Community Ecology, Biodiversity, and Disruptions

Community

A group of populations of different species living closely and capable of interacting.

Habitat

A place or part of an ecosystem occupied by an organism.

Ecological niche

The role and position a species has in its environment.

Fundamental niche

The niche potentially occupied by a species if there were no limiting factors.

Realized niche

The portion of the fundamental niche that the species actually occupies.

Interspecific interactions

Interactions of individuals from one species with individuals of another species.

Competition

A -/- relationship where individuals of different species compete for limited resources.

Predation

A +/- relationship where one species (predator) kills and eats the other species (prey).

Herbivory

A +/- relationship where one organism eats part of a plant or alga.

Symbiosis

When 2 or more species live in direct contact with one another.

Parasitism

A (+/-) interaction where one organism benefits while the other is harmed.

Mutualism

A (+/+) interaction where both organisms benefit from the relationship.

Commensalism

A (+/0) interaction where one organism benefits and the other is not affected.

Facilitation

A (+/+ or 0/+) interaction where one species has a positive effect on another's survival without intimate association.

Species diversity (biodiversity)

The variety of different organisms within a community.

Species richness

The number of different species in a community.

Relative abundance

The proportion each species represents of all the individuals in the community.

Simpson’s diversity index

A calculation of diversity based on species richness and relative abundance.

Keystone species

Species that play a critical role in maintaining the structure of an ecosystem.

Trophic cascade

When the removal of keystone species leads to significant changes in ecosystem structure.

Disturbance

An event that changes a community by removing organisms or altering resource availability.

Ecological succession

The gradual process by which species composition of a community changes after a disturbance.

Primary Succession

Succession that begins without soil, using pioneer species to create it.

Secondary Succession

Succession that occurs following a disturbance where soil remains intact.

Habitat loss

The single greatest threat to biodiversity, often due to agriculture and urbanization.

Overharvesting

The process where organisms are harvested faster than their populations can rebound.

Global change

Alterations to climate and ecological systems that reduce Earth's capacity to sustain life.

Mass extinction

A significant decrease in biodiversity, currently believed to be happening due to human actions.

Biogeographical factors

Large-scale factors, such as latitude and area, that contribute to the diversity observed in species.

Cryptic coloration

camouflage

Batesian mimicry:

harmless species mimics a harmful one

Mullerian mimicry

two or more bad-tasting species resemble each other

Keystone Species: Coral

Coral reefs serve as a keystone species because many other organisms rely upon it as a source of food and shelter

Keystone Species: honey bees

Bees are a keystone species because they serve as pollinators

Pioneer species

the first to grow after the disturbance

Climax community

stable plant community representing the final stage of succession