| Date | May 2010 | Marks available | 2 | Reference code | 10M.3.HL.TZ1.4 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Deduce | Question number | 4 | Adapted from | N/A |
Question
Desert ants (Cataglyphis fortis) use odour to help find their food. When a constant wind is blowing, the ants do not approach food directly. Instead, they walk downwind of the food source and then, when they detect the odour of the food, they follow the odour trail upwind until they reach the food, as shown in the figure below.
To investigate this behaviour pattern, feeders were established at distances of 5 m to 60 m away from the nest. Each feeder consisted of a Petri dish filled with biscuit crumbs. The graph below shows the distribution of downwind approach distances for each different nest-feeder distance.
Outline the relationship between the downwind approach distance and the nest-feeder distance.
Compare the results observed when the feeders were located at 5 m with the feeders at 60 m.
Suggest one possible source of uncertainties or errors in these experiments.
Deduce, with a reason, what type of behaviour pattern is shown by the ants in the experiment.
Markscheme
downwind approach distance increases with increasing nest-feeder distances / the closer the feeder to the nest the shorter the downwind approach distance / direct/positive relationship
feeder at 5 m has smaller downwind approach distances than feeder at 60 m / vice versa;
feeder at 5 m has peak frequency at 50 % whereas at 60 m peak/plateau at 20 %;
narrower range of approach distances for 5 m while wider range of approach distances for 60 m;
feeder at 5 m has peak approach distance at 1 m downwind while feeder at 60 m has peak/plateau 4 m – 4.5 m;
difficulty handling ants / size of ants;
variation of wind;
other odours;
path of trail not easy to measure accurately;
Accept any other reasonable suggestions.
EITHER
innate behaviour / taxis;
because all walking at same angle to constant wind / all turn and follow odour trail when they detect smell;
OR
learned behaviour;
because of repetition/training / following other ants;
Examiners report
Almost all candidates were correctly able to identify the relationship between the downwind approach distance and the nest-feeder distance.
Many were also able to get 2 or 3 marks for this section.
The most common suggestion given was variation in the wind.
Many found this section on the type of behaviour more difficult but both innate and learned were accepted if the candidate was able to support their choice with a good reason.
