1. Pests Aims To study pests in the context of competition, predator / prey relationships and pyramids of numbers and build up of toxins in food chains. To evaluate written text

2. Learning outcomes By the end of the lesson You should have/be able to worked effectively on your own and in small groups to: Use food chains and webs and pyramids to model the build up of pesticides in food chains. (6) Describe that the organisms living in a habitat compete with each other (6) explain that the numbers of a population of predators influence the numbers of prey organisms to evaluate conflicting evidence to arrive at a considered viewpoint (7)

3. In pairs Discuss the meaning of the words pests and pesticides, herbicide, fungicide and insecticide. (3 minutes to discuss the difference.) Match the definitions (2 mins) Copy correct definitions into your books

4. Food webs and chains Watch the video Write down 2 key points

5. Discuss in pairs What is the potential impact of different slug control methods on food webs.

6. How It Works This product is a stomach poison which dehydrates snails after they eat the bait. The added taste deterrent is a bittering agent which prevents most cats and dogs from eating the pellets. Precautions Store away from children and pets. Do not heap – it is wasteful and easy for domestic pets to collect. Dogs may find pellets attractive. If eaten, take to vet immediately. Read all safety directions including rear of pack. Dispose of empty container safely. Do not apply Blitzem Pellets to edible plant parts

7. Environmentally friendly multi purpose pure wool pellets ideal for organic gardening. The hygroscopic nature of wool fibres absorb some of the slimy substance underneath the slugs foot The wool pellet barrier contains abrasive particles irritates and aggravates the slug‘s ‘foot‘

8. Food Chains recap. Draw a food chain for the organisms below

10. Pyramids of numbers

11. quick test

12. Pyramids of numbers represent the numbers of organisms at each stage in a food chain. Study the four pyramids of numbers A, B, C and D.

13. For each of the food chains choose the pyramid of numbers which best represents the food chain. (i)grass → insects → spiders → birds (ii) oak trees → aphids → blue tits → sparrow hawks (iii) grass → rabbits → foxes → fleas

14. Explain the difference between persistent and non-persistent pesticides and the concept of bioaccumulation. What does biodegradeble mean? (Write definitions in your books if not done last lesson) Page 148-149 may help

15. If DDT is banned, why is it still in some of the food I buy? Work in a small group. Read the information on the cards. Then cut them out and sort them into the correct order to answer the question that is the title above. Once you have finished the card sort, discuss the following questions with a partner. 1 Should poor countries be allowed to use DDT when it causes such long-term environmental damage? 2 Which is more important, to save lives by reducing malaria or to protect top predators from a lethal dose of DDT?