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gcse science B4 - G

specific for ocr gateway additonal science B.

what does detritus mean? remains of dead and decaying plants and animals
what are detritivores? animals which depend on detritus for their food
examples of detritivores? earthworms, maggots, woodlice
what do detritivores do? speed up decay as they break the detritus down into smaller pieces, which increases the surface area
why are detritivores important? they recycle chemicals from dead plants and animals
what is another method of using decay? for compost
what conditions speed up the composting process? -warmth -moisture -good aeration (to allow oxygen in)
what happens inside a compost bin? microorganisms respire, which give off heat and warms up the compost, which speeds up decay
what does decay depend on? enzyme action - conditions that speed up enzyme action also speed up decay
what is the optimum temperature for bacteria? 37
what is the optimum temperature for fungi? 25
what are the two types of bacteria? aerobic and anaerobic
why do aerobic bacteria break down dead detritus quickly? because they produce oxygen, which speeds up decay
why do anaerobic bacteria break down dead detritus slowly? because they produce acid conditions, which slows down decay
what is a saprophyte? a fungus that feeds off dead and decaying materials
what happens to the saprophyte's digestive enzymes? released on to the food and break it down into simple soluble substances so the digested food is absorbed easily
what are the 5 ways to preserve food? canning, cooking, vinegar, drying, freezing, adding sugar or salt
how does cooking work? kills bacteria. food poisoning is caused by food being undercooked
how does canning work? killheats food before being canned to kill the bacteria. then sealed in a can to stop any bacteria getting ins bacteriA
how does vinegar work? it's an acid. very few bacteria can grow in acid conditions.
examples of food preserved in vinegar? pickled eggs, chutney
how does drying work? bacteria and fungi can't grow without water
examples of food preserved by drying? cereals
how does freezing work? kills bacteria or slows their growth
how does adding sugar or salt work? kills some bacteria and fungi and stops the growth of others
Created by: jirwin
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