Question 20N.2.HL.TZ0.b
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.2.HL.TZ0.b |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Deduce | Question number | b | Adapted from | N/A |
White clover (Trifolium repens) is native to Eurasia but is now a common plant found worldwide in lawns, next to roads, in pastures and similar habitats.
[Source: © International Baccalaureate Organization 2020.]
Some T. repens plants are able to produce the toxin hydrogen cyanide (HCN) by cyanogenesis. A study at 128 sites (2509 plants) in Toronto (Canada) looked at the proportion of T. repens plants producing HCN. The sites were at regular intervals from the city centre towards rural areas.
[Source: Adapted from Thompson, K.A., Renaudin, M. and Johnson, M.T.J., 2016. Urbanization drives the
evolution of parallel clines in plant populations. Proceedings of the Royal Society B, [e-journal] 283.
https://doi.org/10.1098/rspb.2016.2180.]
To determine whether similar patterns in cyanogenesis were seen in other cities, studies were also carried out around New York City and Boston (USA) and Montreal (Canada).
[Source: Adapted from Thompson, K.A., Renaudin, M. and Johnson, M.T.J., 2016. Urbanization drives the
evolution of parallel clines in plant populations. Proceedings of the Royal Society B, [e-journal] 283.
https://doi.org/10.1098/rspb.2016.2180.]
Deduce whether the pattern of cyanogenesis was the same in all of the areas around all four cities.
[2]
a. Toronto, NYC and Boston show same pattern/all show positive correlation/relationship/WTTE;
b. Montreal shows negative correlation/negative relationship/WTTE so is different;
Here candidates were expected to state that the four cities did not all show the same pattern, as three have a positive correlation, but the fourth city (Montreal) has a weak negative correlation. A few failed to include Toronto among the cities with a positive correlation and instead singled it out for showing a stronger correlation than the others.
