BIOLOGY NOTES
IGCSE (0610) AND GCE (5090)
ALTERNATIVE TO PRACTICAL
FOR EXAMINATIONS FROM 2025
Paper Pattern
Total Marks: 40 Weightage: 20%
Available Time: 1 hour
Question 1: Experimental Interpretation/Design
1. Constructing a Table: (3-5 marks)
o Ensure correct number of columns
o Include proper headings with units (mention units in the heading).
o Fill data correctly in each column.
2. Identifying Variables: (1-3 marks)
o Independent Variable: The one being changed
o Dependent Variable: The one being measured
o Controlled Variables: Factors kept constant to ensure a fair test
3. Identifying Errors/Improvements: (1-3 marks)
o Common Errors: E.g., parallax error, not controlling variables properly,
inconsistent measurements.
o Improvements: E.g., use a colorimeter for colors, take repeated readings for
accuracy, ensure all equipment is properly cleaned to remove impurities.
4. Safety Precautions: (1 mark)
o Wear safety goggles, gloves, and use heat-proof mats when necessary.
o Handle chemicals with care, and make sure to cut away from your skin when
using sharp instruments.
5. Basic Math: (2-3 marks)
o Required to calculate averages, percentages, and percentage increases from
experimental data.
6. Food Tests: (1-3 marks)
Two tests may come together for 4-5 marks
o Benedict’s test for reducing sugars.
o Iodine test for starch.
o Biuret test for proteins.
o Ethanol test for lipids.
o DCPIP for Vitamin C.
7. Designing an Experiment: (6 marks)
o Plan a method that allows for the independent variable to be tested.
o Ensure controlled variables are mentioned, and clearly state the steps.
o Include how data will be collected (e.g., timing using stop watch, measuring gas
using gas syringe)
o Mention to repeat experiments.
8. Drawing a Graph: (4 marks)
o Plot independent variable on the x-axis and dependent variable on the y-axis.
o Use a proper scale and cover more than half the grid.
o Plot points accurately and draw a best-fit line or curve.
o In case of bar charts keep the width of bars and spacing between them same.
9. Explaining results in graph and tables (2-3 marks)
NOTE: Depends upon the graphs and the table and related to the information provided
in them.
Look for patterns in the data; is there a direct or inverse relationship
Identify key trends eg. "As temperature increases, the rate of photosynthesis
increases up to a point, then decreases.
Highlight any anomalies or results that do not follow the trend.
Conclusion from the graph/table: Use the data to explain what the graph shows,
such as peak points, plateaus, or drops.
Relate to scientific principles: For example, if the graph shows an increase in
oxygen production with light intensity, explain this using the concept of
photosynthesis.
Question 2: Drawing a Diagram/Calculations
1. Drawing a Diagram: (4 marks)
o Ensure the drawing occupies 60-80% of the space.
o Lines should be clear with no shading or double lines.
o Label key structures or features, with accurate details, if mentioned in
question.
o Don’t make arrow head while labelling.
2. Magnification Calculations: (3 marks)
o Use the formula:
𝑖𝑚𝑎𝑔𝑒 𝑠𝑖𝑧𝑒
o Magnification=
𝑎𝑐𝑡𝑢𝑎𝑙 𝑠𝑖𝑧𝑒
o Remember unit conversions:
o cm to mm (multiply by 10)
o mm to µ μm (multiply by 1000)
NOTE: Marks for each question may vary year to year (Total marks stay the same)
The question part numbers can also change
Other short questions might come besides these
Important Investigations
1.1 Chlorophyll
To demonstrate the necessity of chlorophyll for photosynthesis, you can use a potted plant
with variegated leaves, which are both green and white. First, destarch the plant by placing it
in complete darkness for 48 hours, ensuring that it uses up all stored starch. After this
period, expose the plant to sunlight for a few days to allow photosynthesis to occur. Next,
boil a leaf from the plant in water for 2 minutes to break down the cell walls, making it
easier to test for starch. The leaf should then be soaked in ethanol, which will remove any
chlorophyll. Afterward, rinse the leaf in warm water to soften it and place it on a white tile.
Finally, add iodine solution to the leaf. If starch is present, the areas with chlorophyll will
turn blue-black, while the white areas will remain orange. This shows that chlorophyll is
essential for photosynthesis.
Example Question: Describe how you would demonstrate the necessity of chlorophyll in
photosynthesis using a variegated leaf.
1.2 Light Intensity for Potted Plants
To investigate how light intensity affects the rate of photosynthesis in a potted plant, first
destarch the plant by keeping it in darkness for 48 hours. Then, cover part of a leaf with a
stencil to prevent light from reaching that area. Place the plant in sunlight for 4 to 6 hours,
allowing the exposed parts of the leaf to undergo photosynthesis. Afterward, remove the
stencil and perform a starch test on the leaf. If starch is present, the area that received
light will turn blue-black, while the covered area will remain yellow or brown, indicating that
light is necessary for starch production.
Example Question: Outline an experiment to investigate the effect of light intensity on the
rate of photosynthesis in a potted plant.
1.3 Light Intensity for Aquatic Plants
To measure the effect of light intensity on photosynthesis in aquatic plants, place a piece of
pond weed upside down in a test tube filled with water. Add sodium bicarbonate to ensure a
constant supply of carbon dioxide (CO₂). Position the test tube in a beaker of fresh water at
25°C. Next, set a lamp at a specific distance from the plant to provide light. Count the
number of oxygen bubbles released by the plant in one minute as an indicator of the rate of
photosynthesis. You should observe that the number of bubbles increases as the lamp gets
closer to the plant, showing that light intensity affects photosynthesis.
Example Question: Explain how you would use aquatic plants to measure the effect of light
intensity on photosynthesis.
1.4 Carbon Dioxide Concentration
To explore the effect of carbon dioxide concentration on photosynthesis, take two destarched
potted plants and cover each with bell jars labeled A and B. In jar A, add sodium bicarbonate
to provide CO₂, while in jar B, add sodium hydroxide to absorb CO₂. Place both setups in
sunlight for at least 6 hours. After the exposure, perform a starch test on the leaves of
both plants. The leaves of plant A should turn blue-black, indicating starch production due to
the presence of CO₂, while the leaves of plant B will remain orange or brown, showing that
CO₂ is necessary for photosynthesis.
Example Question: Design an experiment to investigate the effect of carbon dioxide
concentration on the rate of photosynthesis.
1.5 Transpiration
To measure the rate of transpiration in a plant, start by cutting a leafy shoot underwater to
prevent air bubbles from entering the xylem. Insert the shoot into a potometer filled with
water and trap an air bubble in the capillary tube. Close the tap of the reservoir and allow the
plant to transpire for a set period. Measure the distance moved by the air bubble in the
capillary tube over time. This distance reflects the rate of transpiration; a larger distance
indicates a higher rate of water loss from the plant.
Example Question: How would you measure the rate of transpiration in a plant using a
potometer?
1.6 Effect of Humidity on Water Absorption
To investigate how humidity affects water absorption in plants, create two different humidity
levels by wrapping transparent bags around separate plants. Keep all other variables
controlled, such as temperature and the type of plant used. Place the celery stalks in water
and set up potometers to measure water uptake. Record the distance traveled by the air
bubble in each potometer under different humidity conditions. A larger distance moved by
the air bubble in higher humidity indicates that increased humidity enhances water
absorption.
Example Question: Describe an investigation to determine the effect of humidity on water
absorption in plants.
1.7 Rate of Aerobic Respiration
To demonstrate the process of aerobic respiration, place an active yeast culture in a test
tube connected to another test tube containing hydrogen carbonate indicator. This indicator
will turn purple in alkaline conditions and yellow in acidic conditions. At the start, the
indicator will be red, but after about 15 minutes, if the yeast is actively respiring, the
indicator will change to yellow due to increased carbon dioxide (CO₂) production, indicating
that respiration uses oxygen and produces CO₂.
Example Question: Outline a method to demonstrate the process of aerobic respiration in
yeast.
1.8 Rate of Anaerobic Respiration
To study the effect of yeast concentration on carbon dioxide production, set up two test
tubes with different concentrations of yeast and glucose. Cover the first test tube with a
layer of oil to create anaerobic conditions. Connect this test tube to another containing lime
water, which will turn milky in the presence of CO₂. After 15 minutes, observe the lime
water; it should turn milky if CO₂ is produced, indicating that anaerobic respiration is
occurring. Repeating this experiment with various concentrations will help establish a
correlation between yeast concentration and CO₂ production.
Example Question: How can you investigate the effect of yeast concentration on anaerobic
respiration?
1.9 Rate of Germination
To compare the rate of germination under different conditions, place four seeds in separate
environments: Seed A in dry soil (no water), Seed B in wet soil (water present), Seed C in a
sealed container (no oxygen), and Seed D in a warm environment (ideal temperature). After
a set period, observe and record which seeds germinated. It is expected that Seed B will
germinate the fastest due to the presence of water, while Seed A will not germinate due to
lack of moisture. Seed C will fail due to insufficient oxygen, and Seed D, while having water
and nutrients, may germinate slower if the temperature is not ideal.
Example Question: Discuss the factors affecting the rate of germination and their expected
effects.
1.10 Tropic Response
To investigate phototropism, take three identical potted plants and place one in a box with a
single light source. The second plant should be placed on a clinostat (which rotates slowly),
and the third plant should be kept in complete darkness. After three days, observe the
growth direction of the plants. The first plant will grow towards the light source, the second
plant will grow straight due to the clinostat canceling the light effect, and the third will show
weak growth without light.
Example Question: Describe an experiment to investigate the effect of light on plant
growth.
1.11 Gravitropism
To study gravitropism, place three seedlings of the same type in two petri dishes. One petri
dish will remain stationary, while the second is placed on a clinostat. Ensure all seedlings
have their radicles facing different directions. Provide optimal conditions, such as moist
cotton wool for water and suitable temperatures. After three days, observe the seedlings. In
the stationary dish, all roots will grow downwards due to positive geotropism, whereas in the
clinostat, seedlings will grow in various directions since the clinostat negates the effect of
gravity.
Example Question: Explain how you would investigate the effect of gravity on the growth of
plant roots.
1.12 Rate of Enzyme Activity
To examine how different conditions affect enzyme activity, prepare three test tubes with
equal concentrations of a specific enzyme, but vary one independent variable in each (such
as temperature, pH, or substrate concentration). Maintain all other conditions constant and
incubate the test tubes for the same duration. After incubation, use a suitable test (like
Benedict’s test for sugars or iodine test for starch) to measure the amount of product
formed. This will allow you to determine how each variable influences enzyme activity.
Example Question: Design an experiment to investigate how temperature affects the activity
of a specific enzyme.
1.13 Rate of Osmosis Using Dialysis Tubing
To measure the rate of osmosis, take two dialysis bags filled with different sugar
concentrations: one with 0.5 mol/dm³ sugar solution and the other with 1 mol/dm³. Place
both bags in a beaker of pure water for 10 minutes while ensuring constant temperature.
After the time has passed, measure the change in volume of the solutions in both dialysis
bags. The bag with the higher sugar concentration should show a greater increase in volume,
indicating that osmosis has occurred. Repeat the experiment to confirm results and improve
accuracy.
Example Question: Explain how you would investigate the rate of osmosis using dialysis
tubing.
General Information
1. Safety Precautions:
• Wear safety goggles, gloves, and use heat-proof mats when necessary.
• Handle chemicals with care, and make sure to cut away from your body when using
sharp instruments.
2. Indicators for Gas and Solutions:
• Hydrogen Carbonate Indicator:
o Yellow in high CO₂, purple in low, red with no change.
• Lime Water:
o Turns milky with CO₂.
• Litmus paper:
o Blue litmus paper turns red in presence of CO₂.
3. Positive Food test results:
Benedict’s Test (Reducing Sugars):
• Add Benedict’s reagent and heat in a water bath at 80 ºC . Color change from blue to
green/orange/red.
Iodine Test (Starch):
• Add a few drops of iodine. Color change from brown to blue-black.
Biuret Test (Proteins):
• Add Biuret reagent. Color change from blue to purple.
DCPIP Test (Vitamin C):
• Add a sample to DCPIP. Color change from blue to colorless.
Ethanol Emulsion Test (Lipids):
• Mix sample with ethanol, then add same volume of water. Cloudy emulsion indicates
lipids.
4. Examples for Common Errors and Improvements in Experiments:
a. Parallax Error:
o Occurs when measurements (e.g., liquid levels) are taken from the wrong
angle.
o Improvement: Ensure your eye is positioned directly above the measuring
scale to avoid misreading.
b. Residual Liquid in Containers:
o Remaining liquid can contaminate results.
o Improvement: Thoroughly wash and dry containers with distilled water between
experiments.
c. Lack of Experimental Repeats/Averaging:
o If experiments aren’t repeated, results may not be reliable.
o Improvement: Always repeat experiments and calculate averages to ensure
accuracy.
d. Poor Control of Variables:
o If controlled variables like temperature or pH aren’t well-regulated, the
results might not reflect the true effect of the independent variable.
o Improvement: Use appropriate methods (e.g., Styrofoam to insulate
temperature or buffers for pH) to maintain consistency.
e. Inaccurate Measurement of Color Change:
o Estimating color change by eye can lead to errors.
o Improvement: Use a colorimeter for precise measurements, or place a white
background behind the setup for better contrast.
f. Counting Gas Bubbles:
o Counting bubbles visually can be inaccurate, especially when the rate is fast.
o Improvement: Use a gas syringe to measure the volume of gas produced for
more reliable results.
5. Common Apparatus and their uses:
a. Measuring Cylinder:
o Used to measure liquids accurately. Ensure proper reading by positioning your
eye at the liquid’s meniscus.
b. Test Tubes and Test Tube Rack:
o Test tubes hold small liquid samples, often used for chemical reactions like
food tests. The rack ensures safe handling.
c. Syringes (including Gas Syringe):
o Used to measure liquids and gases precisely. Gas syringes help measure the
volume of gas produced in experiments.
d. Thermometer:
o Measures temperature changes. Always immerse it in the substance you're
measuring and avoid parallax errors by reading at eye level.
e. Stopwatch:
o Crucial for timing reactions or intervals (e.g., counting bubbles in
photosynthesis experiments). It ensures accurate tracking of time.
f. Balance:
o Measures the mass of solids (e.g., measuring powdered substances or small
objects). Always tare (zero) the balance before measuring.
g. Colorimeter:
o Used to measure the intensity of color change in solutions. It provides more
precise data than visual estimation.
h. Bunsen Burner:
o Heats substances. Use a heatproof mat and safety precautions when handling,
such as wearing gloves and goggles.
i. Pipette and Dropper:
o Pipettes are used for accurately measuring small volumes of liquid. Droppers
are useful for adding small amounts of liquids like iodine or Benedict’s
solution in food tests.
j. Petri Dishes:
• Typically used in microbiology and for germination experiments. Petri dishes provide
a sterile environment for seedling or bacterial growth.
k. Potometer:
• Measures the rate of transpiration in plants. The movement of the air bubble in the
capillary tube gives an indication of water uptake by the plant.
l. Ruler/Scale:
• Measures distances or lengths of objects (e.g., measuring how far a liquid travels in a
tube or the length of a leaf). Ensure correct unit conversion (mm, cm).
Always Remember:
1. Familiarize yourself with common apparatus
2. Practice reading scales
3. Be prepared to interpret results, such as trends in data.
4. Be mindful of the examiner – keep your answers clear and structured.
5. Neat diagrams and tables are essential for getting good grades.
6. Try your best to use Terminologies/important terms (limited to those in the
course)
7. Don’t spend too long on a single question
8. Be familiar with basic math such as:
• Average: Add all the values and divide them with the number of readings
𝐶ℎ𝑎𝑛𝑔𝑒
• Percentage Change (can be increase or decrease): x100
𝐼𝑛𝑖𝑡𝑖𝑎𝑙
• And sometimes for area and volume too :)
Command Words From The Syllabus
