AQA Practical handbook for A-level Biology Version 1.3 LATEST 2024 UPDATE

Contents Section Page A Introduction 4 Information about practical work for teachers B Practical work in reformed A-level Biology, Chemistry and Physics 7 C Practical skills assessment in question papers 12 D Guidelines for supporting students in practical work 18 E Use of lab books 20 F Cross-board statement on CPAC 22 G Evidence for the endorsement 31 H Questions from teachers following the first year of the practical endorsement 33 I Cross-board apparatus and techniques and AQA required practical activities 47 Guidelines for teachers and students J Tabulating data 50 K Significant figures 51 L Uncertainties 52 M Graphing 59 N Biological drawing 68 O Statistical tests in Biology 70 P Glossary of terms 77 Guidance on the required practical activities Q Practical ladders and exemplar experiments: Biology 81 A. Introduction Practical work brings science to life, helping students make sense of the universe around them. That’s why we’ve put practical work at the heart of our Biology, Chemistry and Physics A-levels. Practical science allows scientific theory to transform into deep knowledge and understanding – scientific thinking. Through investigation, students uncover the important links between their personal observations and scientific ideas. The purpose of this Practical handbook This handbook has been developed to support you in advancing your students to fluency in science. Over the years, there have been many rules developed for practical work in Biology, Chemistry and Physics. Some have been prescriptive, some have been intended as guidance. Although we have always attempted to be consistent within subjects, differences have emerged over time. Worse, students taking Biology may also be taking Physics and find themselves confronted with contradictory rules and guidance. This practical handbook is an attempt to harmonise the rules and guidance for Biology, Chemistry and Physics. There are occasions where these will necessarily be different, but we will try to explain why on the occasions where that happens. The new A-level specifications accredited for first teaching in September 2015 bring with them a complete change in the way practical work is assessed. No longer will teachers have to force their students to jump through hoops set up by exam boards or worry about how much help they are giving students and whether it’s allowed or not. We have worked with teachers, technicians and examiners to produce this handbook. This is an evolving document, but one that we hope you will be able to use with your students, whether they’re doing A-level Biology, Chemistry or Physics, or a combination of subjects, to improve their practical skills: in the classroom, in the laboratory, in exams, for the endorsement and on to university or the workplace. The latest version will always be on our website. Unless specified, all guidance is common to Biology, Chemistry and Physics at both AS and A-level and subject-specific examples are for illustration only. However, the extent to which a particular aspect is assessed will differ. Teachers should refer to the specifications and specimen materials on our website for more information. The purpose of practical work There are three interconnected, but separate reasons for doing practical work in schools and colleges. They are: 1. To support and consolidate scientific concepts (knowledge and understanding). This is done by applying and developing what is known and understood of abstract ideas and models. Through practical work we are able to make sense of new information and observations, and provide insights into the development of scientific thinking. 2. To develop investigative skills. These transferable skills include: a. devising and investigating testable questions b. identifying and controlling variables c. analysing, interpreting and evaluating data. 3. To build and master practical skills such as: a. using specialist equipment to take measurements b. handling and manipulating equipment with confidence and fluency c. recognising hazards and planning how to minimise risk. By focusing on the reasons for carrying out a particular practical, teachers will help their students understand the subject better, to develop the skills of a scientist and to master the manipulative skills required for further study or jobs in STEM subjects. The reformed A-levels in Biology, Chemistry and Physics separate the ways in which practical work is assessed. This is discussed in the next section. Fluency in science practical work At the beginning of a year 12 course, students will need support and guidance to build their confidence. This could involve, for example, breaking down practicals into discrete sections or being more explicit in instructions. Alternatively, a demonstration of a key technique followed by students copying may support students’ development. This could be a better starting point than ‘setting students loose’ to do it for themselves. Note: Safety is always the responsibility of the teacher. No student should be expected to assess risks and then carry out their science practical without the support and guidance of their teacher. B. Practical work in reformed A-level Biology, Chemistry and Physics Statement on practical work by Glenys Stacey, Chief Regulator at Ofqual, April 2014 Practical work and experimentation is at the heart of science. It matters to science students, their teachers and their future universities and employers. But A-level students do not always have the chance to do enough of it. Practical work counts for up to 30 per cent of the final grades and the vast majority of students get excellent marks for it, but still many enter university without good practical skills. It is possible to do well in science A-levels without doing sufficient or stretching hands-on science, and other pressures on schools can make it difficult for science teachers to carve out enough time and resource to do it if students can get good A-level grades in any event. That is not right – so why is it so? Students are assessed and marked on their performance in set tasks, but these are generally experiments that are relatively easy to administer and not particularly stretching. It has proved extremely difficult to get sufficient variety and challenge in these experiments, and so students do well even if they have not had the opportunity to do enough varied and stretching experimentation, and learn and demonstrate a variety of lab skills. What to do? In future, science A-level exams will test students’ understanding of experimentation more so than now. Those who have not had the chance to design, conduct and evaluate the results from a good range of experiments will struggle to get top grades in those exams. They will also be required to carry out a minimum of twelve practical activities across the two year course – practical activities specific to their particular science, and that are particularly valued in higher education. Students will receive a separate grade for their practical skills (a pass/fail grade). These reforms should place experimentation and practical skills at the heart of science teaching, where they should be, and students going to university to study a science are more likely to go well prepared. They will also change the game for science teachers, enabling them to teach science in a more integrated and stimulating way with more hands on science and to say with justification that without sufficient time and effort put into lab work, their students will struggle to get the grades they deserve. Glenys Stacey, Chief Regulator The reformed AS and A-level specifications will have no direct assessment of practical work that contributes to the AS or A-level grades. There are two elements to the practical work that students must carry out in their study of A-level Biology, Chemistry and Physics: These will be assessed in two ways: 1. Questions in the written papers, assessed by AQA (see section C) 2. The practical endorsement, directly assessed by teachers (see section F) Teachers will assess their students’ competence at carrying out practical work. They will assess each student on at least 12 different occasions. This could be whilst teaching the 12 required practicals, or could be during other practical work of sufficient challenge. At the end of the course, teachers will decide whether or not to award a pass in the endorsement of practical skills. The teacher must be confident that the student has shown a level of mastery of practical work good enough for the student to go on to study science subjects at university. 12 required practical activities Teacher devised practical experiences of sufficient challenge Endorsement of practical skills Students who miss a required practical activity 1. Written exam papers The required practical activities are part of the specification. As such, exam papers could contain questions about the activities and assume that students understand those activities. A student who misses a particular practical activity may be at a disadvantage when answering questions in the exams. It will often be difficult to set up a practical a second time for students to catch up although if at all possible an attempt should be made. Teachers will need to decide on a case by case basis whether they feel it is important for the student to carry out that particular practical. This is no different from when teachers make decisions about whether to re-teach a particular topic if a student is away from class when it is first taught. 2. Endorsement To fulfil the requirements of the endorsement, every student must carry out a minimum of 12 practicals. A student who misses one of the required practicals must carry out another practical to be able to gain the endorsement. In most cases, this can be any experiment of A-level standard. However, students must have experienced use of each of the apparatus and techniques. In some cases, a particular apparatus and technique is only covered in one required practical activity. If a student misses that activity, the teacher will need to provide an opportunity for the student to carry out a practical that includes that activity. The list below shows the apparatus and techniques that are covered by one activity only and alternatives to the required practical. Note: there is a possibility that the student could be asked questions about the required activity in written papers that would not be fully understood by carrying out the alternative. This should be considered when deciding whether to repeat the required activity. 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 objective lenses 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 shade- tolerant 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 named 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 mark-release- recapture technique to estimate the size of a population of woodlice in a garden or school playground/sportsfield. The AS and A-level papers will contain the following types of questions which relate to practical work: 1. Questions set in a practical context, where the question centres on the science, not the practical work. Example (A-level Biology Specimen Paper 1) Example (AS Chemistry Specimen Paper 1) Example (A-level Physics Specimen Paper 3) 2. Questions that require specific aspects of a practical procedure to be understood in order to answer a question about the underlying science. Example (A-level Biology Specimen Paper 2) Example (AS Chemistry Specimen Paper 2) 3. Questions directly on the required practical procedures. Example (AS Biology Specimen Paper 1) Example (A-level Chemistry Specimen Paper 3) 4. Questions applying the skills from the required practical procedures and the apparatus and techniques list. Example (A-level Chemistry Specimen Paper 3) Example (AS Physics Specimen Paper 2) Developed in collaboration with NFER and CLEAPSS Clarify the importance of keeping a lab book or other records of practical work Explain that students need a record of their achievements to guide their learning. Lab books also can be an opportunity to develop a skill used both by scientists and in business. They allow students to accurately and clearly record information, ideas and thoughts for future reference which is a very useful life skill. Warn students against plagiarism and copying Explain the meaning of the term plagiarism and that the use of acknowledged sources is an encouraged and acceptable practice, but trying to pass off other people’s work as their own is not, and will not help them learn. Show students how sources should be cited. Explain the learning criteria for each skill This will help students learn and allow them to know when they have met the criteria. The student lab book contains the criteria, but they own the process and have the responsibility for collecting appropriate evidence of success. Use clearly defined learning outcomes For example, if you are running a practical session to teach students how to use a microscope and staining techniques safely and efficiently, then make sure they know why they are learning this. This will also make it much easier for them to know when they have met the criteria. Start with simple tasks initially Students need to become confident with the apparatus and concepts of practical work before they can proceed to more complicated experiments. It may be more effective to start with simple manipulation skills and progress to the higher order skills. Teach practical work in your preferred order Teach the skills as you see fit and suit your circumstances – the assessment process is aimed to be flexible and help you teach practical work, not to dictate how it should be done. Use feedback Research shows that feedback is the best tool for learning in practical skills. Students who normally only receive numerical marks as feedback for work will need to be trained in both giving and receiving comment-based feedback. Provided it is objective, focused on the task and meets learning outcomes, students will quickly value this feedback. Feedback is essential to help students develop skills effectively. Allowing self and peer review will allow time for quality feedback as well as provide powerful learning tools. However, this is a decision for teachers. The scheme is designed to be flexible while promoting best practice. Don’t give marks We have deliberately moved away from banded criteria and marks to concentrate on the mastery of key practical competencies. The purpose of marking should be changed to emphasise learning. Students should find it easier to understand and track their progress, and focus their work. We would expect most students, with practice and the explicit teaching of skills and techniques, to succeed in most competencies by the end of the course. Give feedback promptly Feedback does not need to be lengthy, but it does need to be done while the task is fresh in the students’ mind. Not everything needs written feedback but could be discussed with students, either individually or as a class. For example, if a teacher finds that many students cannot calculate percentage change, the start of the next lesson could be used for a group discussion about this. Use peer assessment The direct assessment of practical work is designed to allow teachers to integrate student-centred learning (including peer review), into day-to-day teaching and learning. This encourages critical skills. Research indicates these are powerful tools for learning. For example, teachers could ask students to evaluate each other’s data objectively. The students could identify why some data may be useful and some not. This can be a very good way of getting students to understand why some conventions are used, and what improves the quality of results. This also frees up marking time to concentrate on teaching. Use group work This is a very useful skill, allowing students to build on each other’s ideas. For example, planning an experiment or selecting an appropriate statistical test to use at the end of an experiment can be done as a class discussion. Alternatively, techniques such as snowballing can be used, in which students produce their own plan then sit down in a small group to discuss which are the best collective ideas. From this, they revise their plan which is then discussed to produce a new ‘best’ plan. Students do not need to write up every practical that they do in detail. However, it is good practice to have a record of all they do. A lab book could contain this record. It is a student’s personal book and may contain a range of notes, tables, jottings, reminders of what went wrong, errors identified and other findings. It is a live document that can function as a learning journal. Lab books are not a requirement of the CPAC endorsement or the AQA AS and A-level specifications in Biology, Chemistry or Physics. They are highly valued by colleagues in higher education and are an easy way for students to demonstrate their mastery of Competence 5 “Researches, references and reports”. Each institution has its own rules on lab book usage. The following guidelines are an amalgam of guidelines from a selection of companies and universities that use lab books. They are designed to help students and teachers in preparing to use lab books for university but do not represent the only way that books could be used for A-level sciences. Teachers will wish to vary or ignore the following points to suit their purposes. The purpose of a lab book A lab book is a complete record of everything that has been done in the laboratory. As such it becomes important both to track progress of experiments, but also, in industry and universities, to prove who developed an idea or discovered something first. A lab book is a: • source of data that can be used later by the experimenter or others • complete record of what has been done so that experiments could be understood or repeated by a competent scientist at some point in the future • tool that supports sound thinking and helps experimenters to question their results to ensure that their interpretation is the same one that others would come to • record of why experiments were done. Type of book A lab book is often a hard-backed book with bound pages. Spiral bound notebooks are not recommended as it is too easy to rip a page out and start again. It is generally advisable that a lab book has a cover that won’t disintegrate the moment it gets slightly wet. Style Notes should be recorded as experiments are taking place. They should not be a “neat” record written at a later date from scraps of paper. However, they should be written clearly, in legible writing and in language which can be understood by others. Many lab books are used in industry as a source of data, and so should be written in indelible ink. To ensure that an observer can be confident that all data are included when a lab book is examined, there should be no blank spaces. Mistakes should be crossed out and re-written. Numbers should not be overwritten, erased, nor should Tippex be used. Pencil should not be used for anything other than graphs and diagrams. Each page should be dated Worksheets, graphs, printed information, photographs and even flat “data” such as chromatograms or TLC plates can all be stuck into a lab book. They should not cover up any information so that photocopying the page shows all information in one go. Anything glued in should lie flat and not be folded. Content Generally, lab books will contain: • title and date of experiment • notes on the objectives of the experiment (eg apparatus and techniques covered or CPAC assessed) • notes on the method, including all details (eg temperatures, volumes, settings of pieces of equipment) with justification where necessary • estimates of the uncertainty of measurements • sketches of how equipment has been set up can be helpful. Photographs pasted in are also acceptable • data and observations input to tables (or similar) while carrying out the experiment • calculations – annotated to show thinking • graphs and charts • summary, discussions and conclusions • cross-references to earlier data and references to external information. This list and its order are not prescriptive. Many experiments change as they are set up and trials run. Often a method will be given, then some data, then a brief mention of changes that were necessary, then more data and so on. Common Practical Assessment Criteria (CPAC) The assessment of practical skills is a compulsory requirement of the course of study for A-level qualifications in biology, chemistry and physics. It will appear on all students’ certificates as a separately reported result, alongside the overall grade for the qualification. The arrangements for the assessment of practical skills are common to all awarding organisations. These arrangements include: • A minimum of 12 practical activities to be carried out by each student which, together, meet the requirements of Appendices 5b (Practical skills identified for direct assessment and developed through teaching and learning) and 5c (Use of apparatus and techniques) from the prescribed subject content, published by the Department for Education. The required practical activities will be defined by each awarding organisation in their specification; • Teachers will assess students using Common Practical Assessment Criteria (CPAC) issued jointly by the awarding organisations. The CPAC are based on the requirements of Appendices 5b and 5c of the subject content requirements published by the Department for Education, and define the minimum standard required for the achievement of a pass; • Each student will keep an appropriate record of their practical work, including their assessed practical activities; • Students who demonstrate the required standard across all the requirements of the CPAC will receive a ‘pass’ grade; • There will be no separate assessment of practical skills for AS qualifications; • Students will answer questions in the AS and A level examination papers that assess the requirements of Appendix 5a (Practical skills identified for indirect assessment and developed through teaching and learning) from the prescribed subject content, published by the. Department for Education. These questions may draw on, or range beyond, the practical activities included in the specification. Competency Practical mastery In order to be awarded a Pass a student must, by the end of the practical science assessment, consistently and routinely meet the criteria in respect of each competency listed below. A student may demonstrate the competencies in any practical activity undertaken as part of that assessment throughout the course of study. Student may undertake practical activities in groups. However, the evidence generated by each student must demonstrate that he or she independently meets the criteria outlined below in respect of each competency. Such evidence: a. will comprise both the student’s performance during each practical activity and his or her contemporaneous record of the work that he or she has undertaken during that activity, and b. must include evidence of independent application of investigative approaches and methods to practical work. 1. Follows written procedures a. Correctly follows written instructions to carry out experimental techniques or procedures. 2. Applies investigative approaches and methods when using instruments and equipment a. Correctly uses appropriate instrumentation, apparatus and materials (including ICT) to carry out investigative activities, experimental techniques and procedures with minimal assistance or prompting. b. Carries out techniques or procedures methodically, in sequence and in combination, identifying practical issues and making adjustments when necessary. c. Identifies and controls significant quantitative variables where applicable, and plans approaches to take account of variables that cannot readily be controlled. d. Selects appropriate equipment and measurement strategies in order to ensure suitably accurate results. 3. Safely uses a range of practical equipment and materials a. Identifies hazards and assesses risks associated with these hazards, making safety adjustments as necessary, when carrying out experimental techniques and procedures in the lab or field. b. Uses appropriate safety equipment and approaches to minimise risks with minimal prompting.