Animal World
![](https://www.timeforkids.com/wp-content/uploads/2021/08/Animal-Kingdom-cover.jpg?w=1024)
The world is full of animals. They can be classified, or grouped. Read about four groups below.
Salmon are fish.
![](https://www.timeforkids.com/wp-content/uploads/2021/08/K1AnimalGroups_Salmon.jpg?w=1024)
Fish live in water. Fins help them swim. Gills help them breathe. Most fish are covered in scales
scale
FAUZAN MAUDUDDIN—EYEEM/GETTY IMAGES
a small, thin plate that helps form a covering for the bodies of some animals
(noun)
Snakes have scales.
.
Robins are birds.
![](https://www.timeforkids.com/wp-content/uploads/2021/08/K1AnimalGroups_Robin.jpg?w=1024)
Birds have feathers. Most birds have strong muscles. These muscles help birds fly. Birds hatch
hatch
to be born by coming out of an egg
(verb)
Let's watch a chick hatch from an egg.
from eggs. They eat with their beaks.
Frogs are amphibians.
![](https://www.timeforkids.com/wp-content/uploads/2021/08/K1AnimalGroups_Frog.jpg?w=1024)
Amphibians are cold-blooded animals. Their body temperature changes with their environment
environment
PATRICK J. ENDRES—GETTY IMAGES
surroundings
(noun)
Polar bears live in cold environments.
. Amphibians live in water and on land.
Bears are mammals.
![](https://www.timeforkids.com/wp-content/uploads/2021/08/K1AnimalGroups_Bears.jpg?w=1024)
Mammals are warm-blooded animals. Body fat and fur help mammals stay warm. Mother mammals feed their babies milk from their bodies. Humans are mammals too!
Did You Know?
![](https://www.timeforkids.com/wp-content/uploads/2021/08/K1AnimalGroups_Ostritch.jpg?w=1024)
Not all birds can fly. The ostrich is the largest bird in the world. Its wings are too weak to fly. It uses its strong legs to walk and run.