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B4 e-h Pig • What’s wrong with this food chain? • Arrows pointing wrong way • List 3 ways energy is lost as you move up a food chain • Some parts don’t get eaten • Some lost as faeces • Some used in respiration (movement, keeping warm etc) • What is the efficiency of energy transfer in the diagram? • 16.5% • Why can farmers make more money by keeping battery hens in cages than they can from free range? • Less energy is lost in moving and keeping warm so farmers can feed them less • Name 2 biofuels • Biogas (methane) • Bioethanol • Wood • How do you make biogas? • Fermentation • By bacteria • In a digester • Biomass fuels are considered by some to be environmentally friendly. Suggest why this might not be the case. • Natural habitats destroyed to grow biomass • Biomass grown on land normally used for food • Why do farmers use pesticides? • Less of the crop’s energy is lost to pests is a better answer • What are the advantages of biological control? • No toxic chemical • Useful insects not harmed • Top predators not poisoned • Why does crop rotation reduce the need for fertilizers? • Nitrogen-fixing crops can be grown once every 4 years • These contain Nfixing bacteria that change nitrogen gas into nitrates • What 3 conditions do decomposers need to grow? • Oxygen • Water • Warmth • Why does adding sugar or salt preserve food? • Removes water using osmosis • Name 2 uses of decomposing microbes? • Making compost • Breaking down sewage • How does carbon get into plants? • Photosynthesis • List 3 ways carbon is put back into the atmosphere? • Respiration by animals • Respiration by plants • Respiration by decomposers (decomposition) • Combustion • Why is there more carbon dioxide in the atmosphere in the winter? • Less photosynthesis (fewer leaves) • More combustion (heating) • Name 2 bacteria that add nitrates to the soil? • Nitrifying bacteria • Nitrogen-fixing bacteria