morphology

study of form

phylogentic tree

A branching diagram that represents a hypothesis about evolutionary relationships.

population dynamics

The study of how complex interactions between biotic and abiotic factors influence variations in population size.

postzygotic barriers

Barriers that prevent the hybrid zygote from becoming a fertile adult.

prezygotic barriers

A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted

punctuated equilibrium

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

radiometric dating

the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products

relative dating

Method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

sympatric speciation

The formation of new species in populations that live in the same geographic area

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.