| Date | May 2012 | Marks available | 2 | Reference code | 12M.3.HL.TZ2.4 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Compare | Question number | 4 | Adapted from | N/A |
Question
Each spring, the breeding season for various species of toads begins with a mass arrival of females at ponds and lakes. Males arrive later and actively compete for the females. Amplexus (mating embrace) and spawning (depositing eggs in water) then follow. Many environmental variables affect the timing of breeding. The hypothesis that periodicity in reproductive behaviour reflects periodicity in the lunar cycle was tested over several breeding seasons at sites in Wales (UK) and Italy. The lengths of the shaded bars indicate the relative frequencies of the events.
Identify which reproductive event is least influenced by the lunar cycle.
Compare the data for arrival events with amplexus events.
Deduce the relationship between arrival events and amplexus events in moon phases D to F.
The lunar cycle could affect the timing of breeding. Suggest, with a reason, one other environmental variable which could affect the timing.
Markscheme
first spawn/spawning
frequency at full moon/E about the same;
both arrival (event) and amplexus (event) have low/similar frequencies in B and C;
highest frequency for arrival (event) in D whereas highest frequency for amplexus (event) in F;
always some arrivals but amplexus (event) only in B to F / no amplexus (event) in G/H/A;
mass arrival (events) at phases D and E is followed by large amplexus (events) at phases E and F;
full moon/lunar cycle seems to influence timing of both events (in sequence) / OWTTE;
example of environmental condition;
reason for the example;
e.g.:
rainfall;
necessary to maintain pond levels to enable the toads to spawn;
temperature / season / daylength;
affects metabolism / survival of offspring;
Examiners report
Three circular graphs relating toad reproduction events with moon phases were presented as data. A certain number of candidates read the amplexus events as being the least influenced by the lunar cycle instead of the first spawn events in part (a); it is difficult to know if this was due to a misinterpretation of the graph or a misreading of the negative question.
Candidates usually presented good data comparisons in part (b).
but kept comparing data in part (c) where they were expected to find a causality relationship between arrival and amplexus; many provided incorrect answers such as "inversely proportional", trying to find a mathematical relationship.
For part (d), most candidates provided a valid environmental variable, but some of the reasons were either vague or irrelevant (e.g. food, affecting red deer reproduction when the data was about toads).
