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Date May 2021 Marks available 2 Reference code 21M.2.SL.TZ2.1
Level Standard level Paper Paper 2 Time zone Time zone 2
Command term Compare and contrast Question number 1 Adapted from N/A

Question

Honeybees (Apis mellifera) are key pollinators in most ecosystems. The worldwide use of neonicotinoid pesticides has caused concern because they may be contributing to the decline of honeybee populations.

Scientists measured the concentration of five neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) in honey samples from 198 different locations across the world. Each pie chart shows the relative frequency of neonicotinoids in honey samples from a continent.

[Source: Republished with permission of American Association for the Advancement of Science, from A worldwide survey of neonicotinoids in honey, Mitchell, E.A., et al., Science, Volume 358, Issue 6359, 2017. Permission conveyed through Copyright Clearance Center, Inc. https://science.sciencemag.org/content/358/6359/109.full.]

The neonicotinoids can be used alone or together with other neonicotinoids. The percentage of honey samples with 0, 1, 2, 3, 4 or 5 different neonicotinoids in each continent are shown in the stacked bar chart.

[Source: Republished with permission of American Association for the Advancement of Science, from A worldwide survey of neonicotinoids in honey, Mitchell, E.A., et al., Science, Volume 358, Issue 6359, 2017. Permission conveyed through Copyright Clearance Center, Inc. https://science.sciencemag.org/content/358/6359/109.full.]

In order to grow, honeybee larvae are fed royal jelly, a high energy food with very high acetylcholine concentrations.

In an experiment, larvae were bred artificially on a diet with reduced acetylcholine content in the royal jelly. The graph shows the mean survival rate of these larvae compared to control larvae fed on a normal diet.

[Source: Wessler I, Gärtner H-A, Michel-Schmidt R, Brochhausen C, Schmitz L, Anspach L, et al. (2016) Honeybees Produce Millimolar Concentrations of Non-Neuronal Acetylcholine for Breeding: Possible Adverse Effects of Neonicotinoids. PLOS ONE 11(6):e0156886. doi:10.1371/journal.pone.0156886 Copyright: © 2016 Wessler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.]

The concentration of acetylcholine was measured in royal jelly produced by honeybees that had never been exposed to neonicotinoids (control) and honeybees that had been exposed for three weeks to two neonicotinoids; clothianidin and thiacloprid.

Wessler I, Gärtner H-A, Michel-Schmidt R, Brochhausen C, Schmitz L, Anspach L, et al. (2016) Honeybees Produce Millimolar Concentrations of Non-Neuronal Acetylcholine for Breeding: Possible Adverse Effects of Neonicotinoids. PLOS ONE 11(6):e0156886. doi:10.1371/journal.pone.0156886 Copyright: © 2016 Wessler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Identify in which continent the fewest types of neonicotinoid were detected in honey samples.

[1]
a.

Using the data, outline the different use of thiamethoxam in North and South America.

[1]
b.

Identify the total percentage of honey samples contaminated with neonicotinoid pesticides in the continent with the lowest overall levels of contamination.

 

. . . . . . . . . . . . %

[1]
c.

Deduce the conclusions that can be drawn from the data in the graph.

[2]
d.

Suggest a reason for the effect of a diet reduced in acetylcholine on the larval survival rate.

[1]
e.

Compare and contrast the effect of clothianidin and thiacloprid treatments on the concentration of acetylcholine in royal jelly.

[2]
f.

Explain how neonicotinoids affect synaptic transmission in insects.

[3]
g.

Companies that manufacture neonicotinoid pesticides have argued that they do not cause significant harm to honeybees. Construct an argument, based on the data in this question, for serious concern about the manufacture and use of neonicotinoid pesticides.

[4]
h.

Markscheme

Oceania ✔

a.

thiamethoxam is the most used in North America (but not in South America) / CONVERSE
OR
in South America they use different neonicotinoids to thiamethoxam ✔

OWTTE.

Allow numerical comparison.

b.

57 (%) ✔

Allow range 56 % to 58 %.

c.

a. reduced acetylcholine does not affect larval survival in the first two days ✔

b. reduced acetylcholine causes increased mortality from day 3 onwards ✔

c. 90 % versus 40 % survival/other valid numerical comparison by day 5
OR
(much) greater decrease in survival occurs between days 4 and 5/by day 5 for the reduced group ✔

Do not accept answers without times/ days.

d.

(larvae lacking acetylcholine/with reduced AcH cannot survive because) acetylcholine is a neurotransmitter taking message from one neuron to another in synapses of nervous tissues
OR
messages would not pass from one neuron to the other
OR
(larvae) unable to synthesise/produce AcH, so need it from their diet ✔

OWTTE.

e.

a. both neonicotinoids reduce the concentration of acetylcholine in royal jelly (compared to control) ✔

b. clothianidin reduces the concentration of acetylcholine in royal jelly more than thiacloprid (but perhaps not statistically different) ✔

c. clothianidin is used in smaller concentrations (than thiacloprid) so no firm conclusion can be obtained ✔

Need one similarity and one difference.

f.

a. neonicotinoids bind to the (acetylcholine) receptor (in insects) ✔

b. (binding happens) in (cholinergic) synapses/at motor end plate/between motor neuron and muscles ✔

c. neonicotinoids bind irreversibly (to receptors)
OR
(receptors are blocked so) acetylcholine is unable to bind ✔

d. acetylcholinesterase/enzymes cannot break down neonicotinoids ✔

e. (synaptic) transmission prevented ✔

f. (causing) insect paralysis/death ✔

g.

a. neonicotinoids are used in every continent ✔

b. the choice of specific neonicotinoid varies considerably around the world ✔

c. neonicotinoids contaminate honey (so must get into honeybees) ✔

d. only a minority of honey samples from around the world contain no neonicotinoids ✔

e. neonicotinoids reduce the acetylcholine (content of royal jelly)
OR
only a small amount of clothianidin can reduce acetylcholine in royal jelly ✔

f. survival of honeybee larvae is lower if the acetylcholine is lower/content of royal jelly is reduced ✔

h.

Examiners report

In general, the data analysis question was well attempted by the majority of students.

Almost all were able to name Oceania.

a.

In general, the data analysis question was well attempted by the majority of students.

Most identified that the proportion of the pesticide was greater in North than South America. This does not actually mean that a greater mass was used as these were relative frequency graphs.

b.

In general, the data analysis question was well attempted by the majority of students.

Most read the graphs correctly, stating between 56 and 58 %.

c.

In general, the data analysis question was well attempted by the majority of students.

An answer comparing the survival as the days progressed was expected. Answers tended to be too general.

d.

In general, the data analysis question was well attempted by the majority of students.

At least half of the candidates did not know that acetylcholine is a neurotransmitter (section 6.5).

e.

In general, the data analysis question was well attempted by the majority of students.

A compare and contrast question, that required one similarity and one difference. Most were able to state that both treatments reduce the acetylcholine concentration in the royal jelly and that clothianidin reduced it more than thiacloprid. The more astute also commented on the differences in concentrations of the insecticides.

f.

In general, the data analysis question was well attempted by the majority of students.

Those students who had studied synaptic transmission scored well. However, many knew the role of acetylcholine here, but not in Q(1)(e).

g.

In general, the data analysis question was well attempted by the majority of students.

This question was a good discriminator, with better students using the data presented to construct an argument as asked. Weaker students wrote about the function of bees in pollination etc., which is a consequence, but does not answer the question.

h.

Syllabus sections

Core » Topic 4: Ecology » 4.1 Species, communities and ecosystems
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