Pros and Cons of Asexual and Sexual Reproduction - Assignment Example

Topic 1: Why Have Sex?  Sex is critical for reproduction 1. List the advantages and disadvantages of asexual and sexual reproduction. Type of reproduction Advantages Disadvantages Asexual reproduction Maintain genetically code and DNA molecule content from generation to the next Mutations can be passed to the next generation Slow novel genetic combination Survival on varied environment slowed due to genetic maintenance Infection can infect all the species in a particular clone. Higher parasite load Sexual reproduction Harmful mutation ca be removed on the future generation Rapid novel genetic combination Possibility of genetic variability on offspring generation enhancing survival Low parasite load Gene dilution down the generation Natural selection may break-up successful combination Some mates have to suffer severely up to death as they risk getting a mate Sexual cannibalism or not finding a mate when is needed Risks of being infected with sexually transmitted diseases 2. Why can parthenogenesis in the whiptail skink be considered a degenerate form of reproduction? With whiptail skink, parthenogenesis process is used to develop eggs, and only females exist in the population. The uniqueness of whiptail skink parthenogenesis is that ovulation occurs when another females takes up the character of a male during courtship. Thus, it seems in the past many generations males were present and did play the courtship behavior role which is seen as a major role in the species evolution on this generation. D1. Describe several different hypotheses for why sexual reproduction evolved. How do you think some groups of rotifers have managed to exist for millions of years without sex? Hermaphroditism theory evolved to ensure mating is feasible where getting sexual partner is limited. The red queen hypothesis ensures that sexually fertilized offspring have greater survival chances, compared to the asexual form against parasites infestation. Rotifiers have been able to reproduce over the ages via asexual reproduction (parthenogenesis). Parthenogenesis allows unfertilized egg to develop and form identical individual like the mother regardless of the ecological zone solving issues of searching a mate during fertile period (ovulation). Topic 2; Human Reproductive Systems CT1. How could you redesign the male reproductive system so that the path of urine and the path of sperm are separate? Appreciating the current male reproductive system, instead of having the prostate gland, the seminal vesicle and the vas deferens distal portion contract to allow semen into the posterior urethra, a parallel path will flow hand in hand with the urethra. The opening to the posterior urethra to allow semen into the urine system will be closed forever. The redesigned male reproductive system will only alter co-sharing roles such that vas deferens continues on its own path without having to enjoin the urethra. CT2. Animals that reproduce in water typically do not have a penis. What advantage does a penis serve for humans, who reproduce on land? On water the gametes finds a viable environment of floating and remain wet. On land the gametes ought to get protection from drying and cannot float on air thus, should be delivered within the female reproductive system. The penis ensures that during ejaculation the sperms are deposited inside the cervix where the vaginal fluid is present to allow them to swim to the fallopian tube for fertilization. The penis has what disadvantage? Flaccid penis is unable to offer desired sexual satisfaction as it cannot penetrate the female’s vagina. CT3. How could you redesign the female reproductive system so that the vagina is not both the organ of copulation and the birth canal? The reproductive systems in female is both physiologically and anatomically adapted to its function. Hormonal regulation affects various activities and behavior within the system. Given chance, however, and acknowledging the current role played by eahh part within the female reproductive system, I will have the birth canal placed just above the pubic bone on the lower abdomen. The vagina and clitoris will remain as they are for sex stimulation and sexual intercourse. The vagina will also play the role of menstrual cycle. The cervix will be redesigned such that it does on open-up during birth rather it directs the fetus towards the birth canal above the pubic bone. The redesigned birth canal-opening will unplug during birth via subsequent contraction and relaxation of the uterus and allow the fetus and placenta out, with lochia released via the vagina. CT4. Following menopause, females stop producing eggs and cannot get pregnant. Males produce sperm their entire lives. Relate this discrepancy to differences in the reproductive function and expected behavior of the sexes. For females the total germ cells they should have during their lifetime are all ready by the time they are born which is approximately 2, 000,000. This number by early 20s will have dropped to 3, 00, 000. About 400 of the total will be released during ovulation, and most of them will not be utilized during this period hence be released as a menstrual flow. The women fertility declines with age regardless of whether menopause has started, leading to more viable germ cells loss. Thus, the ovaries age-related changes leads to menopause and the female cannot release more viable ovum. Men on the other hand, have to release millions of sperms every ejaculation and sperm production occurs in millions per day until death. Sperms are only produced when men reach puberty, and remain viable until they die although quality of sperms is likely to decline with old age. Topic 3: Human Sexual Response 1. The Masters and Johnson model of human sexual response has how many phases? Four What are they? Arousal, Plateau, Organism and Resolution 4. How do men and women differ with regard to sexual arousal? Females experience changes in the uterine and vaginal anatomy as well as the breasts. Similar to men there is flow of blood to the genitals during sexual arousal. Though increase in blood flow to the genitals leads to vaginal lubrication unlike erection in men. 6. Discuss three controversies about female sexual response. Females may experience several organism as a man experience a single organism. Secondly, women like men has clitoris glans which becomes engorged with blood during arousal like the male penis. In some women penetration alone may lead to organism. The distance between clitoris and vagina determines organism. The intensity sexual experience determines the ejaculation. CT2. Women are more apt to see sexual desire as a means to love, emotional intimacy, or physical closeness. Is this goal consistent with the female’s role of bearing children? Yes. Why? Women like most females spend most of the time nurturing (gestation, lactation, defence roles) and parenting their young ones. The relationship of women with their young ones is built on love, and bonding. Thus, love, emotional intimacy and or physical closeness is correlated with roles of women on parental investation making them choosy on their mates. Topic 4: Animal Mating Systems 1. Why is polyandry uncommon? Human males adapt differently to overcome polyandry by increasing female fertilization chances. For example: ejaculate volume control, different males have completion and specialization, the existing seminal fluid within the vagina is displaced by the penis coronal ridge, and more sperm production is viable subject to large testes size. What sorts of ecological and phylogenetic circumstances might favour polyandry in animals? Limited sexual activity following limited breading season, shortened courtship and interaction period, clear signs of when ovulation is likely to occur in an animal and increased parental care demands. 2. The graph on page 341 shows the relationship between harem size, or the number of females that a male monopolises, and the ratio of male-to-female body length, a measure of sexual dimorphism, in a variety of species of seals. A. What is the most likely cause of this relationship? The harem size is determinant by the capacity of the male to protect the females to ensure successful mating and health off-springs. Thus, the male has to be strong, and health to wade up other males and be fit to successfully copulate as many females as possible a fact which can be measured by observing its body length and weight. On the other hand, the female has to be healthy enough to choose good mate and be able to ensure successful parenting. B. What prediction could you make about the breeding habitat occupied by a species at the lower left of the curve versus one at the upper right? The habitat of breeding for species analyzed at the lower left are likely to have many peripheral males, that deter the dominant male from mating most females or an environment with many peripheral males that the dominant male has to fight off before mating costing the dominant male a lot of energy rather than ensuring successful mating in time. The habitat could also mean the area has many females that the dominant male may not be able to maximize their mating need having low paternity success from the dominant male. The other habitat of the right can mean that the male arrives early in season for breeding, takes control of the area, and has access to many health females that is able to copulate with the females while still in the colony or when leaving to the sea giving the dominant male high chances of successful paternities. Topic 5: Sexual Selection 2. When we see differences between the sexes, we usually assume that they have come about by sexual selection. Can you think of selection pressures other than obtaining mates that might produce such differences? Natural selection is evident where some biological traits may not be common or with time vanish in a particular population as the population evolves to ensure survival hand in hand with reproduction of their bearers. Another aspect is social sex selection. In some cases lack of males or females like in clownfish have sequential hermaphroditism enabling the larger fish to turn to a female though they did start life as males while they were small. Other fish species can turn into male despite having developed as female like in Eastern Blue Groper following insufficiency mating males in the group, the largest fish turns to a male. Temperature dependent sex determination is employed by various species of fish and reptiles where high or low temperatures determines the offsprings to be brought forth and subsequent survival. 3. Males typically compete for access to females and often obtain more than one mate, while females are particular about their choice of mates. In some species, however, the male supplies the female with large “gifts” in the form of captured prey or large, protein-rich sperm packets. What differences might you expect to see in the reproductive behaviour of such species when compared with the typical pattern? Looking at Mormon crickets, the females are choosy as the males compete for them. To entice the females the males offer a nutritious attachment spermatophylax to ensure the female has humble volume for consumptions giving the male sufficient time to release its sperms to the female’s reproductive system a fact which gives a room for increase offspring from the particular males increase a chance for its generation to continue. The female is likely to produce more eggs from the energy derived from extra feeds during mating time. However, when food is insufficient the female will compete for the male. The males will choose the largest female as it will benefit the male by laying more eggs compared to a small-sized female. On the typical case mate choice comes in where one sex will need to invest more during the reproduction. Females and males will choose mates likely to offer play a sex-reversal role whether partially or fully. A. Name and describe the hypotheses proposed to explain the evolution of sexually dimorphic traits. Natural selection: Small male size enables swiftness like in Firefly Photinus pyralis. Large females are linked with increased resources searching for its offsprings. Fecundity: in case of weasel Mustela nivalis smaller size allows earlier age reproduction, and encourages frequent reproductive periods. Small size males enables them to reach maturity early and be able to search for their mates first where competition scramble is a common phenomenon enabling them to father many offsprings Males are likely to choose large females as large females are linked with increased embryonic production like woodfrogs Sexual selection: Large males are likely to have more females per male. Large size in male enables them to win their rivals for a particular mates and or dominate certain territories. Read More