Evolution of Sex

In biology, the evolution of sexuality has been a significant and contentious topic. On the genesis of sex, researchers have delved deeper with a variety of results and conclusions. Thus, experiments on the theories now in use are necessary to examine various hypotheses. The expenditures associated with sustaining universal sex in both plants and animals are very significant. Due to this, sexual reproduction may be less fertile than asexual reproduction. Reviews conducted over the past century have revealed that the two main components that scholars have employed are theories and empirical studies. In this review, some of the most prominent theories that exist only tell us why sex exists but does not tell us clearly the origin of sex. Evolution of sex tries to find the origin of sexually reproducing organisms from a common origin (Beukeboom & Nicolas 56). Whereas sex involves combining of two genetic materials, reproduction is the process of creating a new individual. Some of the prevalent hypotheses concerning evolution include the lottery principle, the tangled bank hypothesis, the red queen hypotheses and the DNA repair hypothesis.

In as far as the theories have been developed, they do not provide a clear evaluation of the origin of sex and thus there is continuous research on the subject to dig deeper. The process of transferring genes to offspring involves the transfer of the DNA stream with all the characteristics it carries.











































Introduction

Here, the paper seeks to find out the reason why some people are born as male and others as females. The study of the evolution of sex chromosomes entirely relies on genetics. Environmental factors such as food access and differences in age can contribute to a population. Normally, a male body functions differently from a female body despite both have the same genome. A genome is an organism complete set of genetics including the DNA. Biologically, there are only two sexes: the female and the male but some scientists believe that there was only one sex and organisms could mate with any other and reproduce. Having two distinctive sexes rather than a universal sex reduces the sexual production possibility by half since different sexes of the same family cannot mate. According to researchers, in the bid to explain sex, one states that the costs of sex are outweighed by its benefits and cannot comprehend how such an act became so widespread (Davies & Stuart 1). After all, the parent gives half of its genes to be offspring and for the dividing cells, they pass their cells over. There are however inherent costs that are incurred by sexual organisms like maintaining the fertilized gametes after fertilization, the incompatibilities passed by Rhesus factor from mother to the child, tissue rejection between the embryo and the mother thus limiting the speed in which reproduction takes place(Beukeboom & Nicolas 107). The relationship of the genes between the mother and the offspring is thus lower unlike in asexual reproduction.

Looking into the background, many single-celled organisms reproduce asexually meaning that only one parent is involved without the need for gamete formation. Sporulation is an example of this reproduction in Protozoa and other organisms. Other examples are budding and regeneration where organisms replace the lost parts. Why then that asexual reproduction was dominated over by sexual reproduction is what the research seeks to find out. This paper seeks to review the implications of sexual dominance over asexual and the organisms that first started mating sexually. The implications of sex evolution theories are also issues that this paper seeks to address.

Sexual reproduction has been found to have more benefits as compared to asexual. Some of the advantages of sexual reproduction include genetic variations and transfer of mutation to different individuals (Mirzaghaderi & Elvira 5). The genetic diversity enables organisms to survive in different and novel environmental conditions. Sexual reproduction has been documented to stay for over billion years and existing in organisms with a long generation time. Asexual produced organisms are unlikely to survive in different conditions because of their direct replication of their parents.

To distinguish male and female, we consider the gamete size. Some organisms are seen to combine gametes of almost same size while others combine of different sizes. The males are seen to have tiny gametes defied by their mobility and abundance, unlike females which are large, immobile and smaller in quantity (Cui 62). When individuals differ in the selection of males, natural selection happens and only the strongest survive. The evolution process not only helps the biologists but also other disciplines in the understanding of how species came into being and why some are extinct. When populations become isolated, either through geographical separation or other ways that hinder genetic transfer, there emerge new species with different traits (Shuker 174). The organisms that get separated may evolve to form other new species with dominant genetic character traits similar or different to that of the mother.

Literature Review

As a way of effectively explaining the genetic diversity and survival of sexually reproduced organisms, scholars use the lottery principle. Scientists argue that asexual reproducing would be like buying many lottery cards but giving same numbers. Sexual breeding, on the other hand, would be like buying few lottery tickets but giving them different numbers. The difference in the sexually produced would diversify survival chances unlike the similar produced. It is the diversity that increases their competitive advantage over other species and thus survival of the fittest.

The tangled bank hypotheses advocated by Charles Darwin also describes the environment as divided into different niches that require survival skills to thrive. It argues that only sex is required to bring the genetic variations and thus enable adaptations to the dynamics of the living space be it in the forest, waters or dry lands (Thatcher 71). According to Brooks (338), when explaining human behavior, genes and environment should always be considered. Thus sexual research should be a continuous activity with new hypothesis each day in a bid to explore the big mystery of where sex came from, where it started and how it started.

In the Evolutionary theory, the red queen hypotheses point out that the probability of extinction in organisms is not related in any way with how long they have survived (Shuker 9). The Earth is likened to being red in claws and teeth. The harsh environmental factors never get easier and even the highly adaptable organisms struggle to exist and have the same extinction chances as the newly formed species. Thus they have to keep running to survive and to improve including sex.

In the DNA repair hypothesis, when body somatic cells die, the germline in them does not die and it is termed immortal (Murray & Jack 297). The reason why old organisms can produce viable young offspring is due to the replacement of old cells by new ones. The repair of the genetic material of the germline happens during sex.

The modern literature trying to explain the origin of sex focuses on the two main categories which include genetic and environmental determinants of sex. Recently, the evolution of sex chromosomes has been known by scientists who used asparagus genome. The published findings in various scientific journals will help in the formation and development of male chromosomes thus breeding. The findings also say that the Y chromosomes can be manipulated to either female or hermaphrodite flower(Beukeboom & Nicolas 56).

In other findings in the Pink News, an asexual worm has been found and it is said that it has not had sex in the last eighteen million years (Benjamin 1). Despite lacking genetic variations, the worm is said to have survived mutations by copying itself. The worm skipped a major meiosis stage of chromosomes reshuffle before replication (Benjamin 1).

The recent studies have been significant in explaining current happenings like pregnancy loss in humans. Explanations have said that the basic cause of pregnancy loss is chromosomal abnormalities due to the meiosis process. Scientists have discovered that a complex breeding result in low survival rates of offspring while organisms with simpler reproduction like mitosis had higher survival rates. An experiment that scientists did with lizards where the lizard that went through complex mitosis had low survival rates while the one that underwent simple mitosis had higher survival chances (Erick 1).

Implications

Despite extensive efforts there exists a knowledgeable gap in where sex evolved from. Owing to the existing theories, it is difficult to carry out sex experiments to organisms due to the nature of the conduct. The researches done shows that all sexual beings originated from an asexual ancestry but does not give a clear indication of where sex began. In conserving species, it is necessary to support sexual breeding to increase survival chances among the beings. As illustrated in this article, the benefits of sex are seen to outweigh the costs. Many eukaryotic (multicellular) species have both sexes in the same plant. Thus it is not clear how sex dominance is of help to such species. As evident in this essay, the sexual dominance of a given animal does not act as a guarantee that it will survive the drastic changes in the surrounding. Besides, some of the dominant organisms do not have the capacity to change their sexual strategies to fit the changes in their body structure thus leading to the extinction of the species.

In Darwin's model of human selection, mating preferences fall into a direct benefit and indirect benefit models where individual chose partners based on the provision of care, territory defense, and nuptial care. This is the case witnessed in today's world with females choosing the male counterpart based on their ability to provide for the family. Females select quality and the best male counterpart but males tend to mate with as many females as possible. Darwin’s model demonstrated the clear relationship between the population size of organisms and the resources available. The situation where the males mate the most number of females helps in ensuring the continual existence of given specie while the females adapt to choosing the best male partners to help enhance the quality of the offspring. An equilibrium state is achieved when the population size equals the available resources. Therefore, all existing life and including humanity is as a result of natural selection and the existing species are the ones that survived. Therefore, the adaptation of various species to the surrounding depends on the sexual strategies.

More research is needed to elaborate further on the origin of sex chromosomes. More research in understanding human complexities should be done so that human beings can learn tolerance in their behaviors. There is also need to understand sexuality if it is a sexual orientation or an inheritance or sexuality fluid. The previously described concept is important in understanding cases of same-sex marriages, lesbianism, and heterosexuality. As seen, at conception, the eggs chromosomes and the chromosomes in the sperm contribute in giving the new offspring the full chromosomal component.

Through these studies, the changes in organisms have been clearly understood. Some organisms change seasonally, depending on variations in temperature, environmental conditions like moisture, precipitation, vegetation, and habitats. If human adaptations responded in response to pressure of evolution, it is expected that organisms would be best suited in that habitat.



Conclusion

In conclusion, therefore, it can be seen that the offspring reproduced through sexual reproduction are well-differentiated genetically since they possess half genes of each parents’. They are well adaptable and can thrive in harsh and novel conditions. The asexually produced on the other hand are the exact replica of their parents and have lower chances of survival environments. It is not the complexity of a reproduction mechanism that yields better offspring as seen in meiosis example of lizards but simple breeding process.

Although sex was a reproduction process, it is nowadays a pleasurable activity among the humans with sexual traditions and cultures taking a totally different direction. In my opinion, the government should sponsor research activities to bring limelight on sexuality issues not only for humans but also for organisms. Allocations should be made to responsible sectors and funds released to enable smooth and effective running of research. These funds should be able to purchase the needed equipment, hiring of professional and trained experts among others. The results of the research studies should be published and made known to the public. Education forums are also necessary for ensuring a well-informed society. Research institutes like The University of Cambridge in Europe is a well-known center for carrying out research. There should also be meaningful experiments allowed in schools to create research-oriented individuals.

This information on findings should also be shared with the involved stakeholders for implementation and taking appropriate course of action





























Work Cited

Benjamin Butterworth. This asexual worm hasn't had sex for 18 million years, Pink News, 2017

Beukeboom, Leo W, and Nicolas Perrin. The Evolution of Sex Determination. , 2014. Print.

Brooks, Robert C. Sex, Genes & Rock 'n' Roll: How Evolution Has Shaped the Modern World. Sydney, N.S.W.: Read How You Want, 2011. Print.

Cui, Ke-hui. "Size differences between human X and Y spermatozoa and prefertilization diagnosis." Molecular Human Reproduction 3.1 (1997): 61-67. Print

Davies, N B, J R. Krebs, and Stuart A. West. An Introduction to Behavioral Ecology. , 2012. Internet resource.

Erick Hamilton, 2017,Pregnancy loss and evolution of sex-linked by cellular line dance, Aug 2,2017, News Media

Mirzaghaderi, Ghader, and Elvira Hörandl. "The evolution of meiotic sex and its alternatives." Proc. R. Soc. B. Vol. 283. No. 1838. The Royal Society, 2016. Print

Murray, Andrew W., and Jack W. Szostak. "Chromosome segregation in mitosis and meiosis." Annual review of cell biology 1.1 (1985): 289-315. Print

Shuker, David M. The Evolution of Insect Mating Systems. Oxford: Oxford University Press, 2014. Print.

Thatcher, Adrian. The Oxford Handbook of Theology, Sexuality, and Gender. , 2015.Print.