Where has that carbon atom been? The carbon cycle is a complex cyclical process through which all of the carbon atoms in existence rotate.
The diagram illustrates the important role that microbes i.e. algae, cyanobacteria and the decomposers, play as primary producers and in the cycling of nutrients.
Photosynthetic organisms like algae, cyanobacteria and plants are capable of using light energy which is trapped by chlorophyll, to convert carbon dioxide and water into oxygen and glucose (food). This process is called photosynthesis.
Organisms that make their own food are called primary producers and are always at the start of the food chain.
Animals and micro-organisms like fungi and bacteria get energy and nutrients by eating other plants, animals and microbes.
Organisms release energy from food (glucose), as well as carbon dioxide and water in the process of aerobic respiration. This energy is used to do the work needed to keep cells and organisms alive. Aerobic respiration requires oxygen.
The decomposers (fungi and soil bacteria) obtain their energy and nutrients from the dead bodies and waste products of other organisms. As dead bodies and waste products break down, they release essential nutrients into the soil.
Green algae and cyanobacteria are found at the beginning of the food chain. They are known as primary producers because they make their own food.