What is fitness and how does it relate to natural selection?

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Explanation:

Fitness is just book-keeping; survival and differential reproduction result from natural selection, which actually is a driving mechanism in evolution. Organisms which are better suited to their environment will reproduce more and so increase the proportion of the population with their traits

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.

answerhomologous structures;