World Library  
Flag as Inappropriate
Email this Article

Reproduction

Article Id: WHEBN0000026310
Reproduction Date:

Title: Reproduction  
Author: World Heritage Encyclopedia
Language: English
Subject: Biology, Being Boiled, Glossary of biology, Reproductive technology, Sterilization (medicine)
Collection: Fertility, Reproduction
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Reproduction

Production of new individuals along a leaf margin of the Miracle Leaf plant, Kalanchoe pinnata. The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.

Reproduction (or procreation) is the sexual and asexual.

In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a plants have the ability to reproduce asexually and the ant species Mycocepurus smithii is thought to reproduce entirely by asexual means.

Sexual reproduction typically requires the involvement of two individuals or cloning.

Contents

  • Asexual reproduction 1
  • Sexual reproduction 2
    • Allogamy 2.1
    • Autogamy 2.2
    • Mitosis and meiosis 2.3
  • Same-sex reproduction 3
  • Reproductive strategies 4
    • Other types of reproductive strategies 4.1
  • Asexual vs. sexual reproduction 5
  • Life without reproduction 6
  • Lottery principle 7
  • See also 8
  • Notes 9
  • References 10
  • Further reading 11
  • External links 12

Asexual reproduction

Asexual reproduction is the process by which an organism creates a genetically similar or identical copy of itself without a contribution of genetic material from another individual. hydra, yeast (See Mating of yeasts) and jellyfish, may also reproduce sexually. For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can also reproduce sexually. Likewise, bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include parthenogenesis, fragmentation and spore formation that involves only mitosis. Parthenogenesis (from the Greek παρθένος parthenos, "virgin", + γένεσις genesis, "creation") is the growth and development of embryo or seed without fertilization by a male. Parthenogenesis occurs naturally in some species, including lower plants (where it is called apomixis), invertebrates (e.g. water fleas, aphids, some bees and parasitic wasps), and vertebrates (e.g. some reptiles,[1] fish, and, very rarely, birds[2] and sharks[3]). It is sometimes also used to describe reproduction modes in hermaphroditic species which can self-fertilize.

Sexual reproduction

Hoverflies mating in midair flight

Sexual reproduction is a ciliates, Paramecium aurelia, have more than two types of "sex", called syngens.[4]

Most [5][6]

Bryophyte reproduces sexually but its commonly seen life forms are all haploid, which produce gametes. The zygotes of the gametes develop into sporangium, which produces haploid spores. The diploid stage is relatively short compared with that of haploid stage, i.e. haploid dominance. The advantage of diploid, e.g. heterosis, only takes place in diploid life stage. Bryophyte still maintains the sexual reproduction during its evolution despite the fact that the haploid stage does not benefit from heterosis at all. This may be an example that the sexual reproduction has a bigger advantage by itself, since it allows gene shuffling (hybrid or recombination between multiple loci) among different members of the species, that permits natural selection of the fit over these new hybrids or recombinants that are haploid forms.

Allogamy

Allogamy is a term used in the field of biological reproduction describing the fertilization of an ovum from one individual with the spermatozoa of another.

Autogamy

Self-fertilization, also known as autogamy, occurs in gametes fused in fertilization come from the same individual. The term "autogamy" is also used for pollination (not necessarily leading to successful fertilization) and describes self-pollination within the same flower, distinguished from geitonogamy, transfer of pollen to a different flower on the same flowering plant,[7] or within a single monoecious Gymnosperm plant.

Mitosis and meiosis

Mitosis and meiosis are types of cell division. Mitosis occurs in somatic cells, while meiosis occurs in gametes.

Mitosis The resultant number of cells in mitosis is twice the number of original cells. The number of chromosomes in the daughter cells is the same as that of the parent cell.

Meiosis The resultant number of cells is four times the number of original cells. This results in cells with half the number of chromosomes present in the parent cell. A diploid cell duplicates itself, then undergoes two divisions (tetraploid to diploid to haploid), in the process forming four haploid cells. This process occurs in two phases, meiosis I and meiosis II.

Same-sex reproduction

In recent decades, developmental biologists have been researching and developing techniques to facilitate same-sex reproduction.[8] The obvious approaches, subject to a growing amount of activity, are female sperm and male eggs, with female sperm closer to being a reality for humans, given that Japanese scientists have already created female sperm for chickens. "However, the ratio of produced W chromosome-bearing (W-bearing) spermatozoa fell substantially below expectations. It is therefore concluded that most of the W-bearing PGC could not differentiate into spermatozoa because of restricted spermatogenesis."[9] In 2004, by altering the function of a few genes involved with imprinting, other Japanese scientists combined two mouse eggs to produce daughter mice.[10]

Reproductive strategies

There are a wide range of reproductive strategies employed by different species. Some animals, such as the sperm storage thereby increasing the duration of their fertility.

Other types of reproductive strategies

Polycyclic animals reproduce intermittently throughout their lives.

Semelparous organisms reproduce only once in their lifetime, such as annual plants (including all grain crops), and certain species of salmon, spider, bamboo and century plant. Often, they die shortly after reproduction. This is often associated with r-strategists.

Iteroparous organisms produce offspring in successive (e.g. annual or seasonal) cycles, such as perennial plants. Iteroparous animals survive over multiple seasons (or periodic condition changes). This is more associated with K-strategists.

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 number 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, some species of starfish (by fragmentation), 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.

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 ensures 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. The meiosis stage of the sexual cycle also allows especially effective repair of DNA damages (see

Life without reproduction

The existence of life without reproduction is the subject of some speculation. The biological study of how the abiogenesis. Whether or not there were several independent abiogenetic events, biologists believe that the last universal ancestor to all present life on Earth lived about 3.5 billion years ago.

Today, some scientists have speculated about the possibility of creating life non-reproductively in the laboratory. Several scientists have succeeded in producing simple viruses from entirely non-living materials.[12] However, viruses are often regarded as not alive. Being nothing more than a bit of RNA or DNA in a protein capsule, they have no metabolism and can only replicate with the assistance of a hijacked cell's metabolic machinery.

The production of a truly living organism (e.g. a simple bacterium) with no ancestors would be a much more complex task, but may well be possible to some degree according to current biological knowledge. A

  • Asexual Reproduction
  • Journal of Biology of Reproduction
  • Journal of Andrology

External links

  • Judson, Olivia (2003) Dr.Tatiana's Sex Advice to All Creation: Definitive Guide to the Evolutionary Biology of Sex. ISBN 978-0-09-928375-1
  • The Evolution of Sex: An Examination of Current Ideas Richard E. Michod and Bruce E. Levin, editors (1987) Sinauer Associates Inc., Publishers, Sunderland, Massachusetts ISBN 0878934596 ISBN 978-0878934591
  • Michod, R.E. Eros and Evolution: A natural philosophy of sex (1994). Addison-Wesley Publishing Company, Reading, Massachusetts ISBN 0201442329 ISBN 978-0201442328

Further reading

  • Tobler, M. & Schlupp,I. (2005) Parasites in sexual and asexual mollies (Poecilia, Poeciliidae, Teleostei): a case for the Red Queen? Biol. Lett. 1 (2): 166-168.
  • Zimmer, Carl. Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures, New York: Touchstone, 2001.
  • "Allogamy, cross-fertilization, cross-pollination, hybridization". GardenWeb Glossary of Botanical Terms (2.1 ed.). 2002. 
  • "Allogamy". Stedman's Online Medical Dictionary (27 ed.). 2004. 

References

  1. ^ Halliday, Tim R.; Kraig Adler (eds.) (1986). Reptiles & Amphibians. Torstar Books. p. 101.  
  2. ^ Savage, Thomas F. (September 12, 2005). "A Guide to the Recognition of Parthenogenesis in Incubated Turkey Eggs". Oregon State University. Retrieved 2006-10-11. 
  3. ^ "Female Sharks Can Reproduce Alone, Researchers Find", Washington Post, Wednesday, May 23, 2007; Page A02
  4. ^ T. M. Sonneborn. Mating Types in Paramecium Aurelia: Diverse Conditions for Mating in Different Stocks; Occurrence, Number and Interrelations of the Types. Proceedings of the American Philosophical Society, Vol. 79, No. 3 (Sep. 30, 1938), pp. 411-434. American Philosophical Society.  
  5. ^ S. P. Otto and D. B. Goldstein. "Recombination and the Evolution of Diploidy". Genetics. Vol 131 (1992): 745-751.
  6. ^ Bernstein H, Hopf FA, Michod RE. (1987) The molecular basis of the evolution of sex. Adv Genet. 24:323-370. Review. PMID 3324702
  7. ^ Eckert, C.G. (2000). 0532:COAAGT2.0.CO;2 "Contributions of autogamy and geitonogamy to self-fertilization in a mass-flowering, clonal plant"]. Ecology 81 (2): 532–542.  
  8. ^ "Timeline of same-sex procreation scientific developments". samesexprocreation.com. 
  9. ^ "Differentiation of female chicken primordial germ cells into spermatozoa in male gonads" 39 (3). June 1997. pp. 267–71.  
  10. ^ "Japanese scientists produce mice without using sperm". Washington Post (Sarasota Herald-Tribune). April 22, 2004. 
  11. ^ Bernstein H, Bernstein C and Michod RE (2011). Meiosis as an Evolutionary Adaptation for DNA Repair. Chapter 19: 357-382 in DNA Repair, Inna Kruman (Ed.), InTech (publisher) ISBN 978-953-307-697-3 Available online from: http://www.intechopen.com/books/dna-repair/meiosis-as-an-evolutionary-adaptation-for-dna-repair
  12. ^ Chemical synthesis of poliovirus cDNA: generation of infectious virus in the absence of natural template
    Scientists Create Artificial Virus
  13. ^ Gibson, D.; Glass, J.; Lartigue, C.; Noskov, V.; Chuang, R.; Algire, M.; Benders, G.; Montague, M.; Ma, L.; Moodie, M. M.; Merryman, C.; Vashee, S.; Krishnakumar, R.; Assad-Garcia, N.; Andrews-Pfannkoch, C.; Denisova, E. A.; Young, L.; Qi, Z. -Q.; Segall-Shapiro, T. H.; Calvey, C. H.; Parmar, P. P.; Hutchison Ca, C. A.; Smith, H. O.; Venter, J. C. (2010). "Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome". Science 329 (5987): 52–56.  
  14. ^ a b Robert Lee Hotz (May 21, 2010). "Scientists Create First Synthetic Cell". The Wall Street Journal. Retrieved April 13, 2012. 
  15. ^ Craig Venter Institute. "FAQ". Retrieved 2011-04-24. 
  16. ^ W. Wayte Gibbs (May 2004). "Synthetic Life". Scientific American. 
  17. ^ "NOVA: Artificial life". Retrieved 2007-01-19. 
  18. ^ Williams G C. 1975. Sex and Evolution. Princeton (NJ): Princeton University Press.

Notes

See also

The point of this analogy is that since asexual reproduction does not produce genetic variations, there is little ability to quickly adapt to a changing environment. The lottery principle is less accepted these days because of evidence that asexual reproduction is more prevalent in unstable environments, the opposite of what it predicts.

lottery tickets as an analogy in one explanation for the widespread use of sexual reproduction.[18] He argued that asexual reproduction, which produces little or no genetic variety in offspring, was like buying many tickets that all have the same number, limiting the chance of "winning" - that is, producing surviving offspring. Sexual reproduction, he argued, was like purchasing fewer tickets but with a greater variety of numbers and therefore a greater chance of success.

Sexual reproduction has many drawbacks, since it requires far more energy than asexual reproduction and diverts the organisms from other pursuits, and there is some argument about why so many species use it.

Lottery principle

There is some debate within the scientific community over whether this cell can be considered completely synthetic[14] on the grounds that the chemically synthesized genome was an almost 1:1 copy of a naturally occurring genome and, the recipient cell was a naturally occurring bacterium. The Craig Venter Institute maintains the term "synthetic bacterial cell" but they also clarify "...we do not consider this to be "creating life from scratch" but rather we are creating new life out of already existing life using synthetic DNA".[15] Venter plans to patent his experimental cells, stating that "they are pretty clearly human inventions".[14] Its creators suggests that building 'synthetic life' would allow researchers to learn about life by building it, rather than by tearing it apart. They also propose to stretch the boundaries between life and machines until the two overlap to yield "truly programmable organisms".[16] Researchers involved stated that the creation of "true synthetic biochemical life" is relatively close in reach with current technology and cheap compared to the effort needed to place man on the Moon.[17]

[13]

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.