• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Role of Sex

Extracts from this document...

Introduction

The Role of Sex This essay aims to determine what the biological role of sex is in the natural world. As a result it is sensible to first define "sex", "Sex n. either of two main groups (male and female) into which living things are placed according to their reproductive functions; fact of belonging to one of these; sexual feelings or impulses or intercourse." (Oxford English dictionary, 1981). This definition suggest that two main areas should be discussed when writing an essay on this subject; why has evolution largely favoured species being separated into males and females, and secondly, why has evolution favoured sexual reproduction over asexual reproduction? Asexual reproduction accounts for the exponential growth of a species or colony. This can be easily demonstrated by spreading a culture of Streptococcus Pneumoniae on an agar plate with minimum medium (MM) then counting the resulting colonies twenty-four hours later. Sexual reproduction on the other hand is usually a slower process and requires a greater input of energy,...the small monkey flower (Mimuslus kelloggii), more than 20% of the energy from photosynthesis is used to make flowers (Moore et al, 1998), with fewer offspring than by asexual reproduction. Why, therefore is it that organisms, which reproduce by asexual means, have no completely over run sexually reproducing species in number? ...read more.

Middle

The least resistant hosts and the least virulent parasites were killed in each generation. Now the asexual population no longer had an automatic advantage. It was predominant most often if there were lots of genes that determined resistance and virulence in each creature. In the model, as resistance genes that worked would become more common, then so too would the virulence genes. Then those resistance genes would grow rare again, followed by the virulence genes. As Hamilton (1978) put it, "antiparasite adaptations are in constant obsolescence." But in contrast to asexual species, the sexual species retain unfavored genes for future use. "The essence of sex in our theory, is that it stores genes that are currently bad but have promise for reuse. It continually tries them in combination, waiting for the time when the focus of disadvantage has moved elsewhere." (Hamilton, 1978) Another theory suggests, "The mutation accumulation hypothesis predicts that sex functions to reduce the population mutational load" (Evolution: Vol. 52, No. 2, pp. 604-610.) According to this idea, sexual lineages persist because they are more efficient than asexual's at clearing their genomes of mutations. With the onset of time, asexual lineages are expected to be eliminated due to the build up of a large mutation load. Potentially, this idea is sound but would require there to be extensive mutation of the order of one per genome, and the mutations would have to affect fitness in a very specific way. ...read more.

Conclusion

This tends to give rise to the more traditional male/female sex roles." (http://www.pbs.org/wgbh/evolution/library/01/6/quicktime/l_016_04.html) This suggests that the role of the male/female system is to allow the female to choose a mate. The idea is that the males will all compete for the females, and so the female has the best opportunity to choose a suitable mate, i.e., the fittest male. In many animal species there are strict sexual rituals that the males must go through to be able to pass its genes onto the next generation, by impressing the female. In some species this involves a fight between the males whereby the strongest will mate with the female. This is so the female will combine with genes from the male who is bigger, stronger and faster. In other species, the ritual may involve elaborate displays, such as the giant peacock, which displays its wings to the female. All in all these rituals serve to maintain a strong gene pool in a population, which can only be maintained by there being two sexes. Overall, the favour of evolution towards sexual reproduction and the sexes that make it possible, seems to give the species a greater chance of survival by maintaining a rich and diverse gene pool. The evolutionary pressure and species interactions that are forced onto species have resulted in these processes, in each species drive to remain alive and abundant. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Genetics, Evolution & Biodiversity section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Genetics, Evolution & Biodiversity essays

  1. Marked by a teacher

    Epping Forest Coursework

    4 star(s)

    These will have to be controlled. One of the variables that will be controlled is the coordinates of the axis showing the plot of land. Also the area will remain the same (225m2) in both light and dark areas. Same equipment will be used in both areas aswell.

  2. HSC maintaining a balance notes

    V) Development of Evolution Lamarck (1744-1829): acquired characteristics Hutton (1726-97): geological change happens gradually over long periods of time. Cuvier (1769-1832): fossils in deeper layers were most different from modern species. Lyell (1797-1875): geological processes occurred at the same rate in the present as they did in the past.

  1. Can relapse in acute lymphoblastic leukaemia (ALL) be prevented?

    The presence or absence and level of residual leukemia showed a strong positive correlation with the risk of relapse at each stage of monitoring. The PCR measurements recognized patients who were at high risk for relapse after the first stages of induction therapy.

  2. GENE EXPRESSION

    Bacterium was able to grow due to pglo resistance to ampicillin. Glow occurred dude to Arabinose (sugar) switching the green Florissant protein on (Pglo contains GFP: green fluorescent protein). Errors or improvement to experiment Possible errors were that, during my experiment I left the dish slightly open when I was

  1. patterns of growth and development

    They are also very aware of their own name. They are now able to control their vocal cords, tongue and breathing. At 15 months a baby may be able to use 10 words, they can point to names people or toys, they will scream to get something and will try

  2. Management style, culture & organizational structure.

    from those cells that have taken up plasmids without the gene. This is where the second marker gene (for resistance to ampicillin) is used. If the foreign gene is inserted into the middle of this marker gene, the marker gene is disrupted and won't make its proper gene product.

  1. Manipulating Reproduction - Have we gone too far?

    There are many ethical and moral issues and question that have been raised like; Should PGD be made widely available, given that there is no treatment or cure for Huntington's chorea? Or should the results of the genetic screening be made available to that of the person relatives or to that of the persons insurance company or employer.

  2. Recombinant DNA, genetically engineered DNA prepared in vitro by cutting up DNA molecules and ...

    The researchers found that people can pick up other people's DNA on their hands, which raised the possibility that DNA found at a crime scene might not belong to the criminal. A new study published in the scientific journal Cell by a team from the University of Munich in Germany,

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work