The diagram shows a pedigree for a family in which some people have a detached earlobe and others have an attached earlobe. Squares represent males and circ...
Question 1 Report
The diagram shows a pedigree for a family in which some people have a detached earlobe and others have an attached earlobe. Squares represent males and circles represent females. Filled symbols show people with detached earlobes. This is a category-based characteristic, unlike the continuous variation in body mass caused by differences in food intake and growth.
(a) What type of variation is earlobe type? [1]
(b) Describe the evidence from Fig. 1 that earlobe type can be inherited. [2]
(c) Give the number of children shown in the second generation. [1]
(d) Explain why body mass is less useful than earlobe type when placing people into a small number of distinct groups. [2]
(e) Draw a bar chart to show the number of children with each earlobe type. Use suitable labels on both axes. [2]
Answer Details
Earlobe type is recorded in distinct categories, unlike body mass, which varies over a continuous range.
- Earlobe type shows discontinuous variation. [1]
- The pedigree shows that a parent has detached earlobes and one child also has detached earlobes. A pattern occurring within a family is evidence that the characteristic can be inherited. [2]
- There are 3 children in the second generation. [1]
- Body mass has many intermediate values and is affected by environmental factors as well as genes. Therefore boundaries between a small number of groups would be arbitrary. [2]
- The children are one detached and two attached. The required bar chart is:
Axes are labelled with earlobe type and number of children; bars have heights detached = 1 and attached = 2. [2]
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