Answer
- Sexual selection vs adaptive selection
Sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).
Example: The female widowbird chooses to mate with the most attractive long-tailed male so that her progeny, if male, will themselves be attractive to females of the next generation—thereby fathering many offspring that carry the female's genes. This will result in more bird species with long tails, because of sexual selection.
Adaptive selection
Whereas in adaptive selection individuals with advantageous traits are able to reproduce successfully, these traits are passed down to the next generations. Type of evolution wherein the changes are driven by natural selection is called adaptive evolution.
Example: Through natural selection, a population of finches evolved into three separate species by adapting to several difference selection pressures. Each of the three modern finches has a beak adapted to its life history and diet.