Scientists sort animals into groups by what they have in common. Animals with a backbone are vertebrates. There are five main groups of vertebrates: mammals have hair and feed their young milk; birds have feathers and lay hard-shelled eggs; fish have scales and gills; reptiles have dry scales; amphibians have smooth damp skin and live on land and in water.
Animals without a backbone are invertebrates. Insects have six legs and three body parts. Spiders have eight legs. Worms, snails and jellyfish are invertebrates too. In fact most animals on Earth are invertebrates.
Worked example
A whale lives in the sea and has a blowhole. Is it a fish or a mammal?
- Check the clues: whales breathe air with lungs.
- They give birth to live young and feed them milk.
Answer:So a whale is a mammal, not a fish.
Key words
- vertebrate
- an animal with a backbone
- invertebrate
- an animal without a backbone
- mammal
- has hair and feeds its young milk
- amphibian
- lives on land and in water, with damp skin
Practise this
New questions every time.
NGSS-referenced: 3-LS4-2