
Concept explainers
What are the three lines of fossil evidence that point to an early origin of life on Earth? Discuss each line and what it tells us about when life arose. What are the implications of an early origin for the possibility of life elsewhere?

The evidence for the early origin of life on earth and to determine the implication of early life for possibility of life elsewhere.
Answer to Problem 1RQ
The three line of evidence for early growth of life on earth are Stromatolites, microfossils and isotopic evidence. If similar conditions like earth are considered than there are quite high chances for existence of life on other planets.
Explanation of Solution
There are three basic line of evidence for early growths of life on earth are as follows:
- 1. Stromatolites: - Stromatolites are distinctive and layered structure of rocks. The ancient stromatolites are identical with the modern stromatolites. The living stromatolite are formed from microbes and are formed from the layers of sediments intermixed with microbes of different species. The comparison of ancient and modern stromatolites are similar, the microbes present on these stromatolites age back to 3.5 billion years and this provides evidence that life on earth dates back to minimum 3.5 billion years back.
- 2. Microfossils: - Microscopic fossils are the second line of evidence. Microfossils can be found from both biological and minerals. The latest discovery of microfossils in Australia, which is believed to be from rocks dates back to 3.426 billion years ago. Cell structure of microfossils is clear and at living condition in earlier day they used to feed on Sulphur for nutrients and energy.
- 3. Isotopic evidence: - Isotopic evidences are the third line of evidence. Every particle has some content of both the isotopes carbon 13 and carbon 12. Carbon 13 isotope is present in fewer ratios in a compound. The recent isotopic evidence from a rock in Greenland dates back to 3.85 billion years back.
From the above evidences, life dates back to almost 3.85 billion years ago on earth which seems quite early with respect to formation of earth. There are no evidences to prove life on other planet but if similar conditions like earth are considered than there are quite high chances for existence of life on other planets.
Conclusion:
Thus, the three line of evidence for early growth of life on earth are Stromatolites, microfossils and isotopic evidence. If similar conditions like earth are considered than there are quite high chances for existence of life on other planets.
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