Gizmo Exploration: Food Chain PDF

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A biology assignment from a very popular and known biology website....

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Student Exploration: Food Chain Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Change your text color for your answers. Define Each Vocabulary Word: consumer- a living creature that eats organisms from a different population ecosystem-a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life energy pyramid- a graphical representation of the energy found within the trophic levels of an ecosystem equilibrium-the current functions of the body are able to keep the body at a stable condition food chain- the sequence of transfers of matter and energy in the form of food from organism to organism population-a group of individuals of the same species living and interbreeding within a given area predator- an organism that primarily obtains food by the killing and consuming of other organisms prey- organisms that predators kill for food Producer- organisms that make their own food 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? B. Where does the producer get its energy?

grass The sun

2. Consumers must eat other organisms for energy. Which organisms are consumers in this food chain? Hawks, snakes, and rabbits

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:

2. Select the BAR CHART tab, and click Play ( each population as time goes by?

2566

Grass: 27300

). What do you notice about

The population of rabbits and grass increases.

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? There are more producers than consumers so it balances out.

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

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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 the predators do not kill their prey then the prey become overpopulated and become a problem.

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 population

Prediction: decrease

Prediction: increase

Prediction: increase

Result: decrease

Result: increase

Result: increase

Halving rabbit population

Prediction: increase

Prediction: decrease

Prediction: decrease

Result: increase

Result: decrease

Result: decrease

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?

The grass decreased, and the snakes and hawks increased.

B. How did halving the rabbit population affect the grass, snakes, and hawks at first? It caused the grass to increase and the snakes and hawks to decrease.

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. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Change

Grass

Rabbits

Hawks

Doubling snake population

Prediction: increase

Prediction: decrease

Prediction: increase

Result: increase

Result: decrease

Result: increase

Halving snake population

Prediction: decrease

Prediction: increase

Prediction: decrease

Result: decrease

Result: increase

Result: decrease

Change

Grass

Doubling hawk population

Prediction: decrease

Prediction: increase

Prediction: decrease

Result: decrease

Result: increase

Result: decrease

Halving hawk population

Prediction: increase

Prediction: decrease

Prediction: increase

Result: increase

Result: decrease

Result: increase

Rabbits

Snakes

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?

Explain why:

When the snakes increased the grass also increased

Increasing the snake population caused a decrease in rabbit population which allowed the grass to increase.

B.How did increasing the hawks affect the rabbits?

Increasing the hawks caused the rabbits to increase

Explain why:

An increase in hawks caused a decrease in the snake population which allowed the rabbit population to increase.

7. Draw conclusions: In general, what effect did removing prey have on predators? It will cause a decrease in predators because they will not have prey to consume.

What effect did removing predators have on prey? It allows the prey to increase because there are no predators to consume them.

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.

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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? The snake and grass populations increased while the rabbit population decreased. This occurred because there are more snakes since there are no hawks consuming them which caused the rabbit population to decrease and the grass population to increase.

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 rabbits are not consuming it since snakes are consuming more rabbits. Also, there are more snakes because they have no predators to consume them.

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 below. I decreased the grass and increased the hawks, snakes, and rabbits. The grass began to

increase greatly and the hawk, snake, and rabbit population decreased drastically.

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 prey and predators

B. A major disturbance that caused the ecosystem to stabilize at a new equilibrium. Decrease in hawks

C. A major disturbance that caused the ecosystem to completely collapse. A decrease in grass

D. (Challenge) A major disturbance that almost caused a total collapse, but that the ecosystem was able to recover from eventually. Taking away the entire population of rabbits

Complete the assessment on Gizmo

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