Learning focus
Develop accurate biological vocabulary, explain structure–function relationships, apply ideas to unfamiliar contexts, and use practical evidence.
Animal kingdom
Animals are multicellular eukaryotes. Their cells have no cellulose walls or chloroplasts. Animals obtain organic nutrients by feeding on other organisms or their products, and many show rapid movement and nervous coordination. They commonly store carbohydrate as glycogen.
Plant and fungus kingdoms
Plants are multicellular eukaryotes with cellulose cell walls and chloroplasts in photosynthetic tissues. They make carbohydrates by photosynthesis. Fungi are eukaryotic but do not photosynthesise. Their body often consists of hyphae forming a mycelium, and they obtain nutrients by secreting enzymes onto food and absorbing soluble products.
Protoctists and prokaryotes
Protoctists are mostly single-celled eukaryotes and are diverse. Some, such as algae, photosynthesise; others feed on organic material. Prokaryotes are bacteria: single-celled organisms without a nucleus. Their DNA is circular and lies free in the cytoplasm.
Viruses
Viruses are not placed in the five kingdoms because they are not cells and do not independently perform all life processes. A virus contains genetic material surrounded by a protein coat. It has no cytoplasm, ribosomes or independent metabolism. It can replicate only after entering a living host cell and using the host’s machinery.
Avoiding overgeneralisation
A kingdom description should use several features. ‘Plants are green’ is weak because non-green plant tissues exist. ‘Fungi are plants without chlorophyll’ is incorrect because fungi differ fundamentally in cell-wall composition, nutrition and organisation. Classification depends on a combination of defining characteristics.
Practical or data skill
Use a feature table to classify unfamiliar organisms into kingdoms. Mark whether a nucleus, cell wall, chloroplast, hypha, multicellular body and saprotrophic nutrition are present.
Examination tip
A virus is not a bacterium. Antibiotics target bacterial structures or processes and do not treat viral infections.
Review questions and suggested answers
Question 1
Why are viruses not placed in the five kingdoms?
Suggested answer
They are not cellular and can replicate only inside living host cells.
Question 2
State one difference between a fungus and a plant.
Suggested answer
A fungus does not photosynthesise and obtains nutrients by absorption; a plant usually photosynthesises.
Question 3
Which kingdom contains bacteria?
Suggested answer
The prokaryote kingdom.
