#2/15 What is a plant?
How does planet Earth work?
Life began in the sea and the first plant-like organisms were single-celled bacteria. Their ancestors can still be found around deep-sea volcanic vents. They ‘breathe’ chemicals like sulphur rather than carbon dioxide and instead of the Sun, they use the faint radiation from molten rock as an energy source.
Land plants we’re familiar with today need sunlight, water and a carbon-rich atmosphere. They originated in a similar way to animals, after bacteria married together. One enabled the plant to breathe carbon dioxide while the other could build cellulose.
Cellulose was really strong, meaning multiple cells could start working together and building. Eventually they created grasses, then trees that could grow 100 m tall.
When plants breathe, they remove carbon (C) from CO2, which leaves O2 (oxygen). Plants have a very different origin to animals and serve a different function.
Plants are at the front line of turning the Sun’s energy into sugars, feeding ecosystems, as well as giving us oxygen to breath.
