Weimer Rachel 2 Food Chain

Name: Date: Format all responses in blue bold font. Student Exploration: Food Chain Vocabulary (refer to vocab file located on the Gizmo site for definitions): consumer, ecosystem, energy pyramid, equilibrium, food chain, population, predator, prey, producer 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 provides food for the other organism. B. Where does the producer get its energy? The producer receives its energy from photosynthesis. 2. Consumers must eat other organisms for energy. Which organisms are consumers in this food chain? The rabbit, snakes and hawks. 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? Hawks: 34 Snakes: 230 Rabbits: 2070 Grass: 2. Select the BAR CHART tab, and click Play (). What do you notice about each population as time goes by? Each organism changes slightly. If populations don’t change very much over time, the ecosystem is in equilibrium. 3. Notice the populations decrease as you go from the bottom of the food chain to the top. Why do you think this is so? Grass is easier to grow and obtain while hawks need more. This diagram, showing decreasing populations at each level, is called an energy pyramid. Activity A: Predator-prey relationships Get the Gizmo ready: • Click Reset (). • Check that the BAR CHART tab is selected. Question: Predators are animals that hunt other animals, called prey. How do predator and prey populations affect one another? The predator and prey populations affect each other because the prey population will decrease if there is an increase in predators. 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. 2. Form hypothesis: How do you think predator and prey populations affect one another? If the prey population increases then so does the predator population. 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 Doubling rabbit populatio n Prediction: Decrease Result: Less grass Prediction: Increase Result: Higher snake population Prediction: Increase Result: Higher hawk population Halving rabbit populatio n Prediction: Increase Result: More grass Prediction: Decrease Result: Less snakes Prediction: Decrease Result: lower hawk population 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. A. How did doubling the rabbit population affect the grass, snakes, and hawks at first? It increased the snakes and hawks while the grass decreased. B. How did halving the rabbit population affect the grass, snakes, and hawks at first? The grass increased while the snake and hawk decreased.