Population Growth Models Flashcards

Which type of survivorship curve is characterized by high survival throughout life followed by rapid die-off in old age?

Answer: Type I

Type I survivorship curves (e.g., humans, elephants) show most individuals surviving to old age before experiencing a steep decline in numbers.

A population modeled with discrete time steps uses the geometric growth equation N(t+1) = λN(t). When is this population declining?

Answer: λ < 1

When λ (the finite rate of increase) is less than 1, each time step produces fewer individuals, so the population shrinks toward extinction.

Stochastic models of population growth are most important for predicting extinction risk in:

Answer: Very small populations where chance events matter greatly

In small populations, random variation in birth, death, and environmental conditions can drive extinction even when deterministic models predict persistence.

The net reproductive rate R₀ = 1 means a population is:

Answer: Exactly replacing itself each generation

R₀ = 1 indicates each individual replaces itself exactly once per generation, meaning the population is stable (neither growing nor shrinking).

Which of the following is a density-independent factor affecting population growth?

Answer: A sudden volcanic eruption

Volcanic eruptions (and other natural disasters) affect populations regardless of their density, making them density-independent limiting factors.

In the logistic model, negative feedback on growth becomes strongest when:

Answer: N approaches K

As N approaches K, the term (K-N)/K approaches zero, creating the strongest negative feedback and nearly stopping population growth.

A population ecologist calculates r = 0.3/year for a species. This value represents:

Answer: The per capita rate of increase under current conditions

r, the intrinsic rate of natural increase, is the per capita rate of population change (births minus deaths per individual) under specific environmental conditions.