Sexual Selection I t was Charles Darwin who originally proposed that the so-called secondary sexual characteristics of male animals -- such as the elaborate tails of peacocks, bright plumage or expandable throat sacs in many birds, large racks in mooses, deep voices in men -- evolved because females preferred to mate with individuals that had those features. Sexual selection can be thought of as two special kinds of natural selection, as described below. Natural selection occurs when some individuals out-reproduce others, and those that have more offspring differ genetically from those that have fewer.
Male—male competition and female mate choice may both play important roles in driving and maintaining reproductive isolation between species. When previously allopatric species come into secondary contact with each other due to introductions, they provide an opportunity to evaluate the identity and strength of reproductive isolating mechanisms. If reproductive isolation is not maintained, hybridization may occur.
English naturalist Charles Darwin revolutionized scientific thinking when he proposed that species evolve over time to become adapted to their environments by means of natural selection in his On the Origin of Species He was initially puzzled, though, by the seemingly useless exaggerated characters often found in animals, particularly males. The long and colorful tail of the peacock, for example, seemed to hinder rather than help its bearer survive.
Sexual selection, the selection pressure on males and females to obtain matings, can result in traits designed to maximize sexual success. The selection pressures on males and females to obtain matings is known as sexual selection. The limiting sex is the sex which has the higher parental investment, which therefore faces the most pressure to make a good mate decision.
Traits that cause an individual to be more successful reproducing than individuals without the trait necessarily increase in proportion in the next generation. So, why is sexual reproduction found in so many species, compared to asexual reproduction? It would appear that the best way to increase the proportion of your genes in the next generation would be to make clones of yourself, as happens in asexual reproduction.
So far all of our discussions of selection have been without much regard for the sex of the individual under selection evolution of the sex ratio to can occur through selection for alleles in either males or females that favor the production of the rare sex. But just as with natural selection individuals may differ in their ability to reproduce, in sexual selection there can be differential reproductive success among individuals of the same sex and species. In order to mate, males need to gain access to females and vice versa, and not all individuals will be equally successful at this task.
This page has been archived and is no longer updated. Charles Darwin proposed that all living species were derived from common ancestors. The primary mechanism he proposed to explain this fact was natural selection: that is, that organisms better adapted to their environment would benefit from higher rates of survival than those less well equipped to do so.
Evolutionary fitness is largely determined by the ability of an organism to survive and successfully produce offspring. Critical to this process is sexual selection, which plays a large role in the determination of mating pairs, and thus which genes are passed on to the next generation. Often, intense competition for mates within a population places selective pressure on traits related to courtship and copulation. Natural selection that results from these pressures is called sexual selection.
Sexual Dimorphism. Understanding the origin of biodiversity has been a major focus in evolutionary and ecological biology for well over a century and several patterns and mechanisms have been proposed to explain this diversity. Particularly intriguing is the pattern of sexual dimorphism, in which males and females of the same species differ in some trait.