| Date | May 2015 | Marks available | 1 | Reference code | 15M.3.SL.TZ1.13 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Identify | Question number | 13 | Adapted from | N/A |
Question
Moths use a variety of sensory processes (including vision, smell and mechanoreception) to locate nectar on flowers. The ability of the nocturnal tobacco hornworm moth, Manduca sexta, to find nectar using mechanoreceptors was investigated using artifical flowers. Three-day-old moths that had no experience of natural flowers were used in the investigation. The artificial flowers had nectar placed at the centre and were made of either paper (with a rough surface to stimulate mechanoreception) or plastic (to reduce mechanoreception). The time taken for moths to discover the nectar (discovery time) over a series of eight trials is shown for the artificial flower types. Vertical bars show the variation in the data.
Identify the trial for each flower type that shows the greatest variation.
Paper:
Plastic:
Compare the data for plastic and paper flowers.
Outline the evidence from the data that the ability to find nectar using mechanoreceptors is a learned behaviour.
Discuss how learning to find nectar using mechanoreceptors could lead to improved chances of survival and reproduction for the tobacco hornworm moth.
Markscheme
Paper: (trial) 1
Plastic: (trial) 5
Both required for [1].
a. discovery time in paper flowers always shorter than plastic flowers;
b. larger variation in data for plastic flowers;
c. decreasing discovery time (over the eight trials) for the paper flowers only;
d. no trend in discovery time for plastic flowers;
e. from trial four discovery time for paper flowers remains fairly constant/slight variation whereas for plastic flowers discovery time increases;
a. mechanoreceptors are touch receptors;
b. discovery time decreases over the eight trials for paper flowers;
c. showing evidence of learning;
d. plastic flowers discovery times show no evidence of learning;
e. paper flowers have a rough surface so mechanoreceptors are more effective / plastic flowers smooth so do not stimulate mechanoreceptors;
a. improved chances of finding food;
b. advantage in dark/conditions when coloured/scented flowers not available;
c. not completely dependent on light/chemoreceptors to find food;
d. more likely to reproduce and pass gene (for mechanoreceptors) to offspring; advantage over other members of the species through learning;
Examiners report
Questions 13 a-c were generally well answered.
Questions 13 a-c were generally well answered.
Questions 13 a-c were generally well answered.
In 13(d) most candidates commented on improved chances of finding food but other suitable answers were rare except for the top grades, which generally made reference to moths flying at night and therefore being unable to use light receptors. Answers involving inheritance were very rare.
