Early Signs Of Life͍ On Earth⤘
For almost a thousand million years ago after the earth formation, there was no life on Earth. The first simple see-dwelling organic structures appeared about 3,500 million years ago . Scientist say that they may have formed when certain chemical molecules were joined together. Prokaryotes, single celled micro organisms such as blue green algae, were able to photosynthesize and thus produce Oxygen.
A thousand million years later, sufficient oxygen had built up in the Earth's atmosphere to allow multicellular organisms to proliferate in the precambrian seas (before 5
70 million years ago). Soft-bodied jellyfish,corals, and seaworms flourished about 700 million years ago. Trilobites, the first animals with hard body frames, developed during the cambrian period(570-510 million years ago).
However it was not until the beginning of the Devonian
period(409-363 million years ago) that early land plants such as Asteroxylon ,formed a water retaining cuticle, which ended their dependence on an aquatic environment. About 360 million years ago, the first amphibians crawled onto the land, although they probably still returned to the water to lay their soft eggs.
By the time the first reptiles and synapids appeared late in the carboniferous, animals with backbones had become fully independent of water.and then slowly all the creatures started evolving on earth and slowly the transformation on the Earth took place.
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