O Level Biology Practical 2020 Answers Patched
O Level Biology Practical 2020: Key Answers & Marking Guide
📊 Part 3: Data Analysis & Graphing
Context: You were likely given a table of results to plot on a graph.
How to Secure the Graph Marks:
- Axis Orientation: The Independent Variable always goes on the x-axis (horizontal), and the Dependent Variable on the y-axis (vertical).
- Scale: The scale must occupy more than 50% of the grid. Do not use odd scales (like counting by 3s or 7s). Stick to 1s, 2s, 5s, or 10s.
- Plotting: Points should be small "x"s or dots with circles. Large dots covering multiple squares lose accuracy marks.
- Line of Best Fit: Do not just "connect the dots." Look for the trend—is it a straight line or a curve? In Biology, curves often plateau (level off), which is a concept frequently tested in 2020 papers regarding limiting factors.
Model Answer (4 marks)
| Test | Observation | Conclusion | | :--- | :--- | :--- | | Benedict’s | Blue (no change) | Reducing sugar absent | | Iodine | Blue-black | Starch present | | Biuret | Blue | Protein absent | | Ethanol | Clear | Fat/lipid absent | o level biology practical 2020 answers
Final identification: Starch solution (or starch suspension). O Level Biology Practical 2020: Key Answers &
Emulsion Test for Fat (Lipids):
Expected Answer:
- Shake solution with 2 cm³ of ethanol.
- Pour the mixture into 2 cm³ of distilled water.
- Positive: A milky white emulsion forms.