Why is a monotreme different from placental mammals and marsupial mammals?

Answer 1

Eutherians, or placental mammals nurse their young in a womb. Protherians like platypus lay eggs and do not have teats but ooze milk through the skin. Marsupials only nurse the young in the body for a very short time before they are born. The progeny live in a pouch suckling for months after birth until old enough to emerge.

Answer 2

Marsupials (such as kangaroos) are pouched mammals which give birth to live young. The young (called joeys) are very undeveloped, with the embryo resembling a bean. The joeys are then carried in a pouch, where they latch on to a teat which swells in their mouth, to continue their development. They complete their development outside the mother's body, in the pouch. Australia has most of the world's marsupials.

Female marsupials have two vaginas, or what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth. As well as two vaginas and two uteruses, female marsupials have two fallopian tubes and two cervixes. Most male marsupials, with the exception of the largest species, the Red Kangaroo, Eastern Grey and Western Grey Kangaroos, have a "bifurcated" or two-pronged penis to accommodate the females' two vaginas.

Monotremes are egg-laying mammals. The young are not born, but hatched. The echidna actually lays its egg straight into a fold of skin, like a pouch, that develops only during breeding season, and this is where the egg is incubated. Soon after hatching, the young echidna is transferred into a burrow. The platypus, the other monotreme, lays its egg/s in a burrow or chamber, and does not have a pouch of any description. Once the young hatch, they also feed off mother's milk. There are only two types of monotremes in the world - the platypus and the echidna. The platypus is endemic to Australia, the short-beaked echidna is native to Australia, and both the short-beaked and long-beaked echidna are found in New Guinea.

Placental mammals, also known as eutherians, make up the largest group of mammals. Placental mammals give birth to a fully developed live young. The young complete their development whilst still inside the mother's body, receiving their nutrients during this time via the placenta, and their bodies are able to function independently of their mother's at birth, unlike marsupials. Placental mammals are found all over the world, including the ocean.

All of these creatures are classified as mammals because they all feed their young on mothers' milk.

Answer 3

Marsupials are mammals with pouches in which they rear their young. Marsupial young are characterised by being extremely small and undeveloped at birth. At birth, they take a long, arduous journey from the birth canal, driven purely by instinct, grabbing hold of the mother marsupial's fur which she has cleaned and made easier to traverse with saliva, to reach the pouch. Upon reaching the pouch, they latch onto a teat which swells in their mouth to prevent them from being accidentally dislodged during the mother's movements. There they stay for months, to complete their development.

Not all marsupials have pouches, e.g. the numbat has a mere flap of skin, but in animals where the pouch is absent, the young are still born undeveloped, and they cling by instinct to the underside of their mother's belly, still firmly attached to teats which swell in their mouths.

On the other hand, the embryo in a placental mammal is fully developed within the mother's uterus, sustained by the placenta, through which it receives all the nutrition it needs. Its organs are fully developed and it is able to survive outside the mother's body once it is born. It requires mothers' milk (or a suitable substitute) when it is born, but it can live independently of the mother, given the right care.

Female marsupials have two vaginas, or what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth. As well as two vaginas and two uteruses, female marsupials have two fallopian tubes and two cervixes. Most male marsupials, with the exception of the largest species, the Red Kangaroo, Eastern Grey and Western Grey Kangaroos, have a "bifurcated" or two-pronged penis to accommodate the females' two vaginas.

Answer 4

The most obvious difference between monotremes and placental mammals is that monotremes lay eggs, while placental mammals give live birth.

The name monotreme is derived from two Greek words meaning "one-holed", because they have just one external opening, the cloaca, for both waste elimination and for reproduction, unlike the placentals. The cloaca leads to the urinary, faecal and reproductive tracks, all of which join internally, and it is the orifice by which the female monotreme lays her eggs.

Answer 5

Most mammals are placentals, but the marsupials are quite different. Marsupials are mammals with pouches in which they rear their young. Marsupial young are characterised by being extremely small and undeveloped at birth. At birth, they take a long, arduous journey from the birth canal, driven purely by instinct, grabbing hold of the mother marsupial's fur which she has cleaned and made easier to traverse with saliva, to reach the pouch. Upon reaching the pouch, they latch onto a teat which swells in their mouth to prevent them from being accidentally dislodged during the mother's movements. There they stay for months, to complete their development.

Not all marsupials have pouches, e.g. the numbat has a mere flap of skin, but in animals where the pouch is absent, the young are still born undeveloped, and they cling by instinct to the underside of their mother's belly, still firmly attached to teats which swell in their mouths.

Female marsupials have two vaginas, or what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth. As well as two vaginas and two uteruses, female marsupials have two fallopian tubes and two cervixes. Most male marsupials, with the exception of the largest species, the Red Kangaroo, Eastern Grey and Western Grey Kangaroos, have a "bifurcated" or two-pronged penis to accommodate the females' two vaginas.

Answer 6

This mammals lay eggs like reptiles, and they have fur and milk. However have no nipple's: there mammary glands just secret milk onto the fur in which there babies lick it. They have one posterior opening for there digestive, urinary and genital discharges. Examples are: duck billed platypus and spiny anteater.

Answer 7

The main difference between monotremes are the other types of mammals is that monotremes lay eggs.

Answer 8

Marsupials have a pouch and placental mammals do not. Marsupial babies leave the womb much earlier than placental babies.