BIOS 230: Community Structure and Ecological Succession

Flashcards covering vocabulary terms related to community structure, food webs, and ecological succession.

Food Web

An abstract representation of feeding relationships within a community.

Links

Arrows from one species to another and indicate flow of energy.

Basal species

Feed on no other species but are fed upon by others.

Intermediate species

Feed on other species, and they themselves are prey of other species.

Top predators

Prey on intermediate and basal species.

Trophic Levels

Broader categories that represent general feeding groups based on the source from which they derive energy.

Autotrophs (producers)

Organisms that can produce their own food.

Heterotrophs (consumers)

Organisms that cannot produce their own food, eat other organisms.

Food Chain

Linear pathway of energy flow in a food web.

Grazing food chain

Lowest trophic level is producers, e.g., plants; energy source: sunlight (photosynthesis).

Detrital (or detritus) food chain

Starts with dead organic matter (detritus) and involves organisms that feed on dead organic materials (detritivores); energy source: Dead organic plants/animals.

Keystone Species

Has impact on community/ecosystem that’s disproportionately to their abundance.

Keystone Predation

The predator enhances one or more inferior competitors by reducing the abundance of the superior competitors.

Direct effects

Directly influence interactions with prey.

Indirect effects

Occur when one species does not interact with a second species directly, but instead influences a third species that does directly interact with the second species.

Apparent Competition

Indirect negative interaction between two species that share common predator, where an increase in the abundance of one prey species leads to a decrease in the abundance of the other prey species.

Bottom-up Control

The structure of food chains and food webs is controlled (limited) by the productivity and abundance of populations in the lower trophic level (producers).

Top-down Control

The predator populations (top trophic level) control the abundance of prey species, and the prey of the prey, and so on.

Succession

Gradual and (seemingly) directional change in community structure through time.

Chronosequences

Groups of sites used to compare communities undergoing succession; different sites in different stages of succession

Sere

The sequence of communities from grass to shrub to forest.

Pioneer Species

Early successional species; often r-strategists; usually have high growth rates, smaller size, high degree of dispersal, and high rates of per capita population growth.

Late successional species

Often K-strategists; usually have lower rates of dispersal and colonization, slower per capita growth rate, and they are larger and longer-lived.

Primary succession

Occurs on a site previously unoccupied by a community; e.g., after glacier retreat, or newly formed volcanic rock.

Secondary succession

Previously occupied (vegetated) sites area is re-colonized after a disturbance.