Community Ecology PT. BIO 2207

A set of vocabulary flashcards covering the fundamental concepts of community ecology, including diversity indices, trophic structures, succession, and habitat dynamics.

Species Diversity

The variety of different kinds of organisms that make up a community.

Species Richness

The total number of different species in the community.

Relative Abundance

The proportion each species represents of the total individuals in the community.

Shannon diversity ($H$)

A widely used index of diversity where $S$ is species richness and $p_i$ is the proportion of each species in the community.

Trophic Structure

The feeding relationships between organisms that determine the organization of a community.

Trophic Level

The position an organism occupies within an ecological pyramid or food pyramid.

Food Chain

The linear transfer of energy and matter from organism to organism up the trophic levels.

Primary Producers

Also known as autotrophs, these organisms make their own food through photosynthesis and make up the first trophic level.

Primary Consumers

Herbivores that directly consume primary producers.

Apex Predator

The consumer located at the top of the food chain.

Decomposers

Organisms that feed on dead animal and plant remains, recycling material into nutrients like carbon and nitrogen.

Food Web

A holistic, non-linear model which shows the interconnected feeding relationships of a community.

Energetic Hypothesis

The suggestion that the length of a food chain is limited by the inefficiency of energy transfer, with only about $10\,\%$ of energy converted to the next higher level.

Biomass

The sum weight of all individuals in a population.

Dynamic Stability Hypothesis

The suggestion that long food chains are less stable than short chains because population fluctuations at lower levels are magnified at higher levels.

Community Structure

The composition of a community measured by species richness and species evenness and how species interact.

Resilience

A community's ability to adapt to change, which increases when more ecological diversity and niches exist.

Species Evenness

A measure of how close in number each species is in a community.

Bottom-up Model

A model ($N \rightarrow V \rightarrow H \rightarrow P$) where mineral nutrients ($N$) control plant numbers ($V$), which then control herbivore ($H$) and predator ($P$) numbers.

Top-down Model

Also called the trophic cascade model ($N \leftarrow V \leftarrow H \leftarrow P$), it postulates that predation is the primary factor that controls community organization.

Community Dynamics

The changes to a community's structure and composition over time.

Nonequilibrium Model

A model proposing that communities constantly change following a disturbance rather than staying in a constant state.

Intermediate Disturbance Hypothesis

Suggests that moderate levels of disturbance create conditions that foster greater species diversity than low or high levels of disturbance.

Ecological Succession

The process of gradual change in the type and number of species of a community over time, often following a disturbance.

Primary Succession

Succession that occurs in new habitats that have not yet been colonized and where soil has not yet formed.

Pioneer Species

The first species to colonize a barren ecosystem, such as bacteria, lichen, fungi, and moss.

Secondary Succession

Succession that occurs where an existing community has been removed by a disturbance but the soil is left intact.

Climax Community

An ecological community in the final stage of succession in which the organisms remain stable and exist in balance.

Habitat Fragmentation

The discontinuance of a natural habitat, often caused by humans, which decreases population size and biodiversity.

Edge Effects

The changes in community structure that occur at the boundary between two habitats, often resulting in greater biodiversity.

Ecotone

A zone of transition between two communities or ecosystems.