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Reproduction In Mammals
[A CASE STUDY OF UHUNMWONDE LOCAL GOVERNMENT AREA OF EDO STATE]
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CHAPTER ONE
INTRODUCTION
1.0 INTRODUCTION
Some very basic facts of human life are:
1. People have no control over whether or not they become alive;
2. Once alive they strive to stay alive;
3. They have a strong and instinctive drive to reproduce;
4. They all eventually die.
Why are these facts ethically important?
Human beings, as organisms, are subject to these facts of life, but uniquely in the living world, we are also able to rationalise and to moralise. We can readily understand that the basic instinct for life is present in other people too, and appreciate that we have a moral duty to protect that instinct in them. This has been termed the presumption in favour of life.
Reproduction is the single most distinguishing characteristic of life. It is the driving force of evolution, which itself is responsible for the diversity of plant and animal species on Earth.
We humans are living organisms and these forces act on us just as any other species with which we share the Earth. We feel the urge to reproduce at a very powerful biological level at various times in our lives. It is not surprising therefore, that over the course of history all aspects of human reproduction have been the subjects of intense moral and ethical debate.
1.1 BACKGROUND OF STUDY
The study of reproduction is a relatively new specialty, and developed in large part from a focus on body politics during second wave feminism in the 1970s. It was also in the 70s, that the first IVF baby was born, making “infertility,†more of a chronic condition as opposed to barrenness or sterility. As new technological advances made it possible for increasing numbers of infertile couples to conceive biological children, more people came forward to seek assistance with reproduction (Angela, 2011)
Reproduction in humans and others mammals is the process by which sperm and egg cells are produced, brought together, join and develop into a new individual. Reproduction is the key to the continued existence of our species. Mammals reproduce by uniting sperm and egg internally in the female body by a process called internal fertilization.
Many mammals reproduce only during particular seasons of the year; not so with humans. Men produce sperm more or less continuously and women ovulate (produce an egg) about once a month. The male reproductive tract consists of the paired gonads (organs that produce sex cells), the testes, where sperm are produced, plus accessory structures that store the sperm, produce secretions to activate them and finally conduct them to the inside of the female reproductive tract.( Richard, 2000).
Mousseau and Roff (1987) conducted a comprehensive review of the heritable variability of the morphological, behavioral, physiological, and life history phenotypes (i.e., measurable traits) that covary with survival and reproductive outcomes in wild, outbred animal populations. The analysis included 1120 heritability estimates– the proportion of variability across individuals that appears to be due to genetic variability—across 75 invertebrate and vertebrate species. Although there was con-siderable variation —across species, contexts, and phenotypes— in the magnitude of the heritability estimate, their analysis indicated that “significant genetic vari- ance is maintained within most natural populations, even for traits closely affiliated with fitness†(Mousseau & Roff, 1987). The median heritability estimates were .26 for life history traits (e.g., age of maturation), .27 for physiological traits (e.g., cardiovascular capacity), .32 for behavioral traits (e.g., mating displays), and .53 for morphological traits (e.g., body size), values that are similar to those found in human populations (Plomin et al, 2001).
Kingsolver et al (2001) reviewed field studies of the relation between the types of traits analyzed by Mousseau and Roff (1987) and survival and re-productive outcomes in wild populations.
As aptly described by Alexander, “lifetimes have evolved to maximize the like-lihood of genic survival through reproduction†(Alexander, 1987), and the focus of life history research is on the suite of phenotypic traits that defines the species’ maturational and reproductive pattern (Charnov, 1993; Roff, 1992). A suite of traits must be considered because of the trade-offs involved in the expression of one phenotype versus another (Williams, 1957). The trade-offs are commonly conceptualized in terms of a competitive allocation of resources (e.g., calories) to somatic effort or reproductive effort, (Alexander, 1987; Reznick, 1985, 1992; Williams, 1966). Somatic effort is traditionally defined as resources devoted to physical growth and to maintenance of physical systems during development and in adulthood (West, et al, 2001), although growth also involves the accumulation, as in increases in body size, of reproductive potential. Reproductive effort is expended during adulthood and is distributed among mating, parenting, and in some species nepotism, that is, investment in kin other than offspring (Emlen, 1995; Hamilton, 1964).
According to David (2003), Reproductive activity takes on two general forms: in semelparity all reproductive potential is spent in one breeding episode, but in iteroparity reproductive potential is allocated across more than one breeding episode. Semelparity is a more risky strategy because reproduction during poor ecological conditions could result in extremely high offspring mortality rates, with no opportunity to reproduce under more favorable conditions. Semelparity is, however, favored when adult mortality is high and thus the probability of surviving to the next breeding season is low. Under these conditions, individuals that devote minimal resources to somatic effort in adulthood and maximal resources to reproductive effort will produce more off-spring than individuals that do not. In contrast, iteroparity is favored when juveniles and adults are likely to survive from one breeding season to the next (e.g., due to low predation risks) and juveniles are unlikely to reproduce successfully (Roff, 1992; Wittenberger, 1979). For these species, the current reproductive effort is bal-anced against the costs of this effort with respect to survival and future reproductive potential. As a result, during each breeding season iteroparous species invest more in maintenance and less in reproduction than semelparous species (Roff, 1992).
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ABSRACT - [ Total Page(s): 1 ]This study examined reproduction in mammals using man as a case study. In the study, some of the main features of reproduction in man are explored. After considering some of the various aspects of reproduction in man and the challenges faced, we move to consider in particular, pregnancy and childbirth. To this effect, a questionnaire was designed that addressed issues relating to pregnancy and childbirth. The primary audiences for the questionnaire were pregnant women/nursing mothers and medical ... Continue reading---
