Photosynthesis Biology Practical Questions And Answers
BIOLOGY PRACTICAL O’LEVEL Photosynthesis | Photosynthesis Biology Practical | Photosynthesis Biology Practical | Photosynthesis Questions With Answers | Photosynthesis
Until 2008, NECTA biology practicals contained three questions. Question 1 was required, and was a food test. Students then chose to answer either question 2 or question 3.
One of these questions was usually classification. The format changed in 2008. Now, the practical contains two questions, and both are required.
Food test and classification remain the most common questions, but sometimes only one of these two topics is on a given exam.
The second question may cover one of a variety of topics, including respiration, transport, coordination, photosynthesis, and movement.
Each question is worth 25 marks.
<> Food test: students must test a solution for starch, sugars, fats, and protein
<> Classification: students must name and classify specimens, then answer questions about their characteristics
<> Respiration: students use lime water to test air from the lungs for carbon dioxide
<> Transport: students investigate osmosis by placing leaf petioles or pieces of raw potato in solutions of different solute concentrations
<> Photosynthesis: students test a variegated leaf for starch to prove that chlorophyll is necessary for photosynthesis
<>Coordination: students look at themselves in the mirror and answer questions about the sense organs they see
Note: These are the most common practicals, but they are not necessarily the only practicals that can occur on the national exam. Biology practicals frequently change, and it is possible that a given exam will contain a new kind of question. Look through past NECTA practicals yourself to get an idea of the kind of questions that can occur
The purpose of this practical is to prove that chlorophyll is required for photosynthesis.
This is done by using iodine to test a variegated leaf for starch. The parts of the leaf containing chlorophyll are expected to contain starch, while the parts lacking chlorophyll are expected to lack starch.
This section contains the following:
- Sample photosynthesis practical with solutions
1. Use iodine tincture from the pharmacy without dilution.
2. Prepare hot water bathes. The water should be boiling.
3. While the water gets hot, send the students to gather small leaves. The best have no waxy coating and are varigated (have sections without green).
4. The leaves should be boiled in the hot water bath for one minute.
5. Each group should then move its leaf into their test tube and cover it with methylated spirit.
6. Each group should then heat their test tube in a water bath. Over time, the leaf should decolorize and the methylated spirit will turn bight green.
7. The chlorophyll has been extracted and moved to the spirit. A well chosen leaf should turn completely white, although this does not always happen.
8. After decolorization, dips the leaves briefly in the hot water.
9. For leaves that turn white, students should test them for starch with drops of iodine solution.
i. Variegated leaf: this is a leaf that contains chlorophyll in some parts, but not in others. Often variegated leaves are green and white or green and red. Look at the flower beds around the school and at the teachers’ houses – they often contain variegated leaves.
ii. Source of heat: anything that boils water – Motopoa is best, followed by kerosene and charcoal
The diagram in figure 8 shown the set up of an experiment to investigate a certain physical process in a plant, follows: –
Study the apparatus set up and then answer the question that
- Which gas is collected in the test tube?
- Where does it come from?
- During which process is this gas produced?
- Write conditions necessary for the process to take place
- Suggest a test for this gas and experiment results.
- What will happen if the apparatus is kept in a dark place?
- What was the aim of the experiment?
- There was a mistake in assembling the apparatus. With a reason, point out that mistake.
- Why is water held up in the test tube without running on the funnel?
Gas which is collected in the test tube is oxygen gas (O2)
Gas collected come from water plant (elodea) i.e. this is a green water ; when exposed to sunlight it produces oxygen gas
This gas is produced during the process called photosynthesis.
Conditions necessary’ for the process (photosynthesis) to take place are
- Carbon dioxide gas
A test for this gas (oxygen) is re- lighting glowing splint (piece of wood)
If the apparatus was kept in the dark place there will be no gas produced by the water plant (elodea) due to the absence of sunlight.
The aim of the experiment was to show that water plant produces oxygen gas during photosynthesis process.
Mistake in assembling the apparatus.
Funnel was not inverted in such a way that test would be inserted to fit so as trap the gas properly as shown in the figure below
The diagram below- shows an experiment set up for a biological investigation. The potted plant was kept in darkness for 48 hours before the experiment. It was then kept in sunlight for several hours. Observe the set up and answer the questions
- Why was the potted plant kept in darkness?
- What will be observed if iodine solution is added to leaves M and N after their chlorophyll is removed?
- Which of the leaves M and N served as a control experiment?
- Name the biological process investigated in the experiment
- Suggest the aim of the experiment
- State the importance of the experiment