Explain how the structures of the eye help to produce a clear image of a near object.
Suggest why people with long eyeballs are unable to see distant objects clearly. You may use the eye diagram in Fig. 5.1.
Comment on how the proportion of people with myopia has altered in this population.
It is believed that myopia results from a mix of genetic and environmental factors. It has been proposed that the changing percentages of people with myopia are due to 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.
Iris colour is controlled by genes. The allele for blue colour, $b$, is recessive to the allele for brown colour, $B$. Explain why a heterozygous blue-eyed person is not possible.