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1. Pollution is when humans put harmful --------- or energy into the -----------. (lesson 25a)
2. Which plants are sensitive to sulphur dioxide in the air? (25a)
3. How are they fighting the effects of acid rain in Swedish lakes? (25a)
4. What happens to the number of living things as you go up a pyramid of numbers? (25b)
5. What happens to the size of each living thing as you go up a pyramid of numbers? (25b)
6. In a Tullgren funnel, tiny animals move away from ----- and ----. (25b)
7. What are the main farm pests? (25c)
8. As pesticides like DDT pass along food chains, their concentration ---------. (25c)
9. Sometimes predators can be used to control a pest. This is called ---------- -------. (25c)
10. Microbes that rot down dead plants and animals are called -----------. (25d)
11. What is the movement of nutrients on land, in freshwater and in the sea called? (25d)
12. How could you show that a fungus had digested (broken down) starch? (25d)
13. What do we call microscopic plants that live in lakes, rivers and seas? (25e)
14. What would the presence of mayfly larvae and stonefly larvae tell you about a river? (25e)
15. What would the presence of only sludge worms and blood worms tell you about a river? (25e)

ANSWERS

• Chemicals, environment.
• Lichens and black spot mould.
• By spraying with lime to neutralise the acid.
• It decreases.
• It increases.
• Light and heat.
• Insects, weeds and moulds.
• Increases.
• Biological control.
• Decomposers.
• A nutrient cycle.
• No blue-black colour with iodine or orange if heated with Benedict's solution.
• Algae.
• It's clean/has lots of oxygen.
• It's polluted/has little oxygen.