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A2 · Practice questions · Species, domains and kingdoms

Domain, kingdom, species.

Six original Cambridge-style questions on classification, from defining a species to placing viruses by their nucleic acid.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Define, divide, rank.

01
Explain
[3 marks]

Discuss the meaning of the term species, comparing the biological and morphological species concepts.

  • Biological: a group of organisms that can interbreed to produce fertile offspring and is reproductively isolated from other groups. ✓
  • Morphological: a group of organisms sharing the same observable physical / anatomical features; can be used for fossils and asexual organisms. ✓
  • Limitation of biological: cannot be applied to fossils, asexual organisms or populations that never meet; limitation of morphological: look-alike species, or great variation within one species (for example male and female). ✓
02
Recall
[3 marks]

State three differences between organisms in the domain Archaea and organisms in the domain Bacteria.

  • Membrane lipids: Archaea have branched chains joined by ether bonds; Bacteria have unbranched fatty acids joined by ester bonds. ✓
  • Ribosomal RNA: the base sequences of rRNA differ (archaeal rRNA is more similar to eukaryotic rRNA). ✓
  • Cell walls: Bacteria contain peptidoglycan; Archaea do not. ✓
03
Recall
[2 marks]

The bottlenose dolphin is Tursiops truncatus. It is in the family Delphinidae, the order Cetacea and the class Mammalia. Name the two ranks above class in its classification, and the rank shown by Tursiops.

  • Above class: phylum (Chordata), then kingdom (Animalia); the domain is Eukarya. ✓
  • Tursiops is the genus. ✓
04
Analysis
[3 marks]

An organism is multicellular, has cell walls, no chloroplasts, stores glycogen and is made of thread-like structures. Identify its kingdom and explain how two of these features rule out the kingdoms Plantae and Animalia.

  • Kingdom Fungi (hyphae / mycelium). ✓
  • It has cell walls, so it is not in Animalia (animal cells have no cell walls). ✓
  • It has no chloroplasts and stores glycogen rather than starch, so it is not in Plantae. ✓
05
Explain
[2 marks]

Explain why viruses are not classified into one of the three domains, and outline how they are classified.

  • Viruses are not cells: they have no cytoplasm, ribosomes or metabolism of their own, so they do not fit any domain of cellular life. ✓
  • They are classified by their nucleic acid: DNA or RNA, and whether it is single-stranded or double-stranded (for example HIV has single-stranded RNA). ✓
06
Recall
[3 marks]

Outline the characteristic features of the kingdom Protoctista and give two examples.

  • Eukaryotic organisms that do not fit into Fungi, Plantae or Animalia. ✓
  • Mostly unicellular, some multicellular (for example seaweeds), with no differentiated tissues; some photosynthesise, others are heterotrophic. ✓
  • Examples: Amoeba, Plasmodium, Paramecium, algae such as Chlorella. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.