| Date | November 2013 | Marks available | 1 | Reference code | 13N.3.SL.TZ0.13 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | 13 | Adapted from | N/A |
Question
The hippocampus plays an important role in memory and spatial navigation. A larger hippocampus relative to brain volume has been associated with better spatial memory in birds. Two subspecies of the white-crowned sparrow, Zonotrichia leucophrys gambelii (migratory) and Zonotrichia leucophrys nuttalli (non-migratory) were compared. The graph shows the relationship between the volumes of the hippocampus and the brain in adult and young sparrows.
Relative hippocampal volume is the ratio between the volume of the hippocampus and the volume of the whole brain (hippocampus/brain).
State the relationship between brain volume and hippocampal volume in the non-migratory sparrows.
Compare the hippocampal volume in migratory and non-migratory young and adult sparrows.
Analyse the data in the scattergraph to find which of the four groups of birds has the highest relative hippocampal volume.
Suggest a reason why this group needs the largest relative hippocampal volume.
It is possible that non-migratory species possess more advanced cognitive skills other than spatial memory. Use the data to evaluate this hypothesis.
Markscheme
as brain volume increases so does hippocampus volume / positive correlation
hippocampus volumes are larger in adults than in young birds;
larger range for migratory;
young non-migratory show wider range of hippocampus volumes than young migratory;
some overlap for non-migratory / none for migratory;
adult migratory (as for any brain volume this group has the largest hippocampal volume) } (allow mathematical explanation)
needed for migration / only adults migrate/remember flight paths
(Do not accept spatial navigation on its own without reference to migration)
Hypothesis supported:
non-migratory have larger brain volume;
larger brain implies more thinking skills;
hippocampus in non-migratory is approx same size as in migratory;
Hypothesis not supported:
only two species/small sample studied so over generalization;
similar hippocampus volume in both migratory and non-migratory birds;
Examiners report
Most candidates received this mark for noting the positive correlation shown in the graph.
This was poorly answered overall, with more than 1 mark seldom being awarded for noting that hippocampus volumes are larger in adults than in young birds. Many looked at hippocampus to brain volume ratios while the question asks only about hippocampus volume.
Most candidates correctly answered both parts (i) and (ii).
Most candidates correctly answered both parts (i) and (ii).
The evaluations done were mainly quite superficial yet many were able to get two marks for this question.
