Biological Sciences
Reproduction
Reproduction is the biological process by which organisms produce offspring. It involves the transmission of genetic material from parent to offspring, ensuring the continuation of a species. Reproduction can occur through sexual or asexual means, and is essential for the survival and diversity of life on Earth.
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8 Key excerpts on "Reproduction"
eBook - PDF- Giuseppe Fusco, Alessandro Minelli(Authors)
- 2019(Publication Date)
- Cambridge University Press(Publisher)
Therefore, the aim of these definitions is not to adopt arbitrary resolutions in a controversial subject, but rather to create the neces- sary conditions for starting our exploration of the biological phenomena. Later in the book, these definitions will hopefully find justification, or at least will be further clarified. 1.1 A First Definition of Reproduction As a starting point we can try to sketch an informal or intuitive concept of Reproduction, i.e. a concept close to common sense. This concept has deep roots in human history, as it emerged through acquiring knowledge of the life cycles of the plants and animals most familiar to us, ourselves included. The roots of our notion of Reproduction are thus clearly pre-scientific. In biology, Reproduction is often defined as the process by which new individuals are produced from pre-existing individuals. This very concise definition is based on a couple of assumptions that, in the common-sense view again, are nearly always taken for granted. Namely, that these ‘new individuals’ (i) are materially generated by portions of the body of pre-existing individuals, which thus take the role of parents, and (ii) somehow qualify as entities of the same kind as their parents. This simple definition, with the accompanying specifi- cations, allows us to delimit this process with respect to other types of produc- tion of biological material (or material of biological origin) that we would not count as Reproduction, such as (i) the individual’s body growth, (ii) the pro- duction of metabolic waste products, (iii) the secretion of organic matter such as the silk used in the construction of cocoons and spider webs, and (iv) the emergence of new individuals directly from the abiotic world, so-called spon- taneous generation (Figure 1.1; Box 1.1). Two main ideas appear to contribute to the concept of Reproduction. One is that ‘new individuals’ are added to the set of existing ones.
eBook - PDF- Peter K.T. Pang(Author)
- 1991(Publication Date)
- Academic Press(Publisher)
Reproduction operates to propagate the individual genome and is thus the single most important bodily function. A variety of protective mechanisms have been adopted by various species to ensure uninterrupted Reproduction. It is in these mechanisms that universality of structure and function can best be demonstrated. In tracing the evolutionary roots of Reproduction and of the reproductive process, it becomes apparent that 4 'universality applies not only to the use of ancient mechanisms in the reproductive systems of higher species but also to the presence of these common mechanisms in other body systems (Farley, 1982; Lavy et al., 1988). In the mammalian repro-ductive tract these mechanisms are involved in the creation of the necessary 1 VERTEBRATE ENDOCRINOLOGY: FUNDAMENTALS AND BIOMEDICAL IMPLICATIONS Volume 4, Part A Copyright © 1991 by Academic Press, Inc. All rights of Reproduction in any form reserved. 2 Gad Lavy et al. microenvironment for gametogenesis, fertilization, embryogenesis, and im-plantation. Exposition and understanding of this perspective on evolution and on the endocrine processes in Reproduction should allow for better understanding of normal function. As well, by shedding some light on devia-tions from normal function, this understanding can lead to therapeutic avenues in animal and clinical populations. What follows is a systematic review of reproductive mechanisms and their underlying bases, with empha-sis on the similarities between species. I. REPRODUCTIVE STRATEGIES A. Sexual and Asexual Reproduction Sexual Reproduction is by far the prevalent form of Reproduction and is utilized by approximately 99% of all vertebrate species. In sexually reproduc-ing animals, the reproductive process requires contribution of genetic mate-rial from two individuals within the species that differ in their sexual pheno-type. There are some instructive exceptions to sexual Reproduction.
eBook - PDFDolly Mixtures
The Remaking of Genealogy
- Sarah Franklin(Author)
- 2007(Publication Date)
- Duke University Press Books(Publisher)
A common distinction between Reproduction and rep-lication is the association of the former with sexual difference and the latter with more primitive copying abilities. However, a counter-view would hold that microbes and bacteria, which have a famously loose ability to exchange genes, are equally recombinant to the higher organisms with their much-vaunted abilities of sexual Reproduction and the capacity to produce completely new individuals. Through cloning, even a single cell can produce a limitless population, and sterile lines can be reproduced, or grown, in perpetuity. The opti-mum all-terrain reproductive option of combining asexual division, or cloning, with the capacity to reproduce sexually exists among most species, including vertebrates such as birds and amphibians. Sexual Reproduction is associated with the higher species because it can be seen as more complex and advanced, whereas replication by mere division is associated with less developed life-forms. 1 The perceived advantage of sexual Reproduction is that it combines rep-lication with the production of genetic variation, or mix. Sex, in the sense of sexual Reproduction, increases mix, which is seen to offer the advantage of maximizing adaptive capacity, or fitness, through variation. Mix, it could be said, adds flex—the ability to change. In the account of making Dolly, The Second Creation (2000), Ian Wilmut argues that compared to asexual replication, sexual repro-duction is expensive, dangerous, and inefficient: ‘‘Asexual reproduc-tion is the obvious way to replicate: start with one individual, split down the middle, and then you have two, or many. By contrast sexual Reproduction is a bizarre and even perverse way to replicate. Two protozoans that seek to reproduce sexually must first fuse, to pro-duce one . . . . Sex, in short, is anti-replication. Replication implies that one individual divides to become two or more.
eBook - PDF- Jennifer Ellie(Author)
- 2011(Publication Date)
- Wiley(Publisher)
9-1 INTRODUCTION To maintain a presence on the planet, all living organisms must reproduce in one way or another. As humans, we may instinctively assume that complex organisms, such as ourselves, are better suited for survival and Reproduction than simpler organisms, such as bacteria. Do you think this a valid assumption or a biased one? Since bacteria are unicellular, they certainly don’t possess any tissues or organs dedicated to Reproduction. Bacteria carry out asexual Reproduction, whereby an organism (aka one bacterial cell) splits into two identi- cal clones following DNA replication. Asexual Reproduction may seem primitive to us, but there are definite advantages to this system. Since bacteria can reproduce in a matter of minutes, for instance, their numbers can grow exponentially within a matter of hours. For humans, Reproduction involves the fusion of gametes (sperm and eggs) pro- duced by the male and female reproductive systems, respectively. Sexual Reproduction increases our genetic diversity and thereby boosts the survival potential of our species as a whole. For example, an infectious disease that proves to be fatal in some (example: malaria) may not be fatal to others due to subtle genetic differences. On the other hand, though, it takes years—if not decades—for humans to pass from one generation to another. This is due, in part, to the fact that humans must complete various developmental stages—prenatal development, infancy, childhood, and adolescence—before Reproduction is even possible. Figures 9.1–9.2 show a side-by-side comparison of the male and female repro- ductive systems. Since so many striking differences are present, it is amazing that male and female genitalia arise from the same (homo-) original embryonic tissues. The term homologous is used when referring to different structures that arise from the same tissue origins during development.
- Sarah Franklin(Author)
- 2013(Publication Date)
- Duke University Press(Publisher)
Indeed it could be said we need some new conceptual tools to describe the human conceptus as a tool. Conventionally, Reproduction has been understood in two distinct senses— as a process of social replacement (as in the Reproduction of labor power), and as a biological process (as in sexual Reproduction). Somewhat confusingly, Reproduction is itself a term derived from manufacturing to refer to copying. This is the exact opposite of what it has meant in the context of biology, where sexual Reproduction is precisely not the same thing as copying, or asexual re- production, also known as cloning. This confusion is compounded by others, and also by a general neglect of the importance of what Marx called the “mode of Reproduction” or the sexual division of labor. Indeed, throughout Marx’s work the former is imagined to be largely explained by the latter. However, from the late twentieth century onward it has been increasingly evident that not only is sexual Reproduction a process that can be dramatically reshaped by technology (which is what the phrase “artifcial Reproduction” means), but that it can be used as a technology (e.g., to produce new life forms, such as transgenic organisms). What ivF very publicly introduces is a form of techno- logical transfer, or passaging, by which the technologization of biological sub- stance becomes a mode of Reproduction—including (and often uniting) not only sexual but also animal, human, digital, informatic, virtual, and mechani- cal Reproduction. Put bluntly, the increasing control of biological reproduc- tion “artifcially” is one of the major technological advances of the twentieth century, and yet one that has only recently begun to be theorized (particu- larly in the work of Haraway). In vitro fertilization is the means by which this new form of technological control has been transferred into the human, thus confrming not only a new means of establishing a pregnancy but a new role for technology in making life.
eBook - PDFBiological Relatives
IVF, Stem Cells, and the Future of Kinship
- Sarah Franklin(Author)
- 2013(Publication Date)
- Duke University Press Books(Publisher)
14 introduction This brings us back to our central question, which is how to evaluate the significance of the fact that humans are now making tools out of reproduc-tive substance, including our own. A question raised by the rapid evolution of ivF technology over the past half century, and in particular its new inter-face with stem cell research, is what it means to consider not only reproduc-tive substance as a technology, but technology as a reproductive substance, as new biological relations and relativities are literally being made by hand, often using handmade tools. Arguably we are not particularly well prepared to address this question by either Marx or Heidegger, or many other theorists of technology, who have not provided many theoretical resources for analyz-ing either Reproduction or reproductive substance. Indeed it could be said we need some new conceptual tools to describe the human conceptus as a tool. Conventionally, Reproduction has been understood in two distinct senses— as a process of social replacement (as in the Reproduction of labor power), and as a biological process (as in sexual Reproduction). Somewhat confusingly, Reproduction is itself a term derived from manufacturing to refer to copying. This is the exact opposite of what it has meant in the context of biology, where sexual Reproduction is precisely not the same thing as copying, or asexual re-production, also known as cloning. This confusion is compounded by others, and also by a general neglect of the importance of what Marx called the “mode of Reproduction” or the sexual division of labor. Indeed, throughout Marx’s work the former is imagined to be largely explained by the latter.
eBook - PDF- Julianne Zedalis, John Eggebrecht(Authors)
- 2018(Publication Date)
- Openstax(Publisher)
If the parent organism is successfully occupying a habitat, offspring with the same traits would be similarly successful. There is also the obvious benefit to an organism that can produce offspring whenever circumstances are favorable by asexual budding, fragmentation, or asexual eggs. These methods of Reproduction do not require another organism of the opposite sex. Indeed, some organisms that lead a solitary lifestyle have retained the ability to reproduce asexually. In addition, in asexual populations, every individual is capable of Reproduction. In sexual populations, the males are not producing the offspring themselves, so in theory an asexual population could grow twice as fast. However, multicellular organisms that exclusively depend on asexual Reproduction are exceedingly rare. Why is sexuality (and meiosis) so common? This is one of the important unanswered questions in biology and has been the focus of much research beginning in the latter half of the twentieth century. There are several possible explanations, one of which is that the variation that sexual Reproduction creates among offspring is very important to the survival and Reproduction of the population. Thus, on average, a sexually reproducing population will leave more descendants than an otherwise similar asexually reproducing population. The only source of variation in asexual organisms is mutation. This is the ultimate source of variation in sexual organisms, but in addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes and the genes are mixed into different combinations by crossovers during prophase I and random assortment at metaphase I. Chapter 11 | Meiosis and Sexual Reproduction 457 The Red Queen Hypothesis It is not in dispute that sexual Reproduction provides evolutionary advantages to organisms that employ this mechanism to produce offspring.
eBook - ePub- Rene Fester Kratz, Donna Rae Siegfried(Authors)
- 2019(Publication Date)
- For Dummies(Publisher)
Chapter 5Reproducing Cells
IN THIS CHAPTERUnderstanding why cells reproduce and how DNA replicates itselfDiscovering how mitosis produces exact copies of cellsMaking egg and sperm cells through meiosisAppreciating the power of genetic diversityAll living things can reproduce their cells for growth, repair, and Reproduction. Asexual Reproduction by mitosis creates cells that are genetically identical to the parent cell. Sexual Reproduction requires a special type of cell division called meiosis that produces cells containing half the genetic information of the parent cell. Meiosis and sexual Reproduction result in greater genetic diversity in offspring and, consequently, in the populations of living things.In this chapter, we explore the reasons that cells divide and present the steps of each type of cell division. We also introduce you to the ways sexual Reproduction adds variety to species of all kinds.Reproduction: Keep On Keepin’ On
Biology is all about life. And, when you think about it, life is really all about continuation — living things keep on keepin’ on from one generation to the next, passing on critical genetic information. Certainly this is one of the core differences between organisms and inanimate objects. After all, have you ever seen a chair or table replicate itself? Only living things have the ability to pass on genetic information and replicate themselves.When cells replicate, they make copies of all their parts, including their DNA, and then divide themselves to make new cells. If a cell makes an exact copy of itself, it’s engaging in asexual Reproduction. Single-celled prokaryotes, such as bacteria, reproduce asexually by binary fission; they’re able to divide quickly and reproduce themselves in as little as 10 to 20 minutes. Some single-celled eukaryotes and individual cells within a multicellular eukaryote also reproduce asexually. However, they use a process called mitosis (which we explain in the later section “Mitosis: One for you, and one for you ”) to produce new generations. If a cell produces a new cell that contains only half of its genetic information, that cell has engaged in sexual Reproduction. A special type of cell division known as meiosis (which we explain in the later section “Meiosis: It’s all about sex, baby
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