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Eco Evo Exam 4(c.18)


Ecotone A boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a major change in the composition of species.
Interdependent communities Communities in which species depend on each other to exist.
Independent communities Communities in which species do not depend on each other to exist.
Species richness The number of species in a community.
Relative abundance The proportion of individuals in a community represented by each species.
Log-normal distribution A normal, or bell-shaped, distribution that uses a logarithmic scale on the x-axis.
Rank-abundance curve A curve that plots the relative abundance of each species in a community in rank order from the most abundant species to the least abundant species.
Species evenness A comparison of the relative abundance of each species in a community.
Simpson's index A measurement of species diversity.
Shannon's index (H') A measurement of species diversity. Also known as Shannon-Wiener index.
Keystone species A species that substantially affects the structure of communities despite the fact that individuals of that species might not be particularly numerous.
Intermediate disturbance hypothesis The hypothesis that more species are present in a community that occasionally experiences disturbances than in a community that experiences frequent or rare disturbaces.
Food chain A linear representation of how different species in a community feed on each other.
Food web A complex and realistic representation of how species feed on each other in a community.
Trophic level A level in a food chain or food web of an ecosystem.
Primary consumer A species that eats producers.
Secondary consumer A species that eats primary consumers.
Tertiary consumer A species that feeds at several trophic levels.
Omnivore A species that feeds at several trophic levels.
Guild Within a given trophic level, a group of species that feeds on similar items.
Direct effect An interaction between two species that does not involve other species.
Indirect effect An interaction between two species that involves one or more intermediate species.
Trophic cascade Indirect effects in a community that are initiated by a predator.
Density-mediated indirect effect An indirect effect caused by changes in the density of an intermediate species.
Trait-mediated indirect effect An indirect effect caused by changes in the traits of an intermediate species.
Community stability The ability of a community to maintain a particular structure.
Community resistance The amount that a community changes when acted upon by some disturbance, such as the addition or removal of a species.
Community resilience The time it takes after a disturbance for a community to return to its original state.
Bottom-up control When the abundances of trophic groups in nature are determined by the amount of energy available from the producers in a community.
Top-down control When the abundance of trophic groups is determined by the existence of predators at the top of the food web.
Alternative stable state When a community is disturbed so much that the species composition and relative abundance of populations in the community change, and the new community structure is resistant to further change.
Created by: BriawnaW



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