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food webs and chains
Ref: B06d

Water vole
Water vole

In the sections on River Wildlife (B09) and Biodiversity (B06), we looked at the variety of plants and living creatures that live in or near rivers and wetlands. These living creatures can be birds (B09b), mammals (B09c), fish (B09d), amphibians (G1), reptiles, insects and other mini-beasts (B09a). All these creatures need energy to live and are dependent on one another for food to give them energy. When an animal eats food, energy passes from the food into the animal.

Plants get their energy from the sun through a process called photosynthesis (G1). Photosynthesis is how plants make food by using solar energy to convert water and carbon dioxide into sugar.

Food chain
Food chain

A food chain shows how energy moves from the sun into plants and animals. Different species eat different foods and are represented by a different food chain. These different food chains can be built up into a food web.

Example 1: a short food chain:
A Reed Mace growing at the edge of a pond gets energy to grow from the sun - its leaves are eaten by a Pond Snail - a Duck eats the Pond Snail.

The sun
The sun



• Draw this food chain by starting with a drawing of the sun and the plant and the animals. Then link these elements with arrows. The arrows show the movement of energy from the sun through the links in the food chain.

Water shrew
Water shrew

 

 

 

 

 



Example 2: a longer food chain:
A waterlily receives energy from the sun, the plant dies back in the winter and the dead leaves from the plant drop down to the bottom of the pond and are eaten by a water louse. The water louse is eaten by a Dragonfly Nymph, which in turn is eaten by a Water Shrew. The Water Shrew is caught and eaten by a Kestrel.


click on the image to open an enlarged printer friendly version of the food web diagram


Wetland Diet Sheet

This list provides information on how some of the river and wetland residents get their energy. All types of animals get their energy from the food they eat and plants get their energy from sunlight.

SPECIES
ENERGY SOURCE (sunlight or food)
Adult Damselfly Other adult insects
Adult Dragonfly Other adult insects
Adult Frog Insects, water worms, snails, slugs, worms
Adult Mayfly Does not eat since it only lives for a day or two, it uses the energy gained when it was a nymph
Adult Newt Water fleas, water worms, caddislfy & mayfly numphs, freshwater shrimp, midge larvae, pond snails
Algae Sunlight
Arrowhead Sunlight
Caddislfy Larva Microscopic plants, algae, microscopic fungi, small particles of dead plants
Cyclops Microscopic animals and microscopic plants
Damselfly Nymph Tadpoles, young fish, cyclops, waterfleas, freshwater shrimps, water lice and beetles
Dead Plant Particles Sunlight
Dragonfly Nymph Tadpoles, young fish, cyclops, waterfleas, freshwater shrimps, water lice and beetles
Duck Pondweed, large water plants, insects, tadpoles, small fish, pond snails
Flatworm Water lice, waterfleas, cyclops, watermite, microscopic animals, tadpoles and caddisfly larva
Freshwater Shrimp Microscopic fungus, small particles of dead plants
Frog Tadpole Microscopic plants, algae, water worms, midge larvae, cyclops
Great Diving Beetle Cyclops, Water fleas, midge larvae, pond snails, nymphs, tadpoles, flat worms, leeches, water boatmen
Eel Stickleback, freshwater shrimps, frogs, dead fish, river snails
Heron Fish, adult frogs and tadpoles, small birds, larger insects
Kestrel Water shrews
Kingfisher Small fish, tadpoles, small frogs, great diving beetle
Leech Insect nymphs, tadpoles, flat worms, water lice, pond snails, midge larvae
Marsh Marigold Sunlight
Mayfly Nymph Microscopic fungi, microscopic animals and plants, small particles of dead plants
Microscopic Animals Microscopic plants, small particles of dead plants
Microscopic Fungus Dead plants
Microscopic Plants Sunlight
Midge Larva Microscopic plants, small particles of dead plants
Newt Tadpole Microscopic plants, algae, midge larvae, cyclops, fresh water shrimps, water worms
Pond Skater Remains of dead plants and dead animals
Pond Snail Large water plants and algae
Reed Mace Sunlight
Trout fry Tadpoles, young fish, cyclops, water fleas, freshwater shrimps, water lice and beetles
Salmon fry Tadpoles, young fish, cyclops, water fleas, freshwater shrimps, water lice and beetles
Sticklebacks Tadpoles, young fish, cyclops, water fleas, freshwater shrimps, water lice and beetles
Water Boatmen Tadpoles, freshwater shrimps, water worms, midge larvae, water fleas, cyclops
Water Flea Microscopic plants, small particles of dead plants
Water Louse Microscopic plants, fungi, small particles of dead plants
Water Mite Body fluids of beetles, water boatmen, pond skaters and insect nymphs
Water Shrew Pond Insects, water worms, tadpoles, small frogs
Water Worm Microscopic fungi, small particles of dead plants

Exercises:

1) Complete the arrows on the food web showing the direction in which energy moves.

2) Using the information in the Wetland Diet Sheet, draw your own food chain - remember that energy always starts with the sun.

  produced by the WESTCOUNTRY RIVERS TRUST as part of the CORNWALL RIVERS PROJECT  
 

www.wrt.org.uk
www.cornwallriversproject.org.uk