Population Growth Details

What is the formula for population doubling time?

td​ = 0.693/r

What does R₀ represent?

Average number of daughters produced per female over her lifetime.

If R₀ > 1, what happens to the population?

It grows.

If R₀ = 1?

Stable.

If R₀ < 1?

It declines.

What two life-table columns are needed to calculate R₀?

• lₓ (survivorship)

• bₓ (age-specific fecundity)

What is generation time?

Average time from the birth of parents to birth of their offspring.

What is the key difference?

• Density-dependent → Strength increases with population size

• Density-independent → Affects population regardless of density

Give examples of density-dependent factors.

Competition, predation, disease, territoriality.

Give examples of density-independent factors.

Climate, storms, frost, hurricanes, drought, wildfire.

Which four main factors determine population growth?

• Birth rate (b)

• Death rate (d)

• Immigration (i)

• Emigration (e)

Write the population growth equation including b, d, i, e.

ΔN=(b−d)+(i−e)

At what population size is logistic growth fastest?

Intermediate population sizes (N = K/2).

Why does growth slow as N approaches K?

Density-dependent factors increase (competition, predation, etc.).