Oh, What a Tangled Web We Weave

Oh, What a Tangled Web We Weave

Background:

            Plants use light energy of the sun to make food.  The food is stored in the cells of the plant.  Plants are called producers because they make food.  Some of the stored energy in the food plants make is passed on to the animals that eat the plants.  Plant-eating animals are called primary consumers.  Animals that eat other animals are called secondary consumers.

            The pathway that food takes through an ecosystem is called a food chain.  A food chain also shows the movement of energy from plants to plant eaters and then to animal eaters.  An example of a food chain can be written:

                        seeds  sparrow  hawk

Some of the food energy in the seeds moves to the sparrow that eats them.  Some of the food energy then moves to the hawk that eats the sparrow.  Normally, only about 10% of the energy produced by the “food” moves to the consumer.  Most of the other energy is used to keep the organism alive and allow it to reproduce.

Because a hawk eats animals other than sparrows, you could make a food chain for each animal the hawk eats.  If all the food chains were connected, the result is a food web.  A food web is a group of connected food chains.  A food web shows many energy relationships.

Goals:

In this exercise, you will:

1. determine what different animals eat in several food chains.
2. build a food web that could exist in a forest ecosystem.
3. identify how a food chain can be shown as a food pyramid.