Energy Flow Through the Ecosystem

case study: Swiss Alpine Food Web

What we need to know/do

  1. What is energy used for and where does it come from?
  2. How is energy moved (and lost) through an ecosystem?
  3. Construct a fully labelled food web


  • Calculate energy loss (as a percentage) from the food web
  • Explain how decrease in populations can cause changes in an ecosystem

The Sun!

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How big is the Sun?

Energy for almost all of the plants and animals (including you!) originates from our Sun.

Plants use this energy to make food (sugars) in a chemical reaction called photosynthesis.

These plants are then eaten by animals and so the energy is passed on

These animals are eaten by other animals....and the energy is passed on again!

Star Size Comparison HD

What is energy used for?

Look at the pictures below, identify the uses of energy in each picture...
Energy is measured in Joules (J)

Food Webs

Food webs are diagrams that show how energy from the sun is used by plants and animals.
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Key words

Producer - plants that use energy from the sun to make food (sugar)

Herbivore - animals that eat plants

Carnivore - animals that eat animals

Omnivore - animals that eat plants AND animals

How to Construct a Food Web