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Sex Reversal
Sex reversal is a biological process whereby the pathway directed towards the already determined-sex fate is flipped towards the opposite sex, creating a discordance between the primary sex fate and the sex phenotype expressed. The process of sex reversal occurs during embryonic development or before gonad differentiation. In GSD species, sex reversal means that the sexual phenotype is discordant with the genetic/chromosomal sex. In TSD species, sex reversal means that the temperature/conditions that usually trigger the differentiation towards one sexual phenotype are producing the opposite sexual phenotype. Sex reversal can occur naturally, by mutations, or can be induced artificially. Sex reversal can be genetically or hormonally induced in laboratory. It can also occur artificially by exposure to endocrine disruptors such as pollutants, including herbicides, which can act as estrogen promoters or inhibitors, for instance by altering aromatase expression. In fish Gonochoris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex-determination System
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two common sexes, males and females, and in other species, there are hermaphrodites, organisms that can function reproductively as either female or male, or both. There are also some species in which only one sex is present, temporarily or permanently. This can be due to parthenogenesis, the act of a female reproducing without fertilization. In some plants or algae the gametophyte stage may reproduce itself, thus producing more individuals of the same sex as the parent. In some species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals this is often accompanied by chromosomal differences, generally through combinations of XY, ZW, XO, ZO chromosomes, or haplodiploidy. The sexual di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Buffalo
The water buffalo (''Bubalus bubalis''), also called domestic water buffalo, Asian water buffalo and Asiatic water buffalo, is a large bovid originating in the Indian subcontinent and Southeast Asia. Today, it is also kept in Italy, the Balkans, Australia, North America, South America and some African countries. Two extant Type (biology), types of water buffalo are recognized, based on Morphology (biology), morphological and Ethology, behavioural criteria: the river buffalo of the Indian subcontinent and further west to the Balkans, Egypt and Italy; and the swamp buffalo from Assam in the west through Southeast Asia to the Yangtze Valley of China in the east. The wild water buffalo (''Bubalus arnee'') is most probably the ancestor of the domestic water buffalo. Results of a phylogenetic study indicate that the river-type water buffalo probably originated in western India and was domesticated about 6,300 years ago, whereas the swamp-type originated independently from Mainland Sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teratogenesis
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology caused by teratogens and also in pharmacology and toxicology. Teratogens are substances that may cause non-heritable birth defects via a toxic effect on an embryo or fetus. Defects include malformations, disruptions, deformations, and dysplasia that may cause stunted growth, delayed mental development, or other congenital disorders that lack structural malformations. These defects can be recognized prior to or at birth as well as later during early childhood. The related term developmental toxicity includes all manifestations of abnormal development that are caused by environmental insult. The extent to which teratogens will impact an embryo is dependent on several factors, such as how long the embryo has been exposed, the stage of development the em ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequential Hermaphroditism
Sequential hermaphroditism (called dichogamy in botany) is one of the two types of hermaphroditism, the other type being simultaneous hermaphroditism. It occurs when the organism's sex changes at some point in its life. A sequential hermaphrodite produces eggs (female gametes) and sperm (male gametes) at different stages in life. Sequential hermaphroditism occurs in many fish, gastropods, and plants. Species that can undergo these changes do so as a normal event within their reproductive cycle, usually cued by either social structure or the achievement of a certain age or size. In animals, the different types of change are male to female (protandry or protandrous hermaphroditism), female to male (protogyny or protogynous hermaphroditism), and bidirectional (serial or bidirectional hermaphroditism). Both protogynous and protandrous hermaphroditism allow the organism to switch between functional male and functional female. Bidirectional hermaphrodites have the capacity for sex chan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cabrera's Vole
Cabrera's vole (''Microtus cabrerae'') is a species of vole native to Spain and Portugal. It is named for Ángel Cabrera, a mammalogist then working at the Museo Nacional de Ciencias Naturales in Madrid. It is the only living member of the subgenus ''Iberomys'', although two fossil species are also known, including ''M. brecciensis'', the likely direct ancestor of the living species. Description Cabrera's vole is one of the largest voles in the genus ''Microtus'', with a body length of and a tail in length. Adults weigh between , up to five times more than other voles native to Spain and Portugal. They have long, thick fur which is brownish olive over most of the body and yellowish in colour on the underparts. The guard hairs are particularly long, reaching as far as out from the body, greater than that in any other ''Microtus'' species. Internally, the caecum is longer than that in most other voles, relative to body size, a feature that may be related to its specialised d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
African Pygmy Mouse
The African pygmy mouse (''Mus minutoides'') is one of the smallest rodents. It is widespread within sub-Saharan Africa, and is kept as a pet in other parts of the world. Like the common and widely introduced european house mouse, it is a member of the enormous superfamily Muroidea, which includes over 1000 different species. It forms a super- species complex with '' Mus musculoides''. Grey to brick-red overall, it is pale on the underside and has small but prominent triangular ears. Adult body length averages long, with a tail. Average adults body weight is . The African pygmy mouse reaches breeding age at about 6 to 8 weeks. Pregnancy lasts for around 20 days and the litter of about three young is born blind and hairless. Average weight of puppies at birth is Their eyes open after 2 weeks, and weaning is complete after 3 weeks. The lifespan is about 2 years, although individual specimens have been reported to live over 4 years in captivity. The African pygmy mouse has a n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Akodon
''Akodon'' is a genus consisting of South American grass mice. They mostly occur south of the Amazon Basin and along the Andes north to Venezuela, but are absent from much of the basin itself, the far south of the continent, and the lowlands west of the Andes. ''Akodon'' is one of the most species-rich genera of Neotropical rodents. Species of ''Akodon'' are known to inhabit a variety of habitats from tropical and tropical moist forests to altiplano and desert. Fossils are known from the late Pliocene onwards. Taxonomy ''Akodon'' is the largest genus in the tribe Akodontini. Three of its synonyms—''Chalcomys'', ''Hypsimys'', and particularly ''Microxus''—have sometimes been regarded as distinct genera. '' Neomicroxus'' was separated in 2013. Previously associated with ''Akodon'', the genera '' Abrothrix'', '' Deltamys'', '' Necromys'', ''Thalpomys ''Thalpomys'' is a genus of South American rodents in the tribe Akodontini of family Cricetidae. Two species are known, both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arctic Lemming
The Arctic lemming (''Dicrostonyx torquatus'') is a species of rodent in the family Cricetidae. Although generally classified as a "least concern" species, the Novaya Zemlya subspecies ''(Dicrostonyx torquatus ungulatus)'' is considered a vulnerable species under Russian nature conservation legislation (included in Red Book of Russian Federation since 1998). Biology It is found only in the Arctic biomes in the Russian Federation, and it is the most common mammal on Severnaya Zemlya. Specimens were once found in England, but they are now extirpated. For the most part, lemmings of the genus ''Lemmus'' can coexist with those of genus ''Dicrostonyx''. Arctic lemmings migrate when population density becomes too great, and they resort to swimming in search of a new habitat. The disappearance of lemmings and the lemming cycles in the Arctic have shown that they are the causes of fluctuations in local breeding among geese and waders. Recovery of lemmings after years of low density is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wood Lemming
The wood lemming (''Myopus schisticolor'') is a species of rodent in the family Cricetidae. It belongs to the rodent subfamily Arvicolinae, so is a relative of the voles, lemmings, and muskrats. It is found in the taiga biome of China, Estonia, Finland, Mongolia, Norway, Russia, and Sweden. Sex determination Wood lemmings produce about three times as many female as male offspring. This is due to an unusual genetic system where they have two different types of X chromosomes, the normal X and a mutated X*. Females with that mutation on their X*-chromosome inhibit the male determining effect of the Y chromosome. This leads to three genetic types of females: XX, X*X and X*Y and one genetic type of males XY. The X*Y females are fertile, but only produce X* ova, which means they only produce female offspring. It is not fully known the extent to which nature balances out the differences in the adult population, but sampling studies seem to suggest males do make up as little as 25% of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goat
The goat or domestic goat (''Capra hircus'') is a species of Caprinae, goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the family Bovidae, meaning it is closely related to the sheep. It was one of the first animals to be domesticated, in Iran around 10,000 years ago. Goats have been used for milk, Goat meat, meat, Animal fur, wool, and Animal skin, skins across much of the world. Milk from goats is often turned into goat cheese, cheese. In 2022, there were more than 1.1 billion goats living in the world, of which 150 million were in India. Goats feature in mythology, folklore, and religion in many parts of the world, including in the classical myth of Amalthea (mythology), Amalthea, in Tanngrisnir and Tanngnjóstr, the goats that pulled the chariot of the Norse god Thor, in the Scandinavian Yule goat, and in Hinduism's goat-headed Daksha. In Christianity and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, '' Eohippus'', into the large, single-toed animal of today. Humans began domesticating horses around 4000 BCE in Central Asia, and their domestication is believed to have been widespread by 3000 BCE. Horses in the subspecies ''caballus'' are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, which are horses that have never been domesticated. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior. Horses are adapted to run, allowing them to quickly escape predator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cattle
Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are called cows and mature male cattle are bulls. Young female cattle are called heifers, young male cattle are oxen or bullocks, and castrated male cattle are known as steers. Cattle are commonly raised for meat, for dairy products, and for leather. As draft animals, they pull carts and farm implements. Cattle are considered sacred animals within Hinduism, and it is illegal to kill them in some Indian states. Small breeds such as the miniature Zebu are kept as pets. Taurine cattle are widely distributed across Europe and temperate areas of Asia, the Americas, and Australia. Zebus are found mainly in India and tropical areas of Asia, America, and Australia. Sanga cattle are found primarily in sub-Saharan Africa. These types, sometime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
