6: Populations
POPULATION ECOLOGY
Population ecology studies the dynamics of species’ populations and how these
populations interact with the environment. Most organisms live in groups
(flocks, schools, nests, etc.) and living in groups provides several advantages:
increased protection from predators, increased chances for mating, and division
of labor.
Population ecology plays an important role in the development of the field of
conservation biology, especially in predicting the long-term probability of a
species persisting in a given habitat.
Biotic Potential
Biotic potential is the maximum reproductive capacity of an organism under
optimum environmental conditions (e.g., sufficient food supply, no predators,
lack of disease). An organism’s rate of reproduction and the size of each litter are
the primary determining factors for biotic potential.
Biotic potential is often expressed as a percentage increase per year (e.g.,
“The human population increased by 3% last year.”). It can also be expressed as
the time it takes for a population to double in size (doubling time).
Significant differences in biotic potential exist between species (e.g., many
large mammals, such as humans or elephants, will typically only produce one or
two offspring per year while some small organisms, like insects, will produce
thousands of offspring per year).
Full expression of the biotic potential of an organism is restricted by
environmental resistance, any factor that inhibits an increase in the number of
organisms in the population. These limiting factors include unfavorable climatic
conditions (e.g., lack of space, light, nutritional deficiencies, and the inhibiting
effects of predators, parasites, disease organisms, or unfavorable genetic
changes).
Factors That Influence Biotic PotentialIncrease Biotic Potential Decrease Biotic Potential