Question 23M.3.HL.TZ2.3
| Date | May 2023 | Marks available | [Maximum mark: 5] | Reference code | 23M.3.HL.TZ2.3 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Outline, State, Suggest | Question number | 3 | Adapted from | N/A |
Laboratory-scale mesocosms were built to investigate the effect of very small contaminants (nanoparticles) on ramshorn snails (Planorbarius corneus).
[Source: Material from: Auffan, M., Tella, M., Santaella, C., Brousset, L., Pailles, C., Barakat, M., Espinasse, B., Artells, E., Issartel,
J., Masion, A., Rose, J., Wiesner, M.R., Achouak, W., Thiery, A. and Bottero, J.-Y., An adaptable mesocosm platform
for performing integrated assessments of nanomaterial risk in complex environmental systems, published 2014, Nature
Scientific Reports, reproduced with permission of SNCSC.]
State two variables measured by the probes.
1:
2:
[2]
- temperature;
- pH;
- minerals / salt concentration / conductivity;
- O2 (concentration);
- CO2 (concentration);
Most candidates could state two variables measured by probes, but many stated variables that could either not be measured by probes, e.g., movement of the snails, or variables that would be present outside the water, e.g., humidity.
Suggest one advantage of using a mesocosm in this type of research.
[1]
environmentally safe/cheaper/control of variables easier;
Candidates often correctly suggested an advantage of using mesocosms.
Outline the requirements for sustainability within a sealed mesocosm.
[2]
- photosynthetic organisms/autotrophs/plants as producers;
- light (as energy source) for photosynthesis;
- nutrient/water recycling (by saprotrophs);
- decomposers/saprotrophs to breakdown (toxic) wastes;
The question is “outline”, so do not accept only a list of variables without a brief account.
Most candidates ignored that outline requires a short description and only gave a list of factors for the requirements of sustainability in a mesocosm instead.
