Population Studies

Abstract

The growth of populations is governed by various factors. Among these are environmental factors, the density of the population, etc. The goal of this article is to describe the different strategies employed by organisms in the struggle for life.

How Popualation Growth is Controlled

In 1798, Malthus predicted that populations would grow exponentially. However, in natural populations there are external factors that control the growth of a population. Population biologists have distinguished two extremes, the r-strategist and the K-strategist. In reality, most populations are some combination of these.

The r-strategist

An r-strategist is characterized by:

1. Small parental investment in the young. The prenatal period is short and postnatal care is minimal. To compensate, an r-strategist produces a large number of offspring, most of whom will not survive long enough to reproduce.
2. The ability to rapidly exploit unpredictable environment opportunities. An example of this is, given a small patch of disturbed soil, dandelions can rapidly fill up the area.

The K-strategist

A K-strategist is characterized by:

1. Large parental investment in their young. K-strategists reproduce slowly, with long gestation periods, to permit the young to develop more in the womb. After birth, the young are tended until they can be reasonably expected to care for themselves.
2. The ability to exploit stable environmental situations. Once the population of a K-strategist has reached the carrying capacity of its environment, the population size stays relatively constant.

Bibliography

Yeargers, Edward K., Ronald W. Shonkwiler, James V. Herod, An Introduction to the Mathematics of Biology With Computer Algebra Models, Birkhauser, Boston, 1996.