Biology - Waste Management (AQA Syllabus A)

In GCSE Science students will look at energy and biomass in food chains. This is the second of three quizzes on that subject and it looks specifically at the decay and recycling of dead and waste material, or waste management.

When we think of waste management we think of dustbin men and litter pickers. Many trees shed their leaves each year and most animals produce droppings at least once a day. All plants and animals eventually die so why are we not knee-deep in leaves, droppings and dead animals in the countryside? Is there someone who goes round cleaning up?

Of course not! It all happens naturally as part of the cycles of life. Waste and dead material will naturally decay. Microorganisms play an important part in decomposing waste material and animal carcasses so that the chemicals from which they are made can be used again by plants. The same material is recycled over and over again and can lead to stable communities.

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In situations where something is removed from the system, the whole food web can break down as the plants do not get the nutrients they need to thrive. That is why farmers need to use fertilisers - as the crops are taken away, no nutrients are put back into the soil naturally so without fertilisers, the next crops would not be as good.

The compost heap in your garden is an artificial form of nature's recycling system. By placing uncooked food waste like vegetable peelings and grass cuttings in a pile or in a composting bin, they can rot down and decay and then be added back to the soil. Humans create vast amounts of rubbish which is taken to landfill sites. Part of the rubbish is garden waste. When this decomposes in a landfill site, the nutrients are wasted. This is poor management. Most local authorities run composting schemes where the garden waste is separated and sent for composting instead of to landfill sites.

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  1. Which of the following methods of packaging does not break down naturally?
    Plastic bags (and other plastic items) that are thrown away now will still be there in landfills in hundreds of years time
  2. Which of the following makes things decay?
    Microorganisms digest the waste and dead materials and use some of the products themselves. Any unused materials are released back to the environment. Worms and woodlice help the process by breaking down larger pieces of detritus into smaller pieces that can be broken down faster. Viruses play no part whatsoever in the decay process
  3. In what form can these materials be returned to the environment?
    They are also returned as leaves, dead plants, dead flowers etc. In other words, they are returned to the environment as waste products and when organisms (or parts of plants) die
  4. Why do living things take things from their environment?
    Plants take carbon dioxide from the air and water containing their nutrients from the soil
  5. Which word correctly describes something that can be broken down by the microorganisms that cause decay?
    All living things are biodegradeable although certain parts of them may take longer than others to decay
  6. Many local authorities run garden waste composting schemes. Which of the following is not an advantage of this?
    There are many benefits to composting schemes and very few disadvantages
  7. Some students carried out an experiment to investigate the rate of decay of a potato. Below are just four of the experiments they tried. In which one would the potato decay fastest?
    This tests whether or not you know the best conditions for decay to take place
  8. How does nature recycle dead and waste materials?
    As they decay, chemicals are released back into the environment that can be used by plants. They can then travel through the food web again
  9. Gardeners will 'turn' their compost regularly. This involves using a garden fork to bring the compost from the bottom of the pile to the top. Which of the following is the scientific reason for doing this?
    There are two types of microorganism that cause decay. Anaerobic ones are dominant where there is little oxygen present. They work slowly and tend to produce a smelly sludge. They also release methane and hydrogen sulfide which are of no use to plants. Aerobic microorganisms work faster and produce a compost that is more like soil
  10. How do microorganisms cause decay?
    Enzymes are chemicals that help to break down other more complex chemicals into smaller chemicals. Some of the smaller chemicals are used by the bacteria and fungi for growth, repair and respiration. The rest are returned to the environment for re-use by plants

Author: Kev Woodward

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