O-LevelBiologyCoordination & Response5090/21 · May/June 2022 · Q110 Marks

The diagram shows human skin.

(a)(i)Identify the parts labelled B and C. B C[2]
(a)(ii)Describe how part B is involved in maintaining a constant body temperature when the external temperature drops.[3]
(b)Part A is unevenly distributed in human skin. Name part A and suggest reasons for this uneven distribution.[3]
(c)The thickness of layer D can change over several months. Suggest and explain one reason for a decrease in the thickness.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] B = blood vessel / capillary / artery / arteriole ;
[1] C = sweat gland ;
[1] less blood flows + in blood vessel / close to skin surface ;
[1] decrease in radiation / heat loss / AW;
[1] vasoconstriction OR blood vessels / arterioles / arteries / part B + narrow / constrict ;
[3] any three from: A is a receptor / nerve ending ; touch / pressure / pain / temperature ; examples of uneven distribution e.g. high density in fingers / lips ; exposed areas + need higher sensitivity AW ;
[2] any two from: fatty / adipose + tissue / cell ; less food eaten / less fat in diet / exercise; so fat used by body + for respiration / release energy ; body using more energy than it is taking in ;

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