DP Biology (last assessment 2024)

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Question 22M.2.SL.TZ2.1a.iii

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

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.]

(a.iii)

Compare and contrast the cumulative increase in mass of the three groups of colonies once they were placed in the field.

[2]

Markscheme
  1. all increased in (cumulative) mass gain up to 5–6 weeks
    OR
    all decreased (in cumulative mass gain) after 6 weeks;
  2. both with neonicotinoids have significantly lower (cumulative) mass than the control colonies (at all periods)
    OR
    colonies exposed to high concentration always had the lowest (cumulative) mass gain;

Accept vice versa.

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