Lesson 1: We All Live in Communities

Lesson Information:

Summary: Students compare roles in human and ocean communities and build a web of interrelationships within an aquatic community.
Duration: 20 minutes
Group Size: Several small groups of three to five students
Materials: Student worksheets

Learning Outcomes

Students will be able to:

• Understand that all living organisms, including humans, live in communities that consist of other living things.
• Explain the similarities and differences between human and natural communities.
• Illustrate the relationships among at least four aquatic community members.

Background

Community is a fundamental ecological concept needed to understand how small changes close to home can bring about changes far away. Simply put, a natural community contains living things that meet their basic survival needs in the same location, such as an estuary, reef, or salt-marsh. These living things can affect one another in a number of ways. Some eat, or are eaten by, others. Some break down dead plant and animal matter and release useful nutrients. Some provide shelter or cover for others. Some modify conditions, creating or eliminating suitable habitat for others. A list of the connections or interrelationships among community members would be almost endless. The basic point is that impacts on one living thing inevitably affect other life forms, often in unseen ways.

In this activity, students investigate the roles of different community members and how they depend on one another.

Procedure

1. Discuss with your students the concept of their home community. Where does it begin and end? What services are provided by different community members? (For example, food production, food distribution, provision of shelter, garbage pickup, police services, and so on; add others based on "Services" listed on the student worksheet). Discuss some of these services and how they represent community interactions and interrelationships. How is the community self sufficient? How is it connected to other communities?
2. Look at the similarities and differences between human and ocean communities. Emphasize that many species provide services in an ocean community. Explain that students will look at one example of an ocean community and try to identify interrelationships within it.
3. Divide the class into groups of three to five students. Hand out student worksheets 1 and 2. Ask the groups to identify members of human communities and the Pacific coastal community that provide each service. Ask the students to list organisms in the ocean community and draw arrows between organisms that are interlinked.
4. Optional: have the students research another ocean community and describe the services provided by members and the links between them.
5. Discuss the results, emphasizing the following points:
1. Communities are collections of living things.
2. Some migratory species, such as eagles, may spend only part of their time in the community. Are they full-fledged community members? Where are the actual boundaries of the community?
3. Organisms within communities interact in many ways. For example, energy is transferred between members of a community through food webs. Or one community member may provide shelter for another. What happens when one species, or community member, is removed?
4. Different communities also interact with each other. Lesson 2 will explore some ways in which human communities depend on ocean communities.

Evaluation

Have students explain the effects of the loss of a community member on at least four other community members.

Student Worksheet 1: Community Members and Interactions

Student Worksheet 2: Pacific Coastal Community Members

The following species are found living together, at least part of the time, along Canada's Pacific coast:

• Kelp plants grow in water up to 40 metres deep in open coastal waters. They form large underwater "forests" that are very productive. Using the sun's energy and nutrients found in the water, some types of kelp can grow up to 30 centimetres per day and reach more than 30 metres in length. They shelter a wide variety of animals, including sea otters, many species of fish, crabs, sea urchins, octopuses, and starfish. They are also a favourite food of sea urchins and abalone.
• Mussels are molluscs that feed on scraps of dead kelp and other algae that they filter out of the water.
• Sea otters feed on small fish called greenling, sea urchins, mussels, and other bottom-dwelling animals. They exert strong control over kelp forest food webs. When sea otters are scarce or absent, sea urchins can become so numerous that they destroy kelp forests. This overabundance, in turn, affects populations of other animals, such as salmon, that rely on kelp forests for shelter and places to forage for food.
• Starfish feed on sea urchins and can help to control the populations in smaller areas.
• Seals and sea lions spend their lives in coastal areas where their food includes fish produced in kelp forests.
• Orca whales live in Pacific coastal areas and feed mainly on seals and sea lions.
• People catch fish, including salmon, that spend parts of their lives in coastal areas. People eat these fish or sell them to make a living.
• Crabs and shrimps live in coastal areas, including kelp forests, and feed on scraps of dead plants and animals that fall to the bottom.
• Bacteria are so tiny that their presence is often forgotten. They break down dead organic materials and animal feces, making the nutrients available to plants such as kelp.
• Bald eagles live in coastal forests and feast on salmon that journey up coastal rivers to spawn.