Biogeography Definitions

Caitlin Dempsey


Biogeography is a field of geography that studies the distribution of species and the geographic factors that influence species and the habitats they occupy.

Here are some common biogeography terms.

Allen’s rule

Allen’s rule is a principle in biogeography that states that animals adapted to cold climates will have shorter limbs and body appendages, while animals adapted to warmer climates will have longer limbs and appendages, to regulate body temperature more efficiently — short limbs reduce surface area to minimize heat loss in cold climates, while long limbs increase surface area to maximize heat loss in warm climates.

Aphotic zone

The aphotic zone is the portion of a lake or ocean where there is little or no sunlight, usually because it is too deep for sunlight to penetrate, and therefore, photosynthesis cannot occur. It is contrasted with the photic zone, which is the area of water that receives enough sunlight for photosynthesis to occur.

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A biome is a large community of vegetation and wildlife adapted to a specific climate. Examples include the desert, tundra, and rainforest biomes.

The Killpecker Sand Dunes in the Red Desert of southwest Wyoming. Photo: Carol Highsmith, public domain via
The Killpecker Sand Dunes in the Red Desert of southwest Wyoming. Photo: Carol Highsmith, public domain via

Biotic Province

A region inhabited by life forms of common ancestry, bounded by barriers that prevent the spread of the distinctive kinds of life to other regions and the immigration of foreign species.

Biotic Interchange

This term describes when two previously separated biotas begin to merge due to the removal of a physical barrier, often leading to significant changes in biodiversity.

Boreal zone

The Boreal Zone is a biogeographical designation for high latitude regions of the Northern Hemisphere that are characterized by the presence of coniferous forests, including the taiga. Boreal climates are generally cold, with winter temperatures often dropping below freezing, and short, cool summers.

A shaded relief map showing the extent of boreal vegetation in Canada.
Map of boreal zone vegetation in Canada. Map: Lambert Conformal Conic map projection, Caitlin Dempsey. Boreal data: Natural Resource Canada, 2009.

Carrying capacity

Carrying capacity refers to the maximum number of individuals of a particular species that a specific environment can sustainably support, given the food, habitat, water, and other necessities available in the environment. It is a key concept in population ecology and environmental science.

Convergent evolution

Convergent evolution is the process in which organisms that are not closely related independently evolve similar traits or characteristics as a result of having to adapt to similar environments or ecological niches, rather than from a close genetic relationship.

An example of convergent evolution is that despite looking similar, New World vultures (found in the Americas) evolved separately from Old World vultures (found Europe, Asia, and Africa).

Three turkey vultures with red heads sitting on the horizontal part of a light pole.
Turkey vultures in the Santa Cruz Mountains. Photo: Caitlin Dempsey.


A region of transition between two biological communities, often characterized by increased species diversity and density.


Endemism refers to species that are native to a single defined geographic location, such as an island, a country, a habitat type, or other defined zone.


Dispersal is the movement of organisms from their birthplace to their breeding site (‘natal dispersal’), as well as the movement from one breeding site to another (‘breeding dispersal’).

Edge species

Edge species are organisms that prefer or are restricted to living near the boundaries of two different habitats, often created by habitat fragmentation or natural environmental transitions.

Fauna and flora

The animals (fauna) and plants (flora) of a particular region, habitat, or geological period.

Habitat fragmentation

Habitat fragmentation is the process by which large, continuous habitats are broken down into smaller, isolated patches, often due to human activities like deforestation, urban development, or agriculture.

Invasive Species

Invasive species are species that are not native to a specific location and have a tendency to spread, causing damage to the environment, human economy, or human health.

Island Biogeography

This is a study within biogeography that tries to establish and explain the factors that affect the species richness of a specific community isolated from other geographic areas by being surrounded by a body of water.


Migration is the seasonal movement of animals from one region to another for feeding or breeding.


Mutualism is the relationship between two species of organisms in which both benefit from the association.


Paleobiogeography is a field of studies the distribution of ancient organisms and their change over time, usually using fossil evidence.

Photic zone

The photic zone is the area in a body of water that receives enough sunlight for photosynthesis to occur.

A fish peeking out from among kelp underwater.
The kelp forests found along the California coast grow in the photic zone in the Pacific Ocean. Photo: Caitlin Dempsey.


A group of individuals of the same species that live in the same area and interbreed.


Also known as botanic geography, phytogeography is the branch of biogeography that is concerned with the geographic distribution of plant species.


The area where a particular species can be found during its lifetime.

Realized niche

The actual space that an organism inhabits and the resources it can access as a result of limiting pressures from other species (predation, competition).

Scurry zone

The scurry zone is a small area around a protective shrub where small rodents and birds will emerge into to forage in the surrounding grassland.

A picture of a shrub surrounded by a bare zone of vegetation and then grassland in the foreground.
A scurry zone between shrubs and native grasses and wildflowers in Edgewood Park and Nature Preserve, Woodside, California. Photo: Caitlin Dempsey.


The evolutionary process by which a new species evolves over time and geography.


Vicariance is when a geographical barrier splits the range of an individual taxon, or a whole biota. This geographic separation results the evolution of those split groups of individual into new variations or species.

Wallace Line

Named after Alfred Russel Wallace, the Wallace Line is a boundary that separates the ecozones of Asia and Wallacea, a transitional zone between Asia and Australia.


This is the branch of biogeography that is concerned with the geographic distribution of animal species.

More geography definitions

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.