Question 19M.2.HL.TZ2.4b
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.HL.TZ2.4b |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | b | Adapted from | N/A |
Some plant families, such as the figwort family, have been reclassified on the basis of evidence from cladistics. Explain the methods that have been used recently to reclassify groups of plants.
[3]
a. «previous» classification used to be based on the appearance/structures of the plant/leaves/flowers/seeds/analogy/phenotype ✔
b. «modern cladistics uses» RNA/DNA nucleotide/base sequencing/amino acid sequencing/homology ✔
c. DNA mutation occurs at a relatively constant rate allowing estimation of when species diverged ✔
d. a shared/common derived characteristic places organisms in the same clade ✔
e. the number of changes in sequences indicates distance from common ancestor
OR
the fewer the differences «in sequences» means the closer the relationship ✔
Many students were able to identify molecular sequencing as a method used to re-classify plants. Fewer were clear on the notion of original classification being mistakenly based on analogous features.
