This picture is an example of early autotrophs.
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Image courtesy of Corel Photography

Early Life

Over a very long time, gradual changes in the earliest cells gave rise to new life forms. These new cells were very different from the earlier heterotrophs because they were able to get their energy from a new source -- the Sun.

Organisms that are able to make their own food (in the form of sugars) by using the energy of the Sun are called autotrophs, meaning "self-feeders". Photosynthesis is the name of the process by which these autotrophs use energy from the sun and eat.

Because the autotrophic bacteria were able to feed themselves by using the energy of the Sun, they were no longer dependent on the same limited food supply as their ancestors and were able to flourish. Over millions of years of evolution, photosynthetic bacteria eventually gave rise to modern day plants.

The appearance of organisms capable of performing photosynthesis was very significant -- if it weren't for the photosynthetic activity of these early bacteria, Earth's atmosphere would still be without oxygen and the appearance of oxygen-dependent animals, including humans, would never have occurred!

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