GOAL:

To develop an understanding of the interdependence of all organisms and the need for conserving natural resources

Populations are dynamic with identifiable characteristics and measurable growth patterns.

Ecology E3.00 To understand methods of analyzing changes in populations

3.01 define and describe the ecological importance of:
a. Population growth rate
b. Life tables and equations
c. Mortality and survival curves
d. Key factors analysis

I. Methods of analyzing population changes
A. Growth rate
B. Population growth rate
C. Life tables and Equations
D. Mortality and survival curves
E. Key factors analysis

COMPONENT OF SCIENCE: Process of Science

GOAL:

To enable students to demonstrate the processes of scienceby posing questions and investigating phenomena through language, methods and instruments of science.

1.6 COMMUNICATING - An essential aspect of science is the act of accurately and effectively conveying oral, written, graphic or electronic information from the preparer to the user.

1.6a - The sharing and disseminating of results should be done in a clear and concise manner.

BENCHMARKS:Style of writing used is partly dependent upon the audience and the nature of the research.

Reporting is clear, concise, and free of error.

TIME REQUIRED:

50 minutes. Possibly two 50-minute instructional periods if you can acquire a resource person.

Pencil, paper, graph paper, calculator(s), life insurance actuaries tables

Key factors analysis, life equations, life tables, mortality curves, population growth rate, sigmoid curve, survival curves

This classroom connector addresses Instructional Objective 3.01.

In the last lesson, we looked at factors that are related to the survival of populations. Today we want to deal with ways to analyze changes in populations. We want to learn these techniques so that we can better understand population dynamics and perhaps even be able to predict changes that occur in populations. However, before we begin our lesson, I would like for you to quickly write what you believe is the chief cause of population change. (Walk around the room to monitor student response. After about two minutes have some of the students share their responses.) (Make appropriate comments and move into your lesson.)

(This lesson will be difficult to teach because it is highly technical. There are several recommendations I would make. Try to obtain a variety of ecology books (secondary or college) and read carefully the sections that deal with these topics. I would also suggest that you obtain help from resource persons. An insurance agent would be able to bring copies of actuaries tables and explain how they are used. A Wildlife Resources Agent or Park Ranger would be able to bring examples of some of the tables they have for wildlife and perhaps could bring some local data and help students to develop some of their own tables. For these reasons I am suggesting that you develop the definitions one day and invite an insurance agent. Then the second instructional period invite a wildlife agent.)

The first method of analyzing a population is based on the population growth rate. The numbers of individuals in the population can be plotted against the time required, to produce a growth rate curve. The population generally begins to grow very rapidly (or exponentially) at first. Then as the factors of environmental resistance begin to exert their influence, the growth rate begins to slow and level off as the environment reaches its carrying capacity. The curve that is produced has an S-shape and is sometimes called a sigmoid curve. Examples would be bacteria in a colony or a culture of protists such as paramecia.

A second method of population analysis is life tables and life equations. A life table is basically a probability table that deals with the probability of death at various ages over an organism's life span. The table gives a picture of mortality and survival. An example is life insurance actuaries. (Have some tables to show students and show them how they are used.) (Even if you are using an insurance resource person later you should still show students a table and tell how they are used.) Life equations are modifications of life tables in that they illustrate changes within the population usually within one breeding season. The equation depicts limitations of growth, seasonal changes (gains and losses) and indicates population losses. They also help to pinpoint when and where the losses occur. Life equations are helpful in the management of wildlife used for hunting.

The third analytical tool used is mortality and survivorship curves. The mortality curve is obtained by graphing the death rate from a life table against the age of death. This is usually done in two phases: one - the juvenile phase, the other for the post juvenile phase.

A survivorship curve is produced by following individuals during their entire lives in order to see at what age each one dies. This is usually accomplished by taking all the individuals born at one time and following them throughout their lives. The number that survives is plotted against age and can be used to predict the probability of surviving to a particular age.

The last analytical method is key factors analysis. A key factor is any condition associate with death rate (mortality) that can be used to predict future trends in a population. These factors can be either biological or environmental and are plotted along with generation mortality data to determine which factor or factors correlate with actual fluctuations in the population. These are mainly used by entomologists to monitor insect populations.

(This is a good time to use your resource people. See note at the beginning of instruction.)

List again the four different methods of analysis of population change we have seen during this lesson. Include an example of how each one may be used. Then tell its importance in helping to understand population dynamics. (Monitor as students write. If you see there is some misunderstanding reteach the appropriate area. Have students share their responses with the class.)

This is the time this file has been accessed since 11/16/96.

The University of Tennessee at Martin is not responsible for the information or views expressed here.

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