Unit A

Module 1 ~ Lesson 2

 Energy and Feeding Relationships

Trophic levels describe feeding relationships in an ecosystem.

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Trophic levels.

Organisms can be identified in many ways, such as through feeding relationships, and organisms can be organized into trophic levels. These levels also indicate the amount of energy available to organisms. Food webs and food chains are used to represent the feeding relationships in an ecosystem. You should be able to identify the trophic level of an organism given a food web or food chain for an ecosystem. 

 Read

Read "How Energy is Transferred in the Biosphere", "Trophic Levels Describe Feeding Relationships in Ecosystems", and "Food Chains and Food Webs" on pages 16 to 18 in your textbook.

Rule of 10.

As organisms go about their daily activities of growth, movement, reproduction etc., much of the energy that they captured is lost as heat and other waste products. The amount of energy lost varies, but is usually around 90%, meaning that 10% of the energy captured by an organism is available to be passed on to the next trophic level. This is a generalization rather than a rule but is referred to as the Rule of 10.  Calculations involving the Rule of 10, or any other energy transfer, will require you to calculate percentages of values.