Sexual Selection Research Paper

Reproductive monogamy is defined as an exclusive sexual relationship between a female and a male based on their sexual interactions. Social Monogamy refers to male and female’s social living arrangement without sexual interactions. It refers to the living patterns, raising offsprings, and obtaining food. Monogamy is common in birds, but also occurs in invertebrates. Why would a male mammal choose to mate with one female when he can mate with more than one? Why would the male stay around instead of finding another female to live with? Many researchers have attempted to answer this question of why some mammals prefer monogamy over polygamy. Vole rats, one of the species that perform monogamous mating, demonstrate pair boding. Male and female pairs of vole rats have been observed together over several months, and the males stay with females even when the female is not reproductively active. A typical vole family in the wild is almost always consisted of one male, one female, and their offspring. In addition, unlike other species in which females are the only ones taking care of the offspring, vole rats share parental roles and even build nests together. Because they show these monogamous behaviors, they have served as a good species/model to learn about monogamy for neuroscientists. In this paper, monogamy, specifically in vole rats, will be explained along with its proximate and ultimate causes of this adaptation.

Sexual selection was an idea proposed by Darwin and refers to the process in which males and females attempt to maximize their chances of reproductive success. Within a species there are certain characteristics that make individuals attractive to potential mates. An example of this is in peacocks, female peacocks are attracted to males with long brightly colored tails, even though this makes them easier to be spotted by predators. This characteristic then evolves within the species due to how males with this characteristic have a higher chance of reproductive success and their characteristics being passed on to surviving offspring.

When one male group doesn’t have the luxury of having females, they form or join a group of males similar to a bachelor’s group. In some of these species, the group of males attacks the one male group in order to take his throne and seize the females (Hoglund, J. 1995). Sometimes, the females may get tired of sharing the male with the other females in the group. Hoglund recorded (1995, pg. 76) “so they seek out males from all male groups to mate with during breeding season. Such influxes occur seasonally between blue monkeys (Rowell, 1988), Hanuman Langurs (Boories et al., 1999), ring-tailed lemurs (Sussman, 1992), and sifakas (Richard 1992).” A nonhuman

In insect species with indirect sperm transfer, sperm is packed in a spermatophore that is either externally attached to the female 's genital opening or introduced into her bursa copulatrix. Sperm transfer is not immediate in these species, and consequently mate guarding has been suggested to function as a mechanism of guarding sperm until it is released from the spermatophore into the female (i.e. spermatophore guarding). Spermatophore guarding is relatively common in insect species with external spermatophores (e.g. Orthoptera; Alcock 1994; Simmons 2001), but supposedly absent in species with internal spermatophores and rapid sperm release (Simmons 2001). This study focuses on two hypothesis associated with mate guarding a tactic of many species that adjust their reproductive behaviour according to the apparent risk of sperm competition. The phenomenon of mate guard to consider sperm competition levels and evolution of internal spermatophore guard is wide spread in insects and other animals. We analyse two hypothesis one the rival exclusion followed by the next spermatophore renewal hypothesis. Results showed that as rival was introduced to the arena of mating of the distinctive original male (guard) in many cases showed a strong aggressive behaviour regardless of whether successively avert the rival. In the second hypothesis certainly majority of the incidents showed an attempt of

Albeit, the sexual selection theory is presumed force of natural selection causing individuals to develop reproductive strategies which maximize the like hood of their producing the fittest possible offspring. Otherwise, suggested a competition between males and competition for females as the two most likely mechanism of sexual selection theory.

According to Darwin's study, however, usually "the male is the more active member in the courtship of the sexes" (p. 229). The female is less eager, even "coy, and may often be seen endeavoring for a long time to escape from the male" (p. 230). This eagerness and passion in the male is natural and even necessary, since "the acquirement of such passions would naturally follow from the more eager leaving a larger number of offspring than the less eager." (p. 231). Sexual selection has a highly important part in differences between the sexes. Woman is more tender and unselfish, owing to her maternal instinct, and her mental powers are based on intuition, rapid perception and imitation. Man, on the other hand, is competitive and ambitious, which often leads to selfishness. He has attained greater eminence in deep though, reason, imagination and in using his senses and hands. "Thus man has become ultimately superior to woman" (Darwin, p. 585).

Sexual sections is one of the processes of natural selection in which there is a competition for sexual reproduction, these competitions can be classified as intersexual or intrasexual. Intersexual competition occurs when one organism, usually female, chooses its partner. Intrasexual competition, on the other hand, happens when species from the same gender compete to sexually reproduce.

Males and females differ considerably in how much they each invest in order to make offspring and a result of this, they approach mating with different methods. Researchers and scientists learn and examine these varying mating systems to explain how males and females pair up. A mating system explains the techniques males and females use to pair up when selecting a mate. It is important to begin by reviewing and understanding the reproductive strategies among primates. The major types of mating systems found in primates are monogamy and polygamy. Monogamy is a practice of mating in which one male pairs with one female. Polygamy also known as bisexual, is a pattern of mating in which a male mates with more than one female and a female mates with more than one male (Wong , 2010). Polygamy is then clarified into polygyny and polyandry. Polygyny is when one male mates with multiple females. Polyandry is when one female mates with multiple males. Recognizing the diversity of mating systems will help in understanding the interactive relationship of sexual size dimorphism and behavior in primates.

The researchers used two different sexual experiences to generate two cohorts of male flies. The first cohort, rejected-isolated, was subjected to courtship conditioning; they experienced 1-hour sessions of sexual rejection by mated females, three times a day, for 4 days. Such conditioning suppresses future male courtship behavior, even toward receptive virgin females. The second cohort of mated-grouped flies experienced 6-hour sessions of mating with multiple receptive virgin females at a ratio of 1:5 for 4 days. Flies from each cohort were then tested in a two-choice preference assay, in which they deliberately choose to consume food with or without 15% ethanol supplementation.

Sexual selection can best be described by the definition given by Darwin himself. Sexual selection is “the advantage which certain individuals have over other individuals of the same species solely in respect of reproduction” (Hosken et al, 2011). Sexual selection occurs throughout the animal kingdom, where male frogs dominate through the depth of their croak, and certain peacocks reign superior based on the colour and intricate detail on their tails. They remain superior to their lesser counterparts as they bear more admirable characteristics, from which they are chosen by females of the same species.

Mate Selection Mate selection is the picking and choosing of sexual partners that can be based on both physical and biological processes. Mate selection, also called sexual selection, is not a random process. Sexual selection is an evolutionary force that explains the never-ending changes of humankind.

The article Models of speciation by sexual selection on polygen by Russell Lande discusses the reasoning behind natural and sexual selection. Russell Lande starts by describing the differences between the processes of natural and sexual selection according to Darwin’s theory of evolution and continues on to question the reasoning for why females prefer extreme phenotypic traits in a polygamous mating system, which is not explained in Darwin’s studies. Russell defined a polygamous mating system as a system in which the male provides little more than gametes in their offspring to the relationships. When this is the case the females have many potential mates and when there is no sexual preference a preference can evolve. This happens because a

Baron and Cohen (2002) suggested, in their E-S theory, that male hunters gained an evolutionary advantage systematising over women who were much more empathetic. With their theory they suggested that during stress responses, men tend to be adapted for flight or fight, whereas females are not. Shields (1975) suggested that men and women evolved to have roles that complemented each other, in order for both genders to survive. This is supported by Ennis et al 2001) who found that men show a better ‘fight or flight’ response, as during exams men’s cortisol levels are higher than women’s during the same time period. However, evolutionary explanations may partially explain why gender roles have developed but the fact that gender roles can differ globally would imply social factors are also involved, so the evolutionary explanations cannot fully explain gender roles.

The first few chapters discuss in depth both the general rules for mate selection and the differences in mate selection and varying preferences for male and female genders. As explained in the intro the author theorizes that the current behavior of humans in relation to mating behavior can be linked to our evolutionary past. He references Charles Darwin 's theory of evolution and his idea of natural selection, which is the the process through which organisms adapt to their environment and in doing so tend to

Sexual dimorphism is any difference, morphological or behavioral, between males and females of the same species. Sexual dimorphism can include differences in weaponry, ornamentation, size, vocalization, chemical signal, gametes, behavior, and parental care. It is seen in exaggerated forms in the birds of paradise, though it is present in many other species as well. In mammals one way sexes are sexual dimorphic is in their size. In many mammalian species the males are larger than the females this is known as sexual size dimorphism or SSD. SSD is cause by many factors but this paper will focus only on those relating to reproduction and feeding.