Animals Classification
Primary 4 · Science and Elementary Technology
Animals Classification
Lesson 2 of 5
15 min
Let's begin
Ishimwe visits his uncle's fish pond near the Nyabarongo. The tilapia swim under the water all day and never come up for air. "Don't they need to breathe?" he asks.
They do! Every animal needs oxygen. Animals just take it in with different body parts.
Mammals, birds and reptiles breathe air into lungs inside their chests. You do too: put a hand on your chest and feel it rise as you breathe in.
Some animals with lungs spend a long time in water, like the hippos in Akagera National Park. But they must come up to the surface to breathe air, because they have lungs, not gills.
Fish breathe with gills, feathery parts on the sides of the head. Water goes in through the mouth and passes over the gills, and the gills take in the oxygen that is mixed into the water. That is how the tilapia in the pond breathe without coming up.
An earthworm has no lungs and no gills. It takes in oxygen through its thin, moist skin. If an earthworm dries out in the hot sun, it cannot breathe. That is why earthworms live in damp soil.
Insects such as grasshoppers and bees have tiny holes along the sides of their bodies called spiracles. Air goes in through these holes and travels through thin tubes to every part of the body.
A baby frog, called a tadpole, lives only in water and breathes with gills. As it grows into a frog it grows lungs. An adult frog breathes with its lungs AND through its moist skin, so it can live on land and in water.
| Breathing part | Animals |
|---|---|
| Lungs | mammals, birds, reptiles, adult frogs |
| Gills | fish, tadpoles |
| Moist skin | earthworms, and adult frogs too |
| Spiracles (tiny holes) | insects |
Tip
Lungs for air, gills for water, skin for worms, holes for insects
Say it four times, pointing to your chest, the sides of your head, your arm and your side.
Try each one first, then tap Show answer to check.
What does a fish use to breathe?
Answer: Its gills, which take oxygen from the water.
Why does a hippo have to come up to the surface of the water?
Answer: It is a mammal with lungs, so it must breathe air.
Uwase finds an earthworm drying on a hot path. Why is this dangerous for the worm?
Answer: An earthworm breathes through its moist skin. If its skin dries out, it cannot breathe.
Name two ways an adult frog breathes.
Answer: With its lungs and through its moist skin.
Where are a grasshopper's spiracles?
Answer: Along the sides of its body.
What you learned today
Sources and credits
The exercises (Try it yourself and the practice questions) are written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
Quick check
What does a fish use to breathe?
