Marvelous Multiple Births Essay, Research Paper
Multiple Birth, birth of more than one offspring at a clip, happening on a regular basis in most mammals, and uncommonly in some of the larger 1s, such as cowss, Equus caballuss, and worlds. In worlds, the inclination to bear more than one progeny is familial ( see Heredity ) , and a female parent who gives birth to twins is likely to hold extra twins. Similarly, a twin-bearing female parent stands a greater opportunity of bring forthing threes. The recent usage of endocrines and drugs to handle female asepsis has increased the incidence of multiple birth, sometimes ensuing in premature bringing of five or six progeny.
Multiple births in human existences arise either from the coincident impregnation of more than one egg cell or from the impregnation of a individual egg cell that divides into two or more parts, each of which develops into a distinguishable embryo ( see Egg ; Embryology ; Reproduction ) . Plural offspring developing from a individual egg are known as indistinguishable ; they are ever of the same sex, resemble one another really closely, and have similar fingerprints and blood types. Offspring produced from separate egg cells are fraternal ; non needfully of the same sex, they have the usual household resemblance of brothers and sisters.
Twinss are the most frequent signifier of multiple birth in worlds, and indistinguishable twins occur merely one-fourth every bit often as fraternal twins. In the U.S. one birth in about 87 is a duplicate birth. Threes are about 87 times rarer than twins, and fours about 87 times rarer than threes. Fives occur in approximately 1 out of 8 million gestations. These figures are for spontaneously happening gestations. When ovulation has been induced by drugs, the incidence rises. Multiple births may be achieved unnaturally by engrafting in the uterus several egg cells fertilized in vitro ( see Infertility ) .
The prenatal and infant mortality rate in multiple gestations is higher than that in individual gestations. The danger of premature birth additions increasingly with the figure of offspring involved.
Phalanger, common name for any of 77 marsupial mammals found merely in the western hemisphere. The opossum scopes in length from 17 to 104 centimeter ( 7 to 41 in ) ,
including the tail, which is from 9 to 54 centimeter ( 4 to 21 in ) long. The common Virginia phalanger is the largest of the phalangers, mensurating 109 centimeter ( 43 in ) , of which one-half is tail. The front pess have five toes with claws ; on the hind pess the outer four toes bear claws, and the inmost toe is apposable, like a pollex, and nailless. The Virginia phalanger is covered with long, sleek, white hair and an undercoating of soft, woolly fur. It has a pointed, slender face and big, wide, bare ears. An phalanger has 50 dentitions. Most species are omnivorous, normally preferring a diet of insects and carrion. They are nocturnal, kiping in a tunnel during the twenty-four hours and runing nutrient at dark ; most are arborical. The yapock, or H2O phalanger, of South America is aquatic, holding webbed back pess for swimming. The Virginia opossum’s habit of shaming decease when threatened has given rise to the look “playing possum.”
Most species have the abdominal pouch feature of pouched mammals ; nevertheless, in some South American species this pouch is fundamental or absent. A female phalanger may hold every bit many as 17 mammillas within the pouch, but 13 is the usual figure. Of the 4 to 24 immature that may be born in a litter, merely 8 or 9 normally survive. The gestation period is about 13 yearss, and the newborn phalangers, approximately 1.4 centimeter ( about 0.55 in ) long and weighing approximately 0.16 g ( about 0.0056 oz ) , are rather undeveloped. They must pass about two months in the female parent & # 8217 ; s pouch attached to the mammillas before they are able to travel approximately.
The Virginia phalanger, found throughout the eastern United States and on occasion in the western provinces, is comestible and considered a daintiness in the South. Opossum fur once had commercial value but is small used now. The name phalanger is often shortened to possum, although the name possum is besides used in mention to certain Australasian pouched mammals unrelated to phalangers.
Raccoon
Scientific categorization: Raccoons make up the genus Procyon of the household Procyonidae. The common North American raccoon is classified as Procyon lotor, and the crab-eating raccoon as Procyon cancrivorus. They are non pouched mammals because they do non hold pouches for their new born.
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