B4 - Its A Green World

Question 1

What are the two main groups of microbes involved in decay?

Answer 1

Bacteria and fungi

Question 2

Describe the experiment used to observe that bacteria and fungi are involved in decay

Answer 2

Bread is left to decay in a lab

Question 3

State and explain 3 conditions that provide a fast rate of decay

Answer 3

Higher temperature = higher rate of respiration so faster rate of decay

More oxygen = higher rate of respiration so faster rate of decay

More water = microbes will grow faster and reproduce more in moist conditions, increasing rate of decay

Question 4

State and explain the purpose of the 2 types of decay organisms (not bacteria and fungi)

Answer 4

Decomposers - chemically break down dead material into ammonium compounds which are released into the soil

Detritivores - feed off of dead material, digest it and pass it out in waste. This increases the surface area of the dead material for decomposers to work on

Question 5

Explain how saprophytic feeding works

Answer 5

Saprophytes release enzymes onto dead material. The enzymes digest the dead material in extracellular digestion. The decomposers then absorb the digested chemicals

Question 6

State and explain 2 ways decay is useful to humans

Answer 6

• Compost - waste can be broken down into compost which can be used to provide nutrients for plant growth
• Sewage - bacteria digest organic waste to make it safe enough to release into natural bodies of water

Question 7

State and explain 7 food preservation methods

Answer 7

• Drying - decomposers cannot grow or reproduce without moisture
• Cooling - slows down rate of reproduction of decomposers
• Freezing - stops reproduction of decomposers
• Adding salt - causes water to be drawn out of microbes by osmosis, killing them
• Adding sugar - causes water to be drawn out of microbes, killing them
• Canning - decomposers cannot respire or reproduce without oxygen
• Adding vinegar - vinegar is an acid which kills decomposers