Evolution: Sexual and Asexual

Evolution: Sexual and Asexual
Name
Institution
Introduction
Usually, organisms have to reproduce as a means of ensuring survival in many generations. Organisms can reproduce sexually, asexually or both. Sexual reproduction has a disadvantage in that it involves a two-fold cost of sex. To explain this, let’s assumes that in a sexual population there arises a mutant female who produces asexually. If the mutant female produces a similar number of offspring, definitely she will produce twice as much offspring as compared to the sexual female. If the offspring inherited the mutation, then they will also reproduce asexually and eventually the mutation will outgrow the sexual population. This indicates that asexual production is advantageous in that it leads to reproduction of more offspring as compared to sexual reproduction. However, most species reproduce sexually because there are some advantages associated with sexual reproduction. It has been demonstrated that sexual offspring have the ability of adapting to changing environment and can persevere unfavorable conditions unlike the asexual offspring.
A number of organisms such as Daphnia magma exhibit both sexual and asexual reproductive pattern. In these organisms, asexual reproduction takes place when the environment is favorable for growth and when the conditions are not very conducive, sexual reproduction takes place. The offspring reproduced sexually remain dormant up to the time conditions becomes favorable (Duncan et al, 2006). This observation supports Fisher-Muller theory which stipulates that under certain conditions, it can be demonstrated that sexual populations have the ability to adapt faster as compared to asexual populations. Since the world is ever changing, sex is more advantageous over long terms. Assume that at two loci possessing alleles A and B new alleles a AND b are privileged when environmental change takes place. Assume that these two alleles a and b arise in the population immediately when the environment change occur. However, both mutations arise most probably in different individuals (Freeman & Herron, 2004). This means that in asexual population alleles a and b will not be brought together within a single individual. Therefore, we can only wait until either alleles a or alleles b fixes in the population, prior to fixing of the other allele form a new mutation. In contrast, when we consider sexual population, alleles Ab and aB individuals can mate and yield ab offspring through recombination. The genotype ab can therefore fix within the population even when mutations a and b did not take place in the same individual. It can therefore be demonstrated that recombination definitely seeps up adaptation when beneficial mutations takes place at a sufficiently high rate (Stearns & Hoekstra, 2005).
Sexual reproduction has some disadvantages which are considered less of a problem. For instant, the number of asexual reproduction offspring increases at twice the rate in every generation as the number of sexual reproduction offspring. Conversely, the fitness of a sexual female is only 50% that of an asexual female. This phenomenon is referred to as two-fold cost of sex. The cost for sexual reproduction is big because it involves mate ch...