Biology 5090/62 — May/June 2016
Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme
Topics Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials · Microscopy and Biological Drawing
Fig. 1.1 shows two leaves from a holly tree. Holly leaves have sharp spines (prickles).
A student decided to investigate whether the number of spines on holly leaves growing nearer to the ground was different from the number of spines on leaves growing higher up on a tree.
The student collected 12 leaves growing 1 metre above the ground and 12 leaves growing 3 metres above the ground. They then counted the number of spines on each leaf.
The student's results are shown in Fig. 1.2.
In the space below, construct a table of these results. Arrange the number of spines on each leaf in rank order, from lowest to highest.
Calculate the mean number of spines on the leaves growing 1 m above the ground and the mean number of spines on the leaves growing 3 m above the ground.
mean number of spines on leaves growing 1 m above ground = ______
mean number of spines on leaves growing 3 m above ground = ______
Construct a bar chart to compare the mean number of spines on leaves growing 1 m above the ground with the mean number of spines on leaves growing 3 m above the ground.
Describe what the student could conclude about the number of spines on holly leaves at 1 m and 3 m above the ground.
Use the information in your bar chart and in Fig. 1.2 to support your answer.
Suggest two ways in which the reliability and validity of these conclusions could be improved.
- ______
- ______
Giving full experimental details, explain how you could compare the numbers of stomata on the upper and lower surfaces of a holly leaf.
The rest of this paper
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