Energy Flow in Food Chains, Food Webs, & Energy Pyramids

Essential Question What does a food chain show us?

Essential Question How is a food web different from a food chain?

Essential Question How is a food chain or food web related to owl pellets?

Essential Question How does energy flow through an ecosystem?

Essential Question How does the amount of energy change as it moves through an energy pyramid?

Food Chains Food chains use pictures or words and arrows to show the movement of energy through the trophic levels of organisms. The trophic level of an organism indicates the position that the organism occupies in the food chain. It shows what it eats and what eats it.

Producers & Consumers The levels are numbered according to how far the particular organism is along the chain. Producers are at level 1. (Plants are producers because they produce their own food.) Herbivores are at level 2. (consumer) Predators are at level 3. (consumer) And so on…

Anything that cannot make its own food must eat to survive. It must “consume” its food! It is a consumer.

Levels of Consumers Primary Consumers  eat producers, mainly herbivores. (caterpillar, rabbits, etc.) Secondary Consumers  eat primary consumers (frogs, fox) Tertiary Consumers  eat secondary consumers (hawk, wolf)

When an organism eats another organism, There is a transfer of energy occurring. When an Organism eats, it gains energy. Some of this Energy is used, and some gets released as heat. For example:

GrassRabbitFox The arrows show the transfer of energy from one organism to the next. Food chains show which organisms eat what. All these organisms depend on each other to survive, this is called INTERDEPENDENCE.

The arrow shows the direction that the energy is moving.

Note: There’s something wrong. What is it?

Why does this look more like a “cycle” than a chain? Let’s discuss this one in detail.

 In this food chain, what is the producer?  What is the first level consumer?  What is the second level consumer?  Is the polar bear the 3 rd level consumer? Explain.

Food Webs Food webs describe the organisms found in interconnecting food chains using pictures or words and arrows. In other words, food webs are a bunch of food chains all together! They describe the complex patterns of energy flow in an ecosystem by modeling who consumes whom or what.

Energy Pyramids An energy pyramid shows the amount of energy that moves from one trophic level to another in a food chain. The most energy is available at the producer level of the pyramid. The availability of energy decreases as it moves up the energy pyramid.

Energy Pyramid Much of the energy is lost when one organism in a food chain eats another. Most of the energy is converted into heat energy Each feeding level represents about a 90% energy loss

The Energy Pyramid

Awesome Web Site! Let’s take a look at the above web site relating to ecology and energy transfer.

Another Cool Site After we look at the above web site, we’ll go on to view the BrainPop video entitled FOOD CHAINS. The BrainPop videos provide further enrichment of topics discussed in class and are interesting as well as easy to understand!

Making a Model  Let’s make a model of an energy pyramid.  The model you will construct will be simple. It will show pictures of the producers and consumers at each level, the names in words, and the trophic levels.  The good news is that this model really is perfect for meeting our objectives relating to energy pyramids.  Make sure you follow all instructions for proper completion of the model.

Acknowledgements All pictures were obtained from various sources on Google Images. None of the pictures/illustrations are mine. Credit is given to all artists/photographers for their work.