Analysis of the subjectThe reproductive systems of marsupials differ markedly from those of placental mammals. During embryonic development, a choriovitelline placenta forms in all marsupials. In bandicoots, an additional chorioallantoic placenta forms, although it lacks the chorionic villi found in eutherian placentas. Female marsupials have two lateral vaginas, which lead to separate uteruses, but both open externally through the same orifice. A third canal, the middle vagina, is used for childbirth. This channel can be transient or permanent. Like all marsupials, the female kangaroo has 3 vaginas and uterus (uteri). The two outermost vaginas are used to transport sperm to the uterus. Babies are born in the middle. Say no to plagiarism. Get a tailor-made essay on "Why violent video games should not be banned"? Get an original essay With this unusual reproductive system, a female kangaroo can be in a state of continuous pregnancy, with a fertilized egg in a uterus waiting to being released, a baby growing in the second womb, one in its pouch and another hopping outside but coming to get milk from its mother. Another unique feature of these animals is that during periods of extreme drought and famine, the female kangaroo may practice birth control by putting growing babies in the womb "on hold", thereby arresting their future development until until conditions improve. This is called embryonic diapause. When the mother's pouch becomes free, the next baby will be born and move into the pouch and the fertilized egg "waiting" in the uterus will begin to develop into a new fetus. Because of this multiple-offspring strategy and other adaptive abilities unique to the kangaroo, populations can increase rapidly when food is abundant. Female kangaroos become pregnant regularly. They expel an egg from their ovary and it drifts into the fallopian tube where, if it encounters sperm, the egg is fertilized and then embeds itself in the wall of its mother's uterus. BUT, here is the big difference between us ordinary mammals and marsupial mammals, no placental connection is formed. Once the marsupial egg has consumed its own yolk to stay alive and develop (just like a bird's egg), it must be born. The total pregnancy therefore only lasts around 28 days! At the end of the pregnancy, the mother-to-be sits down and cleans her pocket. The baby emerges from an opening at the base of its tail called the cloaca. The infant is very small, barely the size of a lima bean. It is pink and largely undeveloped, except for its two front arms which are crucial for reaching up from its mother's belly to the pouch. The baby, who is little more than a fetus, makes this ascent without any help and guided only by his instinct. Once inside the pouch, the baby finds one of his mother's four nipples and takes the tip into his mouth. The baby does not have the muscles to breastfeed at this stage. Instead, the nipple swells inside the baby's mouth, so it cannot come off and milk is secreted very slowly into the baby's mouth. Later, once the baby's jaw is more developed, he will be able to free himself and suckle at will. BABY 1: Firmly attached to the pacifier, the mother kangaroo can basically wipe her paws on it. Baby red kangaroos spend about 235 days in the pouch before emerging, and baby gray kangaroos stay in their pouch for much of the year. Begins to explore outside of mother's pouch. As Joey 2..