There are millions of different species on the planet. Scientists try to group similar organisms together so that they are easier to identify. The groups start big and the organisms within have only a few similarities. As you move down the groups, they get smaller and the organisms have more features in common.

The biggest groups are called kingdoms. The five kingdoms are:

  • Animal
  • Plant
  • Fungi
  • single-celled organisms (Protoctists)
  • Bacteria

The Animal kingdom

The Animal kingdom can be further split into:

Vertebrates - animals with a backbone. These include amphibians, mammals, reptiles, bony fish and birds.

(Clockwise from top-left) A frog, a squirrel, a snake, clownfish.

(Clockwise from top-left): Red-eyed tree frog; Grey squirrel eating nuts; Python coiled up in to a perfect circle; Shoal of clown fish.

Invertebrates - animals without a backbone. These include molluscs, annelids, arthropods and nematodes.

(Clockwise from top-left) Clams, earthworm, a tarantula, Caenorhabditis elegans.

(Clockwise from top-left) Clams, earthworms, a tarantula, Caenorhabditis elegans.

The Plant kingdom

The Plant kingdom can be divided into:

Flowering plants produce flowers for reproduction, eg sunflowers and grass plants

Sunflowers and wheatplants.

Non-flowering plants reproduce using spores, eg ferns and mosses

Fern and moss.