This lesson teaches students the basics of species interdependency within an ecosystem or habitat. Students will perform a simple simulation to see how one species can affect many others, and gain a basic understanding of the importance of biodiversity. For older students, you may want to define and use the word "ecosystem" in the lesson.

Geography, biology, current events, zoology

Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"

Two to three hours

• Computer with Internet access
• Photographs of endangered animals (either online or in print)
• Photographs of human activities that might affect animals' habitats (either online or in print)
• Drawing materials

Students will

• describe the things animals need to survive and the ways in which animals depend on other animals and plants;
• perform a simulation to demonstrate the interdependencies within an ecosystem;
• look at pictures of endangered animals, and explain what they think might happen to other animals and plants if these animals became extinct; and
• draw pictures of animals in their natural habitats, and describe what these animals need to survive.

Ask students to think of some animals that they are familiar with, such as their pets or animals that live outdoors near their homes. Ask them to state the things these animals need to survive, such as water, food, a place to make their home, and enough room to run and roam.

Ask students to think more carefully about the animals they have described. Discuss the following questions with the class:

• What do the animals eat?
• Where do they live?
• How do they depend on the plants and other animals around them?
• What would happen to these animals if their main food source no longer existed?

Assign each student the role of a local plant or animal (more than one student can play the same role). Ask everyone to stand on one side of the classroom. Then ask one "plant" or "animal" to step out of the picture. For example, you could say, "Will all the oak trees please sit down?" The children taking their seats would represent the dying out oak trees in your area.

Ask students if any other species depend on the oak tree (or whatever local species you have asked to sit down). Give them hints if they are unsure (e.g., the squirrel eats acorns). If any species depends on the species you have asked to sit down, those students will have to sit as well. Continue until there are no (or very few) students left standing.

Discuss the implications of the simulation with the class. What happens to the plants and animals in an area when one type of plant or animal dies out? Make sure students understand that all plants and animals in an area (an ecosystem) depend on one another. Can they think of other examples of dependence, such as in their families, with their friends, or at school?

Have students look at pictures of the endangered animals at the Preserving Biodiversity family activity or at the Bagheera Web site. Explain that there are fewer of these animals in the wild than there used to be. Define the word "extinct" and ask students what they think might happen to other plants and animals if these animals become extinct.

Have students look at pictures of animals living in their natural habitats. Choose some pictures beforehand, either from books or magazines, National Geographic's Animals guide or Creature Feature archive, or the Bagheera Web site. Have students draw pictures of these animals and then describe, either in writing or out loud, the things these animals need to remain healthy and happy.

Ask students to brainstorm the reasons why they think some species might be in trouble, in addition to the ecosystem-related reasons they have discussed. Can they think of any ways in which human activities might affect the lives of animals? Show them pictures of construction, recreation, and other human activities, and have them explain how the activities in each picture might affect animals. Ask them to draw pictures of a few of the animals they looked at in the closing, and draw them in their natural habitats. Then have them draw examples of how human activities might cause problems for the animals.

Have students draw pictures of healthy ecosystems in which many plant and animal species coexist. They can get ideas from pictures of natural areas near their homes or other print or Web materials you have available. Ask them to describe, either in writing or out loud, what would happen if the trees or another species were to die off.

Bagheera: A Web Site for Endangered Species
National Geographic: Animals Guide
National Geographic: Creature Feature
National Geographic: Geography Action! 2003—Habitats
World Wildlife Fund