Natural Cycles

Carbon, oxygen and energy cycles

Before plants evolved, the Earth’s atmosphere had more carbon dioxide than today and very little oxygen, not enough for animals to live. Plants, bacteria and phytoplankton − tiny marine plants − photosynthesise, transforming the energy from the sun into stored chemical energy, absorbing carbon dioxide and releasing oxygen.

When organisms respire they take the oxygen up and combine it with carbon to release energy and form carbon dioxide. So the combination of photosynthesis and respiration means carbon, oxygen and energy form an interwoven cycle.

Nitrogen cycle

Nitrogen is essential for all organisms and plants are no exception. Bacteria living on, or even in, some plant roots convert nitrogen from the atmosphere into a form the plant can use. Creatures feeding on these plants release nitrogen in their waste products. When the waste is broken down by microbes the nitrogen is recycled back into the atmosphere.