Answer;
heritable variations for some traits
Explanation;
-Natural selection is the process by which the organisms in a population that are best adapted to the environment increase in frequency relative to less well-adapted forms, over a number of generations.
Four general conditions necessary for natural selection to occur are:
-More organisms are born than can survive.
-Organisms vary in their characteristics, even within a species.
-Variation is inherited.
-Differences in reproduction and survival are due to variation among organisms.
If all four of these conditions occur, which they commonly do in both natural and human-influenced ecological systems, then natural selection will occur.
