Question 22M.2.SL.TZ2.1a.i
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.SL.TZ2.1a.i |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Describe | Question number | a.i | Adapted from | N/A |
There is growing evidence of a decrease in bee populations. This decrease is a serious problem because of their valuable role as pollinators in the ecosystems where they live. Neonicotinoid pesticides have been implicated in this decrease because they have been found at trace levels in the nectar and pollen of crop plants and in the bee colonies.
Scientists placed colonies of a species of bumblebee, Bombus terrestris, in the laboratory to test the effects of different levels of a neonicotinoid on their development. They divided the colonies into three groups:
- The control colonies were given a solution of water and sugar that resembled nectar produced by flowers.
- A second group of colonies was given the same sugar solution containing a neonicotinoid dissolved in it at low concentrations, similar to those found in nature.
- A third group of colonies was given the same sugar solution containing a neonicotinoid dissolved in it at high concentrations, similar to those found in nature.
After two weeks, all colonies were placed in the field to allow the bumblebees to feed naturally.
Describe the effect of neonicotinoid pesticides on the nervous system of insects.
[1]
- blocks synaptic transmission at (cholinergic synapses);
- binds to (acetylcholine) receptors;
A pleasing number were able to correctly describe the effect of the pesticides on the synapses and state the cumulative increase correctly in ai and aii. However, in aiii, many did not see the similarity in pattern for the compare mark. In part b stronger candidates commented on the fact that even at low doses the pesticide had a great effect and that the difference between high and low doses was negligible. Many examiners were bemused by the answers to c(i) where about half of the candidates failed to identify B. lucorum as the most affected species. B. pascuorum and B. terrestris were often incorrectly given. In cii. Better candidates described the overall effects as asked, with weaker candidates just describing each species in turn. In 1d the top candidates looked at all of the data, but those who just stated that the effect was not noticeable as the egg length was not significantly smaller gained the mark.
