4 marksFig. 1 shows a group of male students. They are all the same age.
Fig. 1
The students in Fig. 1 show continuous variation in some of their characteristics.
State three characteristics in which these students show continuous variation.
[3]
State one example of discontinuous variation.
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2 marksSelective breeding of animals is very important to farmers.
Many different breeds of sheep have been produced by selective breeding.
Fig. 1 shows a flock of Merino sheep. This breed of sheep was produced by selective breeding.
Fig. 1
Sheep are important animals in many parts of the world as they produce meat, wool and milk.
Table 1 describes some characteristics of five different breeds of sheep.
Table 1
| breed of sheep | wool yield | wool quality | meat yield | milk yield |
| Arapawa | average | good | poor | average |
| Awassi | average | poor | average | very good |
| Blackbelly | poor | poor | very good | average |
| Merino | good | very good | good | poor |
| Tsurcana | average | good | average | average |
A farmer wants to sell both meat and wool.
Suggest which breed of sheep in Table 1 is the most suitable for this farmer.Â
Give a reason for your choice.Â
4 marksAnother farmer wants to produce a new breed of sheep with both a very good milk yield and a very good quality of wool.
The farmer is able to buy any of the breeds of sheep shown in Table 1.
Describe the process this farmer would use to produce the new breed of sheep on her farm.Â
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3 marksAn ecologist studied the leaves of a plant species.
Fig. 1 shows variation in the type of leaf spike present in the plant species.
Fig. 1
State the type of variation shown in Fig. 1.
[1]
(ii)
Explain why the type of leaf spike is an example of the variation shown in Fig. 1.
[2]
2 marksThe ecologist also measured other features of the leaves of the plant species.
Fig. 2 shows the variation in leaf feature B.
Fig. 2
State two named features of leaves that show the type of variation shown in Fig. 2.
1 markAfter one year, the ecologist recorded the variation in leaf feature B again.
The results are shown in Fig. 3.
Fig. 3
Suggest one reason for the difference in variation of leaf feature B after one year.
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2 marksAll commercial breeds of sheep belong to the species Ovis aries.
Define the term species.
5 marksMerino sheep in South Africa have high quality wool with very thin hairs.
Breeders in New Zealand have used selective breeding programmes to improve the wool of their sheep to match the quality of South African wool.
Describe the steps that breeders would take to breed sheep that have wool with very thin hairs.
3 marksExplain how natural selection differs from selective breeding.
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1 markBlood group is an example of discontinuous variation.
The blood groups of patients in a hospital were recorded.
Fig. 1 shows the results.
Fig. 1
Explain how Fig. 1 shows that blood group is an example of discontinuous variation.
2 marksTable 1 shows different examples of variation.
Tick all the boxes that show examples of discontinuous variation.
Table 1
| Eye colour | Â |
| Foot length | Â |
| Height | Â |
| Tongue rolling ability | Â |
| Body mass | Â |
2 marksVariation can result when mutation occurs.
Define the term mutation.
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2 marksCoat colour in horses is controlled by genes.
The allele for black coat (E) is dominant.
The allele for red coat (e) is recessive.
Place ticks in the table to show the coat colours of horses with each of the following genotypes.
| genotype | black coat | red coat |
| EE | Â | Â |
| Ee | Â | Â |
| ee | Â | Â |
1 markModern horse breeds look very different to each other, but still belong to the same species.
Fig. 1 shows three different horse breeds.
Fig. 1
State the term used to describe the difference between individuals of the same species.
3 marksShire horses have been produced by selective breeding. They are strong and can pull heavy loads.
Describe the process of selective breeding.
2 marksDescribe how natural selection differs from selective breeding.
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3 marksCompare natural selection with artificial selection.
4 marksSelective breeding is an example of artificial selection.Â
The wild mustard plant has undergone extensive selective breeding for hundreds of years. Fig. 1 shows the outcome of this selective breeding and the traits that have been selected for.Â
Fig. 1Â
Outline how selective breeding of the wild mustard plant has led to the development of the kale plant.
3 marksExtended Tier Only
Streptomycin is an antibiotic. Table 1 shows results collected from a study during which scientists examined the effect of streptomycin on a bacterial population over fifteen generations.
The bacterial population consisted of two variants, X and Y.
Table 1
| generation | frequency of variant X in the population | frequency of variant Y in the population |
| 1 | 52 | 51 |
| 2 | 55 | 49 |
| 3 | 64 | 44 |
| 4 | 66 | 41 |
| 5 | 73 | 38 |
| 6 | 76 | 32 |
| 7 | 81 | 26 |
| 8 | 85 | 21 |
| 9 | 89 | 16 |
| 10 | 94 | 12 |
| 11 | 98 | 8 |
| 12 | 99 | 5 |
| 13 | 99 | 2 |
| 14 | 99 | 1 |
| 15 | 99 | 1 |
Describe and explain the data shown in Table 1.
4 marksExtended Tier Only
Explain the process that has led to the change in the frequency of variant X in Table 1.Â
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