Question 21N.2.HL.TZ0.1e
| Date | November 2021 | Marks available | [Maximum mark: 3] | Reference code | 21N.2.HL.TZ0.1e |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Describe | Question number | e | Adapted from | N/A |
In a larger study, California grassland was exposed to elevated temperature and nitrate concentration for five years. The graph shows the total biomass production in individual and in combined treatments. Error bars denote one standard error.
[Source: adapted from Dukes, J.S., Chiariello, N.R., Cleland, E.E., Moore, L.A., Shaw, M.R., Thayer,S., Tobeck, T.,
Mooney, H.A. and Field, C.B., 2005. PLOS Biology, 3(10), e319. https://doi.org/10.1371/journal.pbio.0030319.]
Describe the effects of temperature and nitrate concentration on biomass.
[3]
a. increased temperature raises biomass;
b. increased nitrate raises biomass more than increased temperature;
c. increased nitrate and temperature raises biomass by same amount as nitrate alone;
This was another question where many candidates’ answers lacked discernment. The increase in biomass with nitrate was clearly greater than that with temperature alone, but the increase with nitrate and temperature combined was not significantly different from nitrate alone. A useful way of thinking about answering questions such as this is ‘If I read out my answer to someone over the phone, would they correctly sketch the relative size of the bars without seeing the actual bar chart?’ With many candidates the answer to this would have been no.
