Question

question 4
which criterion is not necessarily true of a trait that has evolved through natural selection?
it varies among individuals.
it is heritable (able to be passed on).
it influences individuals reproductive success.
it increases the individuals life spans.

Explanation:

For a trait to evolve through natural selection, it must vary among individuals (so selection can act on it), be heritable (so it can be passed on), and influence reproductive success (as natural selection is about differential reproduction). However, increasing lifespan is not a necessary criterion. A trait could help in reproduction without necessarily increasing lifespan (e.g., a male peacock's tail helps in mating but may make it more vulnerable to predators, not increasing lifespan).

Answer:

It increases the individuals’ life spans.