Vertebrates come in five familiar groups. Young learners met them one at a time, starting with Mammals. Here we compare them by their body traits.
| Group | Covering | Breathes with | Body temperature | Examples |
|---|---|---|---|---|
| Fish | Scales (most) | Gills | Follows the water | Trout, shark |
| Amphibians | Smooth, moist skin | Gills when young, then lungs and skin | Follows surroundings | Frog, salamander |
| Reptiles | Dry scales | Lungs | Follows surroundings | Snake, turtle, lizard |
| Birds | Feathers | Lungs | Steady (they make heat) | Robin, penguin |
| Mammals | Hair or fur | Lungs | Steady (they make heat) | Dog, whale, bat |
Key idea
Body traits decide the group, not where an animal lives or how it moves: hair and milk for mammals, feathers for birds, gills and fins for fish, dry scales and lungs for reptiles, moist skin for amphibians.
Why it works
Traits like hair, milk and feathers are shared by every member of a group because they were inherited from a common ancestor. Swimming or flying is not: whales swim like fish and bats fly like birds, but their bodies show who their relatives are.
Worked examples
Worked example: A bat
Is a bat a bird?
- A bat has fur, not feathers.
- It feeds its young milk.
Answer: No. A bat is a mammal.
Worked example: A whale
Is a whale a fish?
- A whale breathes air with lungs and has no gills.
- It has a little hair and feeds its young milk.
Answer: No. A whale is a mammal.
Common mistake
Sorting by habitat (whales as fish) or by flight (bats as birds). Check the body: hair and milk mean mammal; feathers mean bird; gills and fins mean fish.