Question 20N.3.HL.TZ0.8a
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.HL.TZ0.8a |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Evaluate | Question number | a | Adapted from | N/A |
Male eastern bluebirds (Sialia sialis) display brilliant UV-blue feathers on their heads, backs, wings and tails. The brightness index of the male was calculated; the larger the score, the brighter the blue feathers. A brightness value of 0 indicates normal male brightness, so birds with negative scores are less bright than normal.
In an experiment to see the mating behaviour of bluebirds, scientists separated pairs of males and females and then allowed females to choose new partners.
The graph shows the relationship between male brightness index and choice of mate by females in eastern bluebirds.
[Source: Reprinted from Animal Behaviour, 78, Liu, M., Siefferman, L., Mays, H., Steffen, J.E. and Hill, G.E., A field test of
female mate preference for male plumage coloration in eastern bluebirds. pp.879–885. 2009 with permission from Elsevier
and The Association for the Study of Animal Behaviour. https://www.sciencedirect.com/journal/animal-behaviour.]
Evaluate the hypothesis that females prefer to mate with males whose feathers are a brighter blue.
[2]
Strengths:
a. (slight) increase in mate choice at higher male brightness index;
Weaknesses:
b. dots are scattered without a trend/no clear correlation
OR
most females choose mates around normal (brightness);
c. insufficient data/information provided;
Allow any other data-based statement.
Most candidates managed to provide at least one evaluation statement, but it was difficult for many to provide a complete evaluation.
