JohnR7 said:
Ok, so does that make sexual selection a part of natural selection?
Not exactly. They are two separate mechanisms, either of which can be a driving force behind the evolution of a population.
Look a peacocks, for example. Female peacocks (peahens) are attracted to males with large colorful tails -- presumably because that is the sign of a healthy, virile male.
So, the bigger and brighter the tail, the more attractive the male is to the female. That's sexual selection.
But it has to stop somewhere, doesn't it? Otherwise we'd see peacocks strutting around with tails the size of SUVs.
As tails get bigger and bigger, eventually they would become a disadvantage, as the peacocks would find it more difficult to fly, move around, find food, or escape from whatever predators peacocks may have.
Between sexual selection and natural selection, a balance would eventually be reached, with peacocks growing tails large enough to attract mates, but still small enough to not be burdensome.
So sexual selection is not "part" of natural selection, since it's possible for the two of them to come into direct conflict.