Students will be able to:
- Demonstrate their understanding that within an ecosystem, all living things are interdependent and interact with one another.
- Demonstrate their understanding that all organisms compete for limited resources within their ecosystem.
- Explain why all organisms play important roles within their ecosystem.
Students take part in an activity that simulates the food chain. They hunt for resources and compete with other organisms in order to survive and reproduce.
Communities/ecosystems, critical thinking, cycles, and interdependence
Science, mathematics, and language arts
interdependence, predator, prey, ecosystem, and food chain
Interdependence and competition are two very important concepts to understand in nature. Organisms of the same population, in the same area, compete for resources such as food, water, and space within an ecosystem. Only those organisms that find enough will survive. In addition, many animals also serve as food for other animals. This relationship is known as a predator/prey relationship or the food chain. The predators depend on the prey for food, and often, the prey depends on the predators to keep their populations under control. This concept is known as interdependence.
Safe and open place outdoors, dry beans of any kind or color, colored pieces of paper to differentiate animals.
- Tell your students that they have become ground squirrels and should find their own "burrow" or living space at the edge of an open area. Liberally scatter about 200 beans over a portion of the ground. These beans become "acorns" that the squirrels must gather in order to eat and survive through the day. Each squirrel must gather five acorns each day, and the day lasts two minutes.
When you say "begin," the ground squirrels come out of their burrows and begin foraging for acorns. They must acquire five acorns and be back in their burrows before the end of the day. Be sure they play safe and occasionally let them know how much time they have left. After the two minutes, go to each squirrel and collect the acorns; any squirrels that do not have the required number of acorns have "died" and must leave the game. Any squirrels with extra acorns may save them until the next day. Re-scatter the collected acorns. (Use the first few rounds as practice. You may adjust the duration of the day or the number of acorns according to your group's performance. Keep it challenging, yet attainable).
- Once the game is moving along smoothly and a few dead squirrels have left the game, you may explain that in nature it takes food and energy to raise a family and that reproduction is an essential part of any organism's life. Therefore, any squirrel that collects five extra acorns in a day, may reproduce and bring a dead squirrel into the game as its young. (You may want to start recording the number of live squirrels at the end of each round. This can be used later to demonstrate that a fluctuating population often expresses a balance in nature.)
- In a squirrel's habitat, there are other things to worry about besides food. There are predators out there that need to eat too! Take several of the dead squirrels and through decomposition, turn them into red-tailed hawks with nests. The hawks must eat one squirrel each day to survive. After they tag a squirrel, they walk the squirrel back to their nest. If they wish to reproduce, they can tag another squirrel. Hawks who do not tag a squirrel will leave the game. It helps to identify hawks with some colored paper on their clothes, and it helps if the hawks begin hunting a few seconds after the squirrels begin foraging. You may want to keep track of the numbers of squirrels and hawks you have during each round; it will enhance your discussion later.
- You can also take a few of the dead squirrels from outside of the game and turn them into rattlesnakes. Rattlesnakes are also predators that eat squirrels (one per day) and may reproduce. Note: rattlesnakes are prey for hawks, and hawks may survive by eating one snake per day.
- (Optional) Other animals may be added to the game. Let your students' creativity run free. Have them create more animals to develop a balanced ecosystem.
Examples: Deer eat acorns but need ten per day. Mountain Lions need one deer and one squirrel per day to survive.
- Name some of the food chains in this game – acorn-squirrel-rattlesnake-hawk.
- Identify the predators and the prey in this activity.
- Discuss how predators are dependent on their prey for food and how the prey are dependent upon the predators to control the population and weed out sick and diseased individuals. Predators and prey are interdependent.
- How are the oak trees and the squirrels interdependent? A: Squirrels eat acorns but bury extras that often grow into new trees.
- How are hawks and oak trees interdependent? A: Hawks roost in oak trees and eat squirrels fed by acorns. Hawks help control the squirrel population so that not all of the acorns are eaten.
- Introduce decomposition. How could a dead squirrel or hawk be decomposed and eventually end up as another organism? What would a forest (or any ecosystem) be like if there were no decomposers? A: Dead plants and animals would pile up.
- Were the squirrels sharing or competing for the acorns? What other animals do squirrels compete with for acorns? A: Deer, mice, gophers, and insects.
Adapted from The SCICON Instructional Guide. Rick Mitchell Ed., Tulare County Department of Education. Used with permission.
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