Glossary
Adaptive Radiation
A process where a single ancestral species rapidly evolves into multiple new species, each adapted to exploit different ecological niches.
Example:
The diverse array of cichlid fish species in Africa's Great Lakes, each with unique feeding strategies and body shapes, is a prime example of adaptive radiation.
Endemic Species
A species that is native to and found exclusively in a specific geographic area, often having a narrow ecological niche.
Example:
The lemurs of Madagascar are a classic example of endemic species, found naturally nowhere else in the world.
Equilibrium (in IBT context)
The stable point in Island Biogeography Theory where the rate of new species arriving on an island (immigration) equals the rate at which existing species disappear (extinction).
Example:
An island's bird population reaches equilibrium when the number of new species colonizing it each year is balanced by the number of species that die out.
Extinction
The complete disappearance of a species from an island or the entire planet, often due to factors like habitat loss, competition, or environmental changes.
Example:
The loss of the last remaining individuals of a unique island-dwelling snail species due to invasive predators would be an extinction event.
Generalist
A species that can thrive in a wide range of environmental conditions and utilize many different types of resources.
Example:
A coyote is a generalist predator, able to adapt to various habitats and consume a diverse diet of small animals, fruits, and even human refuse.
Geographic Isolation
The physical separation of populations by a geographic barrier, such as mountains or oceans, which prevents gene flow and can lead to speciation.
Example:
The formation of the Grand Canyon led to the geographic isolation of squirrel populations on opposite rims, eventually resulting in distinct species.
Immigration
The process by which new species arrive and establish themselves on an island or in an ecosystem from an external source.
Example:
When a storm blows a group of birds from the mainland to a previously uninhabited island, it represents the immigration of new species.
Invasive Species
A non-native species that is introduced to an ecosystem and causes ecological or economic harm by outcompeting native species or altering habitats.
Example:
The introduction of zebra mussels to the Great Lakes, where they clog pipes and outcompete native filter feeders, makes them an invasive species.
Island Biogeography Theory (IBT)
A theory explaining how the size and distance of an island from the mainland influence the number of species it can support, based on a dynamic balance between immigration and extinction rates.
Example:
According to Island Biogeography Theory, a large island like Borneo, close to a continent, tends to have higher biodiversity than a small, remote island like Easter Island.
Natural Selection
The evolutionary process where organisms better adapted to their environment tend to survive and produce more offspring, passing on advantageous traits.
Example:
In a population of peppered moths, darker individuals became more common during the Industrial Revolution because their camouflage against soot-covered trees provided a survival advantage through natural selection.
Specialist
A species that requires very specific environmental conditions or a limited range of resources to survive, making them vulnerable to change.
Example:
The koala is a specialist herbivore, relying almost entirely on eucalyptus leaves for its diet.
Species Richness
The total number of different species present in a particular ecological community or on an island.
Example:
A tropical rainforest with thousands of unique plant, insect, and animal species exhibits very high species richness.