From the Grade 7 Science IRP's:

Describe all organisms in terms of their roles as part of interconnected food webs . Describe ways in which species interact with each other .

Objectives:

1. The student will be able to explain the specific roles certain fish have in the ecology of a lake (for at least four fish).
2. The student will be able to demonstrate how the fish's eating habits and how the parts of the lake they occupy contribute to the ecological balance of a lake.

Materials Needed:

• Blackboard and chalk
• Student notebooks
• Fishes Worksheet #S-4a (Niche)
• Fishes Worksheet #S-4b (Interconnected Food Web)

Vocabulary:

niche, scavenge, forage, fry, ecology, pisciverous, interconnected

Activity:

This lesson will take several periods. Start with what sections of the lake various fish occupy. Bring in the concept of niche. Discuss where, in a lake, the fish mentioned on the worksheet spend much of their time. Discuss how the fish's design (body shape, location of mouth, colouration, body fat, swimming speed) make them suited for their niche.

Body shape:

This affects swimming efficiency. It allows fish to catch food or escape predators

Location of mouth:

This indicates the food source. Big mouths allow the fish to catch other fish easily, smaller mouths are used mainly for insects, Mouths on the bottom of the head are used for scavenging

Colouration and body markings:

This makes for good camouflage. It allows the fish to hide from predators or remain hidden so they can surprise and catch other fish.

Body fat:

This allows the fish to survive in deep cold water

Swimming speed:

Swimming uses up energy and oxygen. In shallower water there is more food and oxygen. Fish can afford to swim fast if they want to. In deep water the opposite is true so fish need to swim slower. This is not always an indicator of what niche a fish occupies. For example suckers move slowly but spend time in shallow areas where their main food source is.

Also focus on the roles that various fish have. This includes

1. scavenging,
2. foraging for insects and other fish (this is this important for the balance of a lake since it keeps a balanced population of various organisms in place), and
3. contributions such as food (some fish produce many young for other fish to forage, also bigger fish provide food for other creatures such as bears, eagles, ospreys, kingfishers and humans) and nutrients to the plants (body wastes and the bodies themselves provide "fertilizer")

After discussing the above, do "Fishes Worksheet #S-4a(Niche)" Organize this activity (individual, cooperative groups, or class wide) as best suits you.

Answers to Worksheet #S-4a:

Trout occupy the drop-off zone where they can come up and feed yet escape predators too. Burbot spend time in deep cold water. Northern pikeminnow spend time in the shoal area where they catch the many small fish that live there. Longnose suckers spend time in the shoal area where they can scavenge among the nutrient rich debris that is found there.

Next focus on the interconnectedness of what happens among organisms in an environment. First examine a simple food chain. List on the board the following: humans, bigger fish, insects, bears, smaller fish, birds of prey. Discuss what eats whom and in what order. In their notebooks, have students draw out the chain in its proper order.

Next amend the above list on the blackboard to read: Predators (bears, birds of prey, humans), Trout, longnose suckers, northern pikeminnows, aquatic insects, aquatic plants. Discuss what each one takes and contributes. Remember to point out that when looking at the fish, it is the fry as well as the adults that are being considered. Hand out "Fishes Worksheet #S-4b (Interconnected Food Web)". Have students complete this worksheet as per instructions.