Brain development, nature and nurtureEdexcel A-Level Biology A: Subtopic test

1. 1
   Researchers sutured shut one eye of young kittens for their first three months of life and then reopened it. Later, recordings from the visual cortex showed that almost no neurones responded to light entering the previously closed eye, and the kittens behaved as if blind in that eye, although its retina and optic nerve were normal. The same procedure carried out on adult cats for three months caused no loss of vision.

   (a)

   Which statement best explains why the adult cats lost no vision?

   [1 mark]

   • AThe critical period for the development of connections in the visual cortex had already passed
   • BAdult cats have more rod cells, which compensate for the closed eye
   • CAdult cats have larger pupils, so more light reaches the open eye
   • DAdult optic neurones conduct action potentials faster than those of kittens

   (b)

   Which conclusion is best supported by the experiment on the kittens?

   [1 mark]

   • AVision is determined entirely by genes before birth
   • BClosing an eye at any age permanently damages the retina
   • CKittens are unable to see at birth and so cannot be tested
   • DVisual stimulation during the critical period is needed for normal development of the visual cortex

   (c)

   Explain how the results of the experiment on the kittens show that nurture, as well as nature, influences brain development.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A baby is born with a cataract that makes the lens of one eye cloudy. Surgeons recommend that the lens is replaced within the first few months of life, rather than waiting until the child is older.

   (a)

   What is meant by the critical period in brain development?

   [1 mark]

   • AThe time at which brain growth stops and no more neurones are made
   • BA limited time early in life when appropriate stimulation is needed for a brain area to develop normally
   • CThe time at which an animal first opens its eyes
   • DThe time when genes alone control the development of the brain

   (b)

   Which observation provides the best evidence that an ability is innate?

   [1 mark]

   • AChildren from different cultures use different gestures to greet people
   • BA child taught to read at the age of five can then read
   • CNewborn babies only a few hours old turn towards a voice and prefer face-like patterns
   • DIdentical twins reared in different homes speak different languages

   (c)

   Explain why replacing the lens after the critical period would not restore normal vision in the affected eye.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A researcher compared scores on a test of spatial reasoning in pairs of twins. The scores of identical twins brought up together were very similar (correlation 0.85). The scores of non-identical twins brought up together were less similar (correlation 0.60). Identical twins who had been brought up in different homes were also very similar (correlation 0.75).

   (a)

   Explain what the correlations suggest about the influence of genes and environment on spatial reasoning.

   [3 marks]

   (b)

   Suggest four limitations of twin studies such as this one in separating the effects of nature and nurture.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Research into brain development has used experiments on animals, including Hubel and Wiesel's work with kittens and monkeys, as well as studies of human babies, patients and twins.

   (a)

   Discuss the moral and ethical issues of using animals in medical research, from two ethical standpoints.

   [6 marks]

   (b)

   Evaluate the methods used to investigate the contributions of nature and nurture to brain development.

   [6 marks]

   Total for question 4: 12 marks

End of questions