Decay

Question 1

Explain why decay is important for plant growth

Answer 1

It releases minerals into the soil for their healthy growth

Question 2

Recognise that food preservation techniques reduce the rate of decay

Answer 2

Canning
Cooling
Freezing
Drying
Adding salt/sugar
Adding vinegar

Question 3

What are the microorganisms used for in decay?

Answer 3

• break down human waste (sewage)

- break down plant waste (compost)

Question 4

Describe how to carry out an experiment to show that decay is caused by the decomposers bacteria and fungi

Answer 4

1. Pour a solution containing nutrients into flask A
2. Boil the nutrient solution to kill microorganisms and drive out air
3. Seal the neck of the flask
4. Pour more of the same nutrient solution into another flask, but this time snap off the neck

Question 5

Describe the effect on the rate of decay when changing temperature?

Answer 5

The microorganisms’ rate of respiration and growth increase until it reaches 40°C (optimum temperature). At this temperature the microorganisms’ growth and respiration rates are as high as they can be. Above this the enzymes denature, so decay stops.

Question 6

Describe the effect on the rate of decay when changing the amount of oxygen?

Answer 6

Increasing the amount of oxygen in the air increases the microorganisms’ rate of respiration, which means they release more energy enabling them to grow and reproduce more quickly. There is no optimum temperature.

Question 7

Describe the effect on the rate of decay when changing the amount of water?

Answer 7

Microorganisms grow quickest in moist conditions, which increases the rate of decay. Having too much or too little water present slows down their growth and, therefore, the rate of decay.

Question 8

What do detritivores, earthworms and maggots do?

Answer 8

They feed on dead and decaying material (detritus)

Question 9

Explain how detritivores increase the rate of decay by producing a larger surface area?

Answer 9

They break down detritus into small particles which have a larger surface area, making it easier for decomposers to feed on.

Question 10

Explain how food preservation methods reduce the rate of decay

Answer 10

Storing food in dry, cold conditions prevents microorganisms and fungi from growing

Question 11

Explain the term saprophyte

Answer 11

Organism that feeds through through absorbing nutrients in solution (usually in dead/decaying material).

Question 12

Recall the key factors in the process of decay

Answer 12

• presence of microorganisms
• temperature
• oxygen
• moisture

Question 13

Explain how saprophytic fungi digest dead material,in terms of extracellular digestion

Answer 13

Fungi is a saprophyte so feeds in dead organic material by secreting enzymes externally onto their food and then absorbing the digested products. This is called extracellular digestion. Saprophytes are essential for decay.