The correct answer is d. 3.5 billion years.
Prokaryotes were the first forms of life on Earth long before simple multicellular life appeared because of their ability to withstand extreme conditions. It is believed that the first living forms were bacteria combined with archaea in the microbial mat (multi-layered sheet).
<span>They are mechanoreceptors that detect pressure, and are found in the skin and also in joints and tendons. Naked nerve endings lie in the centre of the corpuscle surrounded by concentric layers of connective tissue separated by viscous gel.
Looks like an onion.
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Answer: question 6
Explanation: Biogeography The fossil record, Embryology, similarity and vestigial structures, genetics and Observable evolution on small timescales.☺
