| Date | May 2013 | Marks available | 1 | Reference code | 13M.3.SL.TZ1.13 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | State | Question number | 13 | Adapted from | N/A |
Question
Scientists investigated if training has an influence on the learning of birdsong. They studied juvenile zebra finches (Taeniopygia guttata) that had never been exposed to adult bird songs. They measured neuron activity in an area of the brain involved with song learning. This was done during their sleep, first for four nights when the birds had not heard any birdsong during the previous day, and then for a series of nights after days when they were exposed to recordings of adult zebra finches’ songs. In the graph below, the mean neuron activity in the period of no exposure to birdsong was used as a baseline and assigned a value of 1. All other measurements of neuron activity are shown relative to this.
State the difference in neuron activity between nights 2 and 7.
Outline the effect of exposure to birdsong on neuron activity.
Suggest one reason for the large error bars on days 14 and 15.
Evaluate the hypothesis that listening to other zebra finches is important to develop singing ability amongst juveniles.
Markscheme
0.8 (Accept answers from 0.75 to 0.85.)
a. increases neuron activity;
b. increase over three days/increase of about 75 %/of 50–100 %;
c. then plateaus/levels off;
d. large variation on days 14 and 15;
a. small sample so one measure can skew the average / higher average value due to only one measurement;
b. different birds respond differently/nothing being learned;
c. change in behaviour due to biotic/abiotic changes;
a. hypothesis seems to be verified since all points after exposure to birdsong are higher;
b. learning phase (supported by changes on days 5–7);
c. experiment shows only one brain area activity / other factors may also be involved;
Examiners report
In E1 (a) and (b) almost all candidates had correct answers.
In E1, (a) and (b) almost all candidates had correct answers.
(c) appeared to confuse most candidates.
(d) in general answers were on topic, but few students evaluated the hypothesis.
