Activity 4: Background Information
Limiting Factors
In nature, a population varies between some upper and lower limit, depending upon the birthrate, death rate, immigration, and emigration rates. (These are explained in the BioTalk.) Each population is like a swing moving back and forth between two points, or between a high and low number. The lower limit, of course, is zero. At that point the population no longer exists. What is the upper limit on population size?
It depends on the environment and everything that surrounds and affects an organism. The environment may slow the individual’s growth, may kill the individual, or may stimulate the individuals growth and reproduction. In any case, the environment affects individuals and, thus, the ultimate size of a population.
The environment is made up of two parts: the biotic and the abiotic. Both biotic
and abiotic factors affect the size of a population. Any biotic or abiotic factor that
can slow the growth of a population is called a limiting factor. The climate is a group
of limiting factors that affect all plant and animal life. Water is another important limiting factor. All living organisms need water. Another abiotic limiting factor is space. The amount of space needed by a single organism is tied in part to a biotic factor–the availability of food energy. |