Biological Drawings

The CIE AS and A Level Biology (9700) Advanced Practical Skills paper usually requires students to make observations of a photograph or specimen – which will often be on a microscope slide – and to record their observations as a diagram or drawing. A biological drawing looks simple and uncomplicated but it is imperative that students are provided with clear steps to success, lots of WAGOLLs, and plenty of opportunities to develop this important skill throughout the course.

A good biological drawing should:

  • have clear single lines (no ‘fuzzy’ or ‘feathery’ lines)
  • show an accurate overall shape and proportions
  • not include shading or colouring (even the nucleus!)
  • be large, using up most of the space provided but not going outside that space.

Students should use a sharp HB pencil and a good eraser. A ruler should only ever be used for drawing label lines.

Low-power plan diagrams

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This type of diagram only shows the outlines of the different tissues. It should never show individual cells. Students may be familiar with the specimen (e.g. a cross section of a root or stem) but it is important that they only draw what they can see and not what they think they should see. Encourage students to look carefully in order to determine where one tissue ends and another one begins (look for differences in cell shape, size, densities and degree of staining).

For a low-power plan diagram of a microscope slide, CIE require that students are provided with a microscope with a x10 eyepiece lens and low-power objective lens (x10). An eyepiece graticule should also be fitted within the eyepiece and should be visible in focus at the same time as the specimen.

For a low-power plan diagram:

  • do not draw individual cells
  • draw all tissues completely enclosed by pencil lines (no gaps or crossed lines)
  • draw an accurate interpretation of the distribution of the tissues (the eyepiece graticule can be used without calibration to help draw the correct proportions).

High-power diagrams

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A high-power diagram generally does show individual cells. For a high-power diagram of a microscope slide, CIE require that students are provided with a microscope with a x10 eyepiece lens and high-power objective lens (x40).

For a high power diagram:

  • draw only a few representative cells
  • draw the cell wall of all plant cells (usually as a double line)
  • do not draw the nucleus as a solid blob (this is a particularly common error).

Labelling diagrams

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A ruler should always be used to draw label lines. The label lines should stop exactly at the structure or tissue that is being labelled. A sharp pencil should be used for all label lines and labels.

Workbook

Here is a workbook with checklists (self or peer) that I have produced to help AS and A Level Biology students with their biological drawing skills.

 

 

 

CIE Mark Scheme Abbreviations

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Some students (and teachers) remain confused by the abbreviations used in mark schemes. Since completing and then marking past papers is a key element in effective revision for the upcoming examinations, I thought it timely to highlight the following conventions used by Cambridge International Examinations (CIE) at both IGCSE and A Level.

+ ,  

All parts of the answer separated by a plus sign or comma are required to achieve the mark. In the example below, the candidate must refer to assimilates or sucrose and to the fact that they lower the water potential (inside the sieve tube element) in order to gain one mark.

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( )

Information in parentheses does not need to be made explicit in the answer in order for the candidate to achieve the mark/s. See example below.

/

Alternative answers for the same point. In the example below, the candidate can make reference to either folding or coiling and does not need to mention the tertiary structure (in parentheses) in order to be awarded the mark.

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Separates marking points. In other words, semi-colons represent the number of marks available for each answer. Note, that for the example below, full marks are available just for giving the answer (300) whether or not the candidate has also shown their workings out.

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A

Accept. The answer is not the answer the examiner is looking for but has been correctly cued by an equation or extra guidance and therefore acceptable to achieve the mark.

AVP ;

Any Valid Point. One point (note the one semi-colon) can be awarded at the examiner’s discretion if any other valid point has been made by the candidate.

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AVP ;;

Any Valid Point. The examiner can award up to two marks (note the two semi-colons) for two valid points made by the candidate.

R

Reject. This is different to ‘Ignore’ (I) and is a negative marking system. In other words, a mark must be deducted from the total if a ‘Reject’ answer is given. In the example below, if a candidate wrote ‘antibodies produced by T-cells‘ they would not receive a mark (i.e. the point awarded for correctly answering that antibodies are produced is deducted for incorrectly stating that they are produced by T-cells).

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Alternative wording. This is used when the responses are likely to vary more than usual. For example, instead of saying ‘less oxygen enters the blood‘ it would be acceptable to answer ‘less oxygen passes into the blood‘ or ‘less oxygen diffuses into the blood‘ etc.

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Answer underlined

These are key words which must be used by the candidate in order to achieve the mark. Note that grammatical variants and spelling errors (so long as the word can be read phonetically) are accepted.

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Or reverse argument. The reverse argument is equally valid.

I hope this clears up any confusion but if you have any questions about mark schemes and script abbreviations or conventions, please do get in touch.

 

 

 

Cambridge Outstanding Learner Awards

The Cambridge Outstanding Learner Awards reflect the talent and hard work of learners and acknowledges the dedication and commitment of teachers and parents. Our students have now achieved the top score in IGCSE Coordinated Sciences in Thailand for the third year in a row and it was a great privilege to attend this wonderful event at Shrewsbury International School in Bangkok.

Congratulations to all of the winners!