The five kingdoms

Characteristics and classification of living organisms · Features of organisms · note 3 of 5

Spec 1.3.4, 1.3.6

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The five kingdomsSpec 1.3.4, 1.3.6

In short

The five kingdoms are animal, plant, fungus, prokaryote and protoctist. Fungi have cell walls made of chitin, have no chloroplasts and feed by absorbing nutrients. Prokaryotes, such as bacteria, are single-celled with no nucleus. Protoctists are mostly single-celled organisms with a nucleus; some have chloroplasts like plants, and others feed like animals.

All organisms can be placed in one of five kingdoms: animal, plant, fungus, prokaryote and protoctist. The animal and plant features are in the table in the previous section. The other three kingdoms have these main features.

Main features of fungi, prokaryotes and protoctists
Kingdom	Main features	Example
Fungus	Cell walls made of chitin; no chloroplasts, so they cannot photosynthesise; feed by absorbing nutrients from dead or living organisms; body usually made of threads called hyphae (yeast is single-celled); store glycogen; reproduce with spores	Mucor, yeast
Prokaryote	Single-celled; no nucleus (a circular DNA molecule lies free in the cytoplasm, and there may be plasmids); cell wall that is not made of cellulose	Bacteria
Protoctist	Mostly single-celled microscopic organisms with a nucleus; some have chloroplasts like plants, others feed like animals	Amoeba, Chlorella

Comparison chart of the five kingdoms (animal, plant, fungus, prokaryote, protoctist) showing number of cells, nucleus, cell wall, chloroplasts and how each feeds. — The five kingdoms compared. Check nucleus and cell wall first.

Classify an organism by working through the features. Single-celled with no nucleus means prokaryote. Chitin cell walls and no chloroplasts means fungus, even when single-celled like yeast. Single-celled with a nucleus but without chitin walls means protoctist.

Common mistake:

Fungi are not plants. They have chitin walls, no chloroplasts, and they absorb nutrients from their surroundings instead of making food by photosynthesis.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

Frequently asked questions

How do you tell a plant from an animal in classification?

Plants have cellulose cell walls and chloroplasts and make their own food by photosynthesis; animals have no cell walls or chloroplasts and feed on other organisms. Both are multicellular. Plants store carbohydrate as starch and animals store glycogen, and animals usually have a nervous system while plants do not.

What is the difference between insects and arachnids?

Insects have a body in three parts (head, thorax and abdomen), three pairs of legs, one pair of antennae and usually two pairs of wings. Arachnids, such as spiders, have a body in two parts (cephalothorax and abdomen), four pairs of legs and no antennae or wings. Both are arthropods with jointed legs.

How do you tell reptiles and amphibians apart?

Reptiles have dry skin covered with scales and lay eggs with soft, leathery shells, and most live on land. Amphibians have moist, smooth skin without scales and lay jelly-covered eggs in water. Amphibian larvae, called tadpoles, live in water, while the adults often live on land.

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