The answer is the G1 checkpoint
No.
This is because mutations not only help a species survive in certain conditions, but also allows diversity within a population. For instance, a bug species can develop a mutation to bug spray, allowing it to survive through its prey or killers. Therefore, ultimately benefiting and helping the species.
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The precambrian era makes up about 90% of the earths history, but there was little to no living organisms at the time other than microscopic ones. The first eukaryotes were found in the cambrian period after the precambrian period, not only that but at the end of the precambrian era in the Proterozoic era there was a mass extinction of about 70-80% of all living organisms
The answer is; YES
All organisms share one common ancestor in the beginning of life. Different species have branched at different times from common ancestors hence he evolutionary tree looks like tree called a cladogram. The nodes represent the common ancestry while branches depict divergence. Therefore even fruit flies and the fruit bats even though they do not belong to the same species shared a common ancestor at one time in history.
