OpenRevise

Exam questions · Biology · Evolution and Natural Selection

Classification and the Three Domains

  • 6 exam questions
  • 21 marks
  • 9 quick checks
  1. 1 Name [3 marks]

    Name the three domains of living things.

    Show answerHide answer

    Model answer

    Bacteria, Archaea and Eukaryota.

    Mark scheme

    • Bacteria — 1 mark
    • Archaea — 1 mark
    • Eukaryota — 1 mark
  2. 2 State [2 marks]

    State two kingdoms of living things that are in the domain Eukaryota.

    Show answerHide answer

    Model answer

    Any two from: animals, plants, fungi, protists.

    Mark scheme

    • First kingdom — 1 mark
    • Second kingdom — 1 mark
  3. 3 Describe [3 marks]

    Describe how Carl Woese used genetic analysis to suggest the three domain system.

    Show answerHide answer

    Model answer

    Woese compared the sequences of bases in the ribosomal RNA genes of many organisms. He found that the prokaryotes were not one group, because some, now called archaea, were very different from bacteria. This led him to propose three domains.

    Mark scheme

    • Compared gene sequences / rRNA — 1 mark
    • Found two very different types of prokaryote — 1 mark
    • Proposed three domains — 1 mark
  4. 4 Explain [3 marks]

    Explain why the use of genetic analysis changed the classification of living things.

    Show answerHide answer

    Model answer

    Genetic analysis gives information about how closely related organisms are, which cannot always be seen from their appearance. It showed that the prokaryotes were two groups that were as different from each other as from the eukaryotes. So the classification had to be changed.

    Mark scheme

    • Genes show how closely related organisms are — 1 mark
    • Appearance can be misleading — 1 mark
    • Showed prokaryotes are two different groups — 1 mark
  5. 5 Compare [4 marks]

    Compare the five kingdoms system and the three domains system of classification.

    Show answerHide answer

    Model answer

    The five kingdoms system was based mainly on the structure of organisms and the way they feed, whereas the three domains system is based on genetic analysis. In the five kingdoms system all the prokaryotes are in one kingdom, and in the three domains they are in two domains, Bacteria and Archaea. The eukaryotes are in the domain Eukaryota, which includes four of the kingdoms.

    Mark scheme

    • Structure and feeding / genetic analysis — 1 mark
    • Prokaryotes in one group / two domains — 1 mark
    • Five groups / three groups — 1 mark
    • Eukaryota includes four kingdoms — 1 mark
  6. 6 Evaluate [6 marks]

    Evaluate why scientists changed from the five kingdoms to the three domains system, and why this shows how scientific ideas develop.

    Show answerHide answer

    Model answer

    Woese used DNA sequencing to compare the genes of ribosomal RNA, a technique that was not available when the five kingdoms were developed. The results showed that archaea were as different from bacteria as they were from eukaryotes, which could not be seen from structure alone. This gave a more accurate picture of the evolutionary relationships. The idea was published and tested by other scientists, who found more evidence from other genes, so it became accepted. This shows that scientific ideas change when new technology gives new evidence, and that they are tested by others before they are accepted. Classification may change again as more genomes are sequenced.

    Mark scheme

    • DNA sequencing was new technology — 1 mark
    • Compared rRNA genes — 1 mark
    • Archaea very different from bacteria — 1 mark
    • More accurate relationships — 1 mark
    • Tested by other scientists — 1 mark
    • Ideas change with new evidence — 1 mark

Quick check

  1. 1

    How many kingdoms are there in the five kingdoms system?

    1. AFour
    2. BFive
    3. CThree
    4. DSix
    Show answerHide answer

    B: Five

    The five kingdoms are animals, plants, fungi, protists and prokaryotes.

  2. 2

    Which are the three domains?

    1. AAnimals, plants and fungi
    2. BProkaryotes, protists and fungi
    3. CBacteria, Archaea and Eukaryota
    4. DPlants, bacteria and viruses
    Show answerHide answer

    C: Bacteria, Archaea and Eukaryota

    Living things are placed in the domains Bacteria, Archaea and Eukaryota.

  3. 3

    Who proposed the three domain system?

    1. ACarl Woese
    2. BCharles Darwin
    3. CCarl Linnaeus
    4. DGregor Mendel
    Show answerHide answer

    A: Carl Woese

    Carl Woese proposed it in 1977, using genetic evidence.

  4. 4

    In which domain are animals and plants?

    1. ABacteria
    2. BArchaea
    3. CProkaryota
    4. DEukaryota
    Show answerHide answer

    D: Eukaryota

    Animals and plants have cells with a nucleus, so they are in Eukaryota.

  5. 5

    What evidence led to the three domain system?

    1. AFossils
    2. BGenetic analysis
    3. CMicroscope images only
    4. DStone tools
    Show answerHide answer

    B: Genetic analysis

    Comparing the base sequences of genes, such as those for ribosomal RNA, showed three main groups.

  6. 6

    Where are archaea often found?

    1. AOnly in the human gut
    2. BOnly in soil
    3. CIn extreme habitats, such as hot springs
    4. DOnly in the sea
    Show answerHide answer

    C: In extreme habitats, such as hot springs

    Many live in extreme environments such as hot springs, salt lakes and deep-sea vents.

  7. 7

    Which statement about archaea is correct?

    1. AThey have no nucleus and differ genetically from bacteria
    2. BThey have a nucleus
    3. CThey are the same as bacteria
    4. DThey are animals
    Show answerHide answer

    A: They have no nucleus and differ genetically from bacteria

    Archaea are prokaryotes with no nucleus, but they differ from bacteria in their genes and membranes.

  8. 8

    What is the binomial name for humans?

    1. AHomo erectus
    2. BHomo habilis
    3. CSapiens homo
    4. DHomo sapiens
    Show answerHide answer

    D: Homo sapiens

    The two-part name is Homo sapiens, with the genus first and the species second.

  9. 9

    Why can classification based on appearance be misleading?

    1. AOrganisms have no appearance
    2. BUnrelated organisms can look alike
    3. CGenes are always the same
    4. DAppearance is always accurate
    Show answerHide answer

    B: Unrelated organisms can look alike

    Unrelated organisms may look alike because of similar functions, and related ones may look different, so genes give a better guide to relationships.