Precisely how life began on Earth remains unclear. It is believed, however, that life started after the planet had cooled enough for bodies of water to form. Scientists have found fossilized single-celled microorganisms in rocks that date to approximately 3.5 billion years ago. Scientists believe that algae is one of the earliest forms of life on our planet.
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The coal industry has decreased so much because of the push to switch to renewable resources, so people are using alternatives to coal for heating.
