Question 1
Which feature shows discontinuous variation?
- Body mass
- ABO blood group
- Body length
- Leaf length
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Answer: B (1)
Question 2
(a) Describe what is meant by variation. [1] (b) State what is meant by continuous variation. [1] (c) Give one example of continuous variation in humans. [1]
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- (a) differences between individuals of the same species (1)
- (b) results in a range of phenotypes between two extremes (1)
- (c) body length / body mass (1) allow height; reject blood group
Question 3
Body mass shows continuous variation. ABO blood group shows discontinuous variation. Explain the difference in the causes of these two types of variation.
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- blood group / discontinuous variation is caused by genes only (1)
- body mass / continuous variation is caused by genes and the environment (1)
- environmental factor named for body mass, e.g. diet / amount of exercise (1)
Question 4
A student measured the length of 40 leaves from one tree and recorded the results in the table. (a) State the type of variation shown. [1] (b) State the modal class. [1] (c) Explain how the data support your answer to (a). [2]
| leaf length / mm | number of leaves |
|---|---|
| 20–24 | 3 |
| 25–29 | 8 |
| 30–34 | 16 |
| 35–39 | 9 |
| 40–44 | 4 |
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- (a) continuous (variation) (1)
- (b) 30–34 mm (1)
- (c) a range of lengths between two extremes / from 20 mm to 44 mm (1)
- many intermediate lengths / no separate categories / length can take any value (1)
- most leaves in the middle classes and fewest at the extremes (1)
- Max 2 for (c)
Question 5
(a) Define the term mutation. [1] (b) State what mutations produce in a population. [1] (c) Name one factor that increases the rate of mutation. [1]
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- (a) genetic change (1)
- (b) new alleles (1)
- (c) ionising radiation / X-rays / gamma rays / (some) chemicals, e.g. chemicals in tobacco smoke (1) reject heat
Question 6
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean(a) Describe gene mutation. [2] (b) State two other sources of genetic variation in a population. [2]
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- (a) random (change) (1)
- change in the base sequence of DNA (1)
- (b) any two from: meiosis (1)
- random mating (1)
- random fertilisation (1)
- reject mutation in (b); ignore environment
- Max 4
Question 7
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanWhich statement about gene mutation is correct?
- It is a planned change to a gene
- It is a random change in the base sequence of DNA
- It only occurs in gametes
- It always produces harmful features
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Answer: B (1)