| Date | May 2011 | Marks available | 1 | Reference code | 11M.3.SL.TZ2.10 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Identify | Question number | 10 | Adapted from | N/A |
Question
Competition between genetically similar species of birds may lead to changes of one or more characteristics. One characteristic that results from this kind of selection is differences in the beaks. Researchers studied the beak lengths of two species of warblers. The graphs below show the beak lengths of Pine Warblers (Dendroica pinus) and Yellow-throated Warblers (Dendroica dominica) from three geographically isolated areas in the USA.
Identify the species with the shortest mean beak length.
Determine the difference in the mean beak length of the two populations of Yellow-throated Warblers in Midwest and Delmarva.
Compare the range of variation in beak length of the Yellow-throated Warblers in Midwest to the beak length of the Yellow-throated Warblers in Delmarva.
Suggest an advantage for the longer beaks of Yellow-throated Warblers in Delmarva.
Markscheme
Pine Warblers/Dendroica pinus (of Delmarva)
2.6mm (accept answers in the range of 2.5 mm to 2.7 mm)
Yellow-throated Warblers have a bigger range / greater variation (of beak length) in Delmarva than in Midwest (accept numerical values)
Accept converse.
allows them to eat other foods / changes feeding behaviour;
reduces competition with Pine Warblers;
Examiners report
Candidates had little trouble with the data presented in this option and D1 was well answered.
Candidates had little trouble with the data presented in this option and D1 was well answered.
Candidates had little trouble with the data presented in this option and D1 was well answered, though D1 (iii) presented problems for students who did not engage with the command term “compare”.
Candidates had little trouble with the data presented in this option and D1 was well answered.
