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Food Chain - Assignment
Environmental Science (BIOL 1003)
University of Arkansas
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Name: ___________________________ Date: 9/24/21__________
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.
- Producers are organisms that do not need to eat other organisms to obtain energy.
A. Which organism is a producer in this food chain? All plants are producers in a food chain
B. Where does the producer get its energy? The common leftover materials such as water,
carbon dioxide, and minerals can then be reused by producers to make sugar through
photosynthesis. Decomposers get energy through respiration, so they are heterotrophs.
However, their energy is obtained at the cellular level, so they are called decomposers not
consumers.
- Consumers must eat other organisms for energy. Which organisms are consumers in this
food chain? Within an ecological food chain, consumers are cat groups: primary consumers and
secondary consumers. Primary consumers are herbivores, feeding on plants.
Gizmo Warm-up The SIMULATION pane of the Gizmo shows the current population , or number, of each organism in the food chain.
- What are the current populations of each organism?
Hawks: 42 Snakes: 278 Rabbits: 2566 Grass: 27300
- Select the BAR CHART tab, and click Play ( ). What do you notice about each population as time goes by?
While the grass is decreasing at a medium rate the rabbits also die.
If populations don’t change very much over time, the ecosystem is in equilibrium.
- 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 has to be less predators than the other animals to keep order, if there
were more owls the snake population would go down by a lot.
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?
Observe : Run the Gizmo with several different starting conditio ns. You can use the + or – buttons to add or remove organisms, or you can choose Diseased from the dropdown lists.
Form hypothesis : How do you think predator and prey populations affect one another?
Primary consumers, secondary consumers, and tertiary consumers. Primary consumers are herbivores, feeding on plants.
- Predict : Based on your hypothesis, predict how changing the rabbi t 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: The grass will stay a little lower than where it started
Prediction: There will be a lot more snakes
Prediction: There will be more hawks because there are a lot of snakes Result: The grass went up then down to its original number
Result: The population stayed the same
Result: The hawk population stayed the same
Halving rabbit population
Prediction: There will be twice as much grass
Prediction: There will be half as much snakes
Prediction: There will be almost no hawks Result: The population fluxiones then went back to the original number
Result: The population went up to its original number after it went down a little bit
Result: The hawks stayed the same
- 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?
B. How did increasing the hawks affect the rabbits? increasing the hawks also increased the rabbits Explain why: The snakes eat the rabbits with less snakes there can be more rabbits.
- Draw conclusions : In general, what effect did removing prey have on pre dators? It really had no effect because in the end, they all went back.
What effect did removing predators have on prey? This also had almost no effect because they all went to their original numbers in the end.
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.
I think that their population has gone up since they aren’t being hunted as much by the wolves but then the humans start to hunt them.
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?
- 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 hawks start out super low, the rabbit goes down then back to normal and the rest just went up the back to its signal.
- Analyze : Explain why you think the population of each organism changed the way it did. (Use extra paper if necessary.)
I think it did this because the hawks started hunting on the overpopulated snakes and then the rabbits started feeding on the overpopulated grass and then everything went back to normal.
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.
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 species that an ecosystem really relies on goes extinct but a new species joins an ecosystem.
B. A major disturbance that caused the ecosystem to stabilize at a new equilibrium.
A type of producer dies and then a new one goes and replaces it.
C. A major disturbance that caused the ecosystem to completely collapse.
A major species goes extinct and then nothing comes to fill its spot.
D. (Challenge) A major disturbance that almost caused a total collapse, but that the ecosystem was able to recover from eventually.
A producer goes extinct for a little then the topic levels only have each other for food but eventually it finds a new producer.
Food Chain - Assignment
Course: Environmental Science (BIOL 1003)
University: University of Arkansas
