Reproduction is the biological process by which new individual organisms are produced. A biological process is a process of a living Organism (either plant or animal Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism The known methods of reproduction are broadly grouped into two main types: sexual and asexual. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. Human reproduction belongs to sexual reproduction. Human reproduction is the Reproduction of Humans. It is a form of Sexual reproduction, by Sexual intercourse between human Males and
In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Asexual reproduction is not, however, limited to single-celled organisms. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Most plants have the ability to reproduce asexually. Plants are living Organisms belonging to the kingdom Plantae.
Sexual reproduction requires the involvement of two individuals, typically one of each sex. An organism's sex is defined by the gametes it produces males produce male gametes (spermatozoa or Sperm) while females produce female gametes (ova or Egg cells; individual Normal human reproduction is a common example of sexual reproduction.
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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. Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. 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. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Hydra is a Genus of simple fresh-water animals possessing radial symmetry. An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described Budding (also called burgeoning) is the formation of a new Organism by the protrusion of part of another organism These organisms do not have different sexes, and they are capable of "splitting" themselves into two or more individuals. Some 'asexual' species, like hydra and jellyfish, may also reproduce sexually. Hydra is a Genus of simple fresh-water animals possessing radial symmetry. Jellyfish are free-swimming members of the phylum Cnidaria. They have several different basic morphologies that represent several different cnidarian classes including the For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can also reproduce sexually. Vegetative reproduction is a type of Asexual reproduction found in plants and is also called vegetative propagation or vegetative multiplication. Likewise, bacteria may exchange genetic information by conjugation. Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact Other ways of asexual reproduction include parthogenesis, fragmentation and spore formation that involves only mitosis. Parthenogenesis (from the Greek παρθένος parthenos, "virgin" + γένεσις genesis, "creation" is an asexual form There is a separate article about Habitat fragmentation. Fragmentation or Clonal Fragmentation is a form of asexual Reproduction Sporogenesis is the production of Spores in Biology. The term is also used to refer to the process of Reproduction via spores Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei 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 (from the Greek παρθένος parthenos, "virgin" + γένεσις genesis, "creation" is an asexual form An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular A seed (in some plants referred to as a kernel) is a small embryonic Plant enclosed in a covering called the seed coat usually with some stored For soil improvement see Fertilization (soil. Male (♂ refers to the sex of an organism or part of an organism which produces small mobile Gametes called spermatozoa. Parthenogenesis occurs naturally in some species, including lower plants, invertebrates (e. Plants are living Organisms belonging to the kingdom Plantae. An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate g. water fleas, aphids, some bees and parasitic wasps), and vertebrates (e. Water flea is a generic term for a number of small aquatic Crustacea characterised by their jumping or jerky mode of swimming Bees are flying Insects closely related to Wasps and Ants Bees are a Monophyletic lineage within the superfamily Apoidea Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes g. some reptiles,[1] fish, and, very rarely, birds[2] and sharks[3]). Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Sharks ( Superorder Selachimorpha) are a type of Fish with a full cartilaginous Skeleton and a highly streamlined body It is sometimes also used to describe reproduction modes in hermaphroditic species which can self-fertilize.
Sexual reproduction
- Further information: Human reproduction
Sexual reproduction is a biological process by which organisms create descendants that have a combination of genetic material contributed from two (usually) different members of the species. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian Human reproduction is the Reproduction of Humans. It is a form of Sexual reproduction, by Sexual intercourse between human Males and Flies in the Diptera family Syrphidae are commonly known as hoverflies, flower flies, or Syrphid flies. A biological process is a process of a living Organism (either plant or animal Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Each of two parent organisms contributes half of the offspring's genetic makeup by creating haploid gametes. "Haplo" redirects here For the fictional character see The Death Gate Cycle. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete Most organisms form two different types of gametes. In these anisogamous species, the two sexes are referred to as male (producing sperm or microspores) and female (producing ova or megaspores). Male (♂ refers to the sex of an organism or part of an organism which produces small mobile Gametes called spermatozoa. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. Female (♀ is the Sex of an Organism, or a part of an organism which produces ova (egg cells In isogamous species the gametes are similar or identical in form, but may have separable properties and then may be given other different names. For example, in the green alga, Chlamydomonas reinhardtii, there are so-called "plus" and "minus" gametes. A few types of organisms, such as ciliates, have more than two kinds of gametes. The ciliates are one of the most important groups of Protists common almost everywhere there is water — lakes ponds oceans rivers and soils with many ectosymbiotic
Most animals (including humans) and plants reproduce sexually. Plants are living Organisms belonging to the kingdom Plantae. Sexually reproducing organisms have two sets of genes for every trait (called alleles). An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents' genes. Having two copies of every gene, only one of which is expressed, allows deleterious alleles to be masked, an advantage believed to have led to the evolutionary development of diploidy (Otto and Goldstein). Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such eVolution is the third Album by eLDee, it was due to be released in 2008 "Haplo" redirects here For the fictional character see The Death Gate Cycle.
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. Allogamy is a term used in the field of Biological reproduction describing the Fertilization of an Ovum from one individual with the Spermatozoa For soil improvement see Fertilization (soil. An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known
Autogamy
Self-fertilization (also known as autogamy) occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual. A hermaphrodite is an organism having both male and female reproductive organs A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete They are bound and all the cells merge to form one new gamete.
Mitosis and meiosis
Mitosis and meiosis are an integral part of cell division. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Mitosis occurs in somatic cells, while meiosis occurs in gametes. Somatic cells are any cells forming the body of an organism as opposed to Germline cells A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete
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. A chromosome is an organized structure of DNA and Protein that is found in cells.
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 chromosome is an organized structure of DNA and Protein that is found in cells. A diploid cell duplicates itself, then undergoes two divisions (tetroid to diploid to haploid), in the process forming four haploid cells. "Haplo" redirects here For the fictional character see The Death Gate Cycle. "Haplo" redirects here For the fictional character see The Death Gate Cycle. 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 [4]. 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. Female sperm is a term that traditionally refers to a sperm that contains an X chromosome (since when such a sperm fertilizes an egg a female daughter is born produced in the usual way Male eggs are the currently theoretical result of a process in which the eggs of a female would be emptied of their genetic contents (a technique used in the Cloning process More recently, by altering the function of a few genes involved with imprinting, other Japanese scientists combined two mouse eggs to produce daughter mice.
Reproductive strategies
There is 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. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The Northern Gannet ( Morus bassanus, formerly Sula bassana) is a Seabird and is the largest member of the Gannet family Sulidae Others reproduce quickly; but, under normal circumstances, most offspring do not survive to adulthood. For the 2008 British film by Noel Clarke see Adulthood (film. For example, a rabbit (mature after 8 months) can produce 10–30 offspring per year, and a fruit fly (mature after 10–14 days) can produce up to 900 offspring per year. Rabbits are small Mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order These two main strategies are known as K-selection (few offspring) and r-selection (many offspring). In Ecology, r/K selection theory relates to the selection of traits which promote success in particular environments In Ecology, r/K selection theory relates to the selection of traits which promote success in particular environments Which strategy is favoured by evolution depends on a variety of circumstances. eVolution is the third Album by eLDee, it was due to be released in 2008 Animals with few offspring can devote more resources to the nurturing and protection of each individual offspring, thus reducing the need for many offspring. On the other hand, animals with many offspring may devote fewer resources to each individual offspring; for these types of animals it is common for many offspring to die soon after birth, but enough individuals typically survive to maintain the population.
Other types of reproductive strategies
Polycyclic animals reproduce intermittently throughout their lives.
Semelparous organisms reproduce only once in their lifetime, such as annual plants. Botanically an annual plant is a Plant that usually germinates, Flowers and dies in one Year. Often, they die shortly after reproduction. This is a characteristic of r-strategists. In Ecology, r/K selection theory relates to the selection of traits which promote success in particular environments
Iteroparous organisms produce offspring in successive (e. g. annual or seasonal) cycles, such as perennial plants. A perennial plant or perennial ( Latin per, "through" annus, "year" is a Plant that lives for more than Iteroparous animals survive over multiple seasons (or periodic condition changes). This is a characteristic of K-strategists. In Ecology, r/K selection theory relates to the selection of traits which promote success in particular environments
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. Slime Mold is a broad term referring to amoeba-like organisms hence the name slime which feed on microorganisms in decaying vegetable matter hence the name Molds Sea anemones are a group of water dwelling predatory animals of the order Actiniaria; they are named after the Anemone, a terrestrial Flower Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. 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. 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" adverse situations until a swing back to suitability occurs.
Life without reproduction
The existence of life without reproduction is the subject of some speculation. The biological study of how the origin of life led from non-reproducing elements to reproducing organisms is called abiogenesis. In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic 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. The last universal ancestor ( LUA) also called the last universal common ancestor ( LUCA) the cenancestor or "number one" This timeline of the evolution of life outlines the major events in the development
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[5]. The virus is often regarded as not alive. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable 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. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. See also Biological reproduction Self-replication is any process by which a thing might make a copy of itself The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called
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 according to current biological knowledge.
Lottery principle
Sexual reproduction has many drawbacks, since it requires far more energy than asexual reproduction, and there is some argument about why so many species use it.
George C. Williams used lottery tickets as an analogy in one explanation for the widespread use of sexual reproduction[6]. Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. A lottery is a form of Gambling which involves the drawing of lots for a prize Analogy is both the cognitive process of transferring Information from a particular subject (the analogue or source to another particular subject (the target and 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, surviving. Sexual reproduction, he argued, was like purchasing fewer tickets but with a greater variety of numbers and therefore a greater chance of success.
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.
See also
References
- ^ Halliday, Tim R. The breeding season is the most suitable season usually with favorable conditions and abundant food and water for breeding among some wild animals and birds (wildlife In Sociobiology and Behavioural ecology, a mating system is any of the ways in which animal societies are structured in relation to sexual behavior The reproductive system is a system of organs within an Organism which work together for the purpose of Reproduction. ; Kraig Adler (eds. ) (1986). Reptiles & Amphibians. Torstar Books, p. 101. ISBN 0-920269-81-8.
- ^ Savage, Thomas F. (September 12, 2005). A Guide to the Recognition of Parthenogenesis in Incubated Turkey Eggs. Oregon State University. Retrieved on 2006-10-11. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1138 - A massive earthquake struck Aleppo, Syria. 1531 - Huldrych Zwingli is killed
- ^ "Female Sharks Can Reproduce Alone, Researchers Find", Washington Post, Wednesday, May 23, 2007; Page A02
- ^ [1] (timeline of research in the area of same-sex reproduction)
- ^ Chemical synthesis of poliovirus cDNA: generation of infectious virus in the absence of natural template
Scientists Create Artificial Virus - ^ Williams G C. 1975. Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. Sex and Evolution. Princeton (NJ): Princeton University Press.
- S. P. Otto and D. B. Goldstein. "Recombination and the Evolution of Diploidy". Genetics. Genetics (not to be confused with the Indian publication Journal of Genetics) is a monthly Scientific journal publishing investigations bearing Vol 131 (1992): 745-751.
- 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). (2002).
- "allogamy". Stedman's Online Medical Dictionary (27). (2004).
External links
Dictionary
reproduction
-noun
- The act of reproducing new individuals biologically
- The act of making copies
- A copy of something, as in a piece of art; a duplicate.
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