AP Biology Unit 7 Vocabulary (copy)

Speciation

The process by which new species evolve

Genetic drift

A change in allele frequencies that is due to chance events.

Bottleneck

A dramatic reduction in population size that increases the likelihood of genetic drift

Gene flow

The chance in frequencies of alleles as genes from one population are incorporated into those from another.

Mutation

A random event that can cause changes in allele frequencies. It is always random with respect to which genes are affected, although the changes in allele frequencies that occur as a result of the mutation may not be.

Natural selection

The process by which characters or traits are maintained or eliminated in a population based on their contribution to the differential survival and reproductive success of their "host" organisms.

Variation

Natural selection to occur, a population must exhibit phenotypic variance-in other words, differences must exist between individuals, even if they are slight.

Heritability

Parents must be able to pass on traits that are under natural selection. If trait cannot be inherited it cannot be selected for or against.

Reproductive success

A measure of how many surviving offspring one produces relative to how many the other individuals in one's population produce.

Adaptation

A trait that, if altered, affects the fitness of the organism. It is the result of natural selection and can include not only physical traits such as eyes and fingernails but also the intangible traits of organisms, such as lifespan.

Directional selection

Occurs when members of a population at one end of a spectrum are selected against and/or those at the other end are selected for.

Stabilizing selection

This describes selection for the mean of a population for a given allele; has the effect of reducing variation in a given population

Disruptive selection

Selection is disruptive when individuals at the two extremes of a spectrum of variation do better than the more common forms in the middle.

Sexual selection

The process by which certain characters are selected for because they aid in mate acquisition.

Within sex competition

Competition for mates between members of the same sex.

Choice

Refers to the selection of mates by one sex (in mammals, it is usually females who exercise choice over males.)

Honest indicators

Sexually selected traits that are the result of female choice and signal genetic quality.

Artificial selection

When humans become the agents of natural selection (breeding of dogs)

Coevolution

The mutual evolution between two species, which is exemplified by predator-prey relationships.

Convergent evolution

Two unrelated species evolve in a way that makes them more similar. They both respond the same way to some environmental challenge, bringing them closer together.

Convergent characters

Characters are convergent if they look the same in two species, even though the species do not share a common ancestor.

Divergent evolution

Two related species evolve in a way that makes them less similar, sometimes causing speciation.

Parallel evolution

Similar evolutionary changes occurring in two either related or unrelated species that respond in a similar manner to a similar environment.

Sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

Balanced polymorphism

When there are two or more phenotypic variants maintained in a population

Species

A group of interbreeding (or potentially interbreeding) organisms.

Allopatric speciation

Interbreeding ceases because some sort of barrier separates a single population into two (an area with no food, a mountain, etc.). The two populations evolve independently, and it they change enough, then, even if the barrier is removed, they cannot interbreed.

Sympatric system

Interbreeding ceases even though no physical barrier prevents prevents it.

Polyploidy

A condition in which an individual has more than the normal number of sets of chromosomes.

Adaptive radiation

A rapid series of speciation events that occur when one or more ancestral species invades a new environment.

Hardy-Weinberg equilibrium

A special case where a population is in stasis, or not evolving.

Homologous characters

Traits are said to be homologous if they are similar because their host organism arose from a common ancestor.

Embryology

The study of embryonic development.

Ontogeny

The development of an individual

Phylogeny

The evolution history of a species

Vestigial character

Characters that are no longer useful, although they once were.

Fossil record

The physical manifestation of species that have gone extinct.

Microevolution

Evolution at the level of species and population

Macroevolution

the big picture of evolution, which includes the study of evolution of groups of species over very long periods of time.

Gradualism

The theory that evolutionary change is a steady, slow process.

Punctuated equilibria model

Theorizes that evolutionary change occurs in rapid bursts separated by large periods of stasis (no change).

Photosynthesis

The process by which plants generate energy from light and inorganic raw materials. This occurs in the chloroplast and involves two stages: the light-dependent reactions and the light-independent reactions.

Heterotroph theory

Theory that posits that the first organisms were heterotrophs (organisms that cannot produce their own food).

Heterotroph

An organism that must consume other organisms to obtain nourishment. They are the consumers of the world.

Endosymbiotic theory

Proposes that groups of prokaryotes associated in symbiotic relationships to form eukaryotes (mitochondria and chloroplasts)