Pond Food Pyramid

Source:

Adapted from Schools Out - Fieldwork made easy: A teacher's pack for 5-14 Environmental Studies produced by Highland Environmental Network School Group and the Moine Mhor NNR, schools pack (SNH).

Time

10 minutes

You will need

• large group of children (about 20 or more)
• camera (optional)
• black paper discs (one for each person in group1)

Did you know?

The insecticide DDT was widely used in Britain until it was discovered that it was passed up the food chain.  It weakened the egg shells of birds of prey causing reproductive failure, as the eggs broke when the birds sat on them during incubation.

Before the activity

Discuss food chains with the group to ensure that they understand the concept. This is a good activity to do after river or pond dipping when they will have become familiar with small aquatic creatures and have had a chance to think about what the creatures eat and what would eat them.

The activity

Divide the group into

• Group of about 10 = the water plants
• Group of about   6 = the tadpoles (or caddisfly larvae, mayfly larvae)
• Group of about   3 = the trout
• Group of            1 =  the otter (or human or heron) = tallest child

Arrange the groups:

• the water plants sit on the grass
• the tadpoles behind them with their hands on the water plants' shoulders
• the trout stand behind them with their hands on the tadpoles' shoulders
• the otter stands behind the trout with his/her hands on the trouts' shoulders

Take a photo of the food pyramid, for displaying back in class

• ask the class which creatures in the pyramid rely on the water plants for food (tadpoles, trout and otter)
• ask the class which creatures rely on the otter for food (none)

Explain that the food pyramid shows that you need a great abundance of creatures low down in the food chain to support fewer and fewer predators further up.

What happens to the other creatures when all the tadpoles change into frogs and leave the pond? Discuss the importance of a diversity of prey items across all seasons.

Discuss the importance of both Diversity and Abundance of all species in the food pyramid.

Pretend to spray each water plant with a toxic herbicide and give each plant a black paper disc. Get the plants to pass the discs to the tadpoles, the tadpoles to pass them to the trout and the trout to pass them to the otter.

Discuss what happens if poisons or toxins enter a food chain. The poison might not be enough to damage the animals at the bottom of the chain (or they might not live long enough to feel the affects) but how is the poison concentrated as it goes up the food pyramid?

Suggested Follow up

• Discuss the word 'Biodiversity' and get the children to find out what it means
• Research the use of DDT
• Do the activity Responding to Rivers
• Read poems and stories about Rivers

Downloads

• See the Introduction to Biodiversity on this website
• See the pond explorer on the Naturegrid web site to explore pond habitats and their inhabitants, do a virtual pond dip and identify and find out about small pond creatures

Additional Information

• See Biodiversity stories
• The Second Nature pack available from the RSPB, has stories, poems and activities associated with  rivers

Curriculum Links

• Science - main
• Mathematics - linked

Age Range

2,3