2. Objectives Explore the relationship between different animals in ecosystems in terms of energy transfer. Outcomes 3: Draw different diagrams to represent energy transfer in an ecosystem. 5: Explain why not all energy is passed from one level to another. 7: Evaluate the importance of different interactions in ecosystems in terms of energy transfer. Key terms: food chain, web, biomass, pyramid of numbers, trophic level.

3. Energy transfer in the food chain

4. Pyramids of numbers only give an accurate impression of the flow of energy in a food chain if the organisms are of similar size. Measuring the biomass at each trophic level can give a more accurate picture. Pyramids of numbers are a quantitative way of representing food chains. What are the problems of representing food chains in pyramids of numbers? They record the number of organisms at each trophic level in a specified area. What are pyramids of numbers?

5. Numbers or biomass?

6. In a pyramid of numbers, the length of each bar represents the number of organisms at each trophic level in a specified area. As a single tree can support many organisms, this food chain produces an unbalanced pyramid. Understanding pyramids of numbers

7. Understanding pyramids of biomass In a pyramid of biomass, the length of each bar represents the amount of organic matter – biomass – at each trophic level in a specified area. At each trophic level, the amount of biomass and energy available is reduced, giving a pyramid shape.

8. Pyramids of energy Pyramids of energy or productivity show the amount of energy available to the next trophic level. The bars are proportional in size to the energy acquired from the level below. Energy is measured in kilojoules per square metre per year, so seasonal anomalies will not show. Energy is always lost during the transfer from one trophic level to the next so an inverted pyramid cannot be produced. 10,000 kJm -2 year -1 2,100 kJm -2 year -1 180 kJm -2 year -1 10 kJm -2 year -1

9. Draw a food chain 4 organisms long. For it draw a scaled pyramid of energy using the following figures: Producer: 20 000 kJm -2 year -1 Primary consumer: 5 000 kJm -2 year -1 Secondary: 1 000 kJm -2 year -1 Tertiary: 250 kJm -2 year -1 Outcomes 3: Draw different diagrams to represent energy transfer in an ecosystem. 5: Explain why not all energy is passed from one level to another. 7: Evaluate the importance of different interactions in ecosystems in terms of energy transfer. Key terms: food chain, web, biomass, pyramid of numbers, trophic level.

10. Where is energy lost through a food chain? Outcomes 3: Draw different diagrams to represent energy transfer in an ecosystem. 5: Explain why not all energy is passed from one level to another. 7: Evaluate the importance of different interactions in ecosystems in terms of energy transfer. Key terms: food chain, web, biomass, pyramid of numbers, trophic level.

11. Where is energy lost when transferring between organisms? Outcomes 3: Draw different diagrams to represent energy transfer in an ecosystem. 5: Explain why not all energy is passed from one level to another. 7: Evaluate the importance of different interactions in ecosystems in terms of energy transfer. Key terms: food chain, web, biomass, pyramid of numbers, trophic level.

13. Why is it that food chains are generally a maximum of 5 organisms long? Outcomes 3: Draw different diagrams to represent energy transfer in an ecosystem. 5: Explain why not all energy is passed from one level to another. 7: Evaluate the importance of different interactions in ecosystems in terms of energy transfer. Key terms: food chain, web, biomass, pyramid of numbers, trophic level.