To acquaint students with a type of ecosystem (the submerged aquatic vegetation of a bay) and how the different organisms of that ecosystem compete with one another for resources.
This lesson is a study of the plants that comprise the submerged aquatic vegetation (SAV) of a bay, as well as the animals that feed on and live in the SAV. Middle-school students understand that animals eat plants and other animals to survive, but often have trouble understanding that there is not an unlimited supply of food. They do not readily understand that a wide variety of plants and animals must be available for consumption to support the populations of animals sharing the same space. In general, middle-school students benefit from visual aids to help explain the concept that organisms living in the same area share food, space, water, air, and shelter.
In this lesson, students will research plants and animals that live in the submerged aquatic vegetation (SAV) of a bay area. After researching the organisms, students will do class presentations and create a food web using pictures of all of the organisms. At the end of the lesson, they will discuss ideas of organisms sharing food, space, water, air, and shelter.
This lesson makes use of the Chesapeake Bay as an example, but could be adapted as necessary to make use of another bay area of interest. The lesson includes several components (research, oral reports, creation of a food web, and discussion), and will most likely take 3-4 class periods to complete.
You will need to choose organisms (plants and animals) for students to research and create a food web of; these organisms should be relevant to the bay area that you choose to study.
- Animals that live under the water in the sea grass-blue crab; horseshoe crab; pipefish; stickleback; seahorse; sand shrimp; hermit crab; spider crab; amphipod; sea slug; periwinkle snail; and zooplankton.
- Animals that eat submerged plants as a principal food source but live out of the water-waterfowl (such as the Mute Swan); muskrat; and beaver.
- Submerged plants-eelgrass; widgeon grass; wild celery; coontail; redhead grass; and busy pondweed.
To elicit student ideas and generate enthusiasm, ask these questions:
- Have you ever vacationed at the beach?
- If so, what was it like? What kinds of animals did you see there?
- How did those animals use the resources at the beach (e.g., for food, swimming, or nesting)?
- What do you think are some major differences between the ocean and the bay?
To help students focus on the concept that animals eat plants and other animals living in the SAV of a bay, ask these questions:
- Have you ever fished from a dock on the bay?
- Have you ever used a crab trap?
- What did you use as bait when fishing or crabbing? Why?
- Can you describe a source of food for animals living in a bay ecosystem?
- Can you think of plants the smaller animals might eat?
- Who can give us an example of a food chain living in the bay?
- How is a food chain related to a food web?
Tell students that they will investigate organisms and create a food web for the bay grasses. Make sure they understand that plants that live under the surface of the water are commonly referred to as submerged aquatic vegetation (SAV).
If possible, use a presentation station to display the Bay Grasses page from the Chesapeake Bay website, or make copies of this information for students to read and discuss.
Students will research animals or plants living in the bay grass area of the Chesapeake Bay (or the bay of your choice). You may assign several students to research the same plant or animal in order to help students visualize "shared food and space" when creating a class food web.
After it's determined who will research plants and who will research animals, distribute the appropriate research guidelines (Plants of the Bay and Animals of the Bay) and explain the assignment to the students. Direct them to the resources you found ahead of time, and let them know that they will present their research to the class.
Suggested online resources for the research include:
In addition, Life in the Chesapeake Bay, (Lippson, Alice Jane and Robert L. Lippson, Johns Hopkins University Press, 1997) is an excellent reference book.
After students have finished the research, have them present their findings to the class. Students who researched the same organism could present as a group. Next, have students attach the pictures of their organisms to a display area that represents the food web, using yarn or string to create a web between the plants, animals, and sun.
Ask students these questions:
- How is this food web of the SAV of the bay similar to all food webs?
- How is it similar to and different from a food web of a land area?
(Students should understand that the sun is the ultimate source of energy. They should understand that plants make their own food, and animals eat the plants and/or other animals. They could make use of the terms herbivore, omnivore, and carnivore. They should realize that plants and animals die, decompose, and then become part of the food web again.)
- What makes this food web unique? (Specific location, and plant, and animal species.)
Use the overhead, chalkboard, or a presentation station to list similarities, differences, and unique characteristics of bay grass ecosystems.
When all reports are complete, have students provide responses to these questions (written or verbal):
- What could happen if there were not enough plants to support this population of animals? (Populations of animals might die, move to another area, or eat other plants or animals not normally in their food chain. In an extreme situation, the animals could become threatened or endangered. People play a major role in all ecosystems.)
- How could you tell if the plants did not have enough sunlight or space? (Plants might turn brown due to decay or the population of plants might decrease. Many plants decaying or dying would cause the ecosystem to change.)
- Do you think each of the animals has sufficient space to eat, sleep, and reproduce? (If the animals are eating their regular diet, not fighting, and reproducing, then they most likely have the proper amount of food, space, and shelter.)
To promote a higher level of thinking, ask this question:
- What do you predict could happen if blue crabs were completely eliminated from the food web in the bay grasses? (Accept all reasonable answers. Students should begin to understand that if an entire population of blue crabs were wiped out, the other animals such as large fish, waterfowl, small mammals, and humans would have to find a different food source to survive. In addition, blue crabs are scavengers, therefore, other organisms would have to "clean up" the environment.)
Have students read the information at the Checklist of the Marine Flora and Fauna at Seaside Park, Bridgeport, Connecticut website, and then provide answers to the questions below:
- Who can explain the difference between flora and fauna?
- How does this list of animals living in the sea grasses compare to our list of animals living in the bay?
- Do you think they have the same problems sharing food and living space? Why?
Have students design a postcard representing a food web of the bay grasses. Send it home to share with their families.
Get your students involved in a Chesapeake Bay project with the Chesapeake Bay Foundation.