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Question 20N.3.SL.TZ0.b

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Date November 2020 Marks available [Maximum mark: 1] Reference code 20N.3.SL.TZ0.b
Level SL Paper 3 Time zone TZ0
Command term Outline Question number b Adapted from N/A
b.
[Maximum mark: 1]
20N.3.SL.TZ0.b

The cladogram shows where mutations probably occurred in ancestral lines resulting in some animal species being unable to produce ascorbic acid (vitamin C).

 [Source: Drouin, G., Godin, J.-R. and Pagé, B., 2011. The Genetics of Vitamin C Loss in Vertebrates. Current
Genomics, 12(5), pp.371–378.]

Outline the reason for ascorbic acid being described as an essential nutrient in the diet of humans.

[1]

Markscheme

cannot be synthesized by the body;

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