First 300 words of the document:
Decay and carbon cycle:
Living things remove materials from the environment for growth and
other processes. These materials are returned to the environment either
in waste materials or when living things die and decay.
Materials decay because they are broken down (digested) by
micro-organisms. Microorganisms digest materials faster in warm, moist
conditions. Many microorganisms are also more active when there is
plenty of oxygen.
The decay process releases substances which plants need to grow.
In a stable community, the processes which remove materials are
balanced by processes which return materials. The materials are
The constant cycling of carbon is called the carbon cycle. In the carbon
1. Carbon dioxide is removed from the environment by green plants for
photosynthesis. The carbon from the carbon dioxide is used to make
carbohydrates, fats, and proteins which make up the body of plants.
2. Some of the carbon dioxide is returned to the atmosphere when green
3. When green plants are eaten by animals and these animals are eaten by
other animals, some of the carbon becomes part of the fats and proteins
which make up their bodies.
4. When animals respire some of this carbon becomes carbon dioxide and is
released into the atmosphere.
5. When plants and animals die, some animals and microorganisms feed on
their bodies. Carbon is released into the atmosphere as carbon dioxide
when these organisms respire.
6. By the time the microorganisms and detritus feeders have broken down
the waste products and dead bodies of organisms in ecosystems and
cycled the materials as plant nutrients, all the energy originally captured
by green plants has been transferred.