DP Biology (first assessment 2025)

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Question 22N.2.SL.TZ0.c

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Date November 2022 Marks available [Maximum mark: 7] Reference code 22N.2.SL.TZ0.c
Level SL Paper 2 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
22N.2.SL.TZ0.c

Explain how a newly discovered plant species would be classified and named.

[7]

Markscheme

      Naming:

  1. binomial nomenclature / (plant is) given a binomial/double name;
  2. first name is the genus and second name is the species / genus initial upper case and species lower case;
  3. names (of plant species) are international/are universally understood/are published in journals;

    Classification:
  4. study the characteristics/structure/reproduction/chemical properties/DNA (of the plant);
  5. put/classify (the plant) in a group/genus with other similar species;
  6. natural classification corresponds with evolution / natural classification is based on many features;
  7. analogous features/features due to convergent evolution should not be used;
  8. hierarchy of groups/taxa (in traditional classification / 3 or more taxa in correct sequence (kingdom-phylum-class);
  9. two or more of bryophyta, filicinophyta, coniferophyta and angiospermophyta named;
  10. a clade is a group of organisms evolved from a common ancestor;
  11. base sequences/amino acid sequences used to group organisms into clades/deduce evolutionary relationships;
  12. cladograms show the relationships between clades/likely evolutionary divergence of clades;
  13. each branch point/node represents where species are formed via divergent evolution;
  14. species are now classified into a sequence of clades (rather than a rigid hierarchy of taxa);

Mpi accept common names, mosses, ferns etc.

Examiners report

There were a few G2 comments that part (c) on classification was above the level expected at Standard Level. This part was in common with Higher Level, but did only contain material from the Core (cladistics appears in section 5.4). There were a large number of marking points to score on. The naming was well known, as was classification into taxa and the different plant phyla. Some weaker students tried to go all the way back to eukaryotes and prokaryotes and animalia and plantae, giving far too much superfluous information. Good explanations of the use of clades were seen by better candidates.

Syllabus sections