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Activity 9: Predators and Prey
Introduction
So far, we have seen grass and rabbits living in the Virtual Ecosystem. You noticed that the rabbits eat the grass. Have you been wondering if any animals eat the rabbits? Unfortunately for the rabbits, there are also hawks living in their field! Before you experiment with hawks, you must first learn a little more about the food chain in the Virtual Ecosystem.

Grassland ecosystem
In almost all ecosystems on Earth, the sun provides the energy that plants need to grow. There are many types of plants growing on Earth. In a food chain, plants are called producers because they use the sun to produce their own food for energy. There are also many types of animals. Animals are called consumers because they consume or eat other things for energy.

Some animals are herbivores, which means they eat plants. Some animals, called carnivores, eat other animals. Finally, there are decomposers, like mushrooms and earthworms, that break down the dead plants and animals. The Virtual Ecosystem does not show decomposers but real ecosystems need them to clean up.

Virtual Ecosystem Food Chain

In the Virtual Ecosystem, grass is the producer, which means it makes its own food by using energy from the sun. Rabbits and hawks are both consumers. When the rabbits eat the grass, the energy from the grass is transferred to the rabbits. The rabbits need energy to live, be healthy, and have babies. When a hawk eats a rabbit, that energy is then transferred to the hawk.


1. What do you think would happen if there were no producers in the Virtual Ecosystem?
Predators and prey
Hawks are predators, which means they hunt for their food. Rabbits are one of the foods hawks eat. Rabbits are the hawk's prey. Of course, rabbits do not want to be eaten by a hawk! Rabbits need to protect themselves.

Most prey animals have adaptations that help protect them from predators. Rabbits have good hearing, can hide in small holes and run quickly. Another way that rabbits can protect themselves is by blending in with their environment. When animals have fur or skin that helps them blend in with their environment, that is called camouflage or protective coloration.

Can you find the rabbit in the photograph below?
Hunting for prey
You are a hawk and you are hungry! Try to eat as many rabbits as possible. There is a lot of snow in the Virtual Ecosystem, so finding enough food may be difficult. When you start, there will be 10 brown rabbits and 10 white rabbits in the field.

Instructions

1. Press play .
2. Move the hawk using your mouse. Click on a rabbit to eat it. Catch as many rabbits as you can!
3. The model will stop when it is time to look at the graph to see how many white and brown rabbits are left in the field. Click the button next to the graph to make the graph easier to read.
Your challenge: Catch as many rabbits as you can in 30 seconds. Then, take a picture of your graph.
Rabbits caught:







Protective coloration
Look at the picture in your lab book.





2. Were there more white rabbits or brown rabbits at the end? There were more white rabbits. There were more brown rabbits. There were an equal number of rabbits. 3. Why was it more difficult to catch white rabbits?
Hunting in a changing environment
In the snowy Virtual Ecosystem, it was difficult for the hawk to find the white rabbits. White rabbits are adapted to live in the snow. Their color helps them blend in with the environment and hide from predators. Now, there is a population of hawks in the field. They are all hungry! The environment is warming up. Watch what happens as there is less snow over time. Think about how the rabbit population will be affected by this change in the environment.

Instructions

1. Add some grass to the environment by clicking the grass button. Then add rabbits and hawks.
2. Press play .
3. Watch as the field changes from snowy white to brown. You can pause the model at any time to look at the graph.
4. The model will stop when it is time to look at the graph to see how many white and brown rabbits are left. Click the button next to the graph to make the graph easier to read.
Your challenge: Watch the rabbit population change as the environment changes. Is there an environment where the hawks can find both brown and white rabbits easily?



Brown 15 White 15
What does the graph tell us?
You just watched the rabbit population change in response to a changing environment. The Virtual Field went from white to brown, which made it easier for the hawks to catch some rabbits and not others.







4. Look at the graph. What did the Virtual Field look like at time 40 seconds? The Virtual Field was more white. The Virtual Field was more brown. The Virtual Field was white and brown. I don't know. 5. Look at the graph. What did the Virtual Field look like between time 100 and 120 seconds? The Virtual Field was more white. The Virtual Field was more brown. The Virtual Field was white and brown. I don't know. 6. As the environment went from white to brown, what happened to the color of the rabbits in the population? Over time, there were more white rabbits in the population. Over time, there were more brown rabbits in the population. As the environment changed, the numbers of brown and white rabbits in the population did not change.
Challenge question
Are you ready for a challenge? In the snowy field below, hawks can see the brown rabbits against the white snow and can catch them easily! After some time, there will be more white rabbits because the hawks ate the brown ones! Think about this: What would happen if there were no hawks? Would the color of the rabbits matter?







7. What would happen to the rabbit population in the snowy field if there were no hawks? There would be more brown rabbits. There would be about the same number of brown and white rabbits. There would be more white rabbits. 8. If there were no hawks, and the environment changed from snowy to brown, what would happen to the rabbit population? There would be more brown rabbits. There would be about the same number of brown and white rabbits. There would be more white rabbits.
Conclusion
You explored how a change to the environment affected the animal population living in that environment. Think about all the other plants and animals in that ecosystem. All parts of an ecosystem are important and they are all connected.

In the next activity, you will have the chance to do your own experiments with an ecosystem. Click the X at the top of this window to close the activity and save your work.