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Educational Modules

Wetland Biology

Introducing: Population Ecology

The study of population ecology is the study of groups of organisms (a population) and how they distribute themselves through a given area.

In this study we are mainly concerned with the number of individuals that collectively form the population and where are we most likely to find that population. It is important to mention here that a population may be defined for a stated area. For example, we may want to know if the local population of spotted salamanders is rising or declining. To answer this question we would have to define "local". Given that information, we could then set out to determine the current population of spotted salamanders in that stated area. We might indicate on maps where the greatest concentration of spotted salamanders occurred (their distribution), and compare our results with similar studies that may have been conducted earlier.

Using the spotted salamander example, we conduct our investigation. Preliminary results indicate a greater number of individuals in the local population than reported in the last study. The pattern of distribution concentrated the observed salamanders in three main areas. Prior to this investigation we noted fewer spotted salamanders and a wider distribution.Five areas of concentration were identified. Many questions arise from results such as these.

  • Why has there been a change?
  • Is the change part of a natural cycle for this organism or has there been a change in the habitat that accounts for the change?
  • Should we be concerned that there are apparently fewer suitable habitat sites?
  • Are the numbers higher simply because the salamanders are concentrated in fewer sites and are therefore easier to count?
  • Could large numbers of salamanders been missed in the last count due to the inaccessibility of the preferred habitat?
  • Are we really looking at a decline in both suitable habitat and in population size? Density does not necessarily equate with a healthy, sustainable population.

These are just some of the many questions a field biologist or ecologist might address in a comprehensive investigation. You and your classmates will certainly discover other questions pertaining to ecological change as you work through the scenarios presented to you later in this module.

Hint: When you are cast in a particular role, try to assume all of the qualities and attitudes of that cast member. Leave your personal opinions about the issues behind. Try to see the situation through the eyes of the person you will be asked to portray. Have fun with it!