Populations can grow {population growth} exponentially (Malthus). At time t, number n is growth rate r times number n at previous time t - 1: n(t) = r * n(t - 1).
curve
Population growth often has S-shaped curves, with slow increase at first, then exponential growth, and then flattening rate when approaching environmental capacity. Populations typically increase until stopped by environmental shortages.
cycles
Lemming and snowshoe-hare populations have growth and decline cycles. Perhaps, crowding and competition stresses cause cycles.
Undercrowding can be population-limiting factor {Allée's principle} {Allée principle}.
To account for death from food lacks, predators, and diseases, current number n(t) is growth rate r times previous number n(t - 1) times one minus previous number {logistic difference equation}: n(t) = r * n(t - 1) * (1 - n(t - 1)).
If environment has no limiting food, predators, or disease factors, population-increase rate {biotic potential} is maximum.
If no limiting food, predators, or disease factors affect reproduction, population-increase rate {reproductive potential}|is maximum.
Populations have births per 1000 people each year {birth rate}|.
Populations have deaths per 1000 people each year {death rate}|.
Populations have number who survive per 1000 people each year {survival rate}|, which is opposite of death rate.
4-Ecology-Community-Population
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Date Modified: 2022.0225