Population Growth Models Flashcards

In a source-sink metapopulation model, a 'sink' habitat is best described as one where:

Answer: Local deaths exceed local births and the patch requires immigration to persist

A sink is a habitat patch where death rates exceed birth rates (r < 0 locally), so it relies on immigration from productive 'source' patches to maintain its population.

Which population growth model assumes that the per capita growth rate decreases as a linear function of population size?

Answer: Logistic (Verhulst) model

The logistic model assumes a linear negative relationship between population density and per capita growth rate, dropping from r at N=0 to 0 at N=K.

A conservation biologist estimates a minimum viable population (MVP) of 500 individuals for a large mammal. This threshold is primarily set to minimize risk from:

Answer: Genetic drift, inbreeding, and demographic stochasticity

MVP estimates typically account for genetic erosion (drift, inbreeding depression) and random demographic variation that can doom very small populations even in suitable habitat.

Environmental stochasticity in population models refers to:

Answer: Year-to-year variation in environmental conditions affecting population rates

Environmental stochasticity is random temporal variation in habitat conditions (climate, food availability) that causes the whole population's vital rates to fluctuate together.

The Ricker model, commonly used in fisheries, produces population cycles and chaos at high values of which parameter?

Answer: The intrinsic growth rate r

At high values of r, the Ricker model (a discrete-time model) transitions from stable equilibrium to oscillations to chaos, making prediction difficult.

When ecologists speak of 'time lags' in density-dependent population models, they are referring to:

Answer: Delayed regulatory response where current growth depends on past density

Time-lagged models include a delay so that population growth rate responds to density at some past time τ rather than current density, which can cause oscillations.

Which of the following best explains why island populations often show boom-bust dynamics compared to mainland populations of the same species?

Answer: Small island populations are more vulnerable to stochastic events and lack rescue immigration

Small island populations experience stronger demographic and environmental stochasticity, and geographic isolation prevents mainland immigration from buffering local declines.