Tag Archives: a level

CIE Biology: How to Ace Paper 3

This post is specifically for the CIE Biology International A level qualification. What follows are my attempts to help guide students to do the best they can in the advanced practical skills exam, Paper 3. However, the information below is no substitute for proper revision and the dedicated practise of actually carrying out a variety of biology experiments. Additionally, I would strongly recommend you use the past papers section of CIE’s website to sit as many “mock” practical exams as possible.

Command words in a question


  • Say what is going on, e.g. the trend or pattern of results.
  • When describing data, always use units if appropriate (e.g. °C or cm3).


  • Say why a trend or pattern is occurring.
  • When explaining data, always link it to A level Biology.

Although describe and explain are the most common command words, you might find yourself answering questions with any of the following:

  • Calculate: use mathematics to find an answer. E.g. mean, percentage, percentage change, rate, ratio, etc.
  • Measure: use a suitable measuring instrument to take a reading, being sure to include units after the numerical answer.
  • Suggest: there is no one correct answer; you should look through the information you have been given for some clues.

Even more rarely you might find one of the below command words in a question:

  • State: give a brief answer – maybe one word or a phrase.
  • Define: give a definition – these should be concise.
  • Determine: explain how you could take measurements and calculate an answer from these measurements (e.g. in an experiment).

How many answers should I give?

  • If a question states “identify two” then only the first two responses will be marked.
  • If a question states “record observable differences” then all responses will be marked.

How great is the risk?

If a question asks you to “state the hazard with the greatest level of risk” for your practical, do not choose one you deem to be low risk. E.g. warm water in a thermostatically-controlled waterbath set at 30°C, is a hazard that is low risk and so would not gain a mark. A better answer would identify a risk that was either medium or high, e.g. hydrogen peroxide is harmful to the skin. The key is to identify a hazard with “the greatest level of risk”.

Deciding independent variable values

Give five values at roughly even intervals (e.g. every 5°C or 10 cm3) when deciding what values to use for your independent variable. Always use units if appropriate (e.g. °C or cm3).

Recording numbers and drawing tables

Do not go past one decimal place when recording the results from your experiment, usually whole numbers are fine. And always use units if appropriate (e.g. °C or cm3).

Table Headings:

  • Put the independent variable (IV) on the left and dependent (DV) on the right.
  • Draw a line between the top row and the body of the table, e.g. underline the IV and DV.
  • Use the full name of the IV and DV (e.g. temperature of hydrogen peroxide and time taken to rise).
  • Only use units  in the headings, not the body of the table (e.g. temperature of hydrogen peroxide / °C and time taken to rise / s).



  • Record results for at least five values of the IV.
  • Results should show the pattern or trend theoretically expected of the practical.
  • Use whole numbers.
  • Record results for two trials and calculate a mean average.
  • The mean average should be recorded to no more than one decimal place.

Identifying sources of error

Think carefully about your experiment, where might there have been an error? E.g. if you are looking at colour changes this is subjective and will be a source of error. Ensure you state the error and the reason it occurred.

Describe how an element of a practical can be investigated.

  • Use five values.
  • State how these five values will be made, e.g. if the IV is concentration of enzyme, “use simple or serial dilution” or if it is temperature “use a thermostatically-controlled waterbath at 20°C, 30°C, 40°C, 50°C and 60°C”.

Constructing graphs

  • You will normally use data that is given to you in the paper.
  • Put the IV on the x axis, DV on the y axis.
  • Use the full title from the table to label each axis, e.g. “initial rate of catalase activity / s-1“.
  • Always use units if appropriate (e.g. s or seconds but not sec).
  • Look at the values and use a logical scale. E.g. a scale of 0.06 or 0.04 for every large square of graph paper is not logical. However, a scale of 0.05 is logical.
  • Each plot will be checked to see whether it is accurate to within half a small square of the graph paper. It is recommended you use an x mark to do this.
  • There should be no labelling within the area of the graph.
  • Lines will be judged for their quality*.

Bar graphs

  • Ensure lines are not too thick, as the quality of each one will be judged*.
  • Bars can be touching. However, if you chose to leave gaps the gaps must be evenly spaced.
  • The horizontal lines at the top must be perfectly straight, parallel to the x axis.

Drawing diagrams

  • Quality of lines will be judged*.
  • No ruler straight lines for your diagram: nature is not straight!
  • No labels or writing within the drawing.
  • Label only what is asked of in the question.
  • Do not draw in anything that you do not see. E.g. smaller organelles.

Plan diagrams

  • The diagram should be at least 60 mm wide at its greatest width.
  • There should be no shading.
  • There should be no cells in  plan diagram. Do not be tempted to draw them in!
  • Use the correct section of the slide. This will be in the instructions of the questions, but make sure you actually draw what it wants you to!

Diagrams of cells

  • Cells should be at least 50 mm at their greatest width.
  • Draw exactly the number of cells stated in the question.
  • Do not include half cells. The questions always state “whole cells”.
  • Cells should not overlap but may be abutting (e.g. touching each other or sharing an outermost line).


  • Always show your working and the steps you take to come to your answer.
  • Always show units, but do not mix units. E.g. not 1 mm and 50 µm.
  • When converting units, show the conversion. E.g. 1 mm to µm: 1 x 1,000 = 1,000 µm.
  • Try not to go beyond one decimal place, or the same level of precision as is given in the question.
  • Give ratios to the lowest common denominator. E.g. 168:58 should be 84:29.

Comparing observable differences using a table

  • Organise the table as three columns; one for the differences and two for the samples. E.g


  • Underline the headings and divide the columns as per the table above.
  • If asked for differences, do not give similarities!
  • Differences would ideally be “X is thick” and “Y is thin”.

*Quality of lines

Each line you draw for a graph or drawing could be judged for its quality. E.g. whether it has been drawn by a sharp pencil as a thin and continuous line. This is really important as you don’t want to lose silly marks for not sharpening your pencil!


Image by Asim18, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=3129973

Five books all Biology A level students should read

This is part one of a series of posts listing, in no particular order, essential reading for A level Biology students.

  1. The Red Queen: Sex and the Evolution of Human Nature by Matt Ridley

This is truly essential reading for anyone interested in biology. As the title suggests it is a compendium of ideas and thoughts pertaining to evolution and in particular how they might impact on being human. After reading it in the first year of university it immediately had a profound and significant effect on my understanding of the subject. Its many themes have stuck with me throughout and since starting teaching I have come back to it time and again as a source of inspiration for both teaching and improving my understanding of key topics within biology. Each chapter is written in an accessible style and abounds with humour. Whether pondering the absence of male bdelloid rotifers to discussing the Inca sun-king’s “house of virgins” Ridley writes with authority and clarity. Forgive my hyperbole but The Red Queen is among my absolute favourite books; even if you do not study biology put this on the top of your reading list!

  1. The Immortal Life of Henrietta Lacks by Rebecca Skloot

A book with a significant and poignant historical perspective, it looks beyond the science of the immortal HeLa strain of cells to explore the civil rights movement in 1950s America. Consequently this is a perfect recommendation for any student studying History and Biology at A level. Additionally the ethically dubious actions described would also promote great discussion beyond these two subjects. As a journalistic exposé and investigation into an appalling miscarriage of ethical justice it is superb. Furthermore it also highlights the incredible advancements that were made as a result of this malpractice and poses the question; do the ends justify the means in medical research? Beyond being a great book about biology this is also, as the Times reported, “as gripping and rich as any work of fiction you will read”. I am incredibly thankful to my former colleague who gave this to me as a leaving present and whole heartedly recommend it.

  1. Life Ascending: The Ten Greatest Inventions of Evolution by Nick Lane

As a Biology teacher I was amazed when I first read Life Ascending; it is almost a perfect accompaniment to A level Biology. Not only does the chapter-structure mean that you can dip in and out, reading sections that pique the interest at will, but at least six of the chapters are directly relevant to the subject specification. For example it is easy to see how DNA, Photosynthesis, Movement and Sight are connected to A level, but even The Origin of Life (respiration – see Nick Lane’s other cheekily titled Power, Sex, Suicide: Mitochondria and the Meaning of Life) and The Complex Cell (eukaryotic v prokaryotic cells) are germane to Sixth Form study of biology. I would, of course, argue that every chapter was relevant and incredibly useful in building up and linking together the big ideas in biology to create a schema for the subject. Perhaps the best epithet is from the aforementioned Matt Ridley “If Charles Darwin sprang from his grave, I would give him this fine book to bring him up to speed.”

  1. The Epigenetics Revolution by Nessa Carey

This is the book which smashes open the fascinating world of epigenetics. So you think DNA is a stable template that does not change? Think again. Carey describes plenty of inherently interesting examples, even if you weren’t interested in the underlying biology her writing would cause you to be absorbed in these well-written illustrations. One in particular is drawn from the Dutch Hunger Winter and suggests that malnourishment in early pregnancy increases the risk of obesity in not only the children of the malnourished mother, but her grandchildren too. Why? Obviously I would recommend you read Carey’s lucid and accessible narration to find out, but it is the seemingly magical interactions with the nucleotide bases that make up DNA itself that is epigenetics. To me the topic is the future of the subject and if students want to be part of this “revolution” this book is a must-read.

  1. Darwin’s Island by Steve Jones

Admit it, you’re thinking “Ah! The Galapagos Islands”. But no the title actually refers to Britain and is an outstanding account of the experiments Charles Darwin investigated in and around his home county of Kent. Jones writes with wit and enthusiasm, this craftsmanship is best illustrated by the fact that my favourite chapter is the final one entitled The Worm Crawls In which centres on soil.  In some hands thirty-two pages on this topic might drag, but once finished I was inspired to present an assembly on the humble earthworm. More than anything this book allows readers to see past the rightfully headline grabbing HMS Beagle voyage to cast an eye over the incredibly rich and detailed research that does not necessarily receive the credit it is due. As Jones points out Darwin’s visit to the Galapagos Islands only lasted five weeks, compared to the forty years working in Britain.

Part tow in this series of recommended reads is Another book all Biology A level students should read.

Biology A Level: International Rescue?

This blog has been at least a year in the making. In fact ever since 2013 when we decided to change our A level exam board to an International A level, I have tried to keep a check of our rationale for doing so. After giving a talk at a Cambridge International Examinations seminar at the end of November I had written down a long list of reasons and originally planned to post these during the Christmas holiday, but life events rather overtook me. What follows below is a précis of the reasons for leaving AQA and the other domestic exam boards for the exotic climes of an international qualification. As such it focuses on the perceived benefits of the change; I aim to redress this balance, should I need to, in the future with information about limitations. Although it was originally me, as HoD, that initiated and steered a course towards International A levels, my department were very much behind the decision from the off. In fact due to the huge uncertainty of what exactly the new Science A level specifications were going to include and how the practical work would be assessed we “jumped ship” early – officially deciding back in September 2013. Students at Sixth From are now studying the “International” A level from Cambridge International Examinations.

International rescue?

International rescue? (Image taken from Wikimedia Commons)

The decision making process was made easier by our disenchantment with EMPA and ISA “practical examinations”. Students constantly performed well below their attainment in theory papers. In fact with a little (very lightweight, unreliable, insignificant, etc) statistical analysis I demonstrated that on average our Biology A level students were performing one and a half grades below their theory paper attainment; and this is from pupils who carried out practical work almost every week and were scoring close to full UMS in the theory papers. The International A level offers a “proper” practical examination, one beyond any suspicions of “interference” so that students are awarded marks that correspond to their performance in theory papers. I could probably write a whole post on my total disillusionment with the proposed changes to domestic Science A level practicals… I will leave that for another time, suffice to say I am disappointed by the approach of the domestic exam boards and dismayed that practical assessment will not form part of the overall A level grade. More reasons are shared below and are taken from notes I used when discussing International A levels at a CIE seminar held at Somerset House in November. It is a fairly comprehensive list of the motivations behind why I think the award would suit pupils at our school:

  • Natural progression following on from the principles of IGCSE, which we teach at Key Stage 4.
  • Syllabus is more thorough; the content manages to balance a broad range of topics and goes into an appropriate depth of knowledge. In particular it favours breadth of knowledge over “sound bites”.
  • Assessment is not modular, encouraging students to think about the “big ideas in Biology”. This links directly to the syllabus; it is not divided into topics that are then examined in separate papers.
  • Encourages more exhaustive learning and rewards those who work hard and understand the topics.
  • The emphasis is on students carrying out and planning practical work. Experiments are present throughout the two year course…
  • …even more importantly these experiments are formally assessed, thus rewarding students who have grasped basic practical skills. This maintains the significance of actually having to do practicals properly in the classroom whilst learning the course and removes any suspicions of interference. Pupils therefore are awarded marks that match their ability and correspond to attainment in theory papers.
  • Grades are criterion-referenced.
  • Better preparation for university, particularly if students plan to study a biology-related degree.

As stated in my introduction I will be revisiting this list and possibly adding more to it. I also want to share our experiences of actually teaching the qualification as well as any problems we encounter. Perhaps it will prove to be our International Rescue, but for now I am pleased to type: “FIVE, FOUR, THREE, TWO, ONE. THUNDERBIRDS ARE GO!”.

Header image taken from Flickr.