Why do humans and some animals have babies inside the tummy..............?

Question

but other animals and birds lay eggs that hatch outside.

Answer 1

If you could use a time machine to see how different animals evolved, you'd see that babies developing in eggs came before babies developing inside the mother's body.

The first animals lived in water. For the sake of brevity I'm going to skip over many levels of primitive animals here, to vertebrates (animals with backbones). Fish, for instance, lay eggs that have no shell. If you take them out of the water, they'll dry out and die. But this kind of egg works just fine for those animals. Many are eaten by predators, but enough survive to carry on the species.

Some animals evolved traits that allowed them to move onto land. Amphibians (like frogs) are sort of in between, because they come onto land sometimes but still need to go into water regularly and need it for their eggs. Up through this level of evolution, eggs can be fertilized outside of the mother's body. She lays the eggs, and then the father releases his sperm over them to fertilize them.

Reptiles were the first animals that could survive entirely on land. Their eggs have shells, which prevent them from drying out like frog eggs would. Birds evolved later from reptiles, and they also lay eggs with shells. When there are shells, the fathers inject their sperm into the mother's body so the egg can be fertilized before the shell is formed around it. Up to this level, we call animals "oviparous," which means that they lay eggs ("ovi-" means "egg") that hatch outside the mother's body.

The next advancement, ovoviviparous animals, have eggs that stay inside the mother's body ("ovo" for the egg, "vivi" for the live birth). They do not need a shell like reptiles' and birds' eggs do, because they are not exposed to the outside world. The mother's body protects the egg as the baby is developing, and the mother can carry it around instead of having to go back to the nest (though some egg-layers, like turtles, just leave the eggs alone and the newly hatched babies fend for themselves). The eggs hatch inside the mother's body, and the babies are then born. An example of an animal that does this is some kinds of sharks.

An egg is made with food for the baby already inside of it. The baby can only develop inside inside the egg for as long as the food supply lasts. After that, it has to hatch and get food from another source. Marsupials (like kangaroos and koalas) are a special category of animal. After the eggs hatch inside the mother's body, the tiny baby isn't ready to live in the outside world yet so it crawls into a pouch its mother has where it feeds on milk from the mother's body until it's big enough to be "born" a second time by coming out of the pouch.

Viviparous animals have evolved another way to solve the problem of eggs not having enough food for a baby to develop for a long time. The developing baby stays inside the mother's body, like ovoviviparous animals do, but it forms a direct connection with the mother's body. A special organ, called a placenta, forms and attaches to the inside of the mother's uterus (the organ where the babies grow). The umbilical cord attaches the placenta to the baby. Nutrients from food the mother eats gets delivered to the baby through these connections.

Most mammals (animals that feed their children with milk from the mother's body) -- cats, dogs, horses, hamsters, humans, and many more -- are viviparous. Oviparous and ovoviviparous animals have the advantage that if the mother doesn't get much food, the baby won't be affected because it already has all of the food it needs inside the egg. But viviparous animals have the advantage that, as long as the mother does get enough food, the baby can develop for a lot longer before it's born because it can keep getting food from the mother instead of having only what was put into the egg when it was first made.

Answer 2

1) Babies are not inside the 'tummy'. The baby develops inside the female's uterus. The baby is attached to the mother by an umbilical cord -- all nutrients are supplied through the mother's blood by crossing a single cell layer into the baby's blood.

2) A live birth, such as in mammals, allows for greater development. Organ systems and body form are more highly developed in mammals than in other phyla.

3) Since the baby is more highly developed, more nutrients are required during the gestation period. The amount required could not be contained inside the yolk of an egg.

4) Porcupine do not lay eggs. The babies are born alive after a gestation of approximately 107 days. Monotremes -- the scientific name for mammals that lay eggs -- are found only in Australia and Tasmania. There are two types -- the platypus and the echidna.

Answer 3

Hmm good question, but I don't think they miss what they've never known. Babies miss being with people once they know what it is to be held and to see a human face. Most babies don't even realize that a person or object exists when out of sight until about 5 months old and they don't worry about being separated from mom until they're about a year. I think the little guys are just fine and happy.

Answer 4

presumably better survival odds. It's one type of baby-ing: put a whole lot of effort into one kid that you have a good chance of raising to independence successfully, before you go on to the next one. Laying eggs is kind of a defensive variation - if the egg gets eaten, you haven't lost too much, as long as you have a good shot at laying more eggs before you run out of time.

Answer 5

That's because mammals (like humans,dogs,cats , any hot-blooded animal) are born alive while amphibians,the aves group(birds) and reptiles are "hatched from egg"

there are only two mammals in the world that are "hatched form egg" which is the Duck-billed platypus and the porcupine.

Answer 6

to ensure the survival of the babies.
eggs can get stolen by predators and break easily.

Answer 7

because humans and some animals are mamils.. and mamils have babies from the womb (tummy)

Answer 8

because thas the only place they can hold them because orgies dont go to ur head or something u know were they go!