DP Biology (first assessment 2025)

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Question 23M.1A.SL.TZ2.8aii

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Date May 2023 Marks available [Maximum mark: 2] Reference code 23M.1A.SL.TZ2.8aii
Level SL Paper 1A Time zone TZ2
Command term Suggest Question number ii Adapted from N/A
ii.
[Maximum mark: 2]
23M.1A.SL.TZ2.8aii

Breeding plumage can be an important signal for mate selection in birds. Breeding plumage in red knots (Calidris canutus) includes a rusty red colour. Red knots have six recognized subspecies, each with different migratory routes.

The scatter graph shows the overall migration distance and the breeding plumage colouration for different subspecies of red knots. The darkest plumage colouration is 6.

[Source: Used with permission of The Royal Society (U.K.), from Phil. Trans. R. Soc. B, Buehler, D.M. and Piersma, T, 363, 2008;
permission conveyed through Copyright Clearance Center, Inc.]

(ii)

Suggest two reasons, other than mate selection, for variation in plumage colouration in red knots.

[2]

Markscheme
  1. camouflage to avoid predators (in different migratory routes);
  2. different diets (in different migratory routes);
  3. less migratory distance leaves more energy to produce pigments (in plumage);
  4. geographic isolation (due to different migratory routes) leads to different gene pools;

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