Photosynthesis — Part 2: Experiments and the carbon cycle: visual lesson, ICSE Class 10 Biology (Science Paper 3)

Lesson

Experiments on Photosynthesis

Part 2 — proving what a leaf needs, and following carbon round the living world.

In this lesson you will

List the steps of the starch test and explain the purpose of each
Design controlled experiments to show that light, carbon dioxide and chlorophyll are necessary, and that oxygen is released
Describe the carbon cycle

Concept

Keep the potted plant in darkness for one to two days: it uses up its stored starch.

Table of why destarching is needed and what goes wrong without it
Why destarch?	Without it
Leaves start with no starch	Old starch could give a false positive
Any starch found was made during the experiment	The result could not be trusted

Diagram

Boil in water (kills cells). 2. Boil in alcohol in a water bath (removes chlorophyll). 3. Dip in warm water (softens). 4. Add iodine: blue-black means starch.