In this lesson, students model the interactions between the plants and animals in an ecosystem by playing a collection of online games. They also experiment to see how the ecosystem responds to change, as when they increase the number of carnivores. By comparing how different ecosystems—rainforests, deserts, mountains, and mangrove swamps—respond to these changes, students will recognize the general patterns at work in any healthy ecosystem.
- One 60-minute class period
- Understand that all ecosystems require a balance of producers and consumers.
- Explain how and why changing the quantity of one resource in an ecosystem affects the system as a whole.
- Explain how the food eaten by most animals can be traced back to plants.
- Describe how food webs connect plants, animals that eat those plants, and animals that eat those animals.
- Predict how changes to an ecosystem will affect the ecosystem as a whole.
[Note: While these games do allow students to experiment with the ratios of producers (plants) and consumers (animals) in an ecosystem, they are not a complete representation of a fully functioning ecosystem or food web. For example, decomposers such as fungi play a vital role in returning nutrients to ecosystems, but they are not included in the games, nor are students able to alter the nonliving components of the ecosystem, such as sunlight, rainfall, and temperature. Many plants also depend on animals to disperse their seeds or pollinate their flowers, but these relationships also are not addressed in the games.]
Prep for Teachers
- Read through the entire lesson.
- Play each of the games at least one time to familiarize yourself with how it works and what happens when you change variables, such as the quantities of plants, herbivores, and carnivores in the system. Note the bubbles above each organism’s head along the bottom bar of the game screen: clicking on these will bring up a pop-up window with the name of the organism and visuals showing what it needs to eat.
- Bookmark the games on each student device.
- One computer or tablet per pair of student
- Ask your students, “Did anyone eat sunshine for breakfast today?” (You’re sure to hear giggling or a chorus of “No!”) Then ask for a few volunteers to say what they had for breakfast. Jot down their answers on the whiteboard.
- Review the items your students had for breakfast and ask how many of these items came from plants. (While eggs, milk, and meat can ultimately be traced back to plants in an animal’s diet, that isn’t the point of this discussion quite yet.) Students might easily recognize that orange juice comes from oranges and maple syrup comes from maple trees, but you might need to explain that the grains in items like pancakes, cereal, and bread come from plants such as wheat or corn.
- Ask your students what they think those plants might have had for breakfast. Explain that plants make their own food using the energy of the sun. Plants store this energy, and when we eat plants, we also are eating energy that came from the sun. We might not take bites of sunshine, but the energy we get from the foods we eat started out as sunlight shining on plants!
- Introduce the terms herbivore, carnivore, and omnivore. Herbivores are animals that eat plants, carnivores are animals that eat animals, and omnivores are animals that eat both plants and animals. Most people are omnivores—we eat a variety of fruits, vegetables, and meat or other animal products, such as eggs and milk. Spiders are carnivores—they eat other animals, namely, insects. Carnivores are sometimes called predators; your students may be familiar with this term as well. Grasshoppers are herbivores; they eat only plant parts such as grass and leaves. Ask students to propose a way for the sun’s energy to get from a plant to a spider.
- Explain that they will now play a series of online games that challenge them to keep a virtual ecosystem alive by monitoring the numbers of plants, herbivores, carnivores, and omnivores in the ecosystem for 12 virtual days.
- Divide students into pairs and assign each pair to a computer station or tablet. Assign each pair to a specific ecosystem, ensuring that each of the four ecosystems has been assigned to at least one student pair. Have students play one full game.
- When groups have finished, have a short discussion. Were they able to keep their ecosystems alive for all 12 days? What was hard about keeping the ecosystem alive? Did they notice any patterns or rules that explain how to keep the ecosystem alive? Talk about patterns in the context of plants, herbivores, carnivores, and omnivores.
- Have students play another round, keeping in mind any patterns they noticed between the numbers and types of plants and animals alive on each day. Discuss this round. Did the students follow any rules or patterns this time? If so, what were they? Did the rules or patterns they followed help them maintain a healthier ecosystem? Why or why not?
- Have students repeat step 3 in another ecosystem. Be sure that each ecosystem’s game is played by at least one student pair.
- Wrap up with a discussion about the collection of ecosystem games as a whole. Ask students if they noticed any similar patterns among the ecosystems. For example, what happened to each ecosystem if they added more animals than plants? What does this tell them about the makeup of a healthy ecosystem? Can any ecosystem survive if it has more animals than plants? Why or why not? Then, ask students to explain why plants are so important to healthy ecosystems. Circle back to the conversation about sunshine and energy from the beginning of the lesson. Be sure students understand that plants make up the basis of any ecosystem. This means that all the animals that live in an ecosystem, even the ones that eat other animals, depend on plants for their energy. Animals that eat other animals often eat animals that eat plants. A wolf, for example, may eat squirrels. Squirrels eat nuts, berries, and other parts of plants. Wolves then depend on plants, since they provide squirrels with the food they need. What might happen to the ecosystem if it had more carnivores than plants?
- [Optional] These games provide a great way for students to experiment with changing the variables in an ecosystem—a type of biological experiment that’s not easy to design! By playing these games, your students are modeling the interrelationships among the species in an ecosystem. If you would like to explore the interrelationships among plants and animals in greater depth, try one of the following:
- Give students the following rules to follow the next time they play:
- On day 1, add only plants
- On day 2, add only plants
- On day 3, add only herbivores (They can identify which animals are herbivores by clicking on the bubble above the organism; those that eat only plants are herbivores.)
- After day 3, ask students to make a prediction: what might happen if they continued to add only herbivores to the ecosystem? (The herbivores would likely eat all of the plants. Without a food source, the herbivores would then not survive.) Ask students what else might be important for keeping the ecosystem alive. If they need prompting, ask what might eat some of the herbivores, as well as what the herbivores need to eat.
- Have students make up their own pattern for adding organisms to the ecosystem, such as adding two plants, two herbivores, and one carnivore or omnivore every day. Experiment with the variables—what happens if they add more omnivores than plants and herbivores on consecutive days? All predators on another day? Have them make predictions for each set of variables they change. How would the changes affect the ecosystem? Why?
- Give students the following rules to follow the next time they play:
Have students work in pairs or groups to produce a skit, song, poster, or comic strip that shows how the sun’s energy flows all the way through an ecosystem, from a plant to a carnivore. Have students perform their songs or skits for one another, or, if they have produced posters or comics, have students present them to the class.
Next Generation Science Standards Correlations
Disciplinary Core Ideas
- LS2.A: Interdependent Relationships in Ecosystems
- LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
- LS2.C: Ecosystem Dynamics, Functioning, and Resilience
Science and Engineering Practices
- Asking Questions and Defining Problems
- Developing and Using Models
- Using Mathematics and Computational Thinking
- Obtaining, Evaluating, and Communicating Information
- Cause and Effect: Mechanism and Explanation
- Systems and System Models
- Energy and Matter: Flows, Cycles, and Conservation
In this lesson plan, students are introduced to the concept of an ecosystem, and explore how to analyze ecosystems using a systems thinking approach. A class discussion brings out students' ideas about ecosystems and introduces basic information about the components and processes of ecosystems. Next, students encounter a hypothetical ecosystem and gain experience analyzing it the way scientists do. Students then select a local ecosystem and apply what they have learned to analyze it. Finally, students extend their understanding by characterizing three different types of ecosystems and describing their components and processes.
- Define an ecosystem
- Begin to analyze an ecosystem using a systems thinking approach
- Describe the abiotic and biotic components of an ecosystem
- Identify organisms within an ecosystem as producers, consumers, or decomposers
Grade Level: 6-8
- Four 45-minute class periods
Use these resources to create a simple assessment or video-based assignment with the Lesson Builder tool on PBS LearningMedia.
Before the Lesson
- If possible, arrange computer access so students can work in pairs or small groups.
- Print and copy PDF documents for each student.
Part I: Introduction to Ecosystems
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.
- Which kinds of living things can use the energy of the Sun to make their own food?
- How do other types of organisms obtain their energy?
- 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.
Part II: Analyzing Ecosystems
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:
- What are some examples of abiotic components?
- What are some examples of biotic components?
- List some of the processes, or relationships, you think exist among these components.
- Provide an example of a producer and a consumer.
- [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?
- 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?
Part III: Applying Knowledge
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.
- In their notebooks, students should provide a brief description of the ecosystem they have selected.
- 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.
Check for Understanding
Provide each student with a copy of the Comparing Ecosystems PDF Document. Then, have students explore the Biodiversity in the Dzangha-Sangha Rain Forest Flash Interactive, Coral Reef Connections Flash Interactive, and Desert Biome QuickTime Video. Students should extract the information requested on the handout from each resource.
Ask students to write down in their notebooks how using systems thinking helps ecologists understand the interrelationships of components in different ecosystems.