| Date | May 2010 | Marks available | 3 | Reference code | 10M.2.SL.TZ2.1 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Compare | Question number | 1 | Adapted from | N/A |
Question
Male Lepidoptera (butterflies and moths) commonly drink from pools of water or from moist soil. This behaviour, called puddling, was investigated in an undisturbed area where male tiger swallowtails, Papilio glaucus, had been seen puddling.
Four successive sets of experiments were performed under similar conditions of temperature and humidity. In each set, equal samples of sand were spread out evenly on trays and then treated differently. Except for one dry sample (in the first set), all others were saturated with a different liquid. Results of the observations are given in the table below.
Study of the male moth Gluphisia septentrionis revealed that their puddling behaviour can last for hours. Though drinking results in the uptake of hundreds of gut-loads of fluid, this fluid becomes rapidly expelled from the digestive system through frequent anal ejections. In this experiment, the ion concentration change was calculated by subtracting ions ejected from ions taken in. The following data was collected from males drinking laboratory solutions and from natural puddles.
Identify the dissolved element always present in the three samples with most puddling time.
Discuss the relationship between sampling visits (V) and puddling time (T) in experiments 1, 2 and 3.
Analyse the results for experiment 4.
Identify which ion the moths are retaining in their body from the laboratory solutions.
Compare the gain and loss of ions in the male moths which have drunk from laboratory solutions with the changes in those that have drunk from natural puddles.
The diagram below shows the digestive system anatomy of the male and female moth.
Using the diagram above, evaluate the hypothesis that male moths are better adapted than female moths to benefit from puddling behaviour.
Markscheme
sodium/Na
unclear correlation between V and T;
depends on the nature of the substrate and its concentration;
sometimes high V with low T (e.g. experiment 1 for sucrose) / sometimes high V with high T (e.g. experiment 2 for NaCl);
higher salt/NaCl concentrations increase T and V;
increase in puddling with increase in salt/NaCl;
no clear relationship between the number of visits and the concentration of salt/NaCl;
sodium/Na
retention of sodium/Na from laboratory solutions and natural puddles;
definite loss of potassium from laboratory solutions but loss/gain uncertain from natural puddles;
slight loss of magnesium from laboratory solutions and uncertain gain/loss from natural puddles;
calcium uncertain in both cases / variation in data for calcium;
more conclusive results in laboratory solutions / conditions more reliable in laboratory solutions / greater variation in natural puddles;
Accept reference to error bars/ranges in data in place of uncertainty.
males have longer/wider digestive tracts for greater absorption of fluid;
ileum of males has greater surface area;
which allows faster/more absorption in males than in females;
Examiners report
Many candidates answered NaCl instead of Na when asked to identify the dissolved element.
Many candidates were unable to discuss correctly the relationship between sampling visits (V) and pudding time (T) in experiments 1 2 and 3.
Many candidates were unable to see the relationship between the NaCl concentration, the sampling visits (V) and the pudding time (T).
N/A
In part (ii), the majority of the candidates did not compare the gain and loss of each ion between moths which drank from laboratory solutions and moths which drank from natural puddles.
In the case of many candidates, no discussion or analysis was included, only description.
