Lab Practical (Paper 3) Skills

Drawing Cells (See pg 8 of INB for notes, this should be review) Do’s Don’ts HB pencil only Clear, continuous lines Accurate proportions Tissues completely enclosed by lines Label all tissues Correctly identified parts Representative portions or cells Scale bar Shading Textbook versions Individual cells on low power Nucleus as a solid blob on high power

Drawing Cells Other tips: Line must be completely connected (practice a few circles that are completely closed) Individual cell borders must always be drawn! Even if borders touch

Plan diagrams A plan diagram shows the distribution of tissues in a section. It also shows the proportions of the different tissues. Always low power Do not draw any cells in a lower power plan diagram.

Plan diagram guidelines make the drawing fill most of the space provided; leave space around the drawing for labels and annotations (if required by the question) use a sharp HB pencil (never use a pen) use thin, single, unbroken lines (often called ‘clear and continuous lines’) show the outlines of the tissues make the proportions of tissues in the diagram the same as in the section do not include drawings of cells do not use any shading or colouring http://www.youtube.com/watch?v=DxZBYtcBc-o http://www.youtube.com/watch?v=t3FuoBoE9XE

Plan diagram practice

Plan diagrams Add labels and annotations (notes) to your drawing only if you are asked for these in the question. Use a pencil and a ruler to draw straight lines from the drawing to your labels and notes. Write labels and notes in pencil in case you make a mistake and need to change them. You may leave your labels and notes in pencil – do not write over them in ink.

High Power Drawings should show a small number of cells (~3) make the drawing fill most of the space provided; leave space around the drawing for labels and annotations (if required by the question) use a sharp HB pencil (never use a pen) use clear, continuous lines (see above) draw only what is asked in the question, e.g. three cell types or one named cell and all cells adjoining it show the outlines of the cells the proportions of cells in the drawing must be the same as in the section you are drawing plant cell walls should be shown as double lines with a middle lamella between the cells; the proportions of cell walls should be drawn carefully. show any details of the contents of cells – draw what you see not what you know should be present do not use any shading or colouring

High Power Practice

Line Graphs Decide on your axes (independent variable goes on the x axis). Choose an appropriate scale: you don’t have to start at zero, as long as the scale is made clear choose an easy-to-plot numerical scale (multiples of 1,2,4,5 or 10). Make maximum use of the space available. The independent variable (the variable which you have chosen) should be plotted on the x (horizontal) axis – with label and units.

Line Graphs The dependent variable (the results) should be plotted on the y (vertical) axis – with label and units. Plot points accurately and clearly - use a cross x or encircled dot  Generally you should not extend your curve / line beyond the first and last points. More than one curve will need a clearly labeled key. Remember an informative title!

Line graphs A smooth line (straight or curved) should only be drawn if there is good reason to believe that intermediate values, if they were recorded, would fall on the line, e.g. the effect of light intensity on the rate of photosynthesis or the effect of temperature on the rate of reaction of an enzyme. Generally, if you are not sure, join points with a straight line and use a ruler!

Interpolation vs. Extrapolation Using your graph to determine a value by interpolation means that you take readings of intermediate values from the graph you have drawn – you cannot do this where you have joined points with straight lines While extrapolation means that you determine a value by extending the graph – here you have to extend the line or curve according to the trend.

Drawing Tables raw data (results) in a single table ruler used for the border, rows and columns each column is headed: informative description for qualitative data (non- numeric) e.g. “colour of precipitate” physical quantity and the correct SI unit for quantitative (numeric) data used e.g. temperature / °C or temperature (°C) no units in the body of the table (units only in the column headings) table has an informative title

Drawing Tables first column headed with the independent variable further columns to the right contain the dependent variable calculated value from calculations e.g. means, rates, in the columns to the far right of the table (no calculations in the table) all the raw data added to the table recorded to the same number of decimal places and significant figures clear description of colours used e.g. blue, violet, blue/green - vague terms to describe shades (e.g. pale bluish purple) avoided. Note: the term ‘colourless’ or ‘no colour’ rather than ‘clear’ should be used