QUESTION 3: Photosynthesis, biodiversity and classification of microorganisms, animal nutrition

here are the answers to your questions:

3.1.1.
The aim of the investigation is to determine whether light is necessary for photosynthesis.

3.1.2.
The dependent variable in this investigation is the presence or absence of starch in the leaf.

3.1.3.
The plant was destarched by placing it in a dark cupboard for 48 hours.

3.1.4.
The indicator substance/reagent used to test for the presence of starch in the leaf is iodine solution.

3.1.5.
The steps followed during the starch test, in the correct sequence, are:

• Boil the leaf in water for a few minutes to kill the cells and break down cell walls.
• Boil the leaf in alcohol (ethanol) in a water bath to remove the chlorophyll.
• Rinse the leaf in cold water to rehydrate and soften it.
• Spread the leaf on a white tile and add a few drops of iodine solution to its surface.
• Observe the color change: a blue-black color indicates the presence of starch, while a yellow-brown color indicates its absence.