This figure shows a farmer selecting the largest seeds from a crop of wheat plants for planting next year. Fig. 1 uses arrows to show that only selected pla...
Question 1 Report
This figure shows a farmer selecting the largest seeds from a crop of wheat plants for planting next year. Fig. 1 uses arrows to show that only selected plants provide seeds. The farmer wants plants that produce more food grain.
(a) What term describes this method of changing a population of plants? [1]
(b) Describe why the farmer should use seeds from several large plants, rather than one plant. [2]
(c) Give one disadvantage of producing wheat plants with very little genetic variation. [1]
Table 1 shows measurements from an investigation into variation in leaf length in a greenhouse population of bean plants. Fig. 1 shows how a student measured each leaf from the base of the blade to its tip.
| Leaf length / cm | Number of plants |
|---|---|
| 5.0-5.9 | 3 |
| 6.0-6.9 | 11 |
| 7.0-7.9 | 14 |
| 8.0-8.9 | 7 |
(a) Describe the type of variation in leaf length shown in Table 1. [2]
(b) Give one environmental factor that could affect leaf length in these plants. [1]
(c) Explain why leaf length is not determined only by genes. [1]
Answer Details
Selective breeding in wheat
(a) This method is selective breeding, also called artificial selection. [1]
(b) Seeds should be selected from several large plants because these plants may provide a wider range of alleles. This reduces the risk that all offspring inherit the same harmful characteristic. [2]
(c) With very little genetic variation, a disease or environmental change could affect all the plants similarly. [1]
Leaf length in bean plants
(a) Leaf length shows continuous variation. There is a range of values, including intermediate lengths, rather than separate categories. [2]
(b) One environmental factor is light intensity. Water supply, mineral ion availability and temperature are also acceptable. [1]
(c) Leaf length is not determined only by genes because environmental conditions can affect leaf growth. [1]
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