How is the male reproductive system different from other body systems? - once
Digestive system[ edit ] An insect uses its digestive system to extract nutrients and other substances from the food it consumes. This break-down process is known as digestion. The insect's digestive system is a closed system, with one long enclosed coiled tube called the alimentary canal which runs lengthwise through the body. The alimentary canal only allows food to enter the mouth, and then gets processed as it travels toward the anus. The alimentary canal has specific sections for grinding and food storage, enzyme production, and nutrient absorption. The three regions include the foregut stomatodeum 27, the midgut mesenteron 13 , and the hindgut proctodeum how is the male reproductive system different from other body systems?Matthew J. Gibson Department of Biology, Indiana University, Bloomington, IN, United States Elevated rates of evolution in reproductive proteins are commonly observed in animal species, and are thought to be frkm by the action of sexual selection and sexual conflict acting specifically on reproductive traits. Whether similar patterns are broadly observed in other biological groups is equivocal. Here, we examine patterns of protein divergence among wild tomato species Solanum section Lycopersiconto understand forces shaping the evolution of reproductive genes in this diverse, rapidly evolving plant clade. We observed elevated evolutionary rates in reproductive proteins.
However, this pattern was most evident for female- rather than male-specific loci, both broadly and for individual loci inferred to be positively selected. These elevated rates might be facilitated by greater tissue-specificity of reproductive proteins, as faster rates were also associated with more narrow expression domains. In contrast, we found little evidence that evolutionary rates are consistently different in loci experiencing haploid selection gametophytic-exclusive locior in lineages rwproductive quantitatively different mating systems.
Overall while reproductive protein evolution is generally elevated in this diverse plant group, some specific patterns of evolution are more complex than those reported in other largely animal systems, and include a more prominent role for female-specific loci differen adaptively evolving genes. Introduction The rapid evolution of reproductive proteins has been observed across many different animal species, including in groups as diverse as marine invertebrates, insects, and mammals Swanson and Vacquier, a ; Clark et al.
This pattern is especially well established for proteins involved in male-specific functions, such as seminal fluid proteins, and sperm-egg and sperm-reproductive tract interactions.
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Although many factors can influence molecular evolutionary rates, two specific evolutionary forces—sexual selection and sexual conflict—have been proposed as primary drivers of this accelerated evolution, because both processes are expected to differentially affect reproductive traits and the proteins that underlie them. That is, traits mediating male—male competition and male—female mate choice experience unique selection to maximize mating and reproductive opportunities Andersson,and often appear to evolve rapidly between species Ritchie, ; therefore, the loci underpinning these reproductive traits might also be expected to display accelerated evolution and protein divergence between species Swanson and Vacquier, b ; Clark et al. This inference continue reading supported by observations of especially exaggerated protein evolution in male-exclusive and male-biased loci collated in Dapper and Wade,the sex that is usually subject to more intense sexual selection Andersson, Importantly, if sexual selection or conflict are the most critical factors driving rapid reproductive protein evolution, this pattern should be observed in other groups of organisms that also experience these selective forces.
Nonetheless, whether reproductive proteins routinely evolve rapidly in non-animal species remains unclear. Accordingly, angiosperms may also be expected to exhibit elevated evolutionary rates in loci underpinning these traits, similar to those inferred in animals Clark et al.
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Indeed, of the existing studies in angiosperms, some analyses have found evidence for faster protein evolution in reproductive loci Szovenyi et al. However, others have shown more equivocal patterns e.
These more complex findings could reflect the influence of additional factors on rates of protein evolution in plants, including the opportunity for haploid selection and the complex effects of mating system variation. In the first case, plants often express a substantial proportion of their genome during the haploid phase of the life cycle Hafidh et al. Compared to diploid-expressed loci, traits that rely on haploid gene function are expected more info experience both stronger purifying selection against deleterious alleles, and elevated fixation rates stronger positive selection for advantageous alleles, because both deleterious and advantageous alleles will be visible to haploid selection regardless of dominance Charlesworth and Charlesworth, ; Walsh and Charlesworth, ; Immler and Otto, ; Immler, Moreover, gametophytic-exclusive genes could also evolve differently from loci that are expressed in both gametophytic and sporophytic diploid tissue, if the latter also experience additional constraints or antagonistic effects because of their expression during both phases of the life cycle Immler and Otto, ]
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