Decay is a process involving the breakdown of complex
substances into simpler ones by microorganisms.
Decay is important for plant growth because it releases minerals
into the soil for their healthy growth.
The ideal
conditions for the
microorganisms
that cause decay
are those that
increases their
respiration, growth
and reproduction
rates.
Temperature - as temperature is increased, the
microorganisms' rate of respiration and growth increase until
it reaches 40 degrees, which is the optimum temperature.
Above this the enzymes are denatured, so decay stops.
Oxygen - increasing 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. The re is no optimum.
Water - 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.
Bacteria and fungi and saprophytes - they feed on dead organic material by
secreting enzymes externally onto their food and then absorbing the digested
products. This is called extra-cellular digestion. Saprophytes are essential for decay.
Food Preservation
Microorganisms will feed on any source of food and
cause it to decay if the conditions are right. Food can be
preserved by removing one of the conditions needed.
Canning - food can be heated to destroy and sealed to
prevent microorganisms from getting any oxygen
Refrigeration and freezing - food can be kept at low
temperatures to slow down the growth and reproduction
Pickling - low pH slows the growth of microorganisms
by denaturing the microorganisms' enzymes
Adding sugar or salt - conditions to concentrated for the
Drying - reduces the moisture available, preventing growth
Decomposers
When dead organisms or waste material decay,
minerals are released which can then be re-used by
other living organisms, particularly plants.
Various soil organisms, including bacteria, fungi,
earth worms, maggots and woodlice, help with the
process of decay.
Earthworms, woodlice and maggots are known
as detritivores; they feed on dead organisms and
the waste produced by living organisms.
Detritivores speed up the process of decay
because they break down detritus into small
particles which have a large surface area,
making it easier for decomposers to feed on.
The faeces of detritvores also provide food for
decomposers like bacteria and fungi.
Decomposer organisms are used by humans
to break down waste: they feed on human
waste in sewage treatment works and they
break down waste in compost heaps.