Question 20N.2.HL.TZ0.a.i
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.2.HL.TZ0.a.i |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | State | Question number | a.i | 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.]
State the distance from the city centre at which the highest proportion of plants sampled contained HCN.
[1]
32 (km);
Accept answers in the range of 31 to 33 (km).
This was intended to be an easy first mark but only 70 % answered it correctly, with others mostly giving the maximum distance rather than the distance with the highest proportion of plants containing cyanide.
