GOAL:

To develop an understanding of the interdependence of all organism's and the need for conserving natural resources

Populations are dynamic with identifiable characteristics and measurable growth patterns.

Ecology El.00 To understand the characteristics of populations.

1.01 define and demonstrate understanding of:
a. Biotic potential
b. Density
c. Natality
d. Mortality
e. Age distribution.

I. Population characteristics
A. Biotic potential
B. Density
C. Natality
D. Mortality
E. Age distribution.

COMPONENT OF SCIENCE: Unifying Concepts of Science

GOAL:

To enable students to acquire scientific knowledge by applying concepts, theories, principles and laws from life/environmental, physical and earth/space sciences.

2.5 CHANGE - Interactions within and among systems may result in changes in the properties, position, movement, form, or function of systems.

2.5b Cycles of change can be extended in scales of time, space and material.

BENCHMARK: Interdependence conveys a need for all organisms within the environment to develop a natural, uninhibited, rate of change.

BENCHMARK: Predictions can be made regarding the extent of change in any ecosystem with sufficient data on biotic and aboitic factors.

TIME REQUIRED:

1 hour, 20 minutes

Paper, pencils, graph paper

Age distribution, biotic potential, density, dynamic, mortality, natality, population

This classroom connector addresses Instructional Objective 1.01.

Today we will study about some of the characteristics of populations. We have studied about ecosystems. Populations are part of the communities that make up ecosystems. It is important for us to learn about populations so that we can see how all these parts fit together.

Quickly write down the first three things that come to your mind when you hear the word population (walk around the room to monitor student responses.) (Ask selected students to share some of their responses.)

(This is a concept lesson so use definitions and many examples in teaching it.) Today's lesson deals with population dynamics. Does everyone know what a population is? (Wait for a response) Good! That's right, all the organisms of the same kind within a given community is a population. An example would be all the turtles in a pond or all the birds in the meadow. Now, can you think of examples? (responses) (Ask students if they agree. With what are they agreeing or disagreeing?) What does mean? (response) All who agree raise your hand. That's good! Dynamic does mean continuous change. Does anyone know how this applies to populations? (Call on some volunteers and let students comment on the appropriateness of the responses.) Now, we want to talk about some specific characteristics that make populations dynamic systems.

The first of these characteristics is the biotic potential of the population. Biotic potential is defined as the maximum number of offspring that can be produced under optimum conditions. Let me give you an example. Rabbits are sexually mature at 5 months of age. Their gestation period averages 31 days and the average litter size is 6 offspring. It is possible to have 8 litters per year. If we start with 1 fertile female and assume that 0 die and 50 percent of the litter is female, at the end of twelve months we have approximately 1,850 rabbits. There are several factors that prevent populations from reaching their biotic potential and we will consider some of them in the next lesson. Are there any questions about biotic potential? (Deal with questions.)

The second characteristic of populations is the concept of density. Density is defined as the number of individuals in a population in a given unit of space. To illustrate, in the United States, we often talk about the number of people per square mile. In New York City there are many more people per square mile than there are in Samburg, Tennessee. Now you give some examples of population density.

A third characteristic of population dynamics is called natality. Natality adds to the number in a population by reproduction. Another way to speak of natality is in terms of birthrate - the rate at which new individuals are added to a given population through birth. (Check for understanding by having students write specific examples of natality i.e. new calves in the herd, etc.) (Walk around the room to see what students have written.)

The fourth example of population dynamics is mortality. Mortality is the number of deaths in a given time or place, in other words the death rate of the population. For example, if there is a population of 900 oak trees in a forest and after 10 years 140 have died, the mortality is 140 per 10 years, or 14 oaks per year. How does this change a population? (response) Under what conditions can mortality be bad? Under what circumstances can it be good for the population?

The final characteristic of population change for this lesson is age distribution. Age distribution could be defined as the proportion of young, middle aged, and old individuals in a population. A better way would be to refer to pre-reproductive, reproductive and post-reproductive individuals in the population. How can age distribution influence the size of a population? (Wait for appropriate responses from students. If the discussion gets bogged, help by asking some leading questions.)

What are the five things we have talked about today that influence the number of individuals found in a population? (Wait for students to respond. Guide with leading questions if necessary.) How do these factors act together to determine the size of populations? (response) Are populations ever static? (response)

(Use "Turkey Trouble," Project Wild (Secondary) as both supervised and independent practice. Begin by helping the students with the activity, monitoring very carefully to see that each understands what he/she is to do. Since this entire lesson will require about 120 minutes, it would be good to instruct one day, begin "Turkey Trouble," have closure. Continue the second day with "Turkey Trouble" while you continue to monitor the activity, have closure the second day and allow them to finish the activity as independent practice.)

(For an enrichment activity use "Birds of Prey", Project Wild "Secondary".)

What five factors (characteristics) work together to determine the size of populations? How are they interdependent in their influence? (Something of this nature can be used both days as closure. Have students write their responses, then have them share with the class.)

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

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