1. Begin the lesson by writing the word "ecosystem" on the board or on an overhead transparency. Ask students to describe the meaning of the word. At this time, do not judge their answers or correct misconceptions.

2. Write the following words on the board or transparency, "city, forest, aquarium." Ask students which of these three represent an ecosystem. Guide the discussion to bring out that all three are examples of ecosystems, and that they can be large or small and may include humans. Explain that ecosystems are often described as a community of organisms plus the abiotic parts of their environment. Ecosystems are also often described by the major plants found within them (e.g., forest ecosystem).

3. Ask students to look at the word "ecosystem" on the board again. Have them focus on the second part of the word, "system." Ask them what it might mean to look at ecosystems as a system. Help students reach the understanding that each ecosystem is an integrated system of components (biotic and abiotic) and processes.

4. Display the Yellowstone Wilderness Area PDF Document or an image of another wilderness area. Explain that this photo represents an ecosystem. Ask students to list some components of the ecosystem and write them on the board or transparency. Students will name various plants and animals—components of the biosphere—but they may not bring up nonliving components of the ecosystem—such as components of the atmosphere or lithosphere. If students do not mention abiotic components, ask them what other components might play a role. Then help students complete their list of the ecosystem's biotic and abiotic components and explain their importance.

5. Remind students that life requires energy to exist. Ask, "What is the source of energy for this ecosystem?" Guide the discussion to bring out that the Sun is the ultimate source of energy for the ecosystem, and that the energy flow within an ecosystem is one of its system processes. Then ask students to discuss how the interactions of these different organisms (components) contribute to the energy flow (processes) within this system.

1. Which kinds of living things can use the energy of the Sun to make their own food?
2. How do other types of organisms obtain their energy?
3. What happens to the matter (bodies) of organisms after they die?

Guide this discussion to bring out the following:

• Green plants are the only type of organism that can convert the energy of the Sun into chemical energy (food).
• All other organisms must obtain their chemical energy (food) by eating other organisms.
• Some organisms obtain their chemical energy by eating the remains of dead plants and animals. This contributes to the recycling of matter that is found in the ecosystem.
• Diagramming is a powerful way for students to develop an understanding of the complex ways in which the parts of a system interact. Ecologists can trace the flow of energy through an ecosystem by creating a food web. For further illustration of food webs, you might direct students to check out the Antarctic Food Web Game Flash Interactive.

6. Explain to students that they will explore a typical ecosystem and will become familiar with the ways in which scientists describe the components and processes, or relationships, found within the ecosystem. Give each student a copy of the Analyzing Ecosystems PDF Document. Then have students explore the Antarctic Food Web Game Flash Interactive to learn more about ecosystems and answer the questions posed on the handout.

7. After students have finished answering the questions on the handout, ask for volunteers to report their findings.

8. Ask students to reflect on the ecosystem they analyzed in Step 4 and answer the following questions in their notebooks:

1. What are some examples of abiotic components?
2. What are some examples of biotic components?
3. List some of the processes, or relationships, you think exist among these components.
4. Provide an example of a producer and a consumer.
5. [Optional] If time allows, ask students to provide examples of some of the other relationships among the components: parasitism, commensalism, mutualism, and mimicry. How might these kinds of relationships contribute to maintenance of the ecosystem?
6. What do you think might be the advantage of applying systems thinking when analyzing an ecosystem?

When students are finished answering the questions in their notebooks, ask them to share some of their responses to Question (f). This may be a difficult question for students to answer, so a discussion may help them arrive at a better understanding of systems thinking.

9. Explain that although the specific components and their relationships that students analyzed in the previous activity are unique to that ecosystem, the terms and processes are universal and apply to all different types of ecosystems. Provide a couple of additional examples to reinforce the similarity of these relationships from one ecosystem to another. Then have students reflect on what they think defines an ecosystem. Who decides? Why?

10. Instruct students to select a local ecosystem to explore and analyze. If possible, students should visit the ecosystem to make their observations and record them in their notebooks. This can be done as an organized class trip, or students can be asked to make their analysis outside of class time. The following are some suggestions for how to identify an appropriate ecosystem for analysis:

• The ecosystem can be small, such as a terrarium, aquarium, or small pond.
• The ecosystem can be larger, such as a wooded area near home or school.
• The ecosystem can be the local community itself.

1. In their notebooks, students should provide a brief description of the ecosystem they have selected.
2. Students should include the following during their analysis of their ecosystem:
   • A list of biotic and abiotic components
   • A list of producers, consumers, and decomposers
   • [Optional] A list of examples of any parasitism, commensalism, mutualism, and mimicry
   • A food web that shows the energy relationships between the organisms in the ecosystem
    

11. Discuss students' analyses as a class. Ask them what other elements besides energy might flow in an ecosystem.