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Superfetation
Superfetation (also spelled superfoetation – see fetus) is the simultaneous occurrence of more than one stage of developing offspring in the same animal. In mammals, it manifests as the formation of an embryo from a different menstrual cycle while another embryo or fetus is already present in the uterus. When two separate instances of fertilisation occur during the same menstrual cycle, it is known as superfecundation. Humans While proposed cases of superfetation have been reported in humans, the existence of this phenomenon in humans has been deemed unlikely. Better explanations include differential growth between twins due to various reasons such as twin-to-twin transfusion syndrome. Artificially induced superfetation has been demonstrated, although only up to a short period after insemination. A 2008 French study found evidence to suggest that superfetation is a reality for humans, but that it is so rare that there have been fewer than 10 recorded cases in the world. In 20 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fetus
A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal development begins from the ninth week after fertilization (or eleventh week gestational age) and continues until birth. Prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. However, a fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional and some not yet situated in their final anatomical location. Etymology The word ''fetus'' (plural ''fetuses'' or '' feti'') is related to the Latin '' fētus'' ("offspring", "bringing forth", "hatching of young") and the Greek "φυτώ" to plant. The word "fetus" was used by Ovid in Metamorphoses, book 1, line 104. The predominant British, Irish, and Commonwealth spelling is '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilisation
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilisation. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. History In Antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic. In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poeciliid
The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family was the Southeastern United States to north of Río de la Plata, Argentina, and Africa, including Madagascar. Due to release of aquarium specimens and the widespread use of species of the genera ''Poecilia'' and ''Gambusia'' for mosquito control, though, poeciliids can today be found in all tropical and subtropical areas of the world. In addition, ''Poecilia'' and ''Gambusia'' specimens have been identified in hot springs pools as far north as Banff, Alberta. Live-bearing Although the whole family Poeciliidae is known as "live bearers" (viviparous), some species are egg-scattering with external fertilization. All African species are egg-layers, and (with the exception of the members of the genus ''Tomeurus''), all American species are live ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domestic Cats
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of the family. Cats are commonly kept as house pets but can also be farm cats or feral cats; the feral cat ranges freely and avoids human contact. Domestic cats are valued by humans for companionship and their ability to kill rodents. About 60 cat breeds are recognized by various cat registries. The cat is similar in anatomy to the other felid species: they have a strong flexible body, quick reflexes, sharp teeth, and retractable claws adapted to killing small prey. Their night vision and sense of smell are well developed. Cat communication includes vocalizations like meowing, purring, trilling, hissing, growling, and grunting as well as cat-specific body language. Although the cat is a social species, they are a solitary hunter. As a pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including humans). Primates arose 85–55 million years ago first from small terrestrial mammals, which adapted to living in the trees of tropical forests: many primate characteristics represent adaptations to life in this challenging environment, including large brains, visual acuity, color vision, a shoulder girdle allowing a large degree of movement in the shoulder joint, and dextrous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs , to the eastern gorilla, weighing over . There are 376–524 species of living primates, depending on which classification is used. New primate species continue to be discovered: over 25 species were described in the 2000s, 36 in the 2010s, and three in the 2020s. Primates have large bra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sugar Glider
The sugar glider (''Petaurus breviceps'') is a small, omnivorous, arboreal, and nocturnal gliding possum belonging to the marsupial infraclass. The common name refers to its predilection for sugary foods such as sap and nectar and its ability to glide through the air, much like a flying squirrel. They have very similar habits and appearance to the flying squirrel, despite not being closely related—an example of convergent evolution. The scientific name, ''Petaurus breviceps'', translates from Latin as "short-headed rope-dancer", a reference to their canopy acrobatics. The sugar glider is characterised by its pair of gliding membranes, known as patagia, which extend from its forelegs to its hindlegs. Gliding serves as an efficient means of reaching food and evading predators. The animal is covered in soft, pale grey to light brown fur which is countershaded, being lighter in colour on its underside. The sugar glider is native to a small portion of southeastern Australia, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. Kangaroos are indigenous to Australia and New Guinea. The Australian government estimates that 42.8 million kangaroos lived within the commercial harvest areas of Australia in 2019, down from 53.2 million in 2013. As with the terms "wallaroo" and "wallaby", "kangaroo" refers to a paraphyletic grouping of species. All three terms refer to members of the same taxonomic family, Macropodidae, and are distinguished according to size. The largest species in the family are called "kangaroos" and the smallest are generally called "wallabies". The term "wallaroos" refers to species of an intermediate size. There are also the tree-kangaroos, another type of macropod, which inhabit the tropical ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marsupials
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a pouch. Marsupials include opossums, Tasmanian devils, kangaroos, koalas, wombats, wallabies, bandicoots, and the extinct thylacine. Marsupials represent the clade originating from the last common ancestor of extant metatherians, the group containing all mammals more closely related to marsupials than to placentals. They give birth to relatively undeveloped young that often reside in a pouch located on their mothers' abdomen for a certain amount of time. Close to 70% of the 334 extant species occur on the Australian continent (the mainland, Tasmania, New Guinea and nearby islands). The remaining 30% are found in the Americas—primarily in South America, thirteen in Central America, and one species, the Virginia opossum, in North America, nor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sheep
Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated sheep. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Numbering a little over one billion, domestic sheep are also the most numerous species of sheep. An adult female is referred to as a ''ewe'' (), an intact male as a ''ram'', occasionally a ''tup'', a castrated male as a ''wether'', and a young sheep as a ''lamb''. Sheep are most likely descended from the wild mouflon of Europe and Asia, with Iran being a geographic envelope of the domestication center. One of the earliest animals to be domesticated for agricultural purposes, sheep are raised for fleeces, meat (lamb, hogget or mutton) and milk. A sheep's wool is the most widely used animal fiber, and is usually harvested by shearing. In Commonw ... [...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, 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, as this term is used to describe 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 predators, and po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mouse
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus''). Mice are also popular as pets. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter. Mice are typically distinguished from rats by their size. Generally, when a muroid rodent is discovered, its common name includes the term ''mouse'' if it is smaller, or ''rat'' if it is larger. The common terms ''rat'' and ''mouse'' are not taxonomically specific. Typical mice are classified in the genus '' Mus'', but the term ''mouse'' is not confined to members of ''Mus'' and can also apply to species from other genera such as the deer mouse, ''Peromyscus''. Domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable to breeding a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are native to all major land masses except for New Zealand, Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity. Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal, fossorial (burrowing), saltatorial/richochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters. Rabbits, hares, and pikas, whose i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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