Red deer are herbivores common in the highlands of Scotland. They have no natural predators and in some areas culling of the deer is carried out in order to manage their numbers and maintain the species diversity of the ecosystem. A group of scientists read a report which suggested that allowing sheep to graze alongside deer significantly reduces the need to cull the deer. They decided to carry out a survey to investigate the number of deer found grazing at 16 different sites. • 8 sites contained deer and sheep. • 8 sites contained deer but no sheep. • Each site was visited during the first week of April and the first week of July in 2007 and again in 2009. • Each site was 0.25 x 0.25 km. • Within each site, three 10 x 10m study plots were selected at random. • The scientists used dung counts along a 1 x 10m strip around each study plot to provide an estimate of the number of deer and sheep present. Dung is a pile of animal faeces. Fig. 2.1 shows one study plot. [Figure 2.1]

1. (a)Describe a method that the scientists could have used to select the study plots randomly.[2]
2. (b)Suggest why counting the dung may not provide an accurate estimate of deer or sheep numbers.[1]
3. (c)State two variables that were standardised by the scientists.[2]
4. (d)The report that the scientists read suggested that allowing sheep to graze alongside the deer significantly reduces the need to cull the deer in order to maintain species diversity. Explain why the results shown in Fig. 2.2 and Fig. 2.3 do not support this suggestion.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.