Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The Food Chain Gizmo™ shows a food chain with hawks, snakes, rabbits, and grass. In this simulation, the hawks eat snakes, the snakes eat rabbits, and the rabbits eat grass. 1. Producers are organisms that do not need to eat other organisms to obtain energy. A. Which organism is a producer in this food chain? [ The grass ] B. Where does the producer get its energy? [ The sun ] 2. Consumers must eat other organisms for energy. Which organisms are consumers in this food chain? [ The rabbit, snakes, and the hawk. ] Gizmo Warm-up The SIMULATION pane of the Gizmo shows the current population, or number, of each organism in the food chain. 1. What are the current populations of each organism? Grass: [ 27300 ]Rabbits: [ 2566 ]Hawks: [ 278 ]Snakes: [ 42 ] 2. Select the BAR CHART tab, and click Play ( ). What do you notice about each population as time goes by? [ Some of the species decrease in % of balance ] If populations don’t change very much over time, the ecosystem is in equilibrium. 3. Compare the equilibrium populations of the four organisms. Why do you think populations decrease at higher levels of the food chain? [ Because they depend on the lower parts of the food chain to survive. ] If you cannot access all the Gizmo site, you MUST send them a request for help and get your computer configured so it will work. If they are unable to help you, then you MUST use a computer in the library or somewhere else to complete your assignment by the due date. 2 Question: Predators are animals that hunt other animals, called prey. How do predator and prey populations affect one another? 1. Observe: Run the Gizmo with several different starting conditions. You can use the + or – buttons to add or remove organisms, or you can choose Diseased from the dropdown lists. Take a screenshot of your final result and paste here ↓ 2. Form hypothesis: How do you think predator and prey populations affect one another? [ When one population fluxuates the other follows ] 3. Predict: Based on your hypothesis, predict how changing the rabbit population will affect the other organisms at first. Write “Increase” or “Decrease” next to each “Prediction” in the table. Change Grass Snakes Hawks Halving rabbit population Prediction: [ Increase] Result: [ Increase ] Prediction: [ Decrease ] Result: [ Decrease ] Prediction: [ Decrease ] Result: [ Decrease ] Doubling rabbit population Prediction: [ Decrease ] Result: [ Decrease ] Prediction: [ Increase ] Result: [ Increase ] Prediction: [ Increase ] Result: [Increase ] 4. Test: Add rabbits until the population is about twice as large as it was (200% of balance). Click Play, and then Pause ( ) after approximately ONE month. Next to each “Result” line in the table, write “Increase” or “Decrease.” Click Reset and then halve the rabbit population (50% of balance). Record the results for this experiment in the table as well. Take a screenshot of your final result and paste here ↓ A. How did halving the rabbit population affect the grass, snakes, and hawks at first? Get the Gizmo ready: ● Click Reset ( ). ● Check that the BAR CHART tab is selected. Activity A: Predator-prey relationships 3 [ It decreased the hawk and snake population but then balanced out. ] B. How did doubling the rabbit population affect the grass, snakes, and hawks at first? [ It increased the snake and hawk population first then balanced out. ] (Activity A continued on next page)