WJEC Biology for AS Level Student Book: 2nd Edition

concentration is correlated with an increase in the number of flatworms. Explain why the data for flow rate and light intensity decrease the validity of the conclusion. [3] This is AO2 because you are asked to explain the impact of physical factors on practical data. AO2 When handling qualitative data The image below shows chromosomes from a human cell. Draw a circle, labelled A, around the chromosomes that indicate the cell is from a female. Draw a circle, labelled B, around the chromosomes that indicate that the individual has Down’s syndrome. [2] The photograph here provides the data. It is not numerical data but an image, and so is qualitative. AO2 When handling quantitative data In an experiment to determine the water potential of carrot cells, chips of carrot cortex were cut with the dimensions 35mm × 3mm × 3mm, as shown in the diagram. Calculate the total surface area of each chip. [3] The measurements provide quantitative information and you are asked to apply an arithmetical procedure to generate a conclusion. Assessment Objective 3 (AO3) Analyse, interpret and evaluate scientific information, ideas and evidence to: ▪ make judgements and reach conclusions ▪ develop and refine practical design and procedures. The AO3 marks on a paper are awarded for developing and refining practical design and procedures, for making judgements and for drawing conclusions. You may be asked to criticise a method or analysis or be asked how to improve aspects of it. You may be asked to design a method to test a particular hypothesis or asked why you might apply a particular statistical test. You may be asked to interpret a statistical test or draw a conclusion from evidence presented to you. Examination questions will give information in novel situations. As with AO2 questions, you may be presented with unfamiliar scenarios, but you will be tested on how well you use your knowledge to understand and interpret them. For all the experiments you have done, make sure you know how to enhance the accuracy of your method and the repeatability of readings. When you draw a biological conclusion from your results, explain how this has been an adaptive advantage to the organism concerned. AO3 questions are often worth a higher number of marks than AO1 and AO2 questions. They tend to use words such as ‘evaluate’, ‘suggest’ or ‘design’ and often ask you to manipulate experimental data. Here are two examples: AO3 Make judgements and reach conclusions Apple leaves and maize leaves are shown in the images below. Apple branch with leaves Young maize plant showing leaves The numbers of stomata per mm 2 on the two sides of apple and maize leaves are shown in the table. Interpret the data using the images to suggest the relative rates of transpiration from the two sides of the maize leaves and the two sides of the apple leaves. Use the photographs to suggest why these stomatal distributions may be useful to these plants. [4] 35 mm 3 mm 3 mm WJEC Biology for AS Level 8