Teacher Resource Centre

Forest Food Web Activity

TOPIC
Ecological interactions in the boreal forest.

SYNOPSIS
By watching a video and doing an interactive activity, students will be introduced to food webs and ecological interconnections in the forest.

LENGTH
45-60 minutes

CURRICULUM CONNECTIONS
For a complete list of curriculum connections, please go to the Teacher Resource Centre website at www.pc.gc.ca/education.

GOAL
To be introduced to the interconnections of forest ecosystems, using food webs as an example.

MATERIALS

• Food Webs video by Bill Nye "The Science Guy" (optional)
• diagram of food chain and food web
• roll of string
• food chain and web worksheets
• writing materials
• open area

BACKGROUND INFORMATION
Pukaskwa National Park protects a representative portion of the Central Boreal Uplands. This is a section of the boreal forest; the largest ecosystem in the world (see map). The boreal forest was created by and has adapted to the massive forces of ice, fire, insect infestation, and disease. As a result, patchwork stands of trees, large and small, old and young, and at different successional stages supports a wide diversity of bird and mammal species.

Forests are complex, constantly changing systems made up of living and non-living things. All of the components of a forest community are vital to the health of the ecosystem. The non-living or abiotic components of a forest include water, nutrients, rocks, sunlight, and air. The living or biotic components include wildlife (from the smallest insect to the largest mammal), trees, shrubs, wildflowers, ferns, mosses, lichens, fungi, and microscopic organisms.

Interactions between the abiotic and biotic components are easily identified by examining food chains and food webs. A food chain is defined as the transfer of energy from plants to animals through the process of animals eating plants and animals eating other animals. For example, the sun transfers energy in the form of light to green plants. Green plants convert the sunlight into energy which is stored in the plant matter. The energy within plants is transferred to plant-eating animals when the plants are consumed. Energy is also passed from animal to animal as predators consume prey. For example, a simple food chain can consist of a green plant being consumed by an insect and the insect being consumed by a bird. Generally, any one species is represented in more than one food chain.(See diagram).

In forest communities, food chains become more complicated as many animals eat many different foods (energy sources) depending on the availability and abundance of the food. When many different species of plants and animals are interdependent, that is, depending on one another for survival, the process is called a food web. (See diagram.)

All living organisms that function together in a given area interacting with all the non-living and living factors result in a flow of energy. Such interactions lead to clearly defined biotic structures and cycling of materials between living and non-living parts. Ecology is the study of interactions between living things and their environments. The word ecosystem refers to the system of interactions between living and non-living things.

PROCEDURE

1. Review the concept of a forest by asking students what they think of when they hear the word "forest." List their responses as a flow chart. Ask students how the listed items (e.g. trees, birds, bears, chipmunks, etc.) interact. As students respond (e.g. the birds live in the trees, the bear eats the blueberries, the mouse eats the blueberries, the bear eats the mouse, etc.), draw connecting lines between the listed items.
2. Ask students what they think the diagram looks like (a spider web). Introduce the concept of food chains and food webs. Introduce and show the Bill Nye video. Following the Bill Nye video on food webs, ask for comments from students. What was most memorable about the film?
3. Move the students to an open area. Without in-depth explanation, have students stand in a large circle in an open area (preferable outdoors). The teacher should stand in the centre of the circle. Explain that students will be transformed into a forest.
4. Ask students what the first thing is needed for a forest. (Answer: trees - name a specific species e.g. jack pine, white pine, birch, etc.). The student answering correctly becomes a tree and holds on to the end of the string (the teacher remains holding onto the ball of string).
5. Ask the students what lives in a tree. The student with an answer (e.g. bird -name a species) holds onto the string. Continue to ask questions such as what does that animal eat? What else eats that? Where does it live? What eats it? For each answer, each student holds onto the string. Note: make sure at least 4-6 trees are part of the circle. Note: the teacher may wish to have the students lower the string when moving within the circle to each student).
6. When all students are holding onto the string, ask them what it looks like. The result is a web-like construction. Discuss the concepts of food webs and ecosystems. Include ideas on different kinds of ecosystems for example aquatic, desert, arctic, etc.
7. As the students continue to hand onto the string, present the situation where a developer decides to build a cabin in the middle of this forest. But, in order to do so, trees will have to be cut down. On the count of three, have all of the trees gently tug on the string. Ask who felt the tug. Discuss why they felt the tug (e.g. no trees = no food, home, etc.).
8. Proceed to have everyone who felt the tug to gently tug again. Ask who felt the tug. After two or three rounds, everyone should feel the tug. Discuss why. Talk about how humans are part of ecosystems, such as the forest ecosystem. Discuss how humans negatively effect the ecosystem. Does this mean that people shouldn't cut down trees? How can humans prevent mismanagement and destruction of forests.
9. After students complete this discussion, have them drop the string. As the teacher winds up the string, ask how national parks fit into this situation. How do they effect ecosystems? Recap the ideas of interactions between organisms both living and non-living.
10. Upon returning to the classroom, have students complete the food chain and food web worksheets or draw a food web. Remind them of the different interactions between plants and animals, shared food sources, etc. For example, students may wish to colour the arrows different colours i.e. the transfer of energy from plants, to the rabbit, to the owl and wolf is red, the transfer of energy from plants, to the beaver, to the wolf is blue, etc. The images can be used for evaluation and posted throughout the classroom.

ASSESSMENT:
Select a tool to assess the students' work (e.g. video feedback, group dynamics, class contributions, worksheets, food web diagram, etc).

EXTENSIONS

Upgrades:

1. Research different ecosystems and food webs. How do humans part of those systems? How do they impact them? Compare a forest food web and ecosystem to that of another natural region e.g. wetlands, aquatic, desert, arctic, etc.
2. Make a list of the plant and animal life found in your area. Make a food web using these. Don't forget to include humans.

Downgrades:

1. Transfer student food webs to thicker cardboard or plywood. Create food webs with string art.
2. Make a food web of your own diet for the day, e.g. milk from a cow that ate grass, etc. Compare your food web to that of the forest web. Is it more complicated? Why? Why not?

© Pukaskwa National Park of Canada

© Pukaskwa National Park of Canada

© Pukaskwa National Park of Canada

© Pukaskwa National Park of Canada