Efficiency of a food chain

1. Efficiency of a food chain WALT To be able to describe what affects the energy flow in a food chain. To be able to explain how to improve the efficiency of food production

2. Learning Outcomes • All students are able to describe how energy is lost as you go up a food chain. • Most students can give examples of how to improve the efficiency of food production. • Some students can complete calculations on the energy flow through a food chain.

3. Energy loss in food chains

4. Task Draw and label the energy loss of a horse You may use page 31 to help you WILF All students are able to describe how energy is lost as you go up a food chain

5. energy used for growth (input) efficiency = energy supplied (output) How do you calculate efficiency? Energy efficiency can be calculated using the following equation: For example, if grass receives 1,000,000kJ of energy from the Sun and uses 20,000kJ of energy for growth, then: 20,000 kJ efficiency = 1,000,000 kJ = 0.02 = 2%

6. Energy efficiency calculations

7. WILF Some students can complete calculations on the energy flow through a food chain.

8. A luxury item? How can the costs of these food items be compared fairly? A 400g steak costs £4.00. An 800g loaf of bread costs £0.80. This equals £1.00 per 100g. This equals £0.10 per 100g. Why is meat more expensive than bread?

9. How energy efficient is it to eat meat? Food chains can be used to understand why some foods cost more than others. Which of these chains is the most efficient? The first food chain is the most efficient because it contains fewest trophic levels, so less energy will be lost.

10. Is eating meat less energy efficient? Cattle and other livestock are fed grain and cereals. Would it be more energy efficient if humans ate the plant crops instead? If a one-acre field of corn is used to feed cows, it can support one person. If the same area is used to feed humans directly, it can support 10 people. Why is so much energy lost?

11. Task WILF Most students can give examples of how to improve the efficiency of food production Write brief notes on how to improve the efficiency of food production You can use your text book to help you

12. Learning Outcomes • All students are able to describe how energy is lost as you go up a food chain. • Most students can give examples of how to improve the efficiency of food production. • Some students can complete calculations on the energy flow through a food chain.