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# 6.3: Food Chains and Food Webs

Difficulty Level: At Grade Created by: CK-12
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Who eats whom?

Describing the flow of energy within an ecosystem essentially answers this question. To survive, one must eat. Why? To get energy. Food chains and webs describe the transfer of energy within an ecosystem, from one organism to another. In other words, they show who eats whom.

### Food Chains and Food Webs

Food chains and food webs are diagrams that represent feeding relationships. Essentially, they show who eats whom. In this way, they model how energy and matter move through ecosystems.

#### Food Chains

A food chain represents a single pathway by which energy and matter flow through an ecosystem. An example is shown in Figure below . Food chains are generally simpler than what really happens in nature. Most organisms consume—and are consumed by—more than one species.

This food chain includes producers and consumers. How could you add decomposers to the food chain?

A musical summary of food chains can be heard at http://www.youtube.com/watch?v=TE6wqG4nb3M (2:46).

#### Food Webs

A food web represents multiple pathways through which energy and matter flow through an ecosystem. It includes many intersecting food chains. It demonstrates that most organisms eat, and are eaten, by more than one species. An example is shown in Figure below .

This food web consists of several different food chains. Which organisms are producers in all of the food chains included in the food web?

### Summary

• Food chains and food webs are diagrams that represent feeding relationships.
• Food chains and webs model how energy and matter move through ecosystems.

### Practice I

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology $\rightarrow$ Biology for AP* $\rightarrow$ Search: Feeding Relationships
1. What are trophic levels?
2. Describe primary producers.
3. Differentiate between primary, secondary, and tertiary consumers.
4. Define detritus and detritivore.
5. What is a food chain? What is a food web?

### Review

1. Draw a terrestrial food chain that includes four feeding levels.

2. Describe the role of decomposers in food webs.

Feb 24, 2012

Jan 25, 2015