Question 22N.2.HL.TZ0.1f
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.2.HL.TZ0.1f |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Suggest | Question number | f | Adapted from | N/A |
Common shrews (Sorex araneus) are small mammals found in Northern Europe. Their diet includes insects, slugs, spiders, worms and amphibians. They do not hibernate in winter because their bodies are too small to store sufficient fat reserves.
[Source: [Shrew], n.d. [image online] Available at: https://www.pxfuel.com/en/free-photo-jslkw [Accessed 29 October 2021].]
To study brain size in shrews, researchers anesthetize them, X-ray their skulls and measure the height of the braincase (BCH) where the brain is located. The graph shows the relationship between BCH and the brain mass of individual adult shrews.
[Source: adapted from Lá zaro, J., Hertel, M., LaPoint, S., Wikelski, M., Stiehler, M. and Dechmann, D.K.N., 2018.
Journal of Experimental Biology 221. http://doi.org/10.1242/jeb.166595.]
The researchers found that the BCH of any individual adult shrew could vary seasonally. They collected shrews at different times of the year. The BCH of each shrew was compared with its body mass. The results are displayed in the chart.
[Source: adapted from Schaeffer, P.J., O’Mara, M.T., Breiholz, J., Keicher, L., Lázaro, J., Muturi, M.,
Dechmann, D.K.N., 2020. R. Soc. Open Sci. 7. http://dx.doi.org/10.1098/rsos.191989.]
Suggest a reason for the difference in BCH in summer and winter.
[1]
- large brain (indicated by large BCH) requires/uses much energy;
- shrews need/use much energy in winter (other than for the brain);
- much energy used in winter for keeping warm/searching for food;
- food/energy more abundant in summer/less abundant in winter;
- growth between winter and summer (so BCH larger in summer);
Do not accept hibernation/lower metabolic rate/lower body temperature/lower activity levels/less food eaten in winter. Do not accept answers about body mass.
The mark allocation here was rather low, as a proper explanation of the difference between BCH in winter and summer required several linked ideas. Any one of a number of important elements of an explanation was accepted, making it relatively easy to score the mark.
