2006-07-27 22:01:02 · 17 answers · asked by Hamid S 2 in Science & Mathematics ➔ Zoology
one of life's great unknowns //
2006-07-28 05:17:16 · answer #1 · answered by Anonymous · 0⤊ 2⤋
All embryoes ought to be nourished prenatally, no count if interior an eggshell or by a placenta. The eggs of warmth-blooded ainmals (specially birds) ought to be saved heat, yet those of chilly-blooded animals can basically be left the place they are laid. Any embryo that develops interior an egg ought to emerge while the provision of nutrition is ate up, yet a placenta helps the embryo to strengthen extra completely until now delivery, by using fact it (the placenta) promises a delicate supply of nutrition as lengthy because it extremely is mandatory. in basic terms mammals, and not even all of them, have placentas. (The platypus, which has a bill and lays eggs, is labeled as a mammal fairly than a chook by using fact it has 4 legs and suckles its youthful.) Marsupials (e. g. kangaroos) submit to stay youthful yet haven't any placentas. The youthful strengthen in eggs interior the mummy's uterus and are born while that resource of nutrition is exhausted, yet they'e nevertheless little better than fetuses at that component--for this reason the choose for the pouch. The newborns of placental mammals, from sloths on up, would nicely be too helpless to proceed to exist on their very very own, yet they are, in truth, completely developed animals.
2016-12-14 15:19:43 · answer #2 · answered by ? 4 · 0⤊ 0⤋
Usually animals give birth to a baby animal are mammals, like us; The ones lay eggs are raptiles.
Why? Hummm, i think this is coz mammals are more complicated in organs and structure, that's why they need a more complicated and better way of getting"nutured" in the womb of the mother. That's mammals take longer time to give birth also, we need 10 mths right?
2006-07-27 22:07:52 · answer #3 · answered by a V a 4 · 0⤊ 0⤋
Warm blooded animals give birth to live young, except for the Duck-billed Platypus. Cold blooded animals lay eggs.
2006-07-27 22:04:36 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Some animals live in an area where the babies survive better as live births.
Others evolved this way and haven't changed.
Guinea pig babies are born "ready to go" (eyes open, covered with fur and ready to run) while mouse babies are born helpless.
It's what makes it all interesting.
2006-07-28 15:19:16 · answer #5 · answered by lrad1952 5 · 0⤊ 0⤋
The ones that lay eggs are usually reptiles or amphibians.
2006-07-27 22:05:27 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Mammals (like humans)- give birth to live babies.
Reptiles (like a snake) - lay eggs
It's how they were made! It's also how their bodies work!
2006-07-28 02:41:58 · answer #7 · answered by house md rocks! 2 · 0⤊ 0⤋
mamal and cold blooded animal
i.e Humans(mamals=gives birth
Cold blooded (lizard,chickens)= they lay eggs then hatch
It's genetics
2006-07-27 22:08:24 · answer #8 · answered by jules 4 · 0⤊ 0⤋
Ev0luti0n.
2006-07-28 00:22:32 · answer #9 · answered by Anonymous · 0⤊ 0⤋
Because Eggs taste better...ha ha ha
2006-07-28 00:23:41 · answer #10 · answered by Cool Techie 1 · 0⤊ 0⤋
The difference between Mamals and non-Mamals
2006-07-27 22:15:31 · answer #11 · answered by floxy 3 · 0⤊ 0⤋