O-LevelBiologyCoordination & Response5090/21 · May/June 2023 · Q513 Marks

Myopia is an eye condition. If a person has myopia, near objects can be seen clearly but not those that are far away. It can happen when the eyeballs grow slightly too long as shown in Fig. 5.1. [Figure 5.1]

(a)(i)Explain how parts of the eye are involved in producing a clear image of a near object.[4]
(a)(ii)Suggest why individuals with long eyeballs cannot see far-away objects clearly. You may draw on the diagram of the eye in Fig. 5.1.[1]
(b)(i)A country carried out two national health surveys separated by approximately 30 years. Table 5.1 shows the information that was obtained about myopia. Table 5.1 percentage of people with myopia males females age 1971–72 1999–2004 1971–72 1999–2004 12–17 21.7 30.9 26.4 37.0 18–24 22.5 29.7 32.5 46.4 25–34 20.2 38.9 27.8 49.1 Comment on how the percentage of people with myopia has changed in this population.[3]
(b)(ii)It is thought that myopia is the result of a combination of genetic and environmental factors. It has been suggested that the changing percentages of people with myopia is a result of changes in human activities. Suggest a change in human activity and how it could make a person less able to see far-away objects clearly.[2]
(c)Iris colour is genetically determined. The allele for blue colour, b, is recessive to the allele for brown colour, B. Explain why it is not possible to have a heterozygous blue-eyed person.[3]

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 2023). The mark or mark type is shown in brackets.

[1] light is refracted / bent by cornea ;
[1] ciliary muscles / body contract ;
[1] suspensory ligaments become slack ;
[1] lens becomes fatter AW ;
[1] light refracted / bent (more) by lens ;
[1] light/image focused / formed on retina ;
[1] lens bends / refracts light rays too much so they meet before retina / drawn on diagram ;
[1] prevalence of myopia has increased ;
[1] in both males and females / in all age groups ;
[1] increased most in 25–34 age group / older people / females ;
[1] correct quote of comparative data ;
[1] less time spent outdoors / reference to more time spent on activities looking at near objects/computers/mobile phones ;
[1] eyes not trained / not enough practice at looking at far away objects ;
[1] blue-eyed person has two recessive alleles / would be bb ;
[1] blue-eyed person is homozygous / both alleles are the same ;
[1] heterozygous means the alleles are different / heterozygous would be Bb ;
[1] B is dominant / Bb would have brown eyes ;

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