Community Ecology and Species Interactions

Community

A group of different species living and interacting in the same area at the same time.

Community Ecology

The study of how species interact and how communities are structured and function.

Species Richness

The number of different species present in a community.

Latitudinal Diversity Gradient

Species richness increases closer to the equator and decreases toward the poles.

Species Diversity

A measure that includes both the number of species and how evenly individuals are distributed.

Evenness

How similar the population sizes of different species are in a community.

Shannon Diversity Index

A formula used to calculate species diversity using the proportion of each species.

Keystone Species

A species that has a very large impact on its community relative to its abundance.

Habitat Engineer

An organism that physically changes the environment and creates new habitats.

Ecological Niche

The role of a species in its environment, including resource use and interactions.

Fundamental Niche

The full range of conditions a species could use without competition or predators.

Realized Niche

The actual conditions a species uses in nature, limited by competition and predation.

Competition

An interaction where organisms compete for the same limited resource.

Competitive Exclusion Principle

Two species with identical niches cannot coexist; one will outcompete the other.

Resource Partitioning

The division of resources by species to reduce competition and allow coexistence.

Character Displacement

Evolutionary changes in traits that reduce competition between similar species.

Disturbance

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

Succession

The gradual change in species composition of a community over time after a disturbance.

Primary Succession

The development of a community in an area with no prior life and no soil.

Secondary Succession

The rebuilding of a community after a disturbance where soil remains.

Pioneer Species

The first species to colonize a new or disturbed area.

Predation

An interaction where one organism kills and eats another.

Herbivory

An interaction where an organism eats parts of plants.

Parasitism

An interaction where one organism benefits and the other is harmed but not killed immediately.

Mutualism

An interaction where both species benefit.

Commensalism

An interaction where one species benefits and the other is unaffected.

Aposematic Coloration

Bright colors that warn predators an organism is toxic or harmful.

Cryptic Coloration

Camouflage that helps an organism avoid being seen by predators.

Mimicry

When one species resembles another species for protection.

Batesian Mimicry

A harmless species mimics a harmful species to avoid predation.

Müllerian Mimicry

Two harmful species resemble each other to reinforce warning signals.

Physical Defense (Plants)

Structural features like thorns or tough leaves that prevent herbivory.

Chemical Defense (Plants)

Toxic or bad-tasting chemicals that deter herbivores.

Secondary Metabolites

Chemicals not used for basic metabolism that function mainly in defense.

Detoxification

The process by which herbivores break down and eliminate plant toxins.

Symbiosis

A close, long-term interaction between organisms of different species.

Trophic Mutualism

A mutualism where species exchange or share food resources.

Defensive Mutualism

A mutualism where one species protects another in exchange for a benefit.

Dispersive Mutualism

A mutualism where one species helps another reproduce.

Obligate Mutualism

A mutualism where both species depend on each other to survive.

Facultative Mutualism

A mutualism where species benefit but can survive independently.