Exam 3 Study Guide - Community Structure and Dynamics

A comprehensive set of flashcards covering key concepts in community structure and dynamics from the study guide.

Community Structure

The identities and abundances of species within a given area, often referred to as community composition.

Species Richness

The total number of different species present in a community.

Species Abundance

The number of individuals of each species in a community.

Relative Abundance

The proportion of individuals of a particular species relative to the total number of individuals in the community.

Species Evenness

The degree to which the abundances of different species in a community are equal.

Species Diversity

A measure incorporating both species richness and evenness (e.g., Shannon's index).

Alpha Diversity

Diversity within a specific local area or habitat.

Beta Diversity

The change in species composition (identity and abundance) across different locations or environments.

Dominant Species

Species that are particularly abundant or have a high biomass in a community.

Rare Species

Species with low abundance in a community.

Direct Interactions

Interactions between two species (e.g., predation, competition, mutualism).

Indirect Interactions

Interactions where one species affects another through a third species (e.g., trophic cascades, indirect mutualism).

Trophic Levels

The position an organism occupies in a food chain (e.g., primary producer, herbivore, carnivore).

Food Chain

A linear sequence of organisms where each is eaten by the next.

Keystone Predation

Predation by a species that maintains species diversity in a community by preventing competitive exclusion by other species.

Top-Down Control

Community structure is primarily determined by the effects of consumers on lower trophic levels.

Bottom-Up Control

Community structure is primarily determined by the availability of resources at the base of the food web.

Regional Species Pool

The entire set of species that could potentially inhabit a community in a given region.

Dispersal

The movement of individuals from one location to another, often a random process.

Environmental Filters

Abiotic conditions that determine which species from the regional pool can survive and establish in a particular community.

Species Sorting

Influences which species persist and their relative abundances after initial establishment.

Ecological Succession

Changes in species composition and abundance in a community over time.

Disturbance

An event that removes or changes the abundance of species in a community.

Primary Succession

Succession that occurs on newly exposed or formed land where no soil exists.

Secondary Succession

Succession that occurs after a disturbance removes some or most of the existing community but leaves the soil intact.

Chronosequence

A series of sites of different ages that can be used to study successional patterns over time.

r-strategists

Species that are good colonizers, have rapid growth rates, and are typically short-lived.

K-strategists

Species that are competitive, have slower growth rates, and are long-lived.

Climax Community

The theoretical endpoint of succession, characterized by a relatively stable species composition.

Landscape Ecology

The study of how spatial heterogeneity in resources and environmental conditions influences ecological processes across larger scales.

Patches

Distinct, relatively homogeneous areas within a landscape.

Matrix

The dominant background habitat type in a landscape that can act as a barrier to dispersal.

Boundary (Edge)

The zone of transition between a patch and the matrix, often with distinct environmental conditions.

Corridor

A linear feature that connects patches, facilitating the movement of organisms.

Island Biogeography Theory

The theory that species richness on islands is determined by a balance between immigration of new species and extinction of existing species.

Equilibrium Number of Species

The stable number of species on an island when immigration rate equals extinction rate.

Metapopulation

A group of spatially separated subpopulations of a single species that interact via dispersal.

Source-Sink Metapopulation

Dispersal primarily occurs from high-quality source patches to low-quality sink patches.

Classic Metapopulation (Levins Model)

Patches of similar quality with moderate dispersal rates between them, allowing for local extinctions and recolonization.

Metapopulation Stability

The persistence of the metapopulation as a whole depends on colonization of empty patches and extinction of occupied patches.