Lesson 18

How do frogs reproduce and develop?

A frog is a vertebrate. It is also an amphibian. Like all amphibians, a frog lives part of its life in water, and part on land.

A frog’s young life is spent exclusively in water.

As an adult, a frog can live in water, breathing through its skin.

On land, an adult frog breathes through its lungs.

Frogs reproduce in water by external fertilization.

Here is how it happens:

A female lays hundreds, even thousands of eggs. At the same time, the male releases sperm.

The sperm cells fertilize the eggs.

The parents do not stay with the eggs.

Each fertilized egg is called a zygote.

The eggs cluster together and swell. They are protected by a jelly-like material.

In about two weeks, the eggs hatch.

A newly hatched frog is called a tadpole.It doesn’t even look like a frog!

It has a tail and no legs. It cannot live on land, as it breathes through gills.As it grows, legs

appear.

The legs get longer as the tadpole grows.

It starts developing lungs, but still uses gills and its tail.

After about 8 to 12 weeks, the tadpole no longer looks like a tadpole. It is a full grown frog.