Question 7:
Diagram 7.1(a) and Diagram 7.1(b) show the graphs of two types of variation.
(a) Based on Diagram 7.1(a),
(i) state the type of variation [1 mark]
(ii) give one example of characteristic X. [1 mark]
(b) Identify the distribution curve for the graph in Diagram 7.1(b). [1 mark]
(c) Diagram 7.2 (a) shows identical twins J and K. Both of them had fair skin during childhood. Diagram 7.2 (b) show, the skin colour of twin J and twin K after 20 years.
(i) State the factor that causes the change of skin colour of twin J. [1 mark]
(ii) Explain how the factor in 7(c)(i) causes the change in skin colour of twin J. [2 marks]
(d) Twin J is diagnosed with skin cancer due to his work environment but his identical twin does not suffer from skin cancer. If twin J has children, they will not be born with skin cancer. Explain why. [3 marks]
Answer:
(a)(i) Discontinuous variation
(a)(ii) Hair type // Ability to roll the tongue // any suitable examples
(b) Normal distribution // Bell-shaped
(c)(i) Light / environment factor
(c)(ii)
1: Sunlight contains ultraviolet rays
2: Long exposure / high light intensity
3: The existing melanin pigment becomes damaged
4: More melanin pigment is being formed
(d)
1: Somatic cell mutation
2: Not inherited // Only suffered by J
3: No mutation occurs in reproductive cells / gametes
4: J produces normal sperm
Diagram 7.1(a) and Diagram 7.1(b) show the graphs of two types of variation.
(a) Based on Diagram 7.1(a),
(i) state the type of variation [1 mark]
(ii) give one example of characteristic X. [1 mark]
(b) Identify the distribution curve for the graph in Diagram 7.1(b). [1 mark]
(c) Diagram 7.2 (a) shows identical twins J and K. Both of them had fair skin during childhood. Diagram 7.2 (b) show, the skin colour of twin J and twin K after 20 years.
(i) State the factor that causes the change of skin colour of twin J. [1 mark]
(ii) Explain how the factor in 7(c)(i) causes the change in skin colour of twin J. [2 marks]
(d) Twin J is diagnosed with skin cancer due to his work environment but his identical twin does not suffer from skin cancer. If twin J has children, they will not be born with skin cancer. Explain why. [3 marks]
Answer:
(a)(i) Discontinuous variation
(a)(ii) Hair type // Ability to roll the tongue // any suitable examples
(b) Normal distribution // Bell-shaped
(c)(i) Light / environment factor
(c)(ii)
1: Sunlight contains ultraviolet rays
2: Long exposure / high light intensity
3: The existing melanin pigment becomes damaged
4: More melanin pigment is being formed
(d)
1: Somatic cell mutation
2: Not inherited // Only suffered by J
3: No mutation occurs in reproductive cells / gametes
4: J produces normal sperm