Taxonomy & Classification

Question 1 (8 marks)

(a) Any three (1 each):

• Organises the enormous diversity of life into manageable groups.
• Provides a universal system so scientists worldwide communicate unambiguously.
• Reveals evolutionary relationships / shows how organisms are related.
• Enables identification of unknown organisms.
• Allows predictions about shared characteristics. (3)

(b) (3)

• Common names vary by language and region, so the same organism has many names / one name may refer to different organisms (2 marks: any two problems). Why: ambiguity breaks scientific communication.
• Example (1): "robin" refers to different birds in Europe vs North America; or a "buttercup" varies by locality.

(c) (2) Predictive means: once an organism is placed in a group, you can predict it shares characteristics common to that group (e.g. knowing an animal is a mammal predicts it has hair and mammary glands) — because members share common ancestry.

Question 2 (9 marks)

(a) Rules (1 each, max 4):

• Two-part name: genus + species epithet.
• Genus capitalised, species epithet lowercase.
• Whole name italicised (or underlined if handwritten).
• Derived from Latin/Greek (a "dead" universal language).
• After first use, genus may be abbreviated (F. catus).

(b) (3)

• Genus = Felis; species epithet = catus. (1)
• Genus tells you the broader group of closely related species. (1)
• Species epithet, combined with genus, identifies the exact single species. (1)

(c) (2)

• Errors: genus not capitalised ("felis" → "Felis"); epithet wrongly capitalised ("Catus" → "catus"); not italicised/underlined. (1)
• Corrected: Felis catus. (1)

Question 3 (10 marks)

(a) (4, ½ each rounded — full 4 for all correct in order) Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

(b) (2) Any valid mnemonic mapping each initial letter D-K-P-C-O-F-G-S, e.g. "Dear King Philip Came Over For Good Soup." (1 for mnemonic, 1 for correct mapping shown).

(c) (4, ½ each)

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Primates
• Family: Hominidae
• Genus: Homo
• Species: Homo sapiens (epithet sapiens)

Question 4 (10 marks)

(a) (4)

• Domains: Bacteria, Archaea, Eukarya (1).
• Key evidence: ribosomal RNA (16S/18S rRNA) sequence comparison by Carl Woese showed Archaea are genetically as distinct from Bacteria as from Eukarya (2). Archaea also differ in membrane lipids and cell-wall chemistry (1).

(b) (4 — 1 per correct row/column set)

(c) (2, ⅓ each)

• Bacteria (Eubacteria) → Domain Bacteria
• Archaea (Archaebacteria) → Domain Archaea
• Protista, Fungi, Plantae, Animalia → Domain Eukarya

Question 5 (8 marks)

(a) (5) One valid key (award for correct branching logic that separates all four):

1a. Has feathers ........................... Sparrow
1b. No feathers ........................... go to 2
2a. Lives in water / has fins ............. Salmon
2b. Lives (mainly) on land ................ go to 3
3a. Has four legs ......................... Frog
3b. No legs (legless) ..................... Snake

(5 marks: 1 per correct couplet ×3 = 3, plus 2 for all four organisms correctly identified.)

(b) (3)

• "Dichotomous" = dividing into two (branching into two choices at each step) (1).
• Rule: each couplet must present two mutually exclusive alternatives (2) — the two statements must contradict so exactly one applies to any organism.

Question 6 (5 marks)

(a) (3)

• Mutations accumulate in DNA/rRNA over time at a roughly steady rate (1).
• The more differences between two species' sequences, the longer ago they diverged from a common ancestor (1).
• Sequences are aligned and differences counted to build a phylogenetic tree showing branching order/relatedness (1).

(b) (2) Physical similarity can arise from convergent evolution (unrelated organisms adapting similarly), which is misleading; DNA reflects true ancestry, so molecular data reveals relationships appearance hides (e.g. reclassification based on genes).

[
  {"claim":"Taxonomic hierarchy has exactly 8 named ranks", "code":"ranks=['Domain','Kingdom','Phylum','Class','Order','Family','Genus','Species']; result = (len(ranks)==8)"},
  {"claim":"Mnemonic 'Dear King Philip Came Over For Good Soup' maps correctly to rank initials", "code":"ranks=['Domain','Kingdom','Phylum','Class','Order','Family','Genus','Species']; mnem='Dear King Philip Came Over For Good Soup'.split(); result = [w[0] for w in mnem]==[r[0] for r in ranks]"},
  {"claim":"Three domains count is 3 and six kingdoms count is 6", "code":"domains=['Bacteria','Archaea','Eukarya']; kingdoms=['Bacteria','Archaea','Protista','Fungi','Plantae','Animalia']; result = (len(domains)==3 and len(kingdoms)==6)"},
  {"claim":"Dichotomous key of 4 organisms needs 3 couplets", "code":"n=4; couplets=n-1; result = (couplets==3)"}
]