DP Biology (first assessment 2025)

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Question 20N.2.SL.TZ0.a

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.2.SL.TZ0.a
Level SL Paper 2 Time zone TZ0
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 2]
20N.2.SL.TZ0.a

Outline a method that could have been used in this study to measure the numbers of sea urchins per 0.25 m2.

[2]

Markscheme

a. with quadrats (of 0.5 m side / 0.25m2);

b. (quadrats) position determined at fixed distance by transects
OR
(quadrats) position determined at random;

c. random sampling / capture-recapture;

d. average number calculated;

Examiners report

Most candidates did well on this question, especially strong ones, although there was evidence that many candidates are not familiar with population evaluation skills. Candidates should be aware that writing "quadrants" (with a "n") is questionable, and that although it may not be assumed that they knew what echinoderms or sea urchins were, the capture-mark-release-recapture method was not really appropriate to evaluate their numbers, given the very limited areas of 0.25 m2.

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