What is a life cycle?
A life cycle is the changes an animal goes through in its life from a baby to an adult. Life cycles go in circles and keep repeating from one generation to the next.
What is metamorphosis?
Animals like frogs and butterflies go through a process called metamorphosis, they change into something completely different. Caterpillars turn into butterflies and tadpoles turn into frogs.
When tadpoles change into frogs, all the organs of their bodies have to transform to be able to live on land.
The life cycle of a frog
Frogs are amphibians which means they can live on land and in water. They go through many stages in their life:
Stage 1: egg
Frogs lay their eggs in water. They lay lots of eggs at a time because not all of them survive.
Frog eggs float on water and are covered in slimy jelly to protect them. A group of eggs is called a frogspawn.
Frog eggs hatch faster if the water is warm and slower if the water is cold.
Stage 2: tadpole
When an egg hatches, out pops a tadpole (or polliwog). Tadpoles look more like fish than frogs. They do not have any arms or legs. They have long tails and gills to breathe underwater.
For the first 7 days, they use their mouth to stick onto grass, leaves, or stems. After that, they release themselves and start swimming and eating plants and algae from the water. Some also eat smaller tadpoles!
After a few weeks, the tadpole starts to grow back legs and lungs to breathe out of the water. It starts looking more like a tiny frog but it still has its long tail.
Stage 3: young frog
The tadpole starts to grow its front legs and its tail becomes shorter and shorter.
During this stage, the tadpole doesn’t need to eat because it uses the nutrients stored in its tail as food. When just a little stub of a tail is left, it becomes a young frog and hops out of the water onto land.
Stage 4: adult frog
The frog's tail completely disappears and it starts to eat insects. It takes 2-4 years to become a fully grown adult. As it grows it sheds its skin. A frog's skin must never dry out otherwise it will die. To prevent this from happening, its skin produces mucus. This is why frogs often feel slimy.
When a female adult frog lays eggs, the cycle starts all over again.
Did you know?
- Frogs are found on every continent except Antarctica.
- Frogs don’t drink water, they soak it up through their skin.
- Frogs breathe through their nose and skin.
- Frogs can see forwards, sideways and upwards all at the same time. They never close their eyes, even when they sleep.
- Frogs swallow food by pushing down their eyeballs.
- A frog's tongue is attached to the front of its mouth so it can stick it out much further.
- The biggest frog in the world is the goliath frog found in Cameroon, Africa. It can be as heavy as a house cat!
- The smallest frog in the world is the gold frog which measures only 1cm.
- A tadpole's skull is made of cartilage (the same stuff as our nose and ears). The cartilage changes into bone during metamorphosis.