Date | November 2020 | Marks available | 1 | Reference code | 20N.3.sl.TZ0.8 |
Level | SL | Paper | 3 | Time zone | TZ0 |
Command term | Suggest and Justify | Question number | 8 | Adapted from | N/A |
Question
Biomagnification factor, BMF, can be defined as the concentration of a chemical, , in a predator, relative to the concentration found in its prey.
BMF, where ( per body weight)
[Franklin, J., 2015. How reliable are field-derived biomagnification factors and trophic magnification factors as indicators of bioaccumulation potential? Conclusions from a case study on per- and polyfluoroalkyl substances. Available at: https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.1642.] |
Calculate the BMF if a shark consumes mackerel in one year. Each mackerel weighs on average. The per body weight. Assume chemical remains in the shark’s body for two years.
Suggest, with a reason, if fat-soluble or water-soluble xenobiotics would have a larger BMF.
Markscheme
✔
✔
Award [2] for correct final answer.
M2 may also be correctly expressed to SF.
fat-soluble AND pass through lipid membranes/accumulate in cells/fatty tissues
OR
fat-soluble AND less easily excreted/metabolized ✔
Accept “water-soluble” only if an organometallic–protein interaction is mentioned.
Examiners report
Many candidates produced the correct answer for M1 but not as many fully scored. Students did not appear to understand the concept, and many missed the idea of 2 years in the calculation. Students should always clearly show their calculations so examiners can award marks throughout the question and potentially award ECF if possible. It is very difficult to do this when students do not show work clearly.
A well answered question although some did not give a reason.