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Practical work is a core component of the Edexcel A-Level Biology (9BI0) specification. This lesson consolidates the required practicals for photosynthesis and respiration, focusing on experimental design, data analysis, controls, and common sources of error. You must be able to describe, evaluate, and improve these methods.
This is the most commonly examined practical for measuring photosynthetic rate by collecting oxygen gas produced by an aquatic plant.
| Item | Purpose |
|---|---|
| Elodea or Cabomba (aquatic plant) | Photosynthesising organism |
| Sodium hydrogencarbonate (NaHCO₃) solution | Provides constant supply of dissolved CO₂ |
| Bench lamp (with known wattage) | Light source; distance varied to change intensity |
| Ruler / metre rule | Measure distance from lamp to plant |
| Stopwatch | Time the counting period |
| Beaker of water | Acts as heat shield (absorbs infrared) |
| Thermometer | Monitor temperature |
| Audus microburette / photosynthometer | More accurate measurement of O₂ volume than bubble counting |
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