The origin of sex is a highly debated topic with many different theories. The question of sex raises several questions including where did sex come from, what is the purpose of sex, and why is sexual reproduction so widespread in multicellular organisms. The paradox of sex refers to the question of why sex is so widespread in multicellular eukaryotes when it is costly in evolutionary terms.(1) For example, sexual reproduction requires recombination and meiosis and two parents which are both costly requirements. The costs of sexual reproduction include breaking up previously successful combination of genes by recombination, the dilution of one’s genetic contribution by half, and the energy and time costs of finding a suitable mate.(1) Another …show more content…
The term comes from Lewis Carroll’s Alice's Adventures in Wonderland and Through the Looking-Glass where the Red Queen declares "Now, here, you see, it takes all the running you can do to keep in the same place." (10) Valen asserted that “continuing development is needed just in order to maintain its fitness relative to the systems it is co-evolving with.” (11) The red queen hypothesis describes how organisms survive in changing environments by adapting through sexual reproduction.(12) This hypothesis is currently the favorite among evolutionary biologists in attempting to explain the reason for sex.(12) The red queen hypothesis is closely related to the topic of coevolution as sexual reproduction allows for faster adaptation in the evolutionary arms race between hosts and disease or between predators and prey.(13) As species that live at each other's expense co-evolve, they are engaged in a constant evolutionary struggle or arms race for a survival advantage.(13) The hypothesis refers to the possible production and development of unusual gene combinations in the characteristic gene shuffling frequent in sexually reproducing organisms during meiosis.(12) These unusual gene combinations could increase the likelihood of escaping infection.(12) Sexual reproduction is thus considered a mechanism to produce variable offspring that may have new gene combinations and rare genotypes that would provide a survival …show more content…
As a result of the viral infection by two viruses, both viruses would replicate, producing four homologous chromosomes which would then be 'handcuffed' together in such a way preventing further replication.(14) Viral segregation mechanisms ensure that the viral pairs would segregate to either pole of the cell during replication.(14) After a round of replication, there would still be two viral chromosomes attached to each other and viral replication could not continue.(14) As a result, the cell would enter a second replication cycle to segregate the individual viral chromosomes into the host cells.(14) This
11.2) Asexual reproduction involves a single individual / parent who pass duplicates of all its genes to its offspring without the fusion of gametes. Sexual reproduction involves two parents who give rise to offspring that have unique combination of genes inherited from the two parents.
In summary, I have discussed how the sperm and egg reproduce to create new individuals. I have also described the challenges with the sperm trying to reach the egg to reproduce and how the egg only chooses the most optimal sperm for reproduction. Also, discussed how the protein affects reproduction and that they change over time since they are involved in reproduction. There is future research to gain more information on why there is sometimes reproductive failure. This new research will help a great deal in understanding why an egg and sperm cannot reproduce.
"Persistent female choice for a particular male trait values should erode genitive variance in male traits and thereby remove the benefits of choice, yet choice persists” (Miller, Christine and Allen Moore). This phenomenon is know as the Lek Paradox and has puzzled scientists for many years. Throughout all species there has been abundant evidence showing continuous female choice of male traits, yet there is still no definite answer as to what allows for genetic variance to be maintained, and why a specific trait never becomes fixed. Many hypotheses have been theorized and researched, all providing some explanation as to how this variance in species is maintained, from traits signaling resistance to parasites, according to Hamilton and Zuk, to the hypothesis of mutational and environmental affects. Condition-dependence can also provide information as to how the lek paradox is able to exist; this hypothesis will be looked at in this paper.
In telophase, these separate chromatids uncoil to become chromosomes. This division produces two identical cells.
Sexual reproduction is that the union of male and feminine gametes to create a fertilised egg or zygote. The ensuing offspring inherit one-half their traits from every parent. Consequently, they 're not genetically similar to either parent or siblings, except within the case of identical twins. As theorised by Mendel, adults are diploid, meaning as 2N, having 2 alleles offered to code for one attribute. The gametes should be haploid, signified by N, containing just one allele in order that once 2 haploid gametes mix, they manufacture a traditional diploid individual. The method where haploid sex cells are created from diploid parents is known as meiosis, and it happens solely within the reproductive organs.
Some individuals have developed different traits to help them in the process of intra-sexual competition. The organisms with more distinctive traits have greater reproductive success. More genes of those traits are then ‘selected’ and are passed onto the offspring of the organisms. Throughout time variability in these traits becomes
The sexual “arms race” is constantly going on within members of a species. While both male and female are trying to pass on their genes to the next generation, they both try to do this in a different way. Females are attempting to obtain genetic material from the best possible male in order to produce the fittest offspring, while males are trying solely to pass their own genes on to the next generation.
The Red Queen by Victoria Aveyard I read the book, Red Queen, by Victoria Aveyard. The book was published in New York by HarperCollins publishers in the year 2015. The book has 383 pages. I’ve never read a book by Victoria Aveyard before, but I enjoyed the book quite a bit. The book is fiction and it’s both action as well as romance.
The Red Queen by Victoria Aveyard does not require a great imagination. Ms. Aveyard does a splendid job of using imagery. The plot of the novel flows in a way that makes it feel real. The book is told from the perspective of Mare Barrow. Throughout the book we see the occurrences of her life. She progresses a great deal for the duration of the novel.
Darwin states that this struggle need not be competitive in nature and also entails a species’ efficiency at producing offspring. Natural selection works not as an active entity that seeks and exterminates species that are not suited for their environment; instead, it retains variations that heighten a species’ ability to dominate in the struggle for existence and discards those that are detrimental or useless to that species. Stephen J. Gould explains the case of r-selection in which a species’ chances of survival are most reliant on its ability to reproduce rapidly and not on its structure being ideally suited for its environment. Gould’s example shows the beneficial results of perceiving natural selection not as something that changes a species in accordance with its environment but as something that preserves characteristics beneficial in the s... ...
Meiosis, also called reduction division, is a distinct type of cell division that is essential for sexual reproduction to occur. It is one in which two successive divisions of diploid cell occur thereby producing four genetically different haploid daughter cells, also called gametes, each with half the number of chromosomes and thus, half the total amount of genetic material as compared to the amount before meiosis began. Interphase precedes meiosis and thus, paves the way for meiosis to eventuate as the cell’s DNA replicates in the S phase yielding corresponding, identical chromosomes. Interphase sparks the marvelous process of meiosis that allows variation to transpire within the organisms it occurs, hence, giving rise to millions of organisms with unique aspects unlike any other on Earth. Because meiosis is a form of sexual reproduction itself, it is the means through which gametes are produced, each with a reduced number of chromosomes, so that when two gametes fuse during fertilization, not only do they form a diploid zygote with 46 chromosomes, but also have manifested differing features due to the rearrangement (crossing-over) of chromosomes.
Despite the sound logic of the evolutionary argument, it does not account for what humans have had for a long time: contraception. This is why many people prefer to look at how this double standard formed from more of a sociological viewpoint. Women’s sexual con...
The merger of two germinal cells, one being a sperm cell and the other being an egg cell, is complete within twelve hours, at which time the egg is fertilized and becomes a zygote containing forty six chromosomes required to create a new human life. It is during this remarkable process when conception occurs. Conception confirms life and makes that undeveloped human one of a kind (Rorvik & Shettles, 1983, p. 16). Many researchers, as well as scientists, identify the first moments of life as the instant when a sperm cell unites with an ovum, o...
During prophase I, homologous chromosomes pair and form snynapses. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.