9744 04 H2 Biology Practical Notes A-Levels (2025)

9744 / 04 H2 Biology Practical Notes 2025 And Remember Kids 1. If anything said here contradicts what your teachers or tutors told you, prioritise them. 2. Stay calm and read the question carefully, don't assume you know whats gg on just because the apparatus is familiar 3. You’re not special, Cambridge is not going to set a specially difficult paper for you 4. Plot your graph points correctly!!! Losing 1 mark for being 1 square off is throwing!!!. 5. You have plenty of time so don’t stress if you’re stuck js move on 6. If there is an abnormal question you may find comfort in knowing that everyone else will be just as confused as you will be. Microscopy 1. Comparison Questions Generally for microscopy, compare arrangement, shape and size of cells (triangular / rectangular / oblong / oval) You can compare the presence of starch granules / vacuoles / choloplast but I wouldn’t recommend it bcos you can’t really tell the difference between them under a microscope and it may not be a valid marking point in answer scheme, unless it’s a last resort. Dicots VS Monocots Diameter ● Dicots are larger and Monocots are smaller Vascular Bundles (ie Xylem and Phloem) ● Arrangement: Dicot’s are arranged in a ring around the central pith, Monocot’s are clustered at the root ● Number: Dicot’s are limited in number, Monocot’s are numerous ● Shape: Dicot’s are uniform and larger in size. Monocot’s tend to have larger VB present towards the center and smaller VB at the peripherals Pith (central mass of cell) ● Well developed in Dicots, reduced and remains undifferentiated in Monocots Cortex ● Cortex area relative to root is larger in Dicots and smaller in Monocots Endodermis (tissue layer that circles the vascular bundles) ● Present in Dicots, absent in Monocots Number of tissue layers ● Dicots have more as the cells are more differentiated and hence have more distinct organisation Other Possible Comparisons ● Presence of ___ (hair, idk) ● Overall shape of ___ ● Thickness of ___ 2. Limitations / Improvements in microscopy ● Measure all the __(eg vascular bundles)__ ● Larger magnification, easier to measure onioninabox 1

9744 / 04 H2 Biology Practical Notes 2025 ● Take more sections 3. Scale and Magnification Calibration (micrometre) cm = 10 mm = 10 -3 μ m (micrometer) = 10 -6 nm (nanometer) = 10 -9 4x ≡ 25um 10x ≡ 10um 40x ≡ 2.5um 20 eyepiece graticule units = 1 division on stage micrometer = 1×0.05 mm 1 eyepiece graticule units = 0.05/20 = 0.0025mm = 2.5um (1dp) Calculating length of specimen Count no. of eyepiece divisions of the specimen. Convert to um (10 -6 ) (2sf NOT 3sf) Calculating Magnification Magnification = (length of drawing) / (length of specimen)= x(2sf) NOT 3sf 4. Drawing (weird specimens in Annex A) ● Clean Continuous Lines, no fuzzy / half erased lines ● Scale, at least ¾ of given space, better to draw too big than too small ● Proportion (cell wall shld be ⅛ of the radius of the cell) ● Details, tissue layers, organelles etc. ● Label (if required) Do a little sketch as you're looking through the microscope before drawing the real thing. Don’t hard memorise monocot/dicot diagrams, draw what you see. Cambridge is quite harsh on shape and proportion, be sensitive to the shapes. If given a specific observation boundary, do not draw the boundary . The boundary does not exist on the actual specimen. onioninabox 2

9744 / 04 H2 Biology Practical Notes 2025 Experiments Commonly tested topics ● Respiration / Photosynthesis of Yeast or Plants (use of DCPIP / hydrogencarbonate indicator / MnO4 / Colourimeter / Number of bubbles / Gas Collection in syringe) ● Enzymes (comp vs non-comp, amylase and starch, fruit enzyme) ● Water potential (visking tubing, potatoes, diffusion of something) ● Heat loss / Heat gain ● Food tests (Benedict’s test) ● Bacteria (agar plates, culture) ● Molecular Techniques (mainly planning, match parent with child) Specific stuff and what to link them to ● Calcium Chloride / Sodium Alginate solution (make balls of leaf extract / yeast) ● Yeast suspension (must always be in a pH buffer!) ● Delivery Tube (gas collection) ● Lamp (photosynthesis) ● Agar Plate (diameter of colour change / growth of something) ● Scalpel and White Tile (Cutting vegetables) ● Fruits and Vegetables (water potential, starch test, benedict’s test, extract enzyme) 1. Tables Tables are giveaway marks do not throw them :C Multiplication = smallest sf Addition = smallest dp Simple Dilution: either question will give you the factor to dilute by or come up with your own Serial Dilution: Multiples of 2 or 5 only. If you’re having trouble perhaps qn wants you to do simple dilution instead. Always write in full, table should have enough info to stand on its own. (IV) Sample (DV) Mean time taken for colour to turn from red to blue (trial 1+2/2) /min A B > Mean Time (Trial 1+2/2) /s > Rate of respiration (1/mean time) /s -1 Replicate readings = calculate mean, not average eg Mean [(Trial 1 + Trial 2) / 2] / cm 3 I always put the conversion in brackets, I’m not sure if its mandatory but just to be safe onioninabox 3

9744 / 04 H2 Biology Practical Notes 2025 Cambridge Guidelines 1. Colour – before and after , not just final colour Sample Colour change of tube content A Colourless to Purple 2. Average Mean 3. if there is anomaly in data, exclude it from mean calculation, denote the data with [A] So long as your data is consistent with your conclusion, ECF will be given. onioninabox 4

9744 / 04 H2 Biology Practical Notes 2025