What is the life cycle of a frog?

A visit to a pond

In the rainy season, a shallow pond surrounded by trees and tall grass is full of life. Go with a teacher or another adult, wear full sleeves and full trousers, and watch from a distance without disturbing anything. Near the edge of the pond you may see a white, jelly-like substance floating on the water or stuck to water plants. It is a cluster of frog’s eggs, called spawn.

Stages of a frog in a pond

In such a pond you can spot frogs at many different stages at the same time:

• a cluster of round eggs with dark dots, held in jelly (spawn);
• eggs with tiny comma-shaped embryos inside;
• a tadpole with a rounded body and a long tail, but no legs;
• a tadpole like that one, but with two hind legs;
• a froglet, which looks like a little frog with four legs and a short tail;
• an adult frog without a tail, sitting on a leaf.

To put them in order, ask which shape could change into which: eggs become embryos, embryos hatch into tadpoles, tadpoles grow legs, and so on.

The life cycle of a frog

The chapter groups the steps into four stages:

Stage	What it looks like	When
I: Egg (spawn, then embryo)	Eggs in jelly; embryos develop inside	Day 1; embryos by day 3–4
II: Tadpole	First a tail and no legs, then hind legs as well	Day 7–10; legs by 8–10 weeks
III: Froglet	A little frog with a short tail	About 12 weeks
IV: Adult frog	Full-grown frog, no tail, strong legs	About 14 weeks

The egg stage is the shortest: within about 10 days the eggs have hatched into tadpoles. The tadpole stage is the longest, lasting several weeks.

How the frog changes

Tadpoles live in water, and their tails help them swim. As they grow, they develop legs but still keep their tails for a while. Slowly they start to look like little frogs, called froglets. Froglets still live in water but begin to spend some time on land. They keep growing, lose their tails completely, and their legs become strong so they can jump and land. They become adult frogs that live both in water and on land. So during its life cycle a frog changes its body shape, its body parts and even its home.

Frogs and mosquitoes

A mosquito also changes completely as it grows, passing through four stages: egg, larva, pupa and adult. Both animals lay eggs in or near water, and their young stages live in water. But the mosquito has a pupa stage, and the adult flies, while the frog grows legs step by step and the adult hops between water and land.

Do birds change like this?

Not in the same way. A chick that hatches from an egg already looks like a small bird; it simply grows bigger and grows its adult feathers. Frogs and mosquitoes, in contrast, look completely different at different stages. Such changes help them survive and keep their kind going, so we should look after them and the ponds and wetlands they live in. See all the stages of living beings in the Chapter 10 notes.