Populations of some species are prone to extinction for two reasons

1. The landscapes they live in are patchy (making dispersal between populations difficult).

2. Environmental conditions often change in a rapid and unpredictable manner.

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#XL - T Zoology

Population sizes at various times

N_t = N₀e^rt

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#XL - T Zoology

Per capita rate of increase, r, related to the net reproductive rate, R₀

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r, is affected by organismal size and generation time.

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#XL - T Zoology

When conditions are optimal for the population, r is at its maximum rate and is called the intrinsic rate of increase (_rmax).

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#XL - T Zoology

r<0, the population decreases

r=0, the population remains constant

r>0, the population increases