Cheat Sheet Alternate To Practical (Copy)

O Level & IGCSE Biology – Alternate to Practical Paper Cheat Sheet
Paper 6: Key Concepts, Techniques & Exam Strategy

1. Drawing and Labeling Diagrams

• Rules for Biological Diagrams:
  • Use clear, unshaded lines.
  • Use a sharp pencil only.
  • Label with straight lines, no arrows.
  • No sketching/double lines.
  • Labels should be horizontal, not slanted.
  • Avoid crossing label lines.
• Common Diagrams to Practice:
  • Onion epidermis (cells with nucleus and cell wall)
  • Plant cell vs. Animal cell
  • Heart, leaf cross-section, stomata, kidney tubule
  • Apparatus setup (e.g., food tests, respiration)

2. Designing Experiments

• Key Components of a Practical Design:
  • Aim: Clearly state what is being investigated.
  • Variables:
    • Independent: What you change.
    • Dependent: What you measure.
    • Controlled: What you keep constant.
  • Method: Step-by-step with equipment, volumes, times.
  • Control Experiment: Used for comparison, usually lacks the independent variable.
  • Repeat: For reliability.
  • Safety: Gloves, goggles, handle glassware properly.
• Common Topics:
  • Photosynthesis (light, CO₂, chlorophyll)
  • Respiration (limewater test, temperature)
  • Enzyme activity (temperature/pH effect)
  • Germination (water, oxygen, temperature)

3. Graph Drawing Skills

• Axes:
  • Independent variable → x-axis
  • Dependent variable → y-axis
• Line graph:
  • Continuous data (e.g., temperature vs. enzyme activity)
• Bar chart:
  • Discrete data (e.g., types of plants vs. number of stomata)
• Good Practice:
  • Use equal scales with units.
  • Plot points accurately.
  • Use pencil and draw a best-fit curve (not point-to-point unless asked).
  • Title and label both axes.

4. Interpreting Results / Tables / Graphs

• Identify trends and patterns (e.g., increase/decrease).
• Use numerical data in answers (e.g., “Rate increased from 2 cm/min to 4 cm/min”).
• Comment on anomalies/outliers if any.
• Relate results back to biological principles.

5. Food Tests

• Control Test: Always test a sample with water or no enzyme/substance for comparison.

6. Microscope Skills

• Magnification formula:
  • Total magnification = eyepiece × objective lens
  • Image size = Actual size × Magnification
• Use of microscope:
  • Start with lowest power.
  • Focus using coarse and then fine focus.
  • Use millimeters or micrometers for measuring cells.

7. Enzyme Experiments

• Example: Amylase breaking starch
  • Use iodine to test for presence of starch.
  • Take samples every 30 sec.
  • Time taken for starch to disappear = enzyme activity.
• Factors affecting enzymes:
  • Temperature: Optimal ~37°C, too high = denature.
  • pH: Each enzyme has an optimum pH.
  • Concentration: More enzyme = faster reaction.

8. Osmosis and Diffusion

• Diffusion: Movement of molecules from high to low concentration (e.g., perfume).
• Osmosis: Movement of water through a semi-permeable membrane from dilute to concentrated solution.
• Typical Osmosis Practical:
  • Potato in sugar solutions → measure mass change.
  • Increase in mass = water entered (hypotonic)
  • Decrease in mass = water left (hypertonic)

9. Respiration & Germination Practical

• Respiration:
  • Limewater turns milky = CO₂ present.
  • Use of respirometer to measure oxygen uptake.
• Germination Requirements:
  • Water, Oxygen, Warmth
  • Control experiment: seed with no water

10. Common Mistakes to Avoid

• Using pen or sketchy lines in diagrams.
• Not labeling units or missing scales on graphs.
• Ignoring the control in experimental design.
• Writing hypotheses or aims without clarity.
• Ignoring safety instructions in experiment descriptions.

11. Answering Short & Structured Questions

• Use full sentences.
• State what, then why (description + explanation).
• Use scientific vocabulary: e.g., enzyme, substrate, denatured, diffuse.
• When explaining changes, compare both sets of data.

12. Exam Strategy Summary

• Read each instruction carefully.
• Always refer to the data when answering.
• Show working in calculations (if any).
• Time management: don’t overdo diagrams.
• Practice interpreting tables, graphs, experimental setups.