The School House

Aquatic food webs

Objectives
1. To show how animals are interconnected by feeding relationships.
2. To illustrate the effects of habitat disturbance on the food web.

Background
In nature, organisms either make their own food or eat other organisms. Plants are called producers since they make their own food. Other organisms are called consumers because they consume other living things. Consumers include herbivores (plant eaters), carnivores (animal eaters), and omnivores (eat both plants and animals). A food chain is an ordered list of who eats whom. The sun gives energy to plants, which are eaten by herbivores, which are eaten by carnivores, which are eaten by bigger carnivores. A food web is several food chains mixed together.

Procedure
Each person chooses or is assigned a component of an aquatic habitat.
People are assigned cards according to what part of the habitat they are. A yellow card for the sun, green cards for the plants and, for the consumers; brown cards for the herbivores, black cards for the carnivores, and blue cards for the omnivores.

Here's an example,

producers: algae, aquatic plants
herbivores: mayfly nymphs, snails
carnivores: large mouth bass, frogs
omnivore: golden shiners white suckers

1. Once participants have chosen their organisms they can do research on their animals:
   • Make a sketch of your organism.
   • Where does the animal live?
   • What does it need to live, i.e. what are its habitat requirements?
   • What does it eat (prey on)? (How does it eat?)
   • What organisms eat it?
   • What organisms does it live with?
2. Start off with the question, "What is the most essential thing for life on the planet Earth?" The sun is... The person who is the sun holds onto one end of a ball of wool.
3. Next ask who needs sunshine? Plants use the sunshine for photosynthesis. The ball of wool is passed to the other person who is a type of plant, while the sun hangs on. Continue the game in the same fashion, developing a web of interconnecting wool.
4. Next, introduce a disturbance kills or drives away one level of life in the food web. Students whose organisms that are affected pull on their piece of wool, while those who feel the pull raise their hands. This illustrates that if one organism is affected in a community, other creatures may become affected as well. See what effect toxins have at different levels of the food chain.

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