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Hello, three and a half billion years ago this planet was a hostile and barren place.

The atmosphere was toxic and contained no oxygen and life on Earth was restricted to a variety of unsophisticated single-celled organisms

which lived in the sea. But then a new type of organism emerged one with an amazing new

capability. It could harvest energy from sunlight and use it to fuel

its own activities.

This phenomenon is known as photosynthesis and is almost certainly the most important chemical

process on Earth. Plants and some other organisms

depend on it for their energy and almost all life is ultimately reliant on it for its

survival. It's responsible for the food we eat and the air we breathe and without it

Earth would still be sterile rather than as it is teeming with life.

With me to discuss photosynthesis are

Sandinup, a botanist at the Natural History Museum,

Nick Lane, Reader in Evolutionary Biochemistry at University College London,

and John Allen, Professor of Biochemistry at Queen Mary University of London.

Sandy now, would you give us some idea of what

photosynthesis is and why it's so important?

Photosynthesis is one of those things that you always read about,

you hear about at school.

...