WHERE LIFE BEGAN? ~ Suman Blogz

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WHERE THE LIFE BEGAN

The history of planet earth began about 4.6 billion years ago, and the beginning of life on earth dates back almost as far. Scientists have found fossils evidence of once living organisms from what is Precambrian era. This covers the time until the Cambrian period. These fossils represent small, simple life forms. While fossils from the Cambrian period which lasted from 570 million years to 500 million years ago, tell the story of life as seen in the first hard – shelled animals, Precambrian creatures did not have hard structure and their fossils can only hint about life long ago.

Precambrian fossil stromatolites are mound like structure with dark and light bands. Within the light bands, scientists have found traces of tiny one – celled organisms that lived at least 3.5 billion years ago. These organisms which resemble modern bacteria called blue green algae or cyanobacteria, were the first to use the sun’s energy to convert water and dissolved carbon dioxide in to food. This process is known as photosynthesis, releases oxygen as a by-prduct. By adding oxygen to an atmosphere that previously had almost none, these organisms set the stage for the evolution of all creatures that depend on oxygen to live.

Just before animals with shells evolved the first organisms with more than one cell appeared. Their soft bodies left only faint impression in the mud of the seas where they lived, but scientists speculate that many of them are related to creatures living today.

Mats of blue green algae and sediments release oxygen into the Precambrian atmosphere. Moreover, the path of evolution has lead to modern mammals.