Cambridge O Level Biology 5090: Classification (5090) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

This practice set covers Topic 2, Classification, of the Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028 (version 4). It tests every learning outcome in sections 2.1 Concept and use of a classification system and 2.2 Features of organisms. The 5090 syllabus is not tiered, so every question applies to all candidates. Short questions come first, then longer questions that combine several outcomes.

Learn the content first with the classification study guide and the classification revision notes. Course hub: /boards/cambridge/o-level/biology/. Topic checklist: /checklists/cambridge/o-level/biology/.

Questions

1. Frogs from two islands look slightly different. Scientists breed them together in a laboratory. The tadpoles grow into adults that mate and produce tadpoles of their own.

(a) Describe what is meant by a species. [2] (b) Explain whether the frogs from the two islands belong to the same species. [2]

2. Cabbage is Brassica oleracea, turnip is Brassica rapa and onion is Allium cepa.

(a) State which two of these plants are most closely related. Give a reason. [2] (b) A student writes the name of the cabbage by hand as “Brassica Oleracea”. State two corrections needed. [2]

3.

(a) State one feature present in all plant cells but absent from all fungal cells. [1] (b) Name the kingdom whose members have cells with no nucleus. [1]

4.

(a) State two differences between reptiles and amphibians. [2] (b) State one feature of fish that is not found in adult amphibians. [1]

5. The table describes four arthropods.

Arthropod	Body sections	Pairs of legs	Pairs of antennae
W	3	3	1
X	2	4	0
Y	2	5	2
Z	many similar segments	2 on each segment	1

(a) Name the arthropod group of each of W, X, Y and Z. [4] (b) State two features shared by all arthropods that are not shown in the table. [2]

6. Plant P has seeds with one cotyledon and leaves with parallel veins. Plant Q has no flowers and has leaves called fronds.

(a) State whether P is a monocotyledon or a dicotyledon. [1] (b) Predict the number of petals in a flower of P. [1] (c) Name the plant group of Q and state how Q reproduces. [2] (d) State one feature that places both P and Q in the plant kingdom. [1]

7.

(a) State the two main features of a virus. [2] (b) Explain why viruses can only replicate inside living cells. [2] (c) A student says that a virus is a type of prokaryote. Explain why this is incorrect. [2]

8. Use this dichotomous key to identify specimens A to D.

1 a  Has legs ................................ go to 2
  b  Has no legs ............................. go to 5
2 a  Three pairs of legs ..................... ant
  b  More than three pairs of legs ........... go to 3
3 a  Four pairs of legs ...................... mite
  b  More than four pairs of legs ............ go to 4
4 a  Two pairs of legs on most segments ...... millipede
  b  One pair of legs on each segment ........ woodlouse
5 a  Has a coiled shell ...................... snail
  b  No shell ................................ earthworm

Specimen A: no legs, no shell, body of ring-like segments. Specimen B: seven pairs of legs, one pair on each segment. Specimen C: four pairs of legs. Specimen D: three pairs of legs.

(a) Identify specimens A, B, C and D. [4] (b) Name the arthropod group that specimen C belongs to. [1]

9. The table describes four leaves.

Leaf	Divided into leaflets?	Veins	Edge
P	No	Parallel	Smooth
Q	Yes	Branching network	Toothed
R	No	Branching network	Toothed
S	No	Branching network	Smooth

(a) Construct a dichotomous key to identify the four leaves. [5] (b) State which leaf most likely comes from a monocotyledon. [1]

10. Three organisms are described.

• J is made of thread-like hyphae. Its cell walls are not made of cellulose and it has no chloroplasts. It secretes enzymes onto rotting fruit and absorbs the products.
• K is a single cell with a nucleus and chloroplasts. It swims using a flagellum.
• L is a single cell with a cell wall. It has circular DNA free in the cytoplasm and also has plasmids.

(a) Name the kingdom of each organism. For each, give one feature from the description that supports your answer. [6] (b) A student suggests placing J and L in the same group because both can feed on rotting fruit. Explain why this is not a useful basis for classification. [2]

11. The table describes five vertebrates.

Animal	Description
A	Fur on the body; external ears; feeds young on milk; front limbs are wings
B	Dry skin with scales; lays leathery-shelled eggs on land
C	Feathers; beak; cannot fly
D	Wet scales; fins; gills; lateral line
E	Moist skin with no scales; young live in water and have gills

(a) Classify each animal into its vertebrate group. [5] (b) Explain why animal A is classified as a mammal and not a bird, even though it has wings. [2]

Answers

1. (a) A group of organisms that can reproduce [1] to produce fertile offspring [1]. (b) The island frogs produced offspring that were themselves able to reproduce [1], so the offspring are fertile and the frogs are the same species [1]. Examiner insight: “Fertile” is the creditworthy word in both parts; an answer that only says the frogs “can breed” scores the first mark at most.

2. (a) Cabbage and turnip [1]; they share the same genus, Brassica [1]. (b) The species name should start with a lower-case letter: oleracea [1]. The handwritten name should be underlined [1]. Examiner insight: The reason in (a) must name the genus; “they have the same first name” without the term genus may not be credited.

3. (a) A cellulose cell wall [1]. (b) Prokaryote [1]. Examiner insight: Chloroplasts are not accepted in (a) because many plant cells, such as root cells, have none; “all plant cells” rules them out.

4. (a) Reptiles have dry, scaly skin; amphibians have moist skin with no scales [1]. Reptiles lay eggs with rubbery or leathery shells on land; amphibians lay soft eggs without shells in water [1]. (b) Any one: fins / scales / lateral line [1]. Examiner insight: A difference needs both sides stated; “reptiles have scales” alone does not show the contrast and may not earn the mark.

5. (a) W insect [1]; X arachnid [1]; Y crustacean [1]; Z myriapod [1]. (b) Jointed legs [1]; an exoskeleton [1]. (Also accept: a segmented body.) Examiner insight: In (b) the question says “not shown in the table”, so repeating numbers of legs or antennae earns nothing; read the stem carefully.

6. (a) Monocotyledon [1]. (b) Three, or a multiple of three (such as six) [1]. (c) Fern [1]; it reproduces by spores [1]. (d) Cellulose cell walls / chloroplasts so it can photosynthesise [1]. Examiner insight: “Q reproduces asexually” is not enough for (c); the syllabus feature is spores, and the answer must name them.

7. (a) A protein coat [1]; genetic material (DNA or RNA) [1]. (b) A virus is not a cell and has no structures to make copies of itself [1]; it must enter a living host cell and use the cell’s materials to make new viruses [1]. (c) A prokaryote is a cell, with cytoplasm, a cell membrane, ribosomes and a cell wall [1]; a virus has only a protein coat around genetic material, so it is not a cell and belongs to no kingdom [1]. Examiner insight: For (c), two separate points are needed for two marks: what a prokaryote has, and what a virus lacks.

8. (a) A earthworm [1]; B woodlouse [1]; C mite [1]; D ant [1]. (b) Arachnids [1]. Examiner insight: Spelling of names taken from a key is usually tolerated, but a name not in the key, such as “spider” for C, scores zero.

9. (a) One correct key:

1 a  Leaf divided into leaflets ............ Q
  b  Leaf not divided ...................... go to 2
2 a  Parallel veins ........................ P
  b  Branching network of veins ............ go to 3
3 a  Toothed edge .......................... R
  b  Smooth edge ........................... S

Couplet 1 uses one feature with two opposite statements [1]. Couplet 2 uses one feature with two opposite statements [1]. Couplet 3 uses one feature with two opposite statements [1]. Three couplets in total, one fewer than the number of leaves [1]. Each leaf ends at its own letter and none appears twice [1]. (b) P [1], because it has parallel veins. Examiner insight: Other valid keys score full marks; marks are lost when a couplet mixes features, such as “has leaflets” against “smooth edge”.

10. (a) J Fungus [1]; hyphae / cell walls not made of cellulose / no chloroplasts with enzymes secreted and products absorbed [1]. K Protoctist [1]; single-celled but has a nucleus (and chloroplasts) [1]. L Prokaryote [1]; no nucleus, with circular DNA free in the cytoplasm / plasmids [1]. (b) Organisms are classified by features they share, such as cell structure [1]; J has a nucleus and L does not, so they share few features even though they feed in the same place [1]. Examiner insight: The supporting feature must come from the description and match the kingdom; “K is green” or “L is small” earns no credit.

11. (a) A mammal [1]; B reptile [1]; C bird [1]; D fish [1]; E amphibian [1]. (b) A has fur and external ears / feeds its young on milk, which are mammal features [1]; it has no feathers or beak, which every bird has [1]. Examiner insight: Wings are not a defining feature on their own; credit goes to the features the syllabus lists for each group.

Where marks are usually lost

• Writing “can interbreed” for a species with no mention of fertile offspring.
• Writing binomial names with a capital letter on the species name, or not underlining them by hand.
• Building a key with a couplet that compares two different features, or leaving an organism without its own end point.
• Using colour, size or where an organism lives as a key feature.
• Giving chloroplasts as a feature of all plant cells, when root cells have none.
• Saying prokaryotes lack DNA; they lack a nucleus.
• Counting arthropod legs as individual legs when the table gives pairs, or the reverse.
• Giving one-sided differences (“reptiles have scales”) instead of a clear contrast.
• Describing a virus as a cell or as a bacterium.
• Naming an organism not listed in the key you were given.

Next steps

• Classification revision notes
• Classification study guide
• Cell structure and organisation, for the cell features behind the kingdoms
• Cambridge O Level Biology hub
• Printable topic checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028, version 4, published by Cambridge International (Cambridge Assessment International Education). Topic 2: Classification, sections 2.1 and 2.2.