Question

Why can sexual and natural selection be competing forms of selection?

Answer 1

Yes. Natural selection and sexual selection can be the competing forms of selection.

In natural selection, the organisms which are better adapted to their environmental conditions will get survived. They produce more offsprings and in the course of evolution they become dominant and successful by the concept of survival of the fittest. It is pioneerly described by Charles Darwin. For example.. the giraffe neck length is a result of natural selection as they need lengthy neck to survive. Thus those adapted got survived and they transfer their best genes to the further generations. So for this selection, organisms compete each other and best will survive.

Sexual selection is a form of natural selection where the selection promote traits that can increase their mating success. Here competance occurs not for survival but for mating.It can be divided into intrasexual and intersexual.

Intersexual selection : Where member of one sex, probably female select their opposite sex mate based on certain characters like feather, colour, sound, strength etc.. peacock female have more attraction to males having more eyes in feathers and having larger size. The members having these characters will mate and produce offsprings. Thus it get naturally selected by nature.

Intrasexual selection : Where members of same sex, mainly male will fight or compete and those winning will get the mate. So those having certain characters to win the competition will survive and get naturally selected. Ostrich male fights is an example.

Thus sexual and natural selection are the competing forms.
Organisms suicide themselves by having attracting characters to opposite sex but also it attracts the predators too. But still, they are mating and producing offsprings.