Question 21M.2.SL.TZ1.b
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.SL.TZ1.b |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | b | Adapted from | N/A |
The image shows the wings of an insect, bird and bat.
[Source: [insect wing] Halvard Hatlen https://upload.wikimedia.org/wikipedia/commons/0/0f/Dip-trichoceridae-wing.png. [bird wing] University of Maryland, Department of Geology. [bat wing] University of Maryland, Department of Geology.]
Explain how cladistics can be used to investigate evolutionary relationships.
[2]
a. (cladistics) shows evolutionary relationships through a common ancestor ✔
b. cladistics uses DNA/protein/derived/shared anatomical characteristics/traits ✔
c. time of divergence is related to the number of differences in DNA (base sequence) / protein (sequence of amino acids) ✔
d. homologous (versus analogous) traits are used to place an organism in a clade ✔
e. more shared characteristics mean a more recent common ancestor ✔
Candidates found it hard to express themselves without contradiction.
Carrying examples into part (b) made for the most successful answers. Very few gained marks for providing answers that included molecular level cladistic evidence, e.g. DNA, protein sequencing, etc.
