DP Biology (last assessment 2024)

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Question 22M.2.SL.TZ2.1d

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Date May 2022 Marks available [Maximum mark: 1] Reference code 22M.2.SL.TZ2.1d
Level SL Paper 2 Time zone TZ2
Command term Deduce Question number d Adapted from N/A
d.
[Maximum mark: 1]
22M.2.SL.TZ2.1d

There is growing evidence of a decrease in bee populations. This decrease is a serious problem because of their valuable role as pollinators in the ecosystems where they live. Neonicotinoid pesticides have been implicated in this decrease because they have been found at trace levels in the nectar and pollen of crop plants and in the bee colonies.

Scientists placed colonies of a species of bumblebee, Bombus terrestris, in the laboratory to test the effects of different levels of a neonicotinoid on their development. They divided the colonies into three groups:

  • The control colonies were given a solution of water and sugar that resembled nectar produced by flowers.
  • A second group of colonies was given the same sugar solution containing a neonicotinoid dissolved in it at low concentrations, similar to those found in nature.
  • A third group of colonies was given the same sugar solution containing a neonicotinoid dissolved in it at high concentrations, similar to those found in nature.

After two weeks, all colonies were placed in the field to allow the bumblebees to feed naturally.

The mass of the colonies, including adult bumblebees, wax, honey and larvae, was recorded every week. The cumulative increase in mass was calculated and is shown on the graph.

[Source: Adapted from Whitehorn, P.R., O’Connor, S., Wackers, F.L. and Goulson, D., 2012.
Bumble Bee Colony Growth and Queen Production. Science, [e-journal] 336(6079), pp. 351–352.
http://dx.doi.org/10.1126/science.1215025.]

The number of queen bumblebees produced in each colony was recorded. New bumblebee colonies are started by a queen.

[Source: Adapted from Whitehorn, P.R., O’Connor, S., Wackers, F.L. and Goulson, D., 2012.
Bumble Bee Colony Growth and Queen Production. Science, [e-journal] 336(6079), pp. 351–352.
http://dx.doi.org/10.1126/science.1215025.]

A similar study compared the effect of a different neonicotinoid on four different species of bumblebees. The queens were exposed to either control conditions (with no pesticide), or low or high doses of neonicotinoid. The scientists then measured the average length of the developing eggs in the ovaries of the queens.

[Source: Baron GL, Raine NE, Brown MJF. 2017 General and species-specific impacts of a neonicotinoid insecticide
on the ovary development and feeding of wild bumblebee queens. Proc. R. Soc. B 284: 20170123.
http://dx.doi.org/10.1098/rspb.2017.0123 Licensed under a Creative Commons Attribution 4.0
International License https://creativecommons.org/licenses/by/4.0/ Source adapted.]

(d)

Deduce, based on the data presented, whether the levels of neonicotinoids used in agriculture cause direct harm to B. terrestris.

[1]

Markscheme
  1. yes, as even low/both doses (of first neonicotinoid) affect the (overall) development of colonies negatively; (From Graph 1)
  2. yes, as decreased numbers of queens (likely) affect reproductive capabilities; (From Graph 2)
  3. the second neonicotinoid (likely) had less/little/no effect on the bees as it had little effect on egg size; (From Graph 3)

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