IOWA 4-9 SCIENCE PROJECT

TEACHER GUIDE FOR: Prey for the Predator Steve Bartlett
ECOLOGY.591 Grades 7-9

CONCEPT OBJECTIVE:
To introduce students to the basic concepts of the food chain.

PROCESS OBJECTIVE:
Thinking skills developed in this cycle are exploring, predicting, inferring, and hypothesizing.

MATERIALS:
Five pound bag of peanuts in their shells, box of plastic sandwich bags, large area outdoors, such as an outdoor athletic field or in a gym.

EXPLORATION:
Discuss with the students the idea that a food chain is really the transfer of energy from one organism to another in a chain. An example may be drawn on an overhead projector showing the following transfer of energy: plants-grasshoppers-birds-cats. Have the students write down what they had for dinner last night and trace their food items back through a food chain to the original source of energy. An example might be as follows: humans-beef cattle (steak)-grain-sun.

CONCEPT DEVELOPMENT:
Divide the class into mice, snakes and hawks. Let the kids choose what they want to be. Scatter the peanuts over a wide area, an explain that they represent grain. Thus only mice may pick up peanuts since only mice eat grain. When a mouse has five peanuts in its bag, it may eat whatever additional peanuts it now picks up, but must keep the five. The snakes tag the mice to get their bags, and when they have 5 bags, they may start eating. (Always from the bags, since mice are the only ones who may pick up peanuts. If the snakes have grabbed empty bags they get no peanuts). The hawks tag the snakes, and also may start eating when they have 5 bags. Anyone who is tagged is "dead" and goes to the holding area. When students decide for themselves which animal to be, most students will pick hawks. But they quickly discover that the only way anyone gets peanuts is to have mostly mice, fewer snakes, and still fewer hawks.(A possible ratio: l9 mice, 4 snakes, 2 hawks.) And if all the snakes are "dead" the hawks don't get any peanuts and "starve". This brings home to the students the importance of each link in the food chain, and the necessity of leaving the chain unbroken. Once they have fully understood this idea you are ready to discuss subtler aspects of the food chain in the classroom.

APPLICATION:
(1) Divide the class into cooperative learning groups and have them discuss and record what they believe would be the effects of the food chain becoming unbalanced such as more snakes than hawks, more hawks than snakes, snakes dying off, hawks dying off etc. Have each group report to the rest of the class.

(2) Have students research in the library some topics relating to pesticides (such as DDT) entering the food chain on such birds as the osprey, bald eagle, red-tailed hawk and other birds of prey.