Biology · Glossary

What is Two ways to be born?

Also known as: egg · born alive · milk

Definition 8.1 Primary & Middle School Biology · Chapter 8 — How Animals Grow Up

Young animals come into the world in two ways:

  • most hatch from an egg laid by the mother: birds, fish, frogs, snails, insects;
  • others are born alive, coming out of the mother’s body already formed, and drink her milk: cats, dogs, cows, rabbits — and humans.

Examples

Example 8.2 (In the henhouse and in the basket)

The hen lays eggs and sits on them to keep them warm; after three weeks, chicks break the shell and hatch. In the basket by the stove, the cat’s kittens were born alive the same night, and they found her milk within the hour.

Example 8.5 (Kitten to cat)

The newborn kitten drinks milk with closed eyes. At one month it plays and pounces; at six months it hunts like a grown cat; at one year it is an adult, perhaps with kittens of its own. Small cat, bigger cat, cat: the same shape all along the way.

Example 8.7 (The frog’s road)

From the frog’s eggs in the pond hatch tadpoles: round-headed, long-tailed, legless, breathing in water like fish. Then, week by week: back legs appear, then front legs; the tail shrinks away; and one day a small frog climbs out onto the bank. Same animal — rebuilt.

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