11. Populations, Communities, and Ecosystems Free Online FlashCards

What is an ecosystem?

An ecosystem is a community of organisms together with its nonliving, or abiotic, environment.

How is population density calculated?

Density = number of individuals ÷ area or volume sampled.

What is the mark–recapture population estimate?

N̂ = (M × C) ÷ R, where M is initially marked, C is later captured, and R is marked individuals recaptured.

What four processes change population size?

ΔN = (B + I) − (D + E): births and immigration add individuals, while deaths and emigration remove them.

What is carrying capacity?

Carrying capacity (K) is the approximate maximum population size an environment can sustain under particular conditions.

How do density-dependent and density-independent factors differ?

Density-dependent factors become stronger as density rises; density-independent factors affect populations regardless of density.

What does competitive exclusion predict?

The competitive exclusion principle predicts that species with identical limiting resource requirements cannot coexist indefinitely in a stable environment.

What distinguishes a fundamental niche from a realized niche?

A fundamental niche is the full range a species could theoretically use; its realized niche is what it actually occupies after interactions and limits.

How do species richness and evenness differ?

Species richness is the number of species; species evenness describes how similar their abundances are.

How do energy and matter differ in ecosystems?

Energy flows through ecosystems and is eventually released as heat, whereas matter is continually recycled among organisms and the environment.

What does an arrow in a food chain represent?

The arrow points from the organism being consumed to the organism that obtains energy by consuming it.

What is the relationship between GPP and NPP?

NPP = GPP − producer respiration. It is the energy stored as new producer biomass and available to consumers and decomposers.