Question 19M.2.SL.TZ2.e
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.SL.TZ2.e |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Compare and contrast | Question number | e | Adapted from | N/A |
Mice (Mus musculus) have various defence systems against predators such as foxes (Vulpus vulpus) or stoats (Mustela erminea). The mice release specific alarm compounds when under threat that serve as danger signals for other mice. Predators also release scents that the mice can detect.
In one study, mice were exposed to paper soaked in compounds taken from other mice, foxes or stoats in a test chamber. The scientists then measured the reaction of three different groups of neurons used in smelling: G1, G2 and G3, as shown in the diagram.
The percentage of G1, G2 and G3 neurons responding to the mouse, fox and stoat compounds, as well as a control compound, are shown in the chart.
Percentage of response of neurons in mice
[Source: Julien Brechbühl, et al., (2013), PNAS, 110 (12), pages 4762–4767]
The scientists recorded the neural traces (action and resting potentials) of six G1 neurons exposed to the compounds from the different animals. The horizontal bar beneath each trace corresponds to the time of exposure to the test compound.
[Source: adapted from J Brechbühl, et al., (2013), PNAS, 110 (12), pages 4762–4767]
Compare and contrast the effects of the mouse alarm compound and stoat scent on the G1 neurons.
[2]
a. both chemicals cause action potentials
OR
both chemicals respond in the majority of/five/most neurons ✔
b. stoat scent causes a higher action potential/longer/bigger response than mouse alarm compound «in each neuron»
OR
neuron 2 reacts strongly to the stoat scent but has a minimal/no response to the mouse alarm compound ✔
Answers to e were encouraging as most were able to give both the similarity and the difference.
