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Weimer_Rachel_2.2foodchain
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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: Get the Gizmo ready:
Predator-prey • Click Reset ( ).
relationships • 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 Prediction:
Prediction: Decrease Prediction: Increase
rabbit Increase
populatio Result: Higher Result: Higher hawk
Result: Less grass
n snake population population
Halving Prediction:
Prediction: Increase Prediction: Decrease
rabbit Decrease
populatio Result: Less Result: lower hawk
Result: More grass
n snakes 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.
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