Chapter 38: Communities and Ecosystems

niche

includes all of the resources required for survival, growth, and reproduction

Competition

harms both participants. occurs when two or more species try to obtain the same limited resource.

Mutualism

both species benefit, relationship improves the fitness of both partners. +/+

Commensalism

benefits one and does not affect the other, one species benefits, but the other is not significantly affected. +/o

Symbiotic

relationships occur when two species share a close (and often lifelong) relationship in which one typically lives in or on the other.

competitive exclusion principle

the species that acquires more of the resources will eventually "win," while the less successful species will die out.

Resource partitioning

the division of resources to avoid interspecific competition for limited resources in an ecosystem

parasitism

harms onr and benifits another, one species benefits at the expense of another +/-

Herbivores

consume plants.

Predators

animals that kill and eat other animals

prey

An organism that is killed and eaten by another organism

Coevolution

two species evolve together

species richness

is the total number of species occupying a habitat

Species evenness

describes the proportion of a community that each species occupies.

Succession

gradual change in a community's species composition

Primary succession

occurs in an area where no community previously existed
(such as following a volcanic eruption).

Pioneer species

the first to colonize the new area.

Secondary succession

occurs when a community is disturbed but not destroyed.

climax conditions

diversity and composition are stable

trophic level

describes its position in the food chain. Dictates organisms for energy aqured from food.

Primary producers

use energy from an inorganic source (such as sunlight) to produce organic molecules.

Consumers/ heterotrophs

obtain energy from eating producers or other consumers

detritus

dead tissue and organic wastes such as feces.

Decomposers

return the inorganic nutrients in detritus to the environment

food web

realistic depiction of the feeding relationships in a community

Keystone species

central to maintaining diversity in a community.

Primary production

energy trapped by producers and stored as food molecules that consumers can eat.

biomagnification

a chemical becomes most concentrated in organisms at the highest trophic levels

Nitrogen fixation

microbes convert N_2 to a source that cycles through producers and consumers

denitrification

bacteria convert NH4 and NO3 back to N2 and release it to the atmosphere

eutrophication

excessive nutrients ultimately lead to oxygen-poor water that cannot sustain much life