Biosphere Contents

3. Photosynthesis

Two of the most important processes by which organisms modify the environment are photosynthesis and respiration

Photosynthesis is the process by which carbon is transformed from an inorganic form, carbon dioxide, into organic matter. Directly or indirectly, photosynthesis provides the energy for all forms of life on Earth. As well as providing all animals (including us) with food, plant growth affects the composition of the atmosphere, the development of soils, the water cycle, and indirectly the rate and type of weathering of rocks. It is commonly argued that life has formed the atmosphere as it is today, and that this is the major reason for the differences between the atmosphere of the Earth and that of Mars or Venus.

Respiration is the converse of photosynthesis. It is the breakdown of organic matter under aerobic conditions to produce energy and to release oxidised carbon (CO2) back into the environment. It is the process through which organisms produce the energy they require to sustain life.

What are the processes of photosynthesis and respiration, and how do they relate to each other?