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For other uses, see Reproduction (disambiguation) Look up reproduction in Wiktionary, the free dictionary. ...


Reproduction is the biological process by which new individual organisms are produced. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor... Jump to: navigation, search In biology and ecology, an organism (in Greek organon = instrument) is an assembly of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... Jump to: navigation, search Life is a multi-faceted concept. ...


The known methods of reproduction are grouped into two main divisions, sexual and asexual reproduction. In asexual reproduction, an individual can reproduce without the involvement of another individual of that species. The division of a bacterial cell into two daughter cells is a common example of asexual reproduction. It is not, however, limited to single cell organisms. Jump to: navigation, search Sexual reproduction is a process of reproduction involving the merging of two gametes from the same species to produce a new organism. ... Asexual reproduction the simplest form of reproduction and does not involve meiosis, gamete formation, or fertilization. ...


Sexual reproduction, however, requires the involvement of two individuals of a species, typically one of each sex. Normal human reproduction is a common example of sexual reproduction. Generally, more complex organisms reproduce sexually while simpler, usually unicellular organisms reproduce asexually. Wikimedia Commons has media related to: Sex positions Francoeur, Robert T. (ed. ...

Contents


Asexual reproduction

Main article: Asexual reproduction

Asexual reproduction is the biological process by which an organism creates a genetically similar copy of itself without a contribution of genetic material from another individual. Bacteria divide asexually via binary fission; viruses take control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and yeasts are able to reproduce by budding. These organisms do not have different sexes, and they are capable of "splitting" themselves into two or more parts and are even able to regenerate their body parts. Some 'asexual' species, like hydra and jellyfish, may also sexually reproduce. For instance, most plants are capable of vegetative reproduction, reproduction without seeds or spores, but also, they can reproduce sexually, by way of pollination. Likewise, bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include fragmentation and spore formation. Asexual reproduction the simplest form of reproduction and does not involve meiosis, gamete formation, or fertilization. ... Jump to: navigation, search Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Binary fission Binary fission is the asexual reproductive process used by most prokaryotes, which results in the reproduction of a living cell by division into two equal, or near equal, parts. ... Jump to: navigation, search A virus is a microscopic nonliving parasite that infects cells in biological organisms. ... Jump to: navigation, search Species Hydra americana Hydra attenuata Hydra canadensis Hydra carnea Hydra cauliculata Hydra circumcincta Hydra hymanae Hydra littoralis Hydra magnipapillata Hydra minima Hydra oligactis Hydra oregona Hydra pseudoligactis Hydra rutgerensis Hydra utahensis Hydra viridis Hydra is the genus name of a simple, fresh-water animal possessing radial... Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Jump to: navigation, search Yeasts constitute a group of single-celled (unicellular) fungi, a few species of which are commonly used to leaven bread and ferment alcoholic beverages. ... General Biological Meaning Budding is a type of asexual reproduction. ... Jump to: navigation, search Species Hydra americana Hydra attenuata Hydra canadensis Hydra carnea Hydra cauliculata Hydra circumcincta Hydra hymanae Hydra littoralis Hydra magnipapillata Hydra minima Hydra oligactis Hydra oregona Hydra pseudoligactis Hydra rutgerensis Hydra utahensis Hydra viridis Hydra is the genus name of a simple, fresh-water animal possessing radial... Jump to: navigation, search Orders Stauromedusae Coronatae Semaeostomae - Disc jellyfish Rhizostomae Jellyfish (also called jellies or sea jellies as they are not true fish, nor are they made of jelly) are animals that belong to Phylum Cnidaria, included in the class Scyphozoa (from Greek skyphos cup and zoon animal). The... Production of new individuals along a leaf margin of the air plant, Kalanchoë pinnata. ... Bumblebee and honeybee pollinating a sedum telephinum Pollination is an important step in the reproduction of seed plants: the transfer of pollen grains (male gametes) to the plant carpel, the structure that contains the ovule (female gamete). ... Bacterial conjugation is the often regarded as the bacterial equivalent of sexual reproduction or mating; however it is not actually sexual as it does not involve the fusing of gametes and the creation of a zygote, it is merely the exchange of genetic information. ... Fragmentation is a form of asexual reproduction where an organism is split into fragments either intentionally or not. ... Jump to: navigation, search The term spore has several different meanings in biology. ...


Sexual reproduction

Main article: Sexual reproduction

Sexual reproduction is a biological process by which organisms create descendants through the combination of genetic material taken randomly and independently from two different members of the species. These organisms have two different adult sexes, male and female. One of each provides half of the new organism's DNA, creating haploid gametes. These two gametes fuse to form a diploid zygote. Jump to: navigation, search Sexual reproduction is a process of reproduction involving the merging of two gametes from the same species to produce a new organism. ... Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology is the science of life (from the Greek words bios = life and logos = word). ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... Jump to: navigation, search In biology and ecology, an organism (in Greek organon = instrument) is an assembly of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... Wikimedia Commons has media related to: Sex positions Francoeur, Robert T. (ed. ... Jump to: navigation, search Male symbol Male is the sex of an organism, or a part of an organism, which produces sperm. ... Jump to: navigation, search Female symbol Female is the sex of an organism, or a part of an organism, which produces egg cells. ... Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... Jump to: navigation, search A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization. ...


Humans, most animals, and flowering plants reproduce sexually. In mammals, the offspring resemble the adult form, but in other animals, such as butterflies, the offspring can look considerably different. Jump to: navigation, search Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants (also angiosperms or Magnoliophyta) are one of the major groups of modern plants, comprising those that produce seeds in specialized reproductive organs called flowers, where the ovulary or carpel is enclosed. ... For other uses of the term butterfly, see butterfly (disambiguation). ...


Sexually reproducing organisms have two sets of genes for every trait (called alleles). Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents' genes. This recombination of genes every generation leads to strong selective pressure for good genes for survival in the organism's environment. Further, by having two copies of every gene, only one of which is expressed, deleterious alleles can be masked, an advantage believed to have led to the evolutionary development of diploidy (Otto and Goldstein). An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. ... Jump to: navigation, search Gene expression (also protein expression or often simply expression) is the process by which a genes information is converted into the structures and functions of a cell. ... Jump to: navigation, search Charles Darwin, father of the theory of evolution by natural selection. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ...


Mitosis and Meiosis

Mitosis and meiosis are an integral part of cell division. Mitosis occurs in somatic cells, while meiosis occurs in gametes. Jump to: navigation, search Light micrograph of a newt lung cell in early anaphase of mitosis. ... -1... Cell division is the process by which a cell (called the parent cell) divides into two cells (called daughter cells). ... A somatic cell is a type of cell in an organism, such as the human body. ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ...


Mitosis

The resultant number of cell in mitosis is twice the number of cells originally. The number of chromosomes in the daughter cells is the same as that of the parent cell. Jump to: navigation, search Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... This article is about the biological chromosome. ...



Image:Mitosis. ...

Meiosis

The resultant number of cells is four times the number of cells originally present. This results in cells with half the number of chromosomes present in the parent cell. A diploid cell forms two haploid cells. This process occurs in two phases, meiosis I and meiosis II. This article is about the biological chromosome. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ...



Image File history File links The main events in Meiosis File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

Reproductive strategies

There are a wide range of reproductive strategies employed by different species. Some animals, such as the human and Northern Gannet, do not reach sexual maturity for many years after birth and even then produce few offspring. Others reproduce quickly, but under normal circumstances, most offspring do not survive to adulthood. For example, a rabbit (mature after 8 months) can produce 10–30 offspring per year, and a fruit fly (10–14 days) can produce up to 900 offspring per year. These two main strategies are known as K-selection (few offspring) and r-selection (many offspring). Which strategy is favoured by evolution depends on a variety of circumstances. Animals with few offspring can devote more resources to the nurturing and protection of each individual offspring, thus reducing the need for a large number of offspring. On the other hand, animals with many offspring may devote less resources to each individual offspring; for these types of animals it is common for a large number of offspring to die soon after birth, but normally enough individuals survive to maintain the population. Jump to: navigation, search Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens For other uses, see Human (disambiguation). ... Binomial name Morus bassanus Linnaeus, 1758 The Northern Gannet (Morus bassanus or Sula bassana) is a large seabird of the gannet family, Sulidae. ... The term adult describes any mature organism, but normally it refers to a human: one that is no longer a child / minor and is now either a man or a woman. ... Jump to: navigation, search Genera Pentalagus Bunolagus Nesolagus Romerolagus Brachylagus Sylvilagus Oryctolagus Poelagus The bane of Australian farmers - the wild rabbit Rabbits are small mammals in the family Leporidae, found in many parts of the world. ... Binomial name Drosophila melanogaster Meigen, 1830 Drosophila melanogaster (Black-bellied Dew-lover) a dipteran (two-winged) insect, is the species of fruit fly that is commonly used in genetic experiments; it is among the most important model organisms. ... In ecology, K-selection (note : upper case K) relates to the selection of traits (in organisms) that allow success in stable or predictable environments. ... Jump to: navigation, search In ecology, r-selection (note: lower case r) relates to the selection of traits (in organisms) that allow success in unstable or unpredictable environments. ... Jump to: navigation, search Charles Darwin, father of the theory of evolution by natural selection. ...


Asexual vs. sexual reproduction

Organisms that reproduce through asexual reproduction tend to grow in number exponentially. However, because they rely on mutation for variations in their DNA, all members of the species have similar vulnerabilities. Organisms that reproduce sexually yield a smaller amount of offspring, but the large amount of variation in their genes makes them less susceptible to disease.


Many organisms can reproduce sexually as well as asexually. Aphids, slime molds, sea anemones and many plants are examples. When environmental factors are favorable, asexual reproduction is employed to exploit suitable conditions for survival such as an abundant food supply, adequate shelter, favorable climate, disease, optimum pH or a proper mix of other lifestyle requirements. Populations of these organisms increase exponentially via asexual reproductive strategies to take full advantage of the rich supply resources. Jump to: navigation, search Families There are 10 families: Adelgidae - adelgids, conifer aphids Anoeciidae Aphididae Drepanosiphidae Greenideidae Hormaphididae Lachnidae Mindaridae Pemphigidae Phloeomyzidae Phylloxeridae Thelaxidae Aphids or aphides, also known as blight, greenfly, plant lice (superfamily Aphidoidea) are minute plant-feeding insects (1 to 10 mm). ... Typical orders Protostelia    Protosteliida Myxogastria    Liceida    Echinosteliida    Trichiida    Stemonitida    Physarida Dictyostelia    Dictyosteliida Slime moulds are peculiar protists that normally take the form of amoebae, but under certain conditions develop fruiting bodies that release spores, superficially similar to the sporangia of fungi. ... Families Many, see text. ...


When food sources have been depleted, the climate becomes hostile, or individual survival is jeopardized by some other adverse change in living conditions, these organisms switch to sexual forms of reproduction. Sexual reproduction insures a mixing of the gene pool of the species. The variations found in offspring of sexual reproduction allow some individuals to be better suited for survival and provide a mechanism for selective adaptation to occur. In addition, sexual reproduction usually results in the formation of a life stage that is able to endure the conditions that threaten the offspring of an asexual parent. Thus seeds, spores, eggs, pupae, cysts or other "over-wintering" stages of sexual reproduction ensure the survival during unfavorable times and the organism can "wait out" adversarial situations until a swing back to suitability occurs.


The Red Queen hypothesis

Sexual reproduction is best known for providing means of adaptation to an ever-changing environment by adding phenotypic variance to the population. The variation produced by sexual reproduction is not only outward (such as the advent of horns or fusion of digits) but is also physiological. One hypothesis termed the Red Queen Hypothesis says that sexual reproduction leading to variation is as much of an evolutionary arms race against parasites as it is against environmental factors. Variation that arises from sexual reproduction makes it harder for parasites to "get accustomed" to their hosts, ultimately making them less efficient. However, the idea of the hypothesis is that parasites continue to evolve as well, making both species continually change but stay in the same place relative to each other. Organisms that facultively reproduce asexually or sexually usually enter their sexual reproduction phase when pathogens become prevalent in the population.3 The eye is an adaptation. ... The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals. ... In probability theory and statistics, the variance of a random variable is a measure of its statistical dispersion, indicating how far from the expected value its values typically are. ... The Red Queen or Red Queens Race is an evolutionary theory explaining the advantage of sex. ... An evolutionary arms race is an evolutionary struggle between a predator species and its prey (including parasitism) that is said to resemble an arms race. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... Jump to: navigation, search A hypothesis (foundation from ancient Greek hupothesis where hupo = under and thesis = placing) is a proposed explanation for a phenomenon. ... This article is about biological evolution. ...


Life without reproduction

The existence of life without reproduction is the subject of some speculation. It is a misconception, however, that because all life on Earth is related there was at some point in the past a single individual organism as the ancestor of all other organisms. The argument goes that this ultimate-ancestor therefore had no reproductive origin. However, it is species populations that evolve, and a single individual is not the sole progenator of any evolved species; exceptions might be sports that are multiplied vegetatively, but these still arise by reproduction.


Today, some scientists have speculated about the possibility of creating life non-reproductively in the laboratory. One group of scientists has succeeded in producing a simple virus from entirely non-living materials. The production of a truly living organism, such as a simple bacterium, with no ancestors would be a much more difficult task.


Finally, life without reproduction is a feature of many religious Creation myths. The biblical Adam, for example, was created by God and had no ancestors. Creation beliefs and stories describe how the universe, the Earth, life, and/or humanity came into being. ... This article is about the biblical Adam and Eve. ...


Mechanical reproduction

A major goal in the field of robots is self replicating machines. Since all robots (at least in modern times) have a fair number of the same features, a self-replicating robot (or possibly a hive of robots) would need to do the following:

  • Obtain construction materials
  • Manufacture new parts
  • Provide a consistent power source
  • Program the new members

To date, this has not been done.


On a nanotechnical scale, nanomachines might also be designed to reproduce under their own power. This, in turn, has given rise to the "gray goo" theory of Armaggedon, as featured in such science fiction novels as Bloom and Prey. Jump to: navigation, search A mite next to a gear set produced using MEMS, the precursor to nanotechnology. ... Grey goo refers, usually in a science fictional context, to a hypothetical end-of-the-world event involving nanotechnology, in which out-of-control self-replicating robots consume all life on Earth while building more of themselves (a scenario known as ecophagy). ... Bloom, a novel by Wil McCarthy. ... The US Book Cover of the Novel Prey. Prey is a novel (ISBN 0066214122) by Michael Crichton first published in hardback edition in November 2002 and as a paperback edition in November 2003 by Harper Collins. ...


See also

  • Lottery principle -- The idea that sexual reproduction is adaptive because it produces greater diversity.
  • Mass production
  • Parthenogenesis -- (from the Greek παρθενος, "virgin", + γενεσις, "birth") means the growth and development of an embryo or seed without fertilization by a male.

The lottery principle is the term for a theory about why sexual reproduction is so widespread, introduced in 1975 by George C. Williams, a biology professor at Princeton University. ... Mass production is the production of large amounts of standardised products on production lines. ... Kaguya is one success from 460 attempts at growing embryos. ...

References

  1. S. P. Otto and D. B. Goldstein. "Recombination and the Evolution of Diploidy". Genetics. Vol 131 (1992): 745-751.
  2. Pang, K. "Certificate Biology: New Mastering Basic Concepts", Hong Kong, 2003.
  3. Zimmer, Carl. "Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures", New York: Touchstone, 2001.

Genetics is a monthly scientific journal publishing investigations bearing on heredity and variation. ...

External links


  Results from FactBites:
 
MSN Encarta - Reproduction (667 words)
Reproduction is one of the essential functions of plants, animals, and single celled organisms, as necessary for the preservation of the species as eating is for the preservation of the individual.
The typical male reproductive cell, which is known as a sperm, spermatozoon, or spermatozoan, is a motile cell with a head containing the nucleus and a whiplike tail with which it swims.
Plant reproductive cells are roughly similar to animal cells, the male cell being known as the sperm or microgamete and the female cell as the ovum or macrogamete.
Vegetative reproduction - Wikipedia, the free encyclopedia (522 words)
Natural vegetative reproduction is mostly a process of herbaceous and woody perennials, and typically involves structural modifications of the stem, although any horizontal, underground part of a plant (whether stem or a root) can contribute to vegetative reproduction of a plant.
A rhizome is a modified stem serving as an organ of vegetative reproduction.
Man-made methods of vegetative reproduction are usually enhancements of natural processes, but range from simple cloning such as rooting of cuttings to artificial propagation by laboratory tissue cloning.
  More results at FactBites »

 
 

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