Why do mammals produce a low number of offspring?

Answer 1

This question includes an assumption : that mammals don't lay eggs. Well, some do.

Mammals are distinguished from other creatures by two characteristics, which are found in all mammals and no non-mammals. These are the mammalian ear, which includes three tiny bones - the hammer, the anvil and the stirrup, and the nourishment of their offspring by mothers' milk. There are three subdivisions of mammals :-

1. Monotremata. Only three species, the duck-billed platypus and two echidnas. All lay eggs.
2. Marsupialia. These give birth to live young, but in a very small and un-developed state. The young marsupial exits the vagina and crawls up the mother's belly. It finds, and crawls into, a pouch at the top of the belly. This pouch shelters and protects the young marsupial; it also contains a patch of special skin which exudes milk when it is licked. The youngster completes its development safe and snug in the pouch, sometimes for many months. There are many species of marsupials, of which the best known are probably the kangaroo and the koala. The only marsupial found outside Australia is the American opossum.
3. Eutheria. Easily the largest group of mammals, they are often called the 'true mammals'. This description may have come about because early taxonomists had never seen a marsupial, never heard of a monotreme. They thought that the distinguishing mark of a mammal was nipples (aka teats). Non-eutherian mammals don't have these, but they are mammals nonetheless.

It should be noted that every mammalian offspringoriginates from an egg. The difference between the types of mammal comes from whether the embryo develops outside its mother's body (monotremes), develops fully inside its mother's body (eutheria) or develops partly inside mother's body and partly in her pouch (marsupials).

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As to why mammals gave up laying eggs, this is still a mystery. The beginnings of an answer may lie in the fact that evolution is combination of chance and choice. Mutations are largely random, albeit that they usually involve tiny cumulative changes to what went before. Selection is both choice and chance; mutations that give some kind of survival advantage, or sometimes just reproductive advantage, will tend to be favoured. Whether any change is advantageous may depend on the conditions of climate, food supply or competition of other animals at the time of the mutation. It does fairly shriek at us that the rise of monotremes and marsupials occurred before Australia separated from other continents, but eutheria appeared after.

Note. Australia should be taken to include surrounding islands including New Guinea.

Answer 2

Most mammals reproduce by giving live birth. This is simply one of the characteristics of mammals, and it is due to their anatomy.

There are, however, some mammals which do lay eggs. These are the monotremes. There are three species of mammals that lay eggs: the Platypus and two species of echidna, the long-beaked echidna of New Guinea and the short-beaked echidna of Australia.

Answer 3

The three species of monotremes, or egg-laying mammals, can only suckle a small number of young. The platypus, short-beaked echidna and long-beaked echidna are mammals because they feed their young on mothers' milk. The echidna produces just one egg because it incubates the egg in a temporary pouch that develops on its abdomen during breeding season.

Answer 4

They do.

While it is true that most mammals give birth to live young, there are two types of egg-laying mammals. The platypus and the echidna are both egg-laying mammals, or monotremes. They are still classified as mammals because they feed their young on mothers' milk - a characteristic unique to mammals alone.

There are just three known species of egg-laying mammals, or monotremes. They are the platypus and short-beaked echidna (Tachyglossus aculeatus) of Australia, and the long-beaked echidna (Zaglosssus bruijni) of Papua New Guinea. The echidna is sometimes called the spiny anteater, and there are several sub-species of the long-beaked echidna: the Western long-beaked echidna, Sir David's long-beaked echidna and the Eastern long-beaked echidna.

Answer 5

Mammals don't lay eggs except the platypus and the echidna.

Answer 6

some animals do not lay eggs because they are mammals just like humans the only mammal that lays eggs is a platypus.

Answer 7

Mammals dont produce lots of eggs because they do not have the ability to.

Answer 8

because mammals can have only one baby at one time.

Answer 9

Because their breeding method results in most of the offspring surviving to adulthood.

Answer 10

Why do mammals produce only few eggs