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SPERM WARS PDF

Tuesday, April 2, 2019


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Sperm Wars Pdf

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Published to acclaim and controversy a decade ago, Sperm Wars is a revolutionary thesis about sex that turned centuries-old biological assumptions on their. Sperm Wars: The Science of Sex. By Robin Baker. New. York: Basic Books, . pages. Hardcover, $ ISBN Reviewed byPaul H. Citations; Metrics; Reprints & Permissions · PDF. "Sperm Wars: The Science of Sex. By Robin Baker." Journal of Sex Education and Therapy.

Start reading Sperm Wars on your Kindle in under a minute. Don't have a Kindle? Try the Kindle edition and experience these great reading features: Share your thoughts with other customers. Write a customer review. Read reviews that mention sperm competition sperm wars reproductive success robin baker human sexual sexual behavior human sexuality men and women multiple partners well written sperm from different human behavior book to give human nature excellent book book is not based give this book read this book book really book very interesting.

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Kindle Edition Verified download. A must read for every male that is in a relationship or wants to be in one. This is such a profound and absolutely essential work of literature, for any and all humans interested in anything concerning reproduction. Do yourself a favour and download it. Gratuitous story-telling seems focused on generating soft-porn than exemplifying the theory espoused. Not well written nor offering of much info we don't already know.

I was hoping for interesting insight but got weak, circular analysis instead. One person found this helpful. Paperback Verified download.

The story format of this book makes the science very accessible for people beginning to learn about how physiology interacts with sexual psychology. Great read. Well researched book. This book is very empowering. It completely negates the utterly false popular notions out there about sex. See all 75 reviews. site Giveaway allows you to run promotional giveaways in order to create buzz, reward your audience, and attract new followers and customers.

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site Drive Cloud storage from site. Alexa Actionable Analytics for the Web. siteGlobal Ship Orders Internationally. site Inspire Digital Educational Resources. site Rapids Fun stories for kids on the go. They found that variation in sperm length was negatively associated with the level of sperm competition. Because variation in sperm morphology cannot be explained by genomic conflict in these eusocial insects, these results suggest that selection is acting on sperm production machinery to improve sperm quality in response to increased sperm competition.

Despite the apparent evolution of sperm toward a single optimal phenotype, variation in morphology can persist. Some level of variation might always be present within an ejaculate simply because random developmental errors will occur during sperm production.

However, Calhim et al. Calhim et al. Such opposing patterns of selection on sperm morphology depending on male mating roles may help to explain the maintenance of variation in sperm morphology despite selection aimed at eroding this variance. In addition to maintaining variation in sperm length, selection for different sperm phenotypes under different competitive situations could ultimately favor the evolution of distinct sperm morphologies.

Indeed, there are many examples of species that produce heteromorphic sperm, which in animals typically results in the production of both fertile and non-fertile sperm morphs Till-Bottraud et al.

However, by and large, the adaptive significance of sperm heteromorphism is poorly understood and deserves further study. In a variety of species, sperm can form conjugates of two or more individuals, who collectively swim faster than can individual sperm Hayashi , Moore et al.

In muroid rodents, the characteristic hooked morphology of the sperm head can be involved in the production of sperm conjugates, and the curvature of the hook increases with testes size, a widely used proxy for the strength of selection from sperm competition, suggesting that sperm conjugation may be an evolutionary response to selection via sperm competition in this group Immler et al.

The evolution of sperm viability Owing to the relatively paucity of studies, it is currently not possible to draw broad conclusions regarding how sperm viability is influenced by variation in the level of sperm competition.

Sperm wars and the evolution of male fertility

However, there is some evidence that sperm viability influences competitive fertilization success see Table 2. More studies that explore responses to selection on sperm viability are required. Seminal fluid proteins: the neglected weaponary Despite the considerable volume of research that has focused on how selection acts on testes size and sperm production, and sperm form and function, researchers often neglect the critical role that seminal fluids play in imparting motility and fertilization capacity to sperm.

Sperm are delivered from the male, bathed in a complex soup of proteins that are derived from the male accessory glands. Seminal fluid proteins sfps play a role in the nourishment, protection, capacitation, and motility of sperm within the female reproductive tract and should therefore be expected to contribute to a male's fertilization success Poiani In humans, for example, seminogelin I and seminogelin II inhibit sperm motility, while seminal fluid proteases cleave seminogelins after ejaculation, promoting the rapid onset of motility in the female tract Veveris-Lowe et al.

The function of sfps has been the subject of considerable research focus in the Drosophila model system. Given its critical influence, both on sperm performance and on the interactions between sperm and egg at the time of fertilization Clark et al. The evolution of male reproductive accessory glands The male reproductive accessory glands are the principle sites for the manufacture and secretion of sfps. As with testes, there is now good evidence that male expenditure on accessory glands does evolve in response to sperm competition.

A comparative analysis of male reproductive anatomy among rodent species found a positive association between the strength of selection from sperm competition and the size of the seminal vesicles and the anterior prostate, two male reproductive accessory glands that contribute proteins to the seminal fluid Ramm et al.

In Drosophila melanogaster, laboratory evolution studies have shown that accessory gland productivity responds to variation in selection from sperm competition Linklater et al. Thus, Linklater et al. The probability that females will encounter and mate with multiple males and thus the strength of selection from sperm competition was assumed to be greater in populations with a male biased sex ratio.

After more than 60 generations of laboratory evolution, accessory glands evolved greater productivity in male-biased populations compared with populations with a female-biased sex ratio Linklater et al. Similar findings were obtained in a study of Drosophila pseudoobscura in which the strength of selection from sperm competition was manipulated by either enforcing monogamy or controlling the degree to which females could mate polyandrously Crudgington et al.

Interestingly, testes size did not respond to variation in selection from sperm competition in either of these experiments, suggesting that in Drosophila seminal fluids may play an even more important role in determining competitive fertilization success than does the number of sperm a male can produce. Molecular research is now revealing how individual sfps evolve in response to sperm competition. Non-synonymous substitutions change an amino acid while synonymous substitutions do not.

Reproductive proteins facilitate three fundamental stages of reproduction; the transit of sperm through and capacitation within the female genital tract, the storage and survival of sperm before egg release, and the interactions between sperm and egg that culminate in successful fertilization Clark et al.

Genes that encode reproductive proteins involved at each of these stages appear to have evolved more rapidly than other genes. Thus, genome screens from taxa ranging from gastropods Metz et al.

There is good evidence that sexual selection via sperm competition has been instrumental in the evolutionary divergence of sfps. In house mice, the seminal vesicle protein gene Pate4 Svs7 is evolving particularly rapidly Karn et al.

Seminal vesicle proteins are involved in the formation of the mating plug, the size of which is also associated with the strength of selection from sperm competition Ramm et al.

Mating plugs are thought to play a role in the prevention of mating by, and thus sperm competition from, rival males Simmons The rate of evolution of SEMG2 also correlates with the levels of female promiscuity, as does the firmness of the semen coagulum Dorus et al. These studies strongly suggest that in primates too, sfps involved in the formation of mating plugs are under positive selection from sperm competition. Evidence for a role of sperm competition in protein evolution also comes from studies of Drosophila.

Here too accessory gland genes show evidence of strong positive selection Haerty et al. It seems we know much about sfps and their function. However, to place these studies in context, for Drosophila, the number of newly discovered sfps is rising almost exponentially. At last count, sfps had been detected, with just a handful of these having known function Chapman , Findlay et al.

In mice, 69 sfps have been identified from the female reproductive tract following mating Dean et al.

sperm wars pdf

The exploration of sfps and their functional significance is in its infancy but promises to shed light on the functional mechanisms underlying sperm competitiveness. Strategic adjustments in seminal fluid composition Much research has explored male responses to sperm competition in terms of the numbers of sperm ejaculated reviewed earlier. However, there are a growing number of studies that suggest the quality of those sperm may also be adjusted in an adaptive manner.

Work with field crickets, Teleogryllus oceanicus, has shown how the viability of sperm in the ejaculate varies with a male's perceptions of sperm competition Simmons et al. In these insects, males appear able to detect not just the mating status of a female, be she mated or unmated, but also the number of males she has accepted, based on chemical cues left by males during copulation.

Thus, when the perceived risk of sperm competition is elevated, males will produce ejaculates containing sperm of higher viability, but as the number of males competing for fertilizations is increased beyond two males, so that the payoff from a given male's investment in his ejaculate declines, males produce ejaculates containing sperm of decreasing viability Simmons et al. However, these studies beg the question of how males adjust the quality of their sperm? The most likely candidate would appear to be adjustments in seminal fluid.

Because gene transcription is apparently absent in sperm cells, their functionality is largely dependent on post-translational modifications to their protein compliment that are brought about by sfps. Sfps are known to influence the viability of sperm den Boer et al. Seminal fluid may be more costly to produce than sperm themselves Simmons , so that males might be expected to allocate these costly secretions to their ejaculates, depending on the levels of sperm competition.

Recent attempts have been made to model the evolution of male allocation to sfps within Parker's sperm competition game framework. Cameron et al. Their game theoretic analyses did indeed predict that males should invest more on sfps than sperm under these conditions. Theoretical models predict that male fitness could be enhanced by withholding these beneficial sfps from females with whom the risk of lost paternity through sperm competition is high Cameron et al.

Despite these first prospective attempts to model the evolutionary dynamics of seminal fluid investments made by males, few studies have attempted to examine whether males can vary the composition of their seminal fluid in an adaptive manner. The seminal fluid of D. As noted earlier, experimental evolution under elevated levels of sperm competition results in responses to accessory gland size and productivity Linklater et al.Wilkins, J.

Sperm motility is influenced by the selective environment in which it operates i. Are you sure you want to Yes No.

However, all else is rarely equal. Dziminski et al.