Taxonomy & Classification
Level 2 — Recall (definitions, standard textbook items, short reasoning) Time limit: 30 minutes Total marks: 40
Instructions: Answer all questions. Marks are shown in brackets. Write biological terms precisely; spelling of taxonomic names matters.
Q1. State two reasons why biologists classify living organisms. [2]
Q2. Define binomial nomenclature. Using the human species Homo sapiens as an example, state which word is the genus and which is the species (specific epithet). [3]
Q3. The taxonomic hierarchy runs from the broadest to the narrowest rank. Write the eight ranks in the correct order from domain down to species. [4]
Q4. Name the three domains in the three-domain system of classification. [3]
Q5. Copy and complete the table by giving one correct entry for each blank. [6]
| Kingdom | Cell type (pro/eukaryotic) | Nutrition (auto/heterotrophic) |
|---|---|---|
| Plantae | (a) | (b) |
| Fungi | (c) | (d) |
| Animalia | (e) | (f) |
Q6. State three features that distinguish domain Archaea from domain Bacteria. [3]
Q7. Give one distinguishing main feature for each of the following eukaryotic kingdoms: (a) Protista (b) Fungi (c) Plantae (d) Animalia. [4]
Q8. Explain what a dichotomous key is and state what the word "dichotomous" refers to about the choices at each step. [3]
Q9. Below is a simple dichotomous key for four organisms.
1a. Has feathers .......................... go to 2
1b. No feathers .......................... go to 3
2a. Cannot fly ........................... Ostrich
2b. Can fly .............................. Sparrow
3a. Has scales ........................... Snake
3b. No scales, has fur ................... Rabbit
Using the key, identify the organism that: has no feathers, no scales, and has fur. Show the steps you followed. [3]
Q10. Explain how molecular phylogenetics is used in classification, and name one type of molecule commonly compared between organisms. [3]
Q11. State the correct written conventions for a scientific name (give two rules). [3]
End of paper
Answer keyMark scheme & solutions
Q1. [2] — Any two (1 mark each):
- To organise the huge diversity of life into manageable, ordered groups.
- To show evolutionary relationships / common ancestry between organisms.
- To allow a universal naming system so scientists worldwide communicate clearly.
- To aid identification of organisms and prediction of shared characteristics.
Why: classification's purpose is order, communication and reflecting phylogeny.
Q2. [3]
- Binomial nomenclature = a two-word naming system giving each species a unique scientific name consisting of genus + specific epithet (1).
- Genus = Homo (1).
- Species/specific epithet = sapiens (1).
Why: "binomial" = two names; genus first (capitalised), epithet second.
Q3. [4] — Correct order (deduct marks per error; full 4 for all eight correctly ordered): Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.
- 4 marks all correct; 3 marks one slip; 2 marks two slips; etc.
Q4. [3] — 1 mark each: Archaea, Bacteria, Eukarya.
Q5. [6] — 1 mark each cell:
| Kingdom | Cell type | Nutrition |
|---|---|---|
| Plantae | (a) eukaryotic | (b) autotrophic |
| Fungi | (c) eukaryotic | (d) heterotrophic |
| Animalia | (e) eukaryotic | (f) heterotrophic |
Why: all three are eukaryotic; plants photosynthesise (auto), fungi absorb/animals ingest (hetero).
Q6. [3] — Any three (1 each):
- Archaea have membrane lipids with branched (ether-linked) chains; Bacteria have unbranched (ester-linked) lipids.
- Archaeal cell walls lack peptidoglycan; bacterial walls contain peptidoglycan.
- Archaea often live in extreme environments (extremophiles); many bacteria in moderate conditions.
- Differences in rRNA/gene sequences and some RNA-polymerase/histone features (Archaea share some traits with Eukarya).
Q7. [4] — 1 mark each:
- (a) Protista: mostly unicellular eukaryotes (a diverse "catch-all" group).
- (b) Fungi: eukaryotic, heterotrophic by absorption, cell walls of chitin.
- (c) Plantae: multicellular, autotrophic (photosynthesis), cellulose cell walls.
- (d) Animalia: multicellular, heterotrophic by ingestion, no cell walls.
Q8. [3]
- A dichotomous key is an identification tool that leads the user through a series of paired statements about characteristics (1).
- At each step you choose between two alternatives, directing you to the next step or a final identification (1).
- "Dichotomous" means each step offers two (a pair of) contrasting choices (1).
Q9. [3]
- Step 1: no feathers → 1b → go to 3 (1).
- Step 2: no scales, has fur → 3b (1).
- Identification: Rabbit (1).
Q10. [3]
- Molecular phylogenetics compares sequences of molecules (DNA, RNA or proteins) between species (1).
- The degree of similarity/difference in sequence indicates how closely related organisms are and how recently they shared a common ancestor — used to build phylogenetic trees and refine classification (1).
- Example molecule: DNA / rRNA (ribosomal RNA) / a protein such as cytochrome c (1).
Q11. [3] — Any two rules (1½ each, or 1+1+1 for three):
- Genus name capitalised, species name lowercase.
- Both words italicised (or underlined when handwritten).
- Genus written first; may be abbreviated to initial after first use (e.g. H. sapiens).
[
{"claim":"Taxonomic hierarchy has 8 ranks from domain to species",
"code":"ranks=['Domain','Kingdom','Phylum','Class','Order','Family','Genus','Species']; result=(len(ranks)==8 and ranks[0]=='Domain' and ranks[-1]=='Species')"},
{"claim":"Three-domain system names Archaea, Bacteria, Eukarya",
"code":"domains={'Archaea','Bacteria','Eukarya'}; result=(len(domains)==3)"},
{"claim":"Q9 key path for no-feathers/no-scales/fur leads to Rabbit",
"code":"feathers=False; scales=False; fur=True; step='1b' if not feathers else '1a'; ident='Rabbit' if (step=='1b' and not scales and fur) else None; result=(ident=='Rabbit')"},
{"claim":"Q5 all three kingdoms are eukaryotic",
"code":"cells={'Plantae':'eukaryotic','Fungi':'eukaryotic','Animalia':'eukaryotic'}; result=(all(v=='eukaryotic' for v in cells.values()))"}
]