Question 19M.2.SL.TZ2.f
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.SL.TZ2.f |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Deduce | Question number | f | 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]
Deduce whether there is a correlation between the neural traces and the percentage of responding G1 neurons.
[2]
a. there is a positive relationship/correlation between the size of neural traces and the percentage of responding G1 neurons Accept vice versa
OR
the chemicals that cause stronger/higher neural traces also cause the greatest percentage of responding G1 neurons ✔
b. fox and stoat scents have «approximately» the same/similar neural traces and the same percentage of responding neurons/>75 % ✔
c. mouse alarm compounds cause smaller neural traces and smaller percentage of responding neurons/25–75 % ✔
d. control chemicals have no response in both cases
OR
no percentage of «G1 neurons» response and no action potential «in neural traces» ✔
Similarly, in 1f most could see the positive correlation, albeit not stating it, between the size of the trace and the percentage of responding G1 neurons.
