IOWA 4-9 SCIENCE PROJECT

TEACHER'S GUIDE for: Jarring Ecosystems Jay Cutler
Ed. by Rollin Bannow
ECOLOGY.791 Grades7-9

CONCEPT OBJECTIVE:
The concept is environmental resistance.

PROCESS OBJECTIVE:
Thinking skills developed are experimenting, hypothesizing, and inferring.

TEACHER BACKGROUND:
Environmental resistance consists of factors that prevent a population form increasing. For example, introduction of a predator would increase environmental resistance, whereby developing a vaccine would decrease environmental resistance by eliminating a factor that was limiting population increase.

MATERIALS:
Per team of five students.
-five pint jars
-grass-water mixture or pond water
-microscopes, slides, medicine droppers, etc.
-chemicals, such as food, fertilizer, detergent, pesticide and other substances proposed as useful or harmful to pond organisms.

EXPLORATION:
Students will construct and observe aquatic environments to determine the effect of various substances introduced into them. The environments will be constructed in 2 liter pop bottles using pond water and organisms provided by the students. Chemicals suggested and brought in by the students will then be introduced into the systems. See the student activity sheet for instructions.

CONCEPT DEVELOPMENT:
Results from the aquatic environment experiment should be tabulated for the class. Have the students classify the substances introduced into the systems as either increasing or decreasing the environmental resistance. Students should then design a revised experiment that could further examine these substances to determine such factors as the effect of amount or combinations of introduced substances, the effect of ecosystem conditions such as temperature, light, population density, etc., and the effect of different organism combinations.

APPLICATION:
1. Examine ponds in the community to see if they have any characteristics like the laboratory ecosystems.

2. Research examples of similar attempts by mankind to exert influence over the ecosystem by raising or lowering the environmental resistance for certain species. Game management and pest control might be examined.

3. Find examples of natural occurrences that have changed the environmental resistances in the local community. Floods and droughts could be examined.

4. Find examples of inadvertent human intervention that may have affected local environmental resistance. Construction projects and housing developments may have done so.



STUDENT ACTIVITY SHEET

Introduction:
Factors that keep a population from growing are called environmental resistance. Examples of environmental resistance are introducing a new predator into the environment or introducing a poison or toxic substance into the environment. Factors that allow a population to increase result in diminished environmental resistance. Examples of diminished environmental resistance decreasing include the introduction of additional food supply or reducing predators.
You are to observe the small aquatic environments, yours and others, to determine if there are any differences, similarities and changes with time. Look for occurrences of environmental resistance in your simple aquatic environment.


Materials:

Each group should bring in

1. Three 2 l plastic pop bottles.

2. Aquatic plants, zooplankton and other pond life collected in pint jars.

3. Substances which your group believe will increase and decrease environmental resistance. Important: Check with your teacher before actually bringing these.

Directions:

1. Construct three identical (as much as possible) 2 liter plastic pop bottle aquatic environments.

2. Into one bottle, put an amount of distilled water equal to the amount of substance which you will be introducing to the other bottles.

3. Into the each of the other bottles put one of the substances that you brought in to affect the environmental resistance.

4. Make daily observations. Record your observations on your own paper.

What conclusions did you draw from your experiment?



Write five questions that you have concerning the results of your experiment.

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Identify three factors that you believe you should have considered, but didn't, when designing your experiment.

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