DP Biology (first assessment 2025)

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Question 22N.2.HL.TZ0.8c

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Date November 2022 Marks available [Maximum mark: 7] Reference code 22N.2.HL.TZ0.8c
Level HL Paper 2 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
22N.2.HL.TZ0.8c
(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 uppercase 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);

For mpi, common names such as ‘mosses’ are acceptable.

Examiners report

A very wide range of ideas was credited with marks in this question. Most candidates knew that plants are either classified according to their observable traits or the base sequences of their DNA. Many answers also included the hierarchy of taxa used in traditional classification and traits of plant phyla. At least some features of binomial nomenclature were included in most answers. The best answers included changes to plant classification that have resulted from sequence analysis and cladistics.

Syllabus sections