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Viviparity
In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juvenile that is at least metabolically independent. This is opposed to oviparity, where the embryos develop independently outside the mother in eggs until they are developed enough to break out as hatchlings; and ovoviviparity, where the embryos are developed in eggs that remain carried inside the mother's body until the hatchlings emerge from the mother as juveniles, similar to a live birth. Etymology The term "viviparity" and its adjective form "viviparous" both derive from the Latin ''vivus'', meaning "living"; and ''pario'', meaning "give birth to". Reproductive mode Five modes of reproduction have been differentiated in animals based on relations between zygote and parents. The five include two nonviviparous modes: ovulipari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modes Of Reproduction
Animals make use of a variety of modes of reproduction to produce their young. Traditionally this variety was classified into three modes, oviparity (embryos in eggs), viviparity (young born live), and ovoviviparity (intermediate between the first two). However, each of those so-called traditional modes covered a wide range of diverse reproductive strategies. The biologist Thierry Lodé has accordingly proposed five modes of reproduction based on the relationship between the zygote (the fertilised egg) and the parents. His revised modes are ovuliparity, with external fertilisation; oviparity, with internal fertilisation of large eggs containing a substantial nutritive yolk; ovo-viviparity, that is oviparity where the zygotes are retained for a time in a parent's body, but without any sort of feeding by the parent; histotrophic viviparity, where the zygotes develop in the female's oviducts, but are fed on other tissues; and hemotrophic viviparity, where the developing embryos are fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovoviviparity
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch. The young of some ovoviviparous amphibians, such as '' Limnonectes larvaepartus'', are born as larvae, and undergo further metamorphosis outside the body of the mother. Members of genera '' Nectophrynoides'' and '' Eleutherodactylus'' bear froglets, not only the hatching, but all the most conspicuous metamorphosis, being completed inside the body of the mother before birth. Among insects that depend on opportunistic exploitation of transient food sources, such as many Sarcophagidae and other carrion flies, and species such as many Calliphoridae, that rely on fresh dung, and parasitoids such as tachinid flies that depend on entering the host as soon as possible, the embryos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sharks
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birth
Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fetus at a developmental stage when it is ready to feed and breathe. In some species, the offspring is precocial and can move around almost immediately after birth but in others, it is altricial and completely dependent on parenting. In marsupials, the fetus is born at a very immature stage after a short gestation and develops further in its mother's womb Pouch (marsupial), pouch. It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are Ovoviviparity, ovoviviparous, with the eggs being hatched inside the mother's body, and others are Viviparity, viviparous, with the embryo developing inside their body, as in the case of mammals. Human childbirth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oviparity
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles. Ovoviviparity is a special form of oviparity where the eggs are retained inside the mother (but still metabolically independent), and are carried internally until they hatch and eventually emerge outside as well-developed juveniles similar to viviparous animals. Modes of reproduction The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovuliparity
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles. Ovoviviparity is a special form of oviparity where the eggs are retained inside the mother (but still metabolically independent), and are carried internally until they hatch and eventually emerge outside as well-developed juveniles similar to viviparous animals. Modes of reproduction The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or ferti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snake
Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have skulls with several more joints than their lizard ancestors and relatives, enabling them to swallow prey much larger than their heads ( cranial kinesis). To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most only have one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. Lizards have independently evolved elongate bodies without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution, leading to many lineages of legless lizards. These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, althoug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adelphophagy
Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecology, ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well documented, both in ancient and in recent times. The rate of cannibalism increases in nutritionally poor environments as individuals turn to members of their own species as an additional food source.Elgar, M.A. & Crespi, B.J. (1992) ''Cannibalism: ecology and evolution among diverse taxa'', Oxford University Press, Oxford [England]; New York. Cannibalism regulates population numbers, whereby resources such as food, shelter and territory become more readily available with the decrease of potential competition. Although it may benefit the individual, it has been shown that the presence of cannibalism decreases the expected survival rate of the whole population and increases the risk of consuming a relative. Other negative effects may include ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skink
Skinks are a type of lizard belonging to the family (biology), family Scincidae, a family in the Taxonomic rank, infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Skinks are characterized by their smaller legs in comparison to typical lizards and are found in different habitats except arctic and subarctic regions. Etymology The word ''skink'', which entered the English language around 1580–1590, comes from classical Greek and Latin , names that referred to various specific lizards. Description Skinks look like lizards of the family Lacertidae (sometimes called ''true lizards''), but most species of skinks have no pronounced neck and relatively small legs. Several genera (e.g., ''Typhlosaurus'') have no limbs at all. This is not true for all skinks, however, as some species such as the Tribolonotus gracilis, red-eyed crocodile skink have a head that is ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vitellus
Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example because they are laid in situations where the food supply is sufficient (such as in the body of the host of a parasitoid) or because the embryo develops in the parent's body, which supplies the food, usually through a placenta. Reproductive systems in which the mother's body supplies the embryo directly are said to be matrotrophic; those in which the embryo is supplied by yolk are said to be lecithotrophic. In many species, such as all birds, and most reptiles and insects, the yolk takes the form of a special storage organ constructed in the reproductive tract of the mother. In many other animals, especially very small species such as some fish and invertebrates, the yolk material is not in a special organ, but inside the egg cell. As ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudemoia Entrecasteauxii
''Pseudemoia entrecasteauxii'', also known commonly as Entrecasteaux's skink, the southern grass skink, the tussock cool-skink, and the tussock skink, is a species of lizard in the family Scincidae. The species is endemic to Australia. Geographic range ''P. entrecasteauxii'' is found in the south-east of the continent of Australia, as well as in Tasmania and the islands of Bass Strait. Habitat Although it occurs in a variety of habitats, ''P. entrecasteauxii'' is most commonly found in open grassy woodlands. Cogger HG (1979). ''Reptiles and Amphibians of Australia''. Sydney: Reed. Longevity The southern grass skink has a lifespan of about 5 or 6 years. Description ''P. entrecasteauxii'' grows up to in length (not including the tail). Male skinks change colouration during the breeding season. Etymology The specific name, ''entrecasteauxii'', is in honor of French naval officer and explorer Antoine Bruni d'Entrecasteaux. Reproductive biology The southern grass skink h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intra-uterine Cannibalism
Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well documented, both in ancient and in recent times. The rate of cannibalism increases in nutritionally poor environments as individuals turn to members of their own species as an additional food source.Elgar, M.A. & Crespi, B.J. (1992) ''Cannibalism: ecology and evolution among diverse taxa'', Oxford University Press, Oxford ngland New York. Cannibalism regulates population numbers, whereby resources such as food, shelter and territory become more readily available with the decrease of potential competition. Although it may benefit the individual, it has been shown that the presence of cannibalism decreases the expected survival rate of the whole population and increases the risk of consuming a relative. Other negative effects may include the increa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
