Decay (Biology GCSE)

Uploaded by freeeschool on 04.09.2012

GCSE Biology - Decay
Hello! Welcome to GCSE Science video about the process of decay. We are going to look
at the process of decay and how it helps to recycle nutrients in the environment.
It starts off with a few examples of couple of living things. We got trees and plants,
a hedgehog and a mouse just as examples. We start off with a look at the plants. We know
that plants require nutrients from the soil. We are not talking about actual food here;
we are just talking about nutrients that are required for healthy growth. For example,
plants need something like magnesium which is required for the production of chlorophyll
which then absorbs sunlight for photosynthesis. Another example is nitrate which is required
for the production of proteins which helps growth. Other examples are phosphates and
there are lots you can list off, but the key thing is that these nutrients are required
for the healthy growth of the plant.
These animals also require some of these nutrients. The mineral ions that are produced in the
plants and they get that by eating the plants. There are other animals that might eat these
animals and they will get their nutrients by eating these animals which have actually
eaten the plants. But over a period of time, we also know that these living things will
produce waste. For example: urine and feces, but also over a longer period of time, the
tree will lose its leaves and eventually all these living things will at some point die.
Now, when they die, they don’t just sit around in the soil or in the ground. They
naturally go through a process of decay.
The key kind of living thing that carries out decay is microorganisms or microbes. There
are other things like worms, maggots and other kinds of living things that will eat all these
material and help to return the nutrients back into the soil. One of the key ones is
microorganisms and what they do is they eat the bodies of the plants and animals and they
return a lot of these nutrients back into the soil. That means that once those nutrients
are back in the soil, they are available for other plants to remove those nutrients and
grow. They make soil much more fertile.
That’s the key overall idea of decay in the environment and how the nutrients are
recycled. Sometimes, people like to try and do this artificially. The reason why they
do it artificially is because they produce a substance called compost. That compost can
be put onto soil or mixed with soil to make it much more fertile and give it lots of nutrients
to help the healthy growth of plants. The way this works is very simple, very straightforward.
We’ve got decaying plant material and in fact, you could also use kitchen waste and
food that has been wasted as well. You can put all that material into a container that
might look something like this and then you can create the perfect conditions for decay.
The key things that are required, the microbes or microorganisms but they are just there
anyway, but they need three key conditions there. They are warmth, moisture which is
basically water and they need oxygen.
If you got the optimal conditions of warmth, moisture and oxygen, the decay of this material
is going to happen much more rapidly. One way in which we can get the warmth is once
the microbes are in there, they carry out a process called respiration and that produces
heat. One source of heat or warmth for this process is the respiration that microbes are
carrying out. You do have to be careful because sometimes the temperature can get quite high
and if it gets too high, it’s going to slow the process down because it could be too high
and it might kill the microorganisms. But respiration produces heat, so that’s one
method of getting the warmth. Moisture could come from rainwater and so on. But the option
over here, in this container, we’ve got all these holes and these holes allow air
to enter. Air contains oxygen and that is important for the process of respiration carried
out by the microbes. It is important that we have these air holes in there to allow
the oxygen in for respiration in order for this plant material to decay. If we got a
wet temperature and the right levels of moisture and the right amount of oxygen or plenty of
oxygen circulating in, these is going to decay as quickly as possible and you are going to
end up with your compost as quickly as possible.
The only other point that I’m going to make here is related to this issue of respiration
and heat. I have seen a question asked in papers before about this being actually mixed
or somewhat coming along and just turning this over and mixing it and remixing it and
why they would do that. One of the reasons is to release some of the heat that is generated
or built up inside and also to mix to make sure the microbes are everywhere and that
air can get in quite evenly. But that’s basically the overall outline of the process
of decay and the key things that you need to know.
[end of audio – 05:42] GCSE Biology - Decay