B4g: Decay

We try to prevent food going off (decaying) but we want decay to happen when sewage is treated or when compost is made. This item is concerned with the process of decay and some examples. The experiments on decay provide the opportunity to plan a test of a scientific idea, analyse and interpret data using qualitative and quantitative techniques, present information and draw a conclusion using scientific and technical conventions. The survey of preservation techniques provides the opportunity to use ICT sources and tools to collect secondary data. 

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What are the four key factors in the process of decay?
Presence of microorganisms, temperature, oxygen and moisture.
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Why is decay important for plant growth?
It recycles important nutrients for plant growth.
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What two things are microorganisms used to do?
To break down human waste (sewage) and break down plant waste (compost).
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What seven preservation techniques reduce the rate of decay?
Canning, cooling, adding salt vinegar and sugar, freezing and drying.
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What effect does high temperatures have on decay?
Prevents decay.
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What effect does low temperatures have on decay?
Slows decay.
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What effect does lack of oxygen have on decay?
Slows decay.
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What effect does lack of water have on decay?
Slows decay.
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Why does high temperatures prevent decay?
Enzymes and proteins denatured, decomposers killed.
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Why does low temperatures slow down decay?
Reduced rates of reaction, and rate of growth and reproduction of decomposers reduced.
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Why does lack of oxygen temperatures slow down decay?
Oxygen is needed for respiration by decomposers.
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Why does lack of water temperatures slow down decay?
Water is needed for transport and to support reactions inside decomposers.
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What is detritus?
Dead and decaying material.
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List three detritivores.
Maggots, woodlice and earthworms.
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What do detritivores feed on?
Detritus.
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How do detritivores increase the rate of decay?
They break detritus into smaller pieces, which increases the surface area.
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What is meant by the term saprophyte?
Organisms that feed on dead material by releasing enzymes which break complex compounds into simple soluble ones that the decomposer can absorb. This process is called extracellular digestion.
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How does canning reduce the rate of decay?
The sealed can is heated to kill bacteria. When it cools, no more bacteria can enter.
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How does freezing reduce the rate of decay?
Bacteria cannot reproduce at low temperatures and the water in the food is frozen.
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How does adding salt/sugar reduce the rate of decay?
Removes water by osmosis. Removing water prevents the microorganisms from growing, or digesting the food.
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How does adding vinegar reduce the rate of decay?
Reduces the pH to prevent the enzymes in the microorganisms from working.
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How does drying reduce the rate of decay?
Removing water prevents the microorganisms from growing, or digesting the food.
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How does cooling reduce the rate of decay?
The food is kept at a low temperature so bacteria cannot reproduce (they are not killed).
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Other cards in this set

Card 2

Front

Why is decay important for plant growth?

Back

It recycles important nutrients for plant growth.

Card 3

Front

What two things are microorganisms used to do?

Back

Preview of the front of card 3

Card 4

Front

What seven preservation techniques reduce the rate of decay?

Back

Preview of the front of card 4

Card 5

Front

What effect does high temperatures have on decay?

Back

Preview of the front of card 5
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