Senescence . Question 5 options: a) begins at the moment of conception and accelerates after age 40 b) occurs across all parts of the body at the same time and speed c) begins once body structures reach maximum capacity and efficiency d) occurs because the physical body wears out from use

c. Senescence begins once body structures reach maximum capacity and efficiency

Explanation: Senescence is simply ‘growing old’. Aging sets in at the time when physical development is complete - when a person reaches their ‘prime’. After that a person is ‘past their prime’ which is the subjective recognition of the on set of gradual deterioration. The biological rationale is that the purpose of life is to survive to reproductive age and to reproduce, and in some species to assist progeny to survive to reproductive age. Beyond that, survival has limited value.

An analogy is the length of an elephant’s trunk. It is as long as it needs to be, determined by natural selection, but no longer than it needs to be for optimum efficiency, again determined by natural selection.

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explanation:

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during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.