Baker bellis sperm competition
The results of the selection experiment for remating speed in both fast and slow lines for D. Biometrical and planned comparison analysis. Uterine contractions during orgasm are suggested to increase the likelihood of conception Baker and Bellis, Advocates of the sperm competition theory argue that a longer penis provides sperm delivery closer to the cervix and gives sperm a head start in their competition with rivals. Third, the reproductive costs, in terms of lost mating opportunities must be outweighed by the reproductive gains. Alternatively, larger males may be able to monopolize females when they are more receptive.
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SPERM COMPETITION AND THE EVOLUTION OF NONFERTILIZING SPERM IN MAMMALS.
Females of many species may also remate to guard against abnormal chromosome numbers, defects due to long term sperm storage, or sterile or sub-fertile ejaculates Halliday and Arnold, Drosophila males contribute to oogenesis in a multiple mating species. Clutch size and mating frequency in parasitic Hymenoptera. Second, some of the evidence advanced for the existence of nonfertilizing sperm does not in fact support the idea. Frequency of multiple insemination in a natural population of Drosophila montana. P' is the number of offspring fertilized by a male genotype after a female remates; P1, when he was the first male and P2, when he was the second male Boorman and Parker, ; Gromko et al. The advantage of female remating is to guard against genetic incompatibility Tregenza and Wedell,
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Kamikaze Sperms or Flawed Products? | Psychology Today
Cosmetic Surgery and the Psychology of Aging. In the same species Bundgaard and Barker found strong sperm displacement, also with considerable variation between different combinations of first and second males. As with so much of reproduction, they leave that task to the females! There are examples of both increasing and decreasing last male precedence with a longer mating interval. It has also been conjectured that males have evolved to produce large quantities of sperm in order to confuse or otherwise confound female's cryptic system of selection. A genetic evaluation of mating system and determinants of individual reproductive success in Atlantic Salmon Salmo salar L. Several investigators have suggested that the frequency of remating is influenced by density.
As a result, sperm competition should enhance sexual conflict and thus lead to the evolution of characters that increase reproductive success in one sex, while they are costly to the other. Back Find a Therapist. Selfish genetic elements such as cellular endosymbionts, transposable elements, segregation distorters, maternal effects, lethal and genomically imprinted genes, can modify maternal and paternal haplotypes enough to make them unable to combine and produce a viable zygote Zeh and Zeh, When they artificially selected single lines for fast remating in both sexes, a relatively small number of genes, deviations from additive gene action, and involvement of the X-chromosome were found Pyle and Gromko, They reported on experimental mixing of semen samples from two men, which apparently increased the proportion of dead and coiled-tail sperms. Sperm Wars is a primarily nonfiction book by evolutionary biologist Robin Baker.