Keystone species
Species that has an unusually large effect on its ecosystem (holds together an ecosystem).
Habitat
All of the biotic and abiotic factors in the area where an organism lives.
Ecological niche
Physical, chemical and biological factors that a species needs to survive, stay healthy and reproduce.
Competitive exclusion
When 2 species are competing for the same resources in the same ways, one species will always better suited to the niche, and the other species will be pushed into another niche or become extinct.
Ecological equivalent
Species that occupy similar niches but live in different geographical regions.
Interspecific competition
Two different species compete for the same resources.
Intraspecific competition
Members of the same species compete for resources.
Symbiosis
Close ecological relationship between two or more organisms of different species.
Mutualism
Interspecies interactions in which both species benefit.
Commensalism
Relationship between two organisms in which one organism receives ecological benefits from another while the other is neither benefited or harmed.
Parasitism
Similar to predation is that one organism benefits while the other is harmed, parasite benefits by keeping the host alive.
Population density
Measurement of the number of individuals living in a defined space.
Population dispersion
Way in which individuals of a population are spread in a certain area.
Clumped dispersion
Individuals live close together for protection, mating or access to food.
Uniform dispersion
Species live at specific distances from one another due to competition for limited resources.
Random dispersion
Species live spread randomly within an area or volume.
Factors that affect the size of population
Immigration, births, emigration, death.
Exponential growth
Occurs when the population size increases dramatically over time.
Logistic growth
Population begins with a period of slow growth, followed by exponential growth and then stable growth.
Carrying capacity
The maximum number of individuals of a particular species that the environment can normally and consistently support.
Population crash
Dramatic decline in the size of a population over a short period of time.