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Arrhenotoky
Arrhenotoky (from Greek ἄρρην ''árrhēn'' "male" and τόκος ''tókos'' "birth"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthenogenesis produces exclusively female offspring, hence the distinction. Overview The set of processes included under the term arrhenotoky depends on the author: arrhenotoky may be restricted to the production of males that are haploid (haplodiploidy); may include diploid males that permanently inactivate one set of chromosomes (parahaploidy); or may be used to cover all cases of males being produced by parthenogenesis (including such cases as aphids, where the males are XO diploids). The form of parthenogenesis in which females develop from unfertilized eggs is known as thelytoky; when both males and females develop from unfertilized eggs, the term "deuterotoky" is used. In the most commonly used sense of the term, arrhenotoky is synonymous with hapl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thelytoky
Thelytoky (from the Ancient Greek, Greek θῆλυς ''thēlys'' "female" and τόκος ''tókos'' "birth") is a type of parthenogenesis and is the absence of mating and subsequent production of all female diploid offspring as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in about 1,500 species, about 1 in 1000 of described animal species, according to a 1984 study. It is more common in invertebrates, like arthropods, but it can occur in vertebrates, including salamanders, fish, and reptiles such as some Cnemidophorus, whiptail lizards. Thelytoky can occur by different mechanisms, each of which has a different impact on the level of zygosity, homozygosity. It is found in several groups of Hymenoptera, including Apidae, Aphelinidae, Cynipidae, Formicidae, Ichneumonidae, and Tenthredinidae. It can be induced in Hymenoptera by the bacteria ''Wolbachia'' and ''Cardinium''. Advantages of thelytoky Species may encounter a few advantages employ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thelytokous Parthenogenesis
Thelytoky (from the Greek θῆλυς ''thēlys'' "female" and τόκος ''tókos'' "birth") is a type of parthenogenesis and is the absence of mating and subsequent production of all female diploid offspring as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in about 1,500 species, about 1 in 1000 of described animal species, according to a 1984 study. It is more common in invertebrates, like arthropods, but it can occur in vertebrates, including salamanders, fish, and reptiles such as some whiptail lizards. Thelytoky can occur by different mechanisms, each of which has a different impact on the level of homozygosity. It is found in several groups of Hymenoptera, including Apidae, Aphelinidae, Cynipidae, Formicidae, Ichneumonidae, and Tenthredinidae. It can be induced in Hymenoptera by the bacteria ''Wolbachia'' and ''Cardinium''. Advantages of thelytoky Species may encounter a few advantages employing this form of mating system. Thely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Mite
Spider mites are members of the family Tetranychidae, which includes about 1,200 species. They are part of the subclass Acari (mites). Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs, and can cause damage by puncturing the plant cells to feed. Spider mites are known to feed on several hundred species of plants. Description Spider mites are less than in size and vary in color. They lay small, spherical, initially transparent eggs and many species spin silk webbing to help protect the colony from predators; they get the "spider" part of their common name from this webbing. Life cycle Hot, dry conditions are often associated with population build-up of spider mites. Under optimal conditions (approximately 27 °C), the two-spotted spider mite can hatch in as little as 3 days, and become sexually mature in as little as 5 days. One female can lay up to 20 eggs per day and can live for 2 to 4 weeks, laying hundreds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haplodiploid Sex Determination In Honey Bees
Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex in all members of the insect orders Hymenoptera ( bees, ants, and wasps) and Thysanoptera ('thrips'). The system also occurs sporadically in some spider mites, Hemiptera, Coleoptera (bark beetles), and rotifers. In this system, sex is determined by the number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female, and an unfertilized egg develops as a male. This means that the males have half the number of chromosomes that a female has, and are haploid. The haplodiploid sex-determination system has a number of peculiarities. For example, a male has no father and cannot have sons, but he has a grandfather and can have grandsons. Additionally, if a eusocial-insect co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproduction In Animals
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.John Maynard Smith ''The Evolution of Sex'' 1978. Sexual reproduction typically requires the sexual interaction of two specialized reproductive cells, called gametes, which contain half the number of chromosomes of normal cells and are created by me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudo-arrhenotoky
Pseudo-arrhenotoky or paternal genome elimination is the phenomenon where males develop from fertilized eggs but the paternal genome is heterochromatinized or lost in the somatic cells and not passed on to their offspring. This phenomenon occurs in certain mites, beetles and mealybugs and scale insects. When the males have a diploid number of chromosomes they are termed ''parahaploids'' as the paternal genes are not expressed at all. The paternal chromosomes are inactivated by heterochromatization in all the cells at an early embryonic stage. The adult cells have one set of inactive ''H chromosomes'' and one set of euchromatin ''E chromosomes''. These H chromosomes are eliminated from the sperm during or just before spermatogenesis. In a few other species all the cells in an adult are haploid due to elimination of the paternal chromosomes at an early developmental stage. This variant is called the ''diaspidid system'' after the scale insect clade (Diaspididae) where it was discover ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genomic Imprinting
Genomic imprinting is an epigenetic phenomenon that causes genes to be expressed or not, depending on whether they are inherited from the female or male parent. Genes can also be partially imprinted. Partial imprinting occurs when alleles from both parents are differently expressed rather than complete expression and complete suppression of one parent's allele. Forms of genomic imprinting have been demonstrated in fungi, plants and animals. In 2014, there were about 150 imprinted genes known in mice and about half that in humans. As of 2019, 260 imprinted genes have been reported in mice and 228 in humans. Genomic imprinting is an inheritance process independent of the classical Mendelian inheritance. It is an epigenetic process that involves DNA methylation and histone methylation without altering the genetic sequence. These epigenetic marks are established ("imprinted") in the germline (sperm or egg cells) of the parents and are maintained through mitotic cell divisions in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apomixis
In botany, apomixis is asexual development of seed or embryo without fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils. Apomictically produced offspring are genetically identical to the parent plant, except in nonrecurrent apomixis. Its etymology is Greek for "away from" + "mixing". Normal asexual reproduction of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis. In contrast to parthenocarpy, which involves seedless fruit formation without fertilization, apomictic fruits have viable seeds containing a proper embryo, with asexual origin. In flowering plants, the term "apomixis" is used in a restricted sense to mean agamospermy, i.e. clonal reproduction through seeds. Although agamospermy could theoretically occur in gymnosperms, it appears to be absent in that group. Apogamy is a related term that has had various meanings over time. In plants with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotifer
The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first described by John Harris (writer), Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703. Most rotifers are around long (although their size can range from to over ), and are common in freshwater environments throughout the world with a few Seawater, saltwater species. Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are Sessility (zoology), sessile, living inside tubes or gelatinous holdfast (biology), holdfasts that are attached to a substrate. About 25 species are colonial (e.g., ''Sinantherina semibullata''), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tityus Metuendus
Tityus may refer to: * A giant from Greek mythology (see Tityos Tityos or Tityus (Ancient Greek: Τιτυός) was a giant from Greek mythology. Family Tityos was the son of the mortal princess Elara and the god Zeus. He had a daughter named Europa who coupled with Poseidon and gave birth to Euphemus, o ...) * A genus of scorpions (see ''Tityus'' (genus)) Art * ''The Punishment of Tityus'' (Michelangelo) * ''Tityus'' (Titian) * ''Tityos'' (Ribera) {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
