Question 22M.2.HL.TZ1.e
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.HL.TZ1.e |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Estimate | Question number | e | Adapted from | N/A |
In winter when temperatures drop, brown bears (Ursus arctos) enter a cave and hibernate. The graph shows the mean values for the body temperature, heart rate and activity of 14 brown bears throughout the year. The grey shaded areas indicate the periods when the bears are in transition between hibernation and normal activity.
[Source: Adapted from Evans, A.L., Singh, N.J., Friebe, A., Arnemo, J.M., Laske, T.G., Fröbert, O., Swenson, J.E. and Blanc,
S., 2016. Drivers of hibernation in the brown bear. Frontiers in Zoology, 13(7). This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).]
It was observed that during hibernation bears are not susceptible to osteoporosis, a condition characterized by a decrease in the density of bone, resulting in porous and fragile bones. This condition may develop in humans during long periods of inactivity and with increasing age. The graph shows the porosity of the tibia bones of black bears (Ursus americanus) and humans at different ages. Age is expressed as the proportion of normal life span.
[Source: Adapted from Journal of Biomechanics, 39(8), Donahue, S.W., McGee, M.E., Harvey, K.B.,
Vaughan, M.R. and Robbins, T., Hibernating bears as a model for preventing disuse osteoporosis,
pp. 1480–1488. Copyright (2006), with permission from Elsevier.]
The life expectancy of a human at the time of the study was 80 years. Estimate the porosity of the bones of the individual who was approximately 32 years old.
[1]
6 %;
Accept answers in the range 6.0 to 6.5 %.
Percentage sign required.
This question was very unusual in that the discrimination index was negative — stronger candidates were slightly less likely to answer correctly than weaker candidates, for reasons that are not obvious! Only a minority gave the expected answer of 6 %. A very common answer was 7 %, which is reached by calculating the age proportion correctly as 0.4 but using the trend line rather than the data point for the individual who was 32 years old. Careful reading of the question was needed to avoid this mistake.
