APES Unit 3


a trait that helps an organism survive and reproduce

adaptive radiation

process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms

artificial selection

selection by humans for breeding of useful traits from the natural variation among different organisms


Overall weather in an area over a long period of time


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


the struggle between organisms to survive in a habitat with limited resources


organism's role, or job, in its habitat


the process by which species gradually change over time


disappearance of a species from all parts of its geographical range


preserved remains of ancient organisms

gene flow

exchange of genes between populations

genetic drift

The gradual changes in gene frequencies in a population due to random events


change in a DNA sequence that affects genetic information

Fundemental niche

All the resources a species is capable of using

generalist species

Species with a broad ecological niche. They can live in many different places, eat a variety of foods, and tolerate a wide range of environmental conditions. Examples are flies, cockroaches, mice, rats, and human beings. Compare specialist species.

geographic isolation

separation of populations as a result of geographic change or migration to geographically isolated places


Place where an Organism lives

macro evolution

evolution on a large scale, this leads to the formation of new species

micro evolution

changes in genes over time

mass extinction

event in which many types of living things become extinct at the same time

natural selection

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

specialist species

Species with a narrow ecological niche. They may be able to live in only one type of habitat, tolerate only a narrow range of climatic and other environmental conditions, or use only one type or a few types of food.

reproductive isolation

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


formation of new species

succulent plants

plants that survive in dry climates by having no leaves, thus reducing the loss of scarce water

broadleaf evergreen

tall trees with big leaves that remain green all year

broadleaf deciduous plants

plants such as oak and maple trees that survive drought and cold by shedding their leaves and becoming dormant

coniferous evergreen plants

Cone-bearing plants (such as spruces, pines, and firs) that keep some of their narrow, pointed leaves (needles) all year.


an arid region with little or no vegetation


plant that is not rooted in soil but instead grows directly on the body of another plant


an ecosystem in which many trees grow


biome characterized by fertile soils with a thick cover of grasses


layer of permanently frozen subsoil in the tundra


a large area of level or rolling land with grass and few or no trees

theory of island biogeography

The number of species found on an island is determined by a balance between two factors: the immigration rate (of species new to the island) from other inhabited areas and the extinction rate (of species established on the island). The model predicts that

native species

species that have naturally evolved in an area

non native species

An introduced, alien, exotic, non-indigenous, or non-native specie is a species living outside its native distributional range, which has arrived there by human activity, either deliberate or accidental.

invasive species

species that enter new ecosystems and multiply, harming native species and their habitats

indicator species

species that serve as early warnings that an ecosystem is being damaged, ex trout

Keystone species

a species that influences the survival of many other species in an ecosystem

resource partitioning

in a biological community various populations sharing environmental resources through specialization thereby reducing direct competition


one organism lives on or inside another organism and harms it


a relationship between two species in which both species benefit


symbiotic relationship in which one member of the association benefits and the other is neither helped nor harmed

interspecific competition

Competition between members of different species

intraspecific competition

in a community competition for resources among members of the same species

primary succession

an ecological succession that begins in a an area where no biotic community previously existed

secondary succession

succession on a site where an existing community has been disrupted

pioneer species

first species to populate an area during primary succession


During succession, one species prepares the way for the next (and may even be necessary for the occurrence of the next)


early species inhibit colonization by others, later species established only when early species disturbed

intermediate disturbance hypothesis

The concept that moderate levels of disturbance can foster greater species diversity than low or high levels of disturbance.

precautionary principle

A guiding principle in making decisions about the environment, cautioning to consider carefully the potential consequences of actions

resource partitioning

in a biological community various populations sharing environmental resources through specialization thereby reducing direct competition