An investigation was carried out into the population of a species of vole in one area of the USA. The population was sampled during the first two weeks of August between 1983 and 2004. Traps for catching small mammals were placed at equal distances along the same parallel line transects. Each year, the number of voles caught per 1000 traps was recorded. [Figure 3.1]

1. (a)Identify three ways in which this investigation has been standardised. 1 2 3[3]
2. (b)Over the period of the study, it was found that 8 out of every 50 voles in this population had black fur, whilst all the other voles had brown fur. Fur colour in voles is controlled by a single gene, A/a. Voles with black fur have the genotype aa. The Hardy-Weinberg principle states that: p + q = 1 p² + 2pq + q² = 1 p = the frequency of the dominant allele q = the frequency of the recessive allele Use the Hardy-Weinberg principle to calculate the expected number of voles heterozygous for fur colour that were recorded in 1997. Give your answer to the nearest whole number. number of voles per 1000 traps which are heterozygous for brown fur in 1997 = ...............[3]

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