Gizmo Food Chain SE PDF

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food chain gizmo...

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Name: ____

Student Exploration: Food Chain Vocabulary: 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? __grass___________________ B. Where does the producer get its energy? ________sunlight_______________

2. Consumers must eat other organisms for energy. Which organisms are consumers in this food chain? ______________rabbits, 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: _42_ Snakes: _278__ Rabbits: _2566_ Grass: 27300

2. Select the BAR CHART tab, and click Play ( ). What do you notice about each population as time goes by? ____the consumers are increasing and the grass is decreasing.___________ 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? _________Because the more you go up the less energy there is to keep the consumers alive_________

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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? 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 there’s more predators they eat more prey then will die because there’s no prey.___

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 Doubling rabbit population Halving rabbit population

Grass

Snakes

Hawks

Prediction: decrease

Prediction: decrease

Prediction: decrease

Result: decrease

Result: increase

Result: increase

Prediction: increase

Prediction: increase

Prediction: increase

Result: decrease

Result: 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. A. How did doubling the rabbit population affect the grass, snakes, and hawks at first?

By doubling the rabbit population it caused the grass to decrease, the snakes __

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This diagram, showing decreasing populations at each level, is called an energy pyramid.

increased and the hawks increased. __By doubling the rabbit population, the amount of grass decreased and the snakes and hawks increased__ B. How did halving the rabbit population affect the grass, snakes, and hawks at first? __by halving the rabbit population the grass increased while the snakes and hawks decreased.__

(Activity A continued on next page)

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This diagram, showing decreasing populations at each level, is called an energy pyramid. Activity A (continued from previous page) 5. Predict: Predict how changing the snake and hawk populations will affect the other organisms within the first month. In the tables below, write your predictions. Change Doubling snake population Halving snake population Change Doubling hawk population Halving hawk population

Grass

Rabbits

Hawks

Prediction: increase

Prediction: increase

Prediction: decrease

Result: increase

Result: decrease

Result: increase

Prediction: decrease

Prediction: decrease

Prediction: decrease

Result: decrease

Result: increase

Result: decrease

Grass

Rabbits

Snakes

Prediction: decrease

Prediction: increase

Prediction: decrease

Result: decrease

Result: increase

Result: decrease

Prediction: increase

Prediction: decrease

Prediction: increase

Result: increase

Result: decrease

Result: increase

6. Test: Click Reset. Try each experiment with the Gizmo. Record each result after one month. A. How did increasing the snakes affect the grass? ____it increased the amount______ Explain why: _________less rabbits more grass________________ ___________________________________________________________________ B. How did increasing the hawks affect the rabbits? __the amount of rabbits increased____ Explain why: ___more hawks eat snakes, less snakes to eat the rabbits___ ___________________________________________________________________

7. Draw conclusions: In general, what effect did removing prey have on predators? ______ the less prey predators will consume the less predators there will be cause there’s less food_______ What effect did removing predators have on prey? _________the less predators the more prey since no one is eating them.________________ __________________

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This diagram, showing decreasing populations at each level, is called an energy pyramid. Extend your thinking: In North America, many top predators, such as wolves, have been driven nearly to extinction. What effect do you think this has on their main prey, deer? Write your answer on a separate sheet, and/or discuss with your classmates and teacher. Activity B: Long-term changes

Get the Gizmo ready:  Click Reset.  Select the GRAPH tab.

Question: An ecosystem is a group of living things and their physical environment. How do ecosystems react to major disturbances? 1. Observe: Kill off most of the hawks using the – button, and then click Play. Observe the GRAPH for about 12 months, and then click Pause. What happens?

By killing off the hawks the snake and grass populations increased while the rabbits decreased. This happened because there are more snakes since the hawks are not consuming them causing the rabbit population to decrease which allowed the grass to ____

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This diagram, showing decreasing populations at each level, is called an energy pyramid.

increase. By killing off the hawks the snake and grass populations increased while the rabbits decreased. This happened because there are more snakes since the hawks are not consuming them causing the rabbit population to decrease which allowed the grass to increase. ___the snake and grass population increased while the rabbit population decreased because there was more snakes to eat all the rabbits. ___ 2. Analyze: Explain why you think the population of each organism changed the way it did. (Use extra paper if necessary.) ____ the grass increased because the rabbits weren’t eating it, and the snakes were eating all the rabbits, and there were more snakes since most of the hawks were gone.

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This diagram, showing decreasing populations at each level, is called an energy pyramid.

3. Experiment: Click Reset. Try making other changes to the ecosystem. Use the + or – buttons, or choose Diseased from the dropdown lists. Click Play and observe for at least 12 months. Record what happens on another sheet of paper or in your notes. ____I decreased the rabbits, hawks and snakes and increased the grass, after 12 months the decreased slightly, the rabbits didn’t change but the snakes and hawks both increased______

4. Summarize: Give at least one example of each of the following: A. A major disturbance that the ecosystem was able to recover completely from. _________a decrease in predators and prey ___________ B. A major disturbance that caused the ecosystem to stabilize at a new equilibrium. __________a decrease in snakes _________________________________ C. A major disturbance that caused the ecosystem to completely collapse. ________the elimination of grass__________ D. (Challenge) A major disturbance that almost caused a total collapse, but that the ecosystem was able to recover from eventually. _______________taking away only some of the snakes ___________

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