Principles of Ecology and Evolution

Ecology

The study of the interactions between organisms and their environment and how these interactions determine the distribution and abundance of the organisms.

Biotic factors

Living parts of the environment, including organisms and their interactions with each other.

Abiotic factors

Non-living parts of the environment, such as sunlight, temperature, waves, salinity, and naturally occurring events.

Biosphere

The entire set of living things on Earth and the environment in which they interact.

Ecosystem

The entire habitat, including all the abiotic features and all the living species within it that interact.

Community

A group of populations, each belonging to a different species and all living in the same geographical area.

Population

A group of individuals of the same species in an area responding to the same environmental factors and freely mixing with one another.

Individual

A physiologically independent organism.

Species

A natural group of actually or potentially interbreeding individuals isolated from other such groups.

Niche

The role of an organism in a community, which can be specialized (narrow) or generalized (broad). It can also refer to the range of environments over which a species is found.

Diversity

The variety of species that live in a community or ecosystem.

Abundance

The number of individuals within a unit area or volume.

Territoriality

The defense of an area or home range by an organism.

Predation

When one organism kills and consumes another.

Optimal foraging theory

A behavioral ecology model that predicts how animals behave when searching for food, based on maximizing net energy gained.

Predator avoidance

Behaviors and adaptations that prey species have evolved to avoid being eaten by predators.

Mechanical defense

Physical structures or features that deter predators, such as spines or hard shells.

Chemical defense

Toxic compounds, distasteful secretions, or toxic metals that defend organisms against predators.

Commensalism

A relationship between two species where one benefits and the other is unaffected.

Mutualism

A relationship between two species where both benefit.

Parasitism

A relationship between two species where one