Biology If a student misses this required practical activity… …they won’t have covered this apparatus and technique. Other practicals within an A-level Biology course involving this skill 2. Preparation of stained squashes of cells from plant root tips; set-up and use of an optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index d. use of light microscope at high power and low power, including use of a graticule. Examination of permanent mounts of any tissue, related to specification content, in which students use both high- and low-power objectives of an optical microscope and use a stage micrometer and eyepiece graticule to measure the actual size of cells. 7. Use of chromatography to investigate the pigments isolated from leaves of different plants, eg leaves from and shade-intolerant plants or leaves of different colours g. separate biological compounds using thin layer/paper chromatography or electrophoresis. Separation of any aqueous mixture related to specification content, eg, sugars or amino acids, by paper or thin layer chromatography. Extraction of 'chlorophyll' from a plant or alga and separation of its constituent pigments by paper or thin layer chromatography. Separation of DNA fragments by electrophoresis. 12. Investigation into the effect of a named environmental factor on the distribution of a given species k. use sampling techniques in fieldwork. Use of random quadrats to investigate the pattern of distribution of a sessile organism. Examples include daisies in a school playing field, epiphytes on the bark of a tree and limpets on a rocky shore. Use of the technique to estimate the size of a population of woodlice in a garden or school playground. Chemistry If a student misses this required practical activity… …they won’t have covered this apparatus and technique. Other practicals within an A-level Chemistry course involving this skill 1. Make up a volumetric solution and carry out a simple acid-base titration e. use volumetric flask, including accurate technique for making up a standard solution. Make up a standard solution for any other volumetric exercise. shade-
No Student’s t-test Further guidance on teaching statistics in Biology The Department for Education criteria for A-level Biology (GCE AS and A-level subject content for biology, chemistry, physics and psychology) include the following mathematical skills that are relevant to statistics. Code Mathematical skill Exemplification of mathematical skill in the context of biology MS 1.9 Select and use a statistical test Students may be tested on their ability to select and use: • the chi-squared test to test the significance of the difference between observed and expected results • the Student’s t-test • the correlation coefficient. MS 1.10 Understand measures of dispersion, including standard deviation and range Students may be tested on their ability to: • calculate the standard deviation • understand why standard deviation might be a more useful measure of dispersion for a given set of data, eg where there is an outlying result. The description of these skills has been included verbatim in AQA’s specification for AS and A-level Biology. Since these statements are not in bold type, they could all potentially be examined in both AS and A-level papers. In teaching the AQA Biology AS and A-level specifications, we recommend that ‘the correlation coefficient’ with which students become familiar is Spearman’s rank, as in the legacy specification. Ultimately, though, the choice is left to the teacher. Consequently, if a question in a written test requires students to recognise that a correlation coefficient is the appropriate statistical test to use with given data, the answers ‘Spearman’s rank’, ‘correlation coefficient’ or any named correlation coefficient will be credited. In written examinations, students be asked to perform simple calculations such as finding a mean value. Students will not be asked to perform a calculation using a statistical test (or to calculate the standard deviation of a mean). This policy reflects the recognition by examiners and