Animals that do not develop in a placenta will develop outside of the uterus rather than in. Kangaroos and Koalas use pouches to develop their young.
They develop by feeding from the yolk of the egg that the frog has laid and that is the equivalent of a placenta.
in the egg
The same way every animal before mammals evolved did it. The egg contains a yolk loaded with nutrients that they live off and the shell has pores that let air in and carbon dioxide out for their respiration.
Placenta is used by certain mammals to nurture embryos that will develop into a baby that will be born live. Birds, however, don't give birth to live young. Instead, they lay eggs, and the embryo inside the egg is nurtured by a nutrient and energy rich yolk sac, rather than by a placenta.
Most mammals are placental mammals: they develop in a placenta before birth. Marsupials also develop in a placenta, but they are delivered much earlier and the placenta is less developed. Monotremes develop within an egg, which is kept inside the mother for some time before it is laid. It hatches several days later.
Placental mammals and marsupials develop in a placenta within the uterus before being delivered. Monotremes develop in an egg.
The young of placental mammals develop within a placenta. The placenta is a thick membrane that is connected to the inside of the uterine wall. The umbilical cord connects the baby to the inside wall of the placenta. Nutrients and oxygen go from the mother's blood stream through the placenta, down the umbilical cord, and into the baby. The baby releases waste products and carbon dioxide, which travel up the umbilical cord, through the placenta and into the mother's blood stream.
Identical twins may or may not share the same placenta . Identical twins develop when a fertilized egg splits. Depending on when the split occurs will determine if the twins share a placenta, with either one or two chorions and amnions, or if they each develop their own placentas.
example of develop inside the body of animals
it passes oxygen and nutrients
The placenta is what gives the baby blood, nutrients and oxygen from the mother while in the womb. Without the placenta, the baby would have no way of surviving.
ectoderm