Animals and their groups

There are millions of kinds of animals. Animals with a backbone (vertebrates) are sorted into five groups: fish, amphibians, reptiles, birds and mammals. We can also sort animals by what they eat: carnivores eat meat, herbivores eat plants, and omnivores eat both.

Key facts

  • Fish live in water, breathe with gills, have scales and fins, and most lay eggs.
  • Amphibians, like frogs and newts, have smooth, moist skin. They start life in water and many live on land as adults. They lay their eggs in water.
  • Reptiles, like snakes, lizards, crocodiles and tortoises, have dry, scaly skin. Most lay eggs with leathery shells on land.
  • Birds have feathers, wings and a beak, and lay eggs with hard shells. Most birds fly, but some can’t, like penguins and ostriches.
  • Mammals have hair or fur and feed their babies on milk. Most give birth to live young. Humans, whales and bats are mammals.
  • Carnivores eat other animals, herbivores eat only plants, and omnivores eat both plants and animals.
  • Animals without a backbone are invertebrates: insects have 6 legs and spiders have 8.

Worked examples

Example 1

Which group does each animal belong to: a shark, a frog, a snake, an owl, a rabbit?

  1. A shark has gills, fins and scales and lives in water: a fish.
  2. A frog has smooth, moist skin and lays its eggs in water: an amphibian.
  3. A snake has dry, scaly skin: a reptile.
  4. An owl has feathers and a beak: a bird.
  5. A rabbit has fur and feeds its babies on milk: a mammal.

Answer: shark: fish; frog: amphibian; snake: reptile; owl: bird; rabbit: mammal

Example 2

A rabbit eats grass, an owl eats mice, and a bear eats berries, fish and honey. Is each one a carnivore, a herbivore or an omnivore?

  1. The rabbit eats only plants: a herbivore.
  2. The owl eats only other animals: a carnivore.
  3. The bear eats plants (berries) and animals (fish): an omnivore.

Answer: rabbit: herbivore; owl: carnivore; bear: omnivore

Example 3

A whale lives in the sea and has fins. Is it a fish?

  1. Fish breathe with gills. A whale comes up to breathe air with lungs.
  2. Fish lay eggs. A whale gives birth to live young.
  3. A whale feeds its baby on milk, like every mammal. So a whale is a mammal, not a fish.

Answer: no, it is a mammal: it breathes air with lungs, feeds its young on milk and gives birth to live young

Example 4

How many legs do 3 spiders have?

  1. A spider has 8 legs. Add 8 for each spider.
  2. 8, 16, 24.

Answer: 24