Growth Curve Modeling: Theory and Applications

10

FUNDAMENTALS OF POPULATION DYNAMICS

10.1 THE CONCEPT OF A POPULATION

A population is essentially a group of individuals of the same species¹,² living within a limited area. The term population can refer to a group of bacterial organisms, animals, plants, birds, fish, humans, etc. But whatever the group under discussion, it is, first and foremost, a collection of individuals; that is, each and every member of a population is considered to be an individual. In addition, for the sake of simplicity, we shall limit our discussion of populations to those composed of a single species—a separate and distinct biological group found within a given space. While structurally some populations can be quite complex, the simplest type of population is one with nonoverlapping generations—one generation dies out before the next generation is born (some fish species, seasonally breeding insects, and annual plants come to mind). In the light of this definition, it is the human population (among others) that exhibits overlapping generations.

Let the function P(t) denote the size of a single-species population at time t. Here “size” may be the number of individuals or the collective biomass of the group. In fact, it can also be the average spatial density of a population or, for aquatic populations, the average concentration per unit of water.

It should be evident that the population of a biological species is affected by many factors such as birth and death rates, migration (immigration and emigration), ...