Exponential
growth
Bacteria grown in the lab provide an excellent example
of exponential growth. In exponential growth, the population’s growth
rate increases over time, in proportion to the size of the population.
The
key concept of exponential growth is that the population growth rate —the
number of organisms added in each generation—increases as the population gets
larger
Logistic
growth
Exponential growth is not a very sustainable state of
affairs, since it depends on infinite amounts of resources (which tend not to
exist in the real world).
Exponential growth may happen for a while, if there
are few individuals and many resources. But when the number of individuals gets
large enough, resources start to get used up, slowing the growth rate.
Eventually, the growth rate will plateau, or level off, making an S-shaped
curve. The population size at which it levels off, which represents the
maximum population size a particular environment can support, is called the carrying
capacity
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