Human And Sexual Selection For Reproductive Advantage Essay

812 Words Nov 15th, 2016 4 Pages
Sexual dimorphism in body size between males and females helps contribute to both natural and sexual selection for reproductive advantage. However, it is not known why these differences exist in most species and how it may be controlled. Several case studies were performed on Sceloporus lizards, including those of male-larger species and female-larger species, as well as the Western diamond-backed rattlesnake, Crotalus atrox, which is a male-larger species. The main question revolves around whether sexual size dimorphism, SSD, is predominantly influenced by genetic or environmental causes. Possible determinants for SSD in these squamate reptiles may be the availability of food, amount of testosterone in the body, and/or the portion of energy used for growth or reproduction (John-Alder et al. 2007). It was originally hypothesized that SSD was partially due to the strength of selection on male and female body size. Large body size in females can increase their number of eggs, therefore increasing their fecundity (John-Alder et al. 2007). Species that select for a trait pertaining to a higher number of offspring should favor females of larger size. On the other hand, large body size in males can increase their access to potential mates, leading to higher reproductive success (Cox et al. 2003, 2007). Species that select for a trait to aid in an organism’s ability to obtain a mate should favor larger size in males. While it is true that fecundity and sexual selection may cause…

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