Group of interacting populations that live in the same geographic area at the same time

Biological community and all the nonliving factors that affect it

Large group of ecosystems that share the same climate and have similar types of communities

Relatively thin layer of Earth and its atmosphere that supports life

Any living factor in an organism's environment

Any nonliving factor in an organism's environment, such as soil, water temperature, and light availability

Number of different species living in a specific area

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

The variety of genes within a given species

The number and relative abundance of species in a biological community.

The variety of ecosystems within a given region

Nonnative species deliberately or accidentally introduced into a new habitat

Species that normally live and thrive in a particular ecosystem

Species that is found in only one area; such species are especially vulnerable to extinction

Species that serve as early warnings that a community or ecosystem is being degraded

A species whose numbers are so small that the species is at risk of extinction