AP BIOLOGY UNIT 7

Catastrophism

a principle that states that geologic change occurs suddenly

Uniformitarianism

is the idea that the geologic processes that operate today also operated in the past

Adaptations

traits that improve an individual's ability to survive and reproduce

Natural Selection

process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest

Homology

the quality of being similar or corresponding in position or value or structure or function

Homologous Structures

same structure but different function

Analogous Structures

species that have the same function but different structure

Convergent Evolution

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

Evolutionary Tree

A branching diagram that reflects different species that in the beginning originated from a common ancestor however as time passed they diverged

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

Microevolution

small populations are most affected, evolution on the smallest scale—a generation-to-generation change in the frequencies of alleles within a population

Geographic Variation

Differences between the gene pools of geographically separate populations or population subgroups.

Cline

A graded change in a character along a geographic axis.

Population

a group of organisms of the same species populating a given area

Gene Pool

all of the alleles in all the individuals that make up a population

Hardy-Weinberg Principle

principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change

Genetic Drift

change in the gene pool of a population due to chance

Founder Effect

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

Bottleneck Effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Gene Flow

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

Relative Fitness

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population

Directional Selection

form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

Disruptive Selection

form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

Stabilizing Selection

form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

Sexual Selection

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

Sexual Dimorphism

Differences in physical characteristics between males and females of the same species. For example, humans are slightly dimorphic for body size, with males being taller, on average, than females of the same population.

Intrasexual Selection

A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.

Intersexual Selection

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.

Heterozygote Advantage

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

Speciation

the formation of new species as a result of evolution

Macroevolution

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

Reproductive Isolation

separation of species that prevents them from interbreeding and producing fertile offspring

Hybrid

an organism that is the offspring of genetically dissimilar parents or stock

Prezygotic Barrier

a barrier that can not be able to produce fertile offspring at all

Postzygotic Barrier

Any of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults.

Allopatric Speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.

Sympatric Speciation

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

Hybrid Zone

a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

Punctuated Equilibrium

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