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UPDATED TO 2023-2025 SYLLABUS
CAIE CHECKPOINT
SCIENCE
SUMMARIZED NOTES ON THE THEORY SYLLABUS
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CAIE CHECKPOINT SCIENCE
1. How Plants Grow
1.1. Testing for starch
Plant cells are found to contain colourless grains of
starch under the microscope. This is quite difficult to see,
so dilute solution of iodine is added. This makes the
starch turn blue-black.
1. Place a leaf in boiling water for few minutes. This
removes the cell wall and allows the starchidentifying agent iodine to enter the cells.
2. Now put the leaf in a test-tube of ethanol and hold it
above a warm water bath. Ethanol is volatile and
cannot be directly heated. It removes the greenpigment chlorophyll and allows us to see the colour
change easily.
3. Use tweezers to place the leaf on a petri-dish.
4. Add few drops of iodine solution.
5. The leaf turns blue-black in the presence of starch.
1.2. De-starching a plant
In an experiment where you have to check if starch has
been made by the plant, you have to start out with a
plant that does not contain starch.
1. A green plant with leaves containing starch must be
left in darkness for 2-3 days. Cutting off access to
light prevents photosynthesis, and glucose (simpler
form of starch) isn’t produced.
2. Test the leaves to make sure they’re starch-free.
3. This is a de-starched plant.
1.3. Effect of CO2 on starch production
Soda Lime- substance that absorbs Carbon dioxide and
takes it out of the air.
Sodium hydrogencarbonate solution - liquid that
releases Carbon dioxide into the air.
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1. Set up two identical destarched plants and cover
them with transparent plastic bags, sealing them
around the pot using elastic bands.
2. Before sealing them, place a small dish of soda lime
inside pot A and a dish of sodium hydrogencarbonate
inside B.
3. Leave both plants in daylight for a few hours.
4. Test a leaf from plant A and a leaf from B for starch.
5. Conclusion - leaf from plant with soda lime (absorbs
CO2) didn’t contain starch, this suggests that CO2 is
necessary for starch production.
1.4. Investigating oxygen production in
plants
Water plants can be used to investigate the gases
produced as they escape from the leaf surface in
bubbles that are easily seen and collected.
1. Set up two samples of pondweed as shown in the
figure.
2. Place one sample in a sunny spot, and the other in
the dark.
3. After a week, examine the gas collected in the two
test tubes.
4. The plant under sunlight would have produced gas,
and the plant in the dark would have not.
5. Test the gas using a glowing splint. The splint should
re-ignite, showing that the gas contained more
oxygen than normal air.
1.5. Biomass
Is the amount of matter or mass in a living thing, and can
be found by weighing it.
Wet biomass - mass of a living thing when it is alive.
Dry biomass - mass of a living thing when it’s dead and
dried out (water is removed)
It is used to monitor the environment and as an
approximate measure of a species within a habitat.
1.6. Minerals
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CAIE CHECKPOINT SCIENCE
Soil contains substances called mineral salts.
Plants need different mineral salts in different amounts
to survive.
The minerals dissolve in the water in the soil and are
taken up by the plants via the roots.
They move through the plant to where they’re needed.
1.7. Transport of water in plants
Root hair cells
Root hair cells - tiny hair like projections in the roots
that increase the surface area of absorption.
They grow between soil particles and take in large
quantities of water.
Water in the soil is drawn in to replace the water that has
evaporated from the leaves.
Plants do not require energy to take in water.
Mineral salts are dissolved in soil water, and root cells
use energy made from respiration to take in the salts.
Roots get oxygen to respire from the air spaces between
soil particles.
Xylem and Vascular bundles
The root has the ability to push water up the plant only a
little way.
Water reaches all parts of the stem due to the action of
the leaves.
1.8. Role of the leaf
Structure
Epidermis- upper and lower layer of the leaf, one cell
thick.
Outer surface of epidermal cells has a layer of wax which
prevents water passing in/out of the leaf.
Palisade tissue- layer of palisade cells found below
upper epidermis, involved in making food.
Spongy Mesophyll tissue- layer of cells below palisade
layer, make food and also provide a surface for
evaporation of water.
Vascular bundle- contains xylem tissue (carries water
and minerals) and phloem tissue (carries amino acids
and sucrose)
Leaves and water
When water evaporates from cells in the spongy
mesophyll layer, water vapour forms.
If there is less water vapour outside than inside the leaf,
water vapour diffuses out through the stomata.
This makes the spongy mesophyll cells short of water, so
they take more from the xylem tissue in the veins.
The water lost in the veins is replaced by water passing
up the xylem in the stem and root.
Transpiration- process by which plants lose water from
their leaves.
Transpiration stream- movement of water from the
roots through the stem due to loss of water in the leaves
Cells in the plant form tubes to transport water. They
form columns in the plant and the cells die, causing the
walls between them to break down - forming tubes.
Each water conducting tube is called a xylem
(pronounced zylem) vessel.
A group of vessels form a xylem tissue, which make up
a part of structures called vascular bundles.
They run through the plant from the root to the leaf
where they form leaf veins.
Roots and water
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Testing for transpiration
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CAIE CHECKPOINT SCIENCE
1. Place a plastic bag around the shoot of a pot plant.
2. Wait for a day, and test the liquid collected inside the
bag.
3. If it is water, it should turn cobalt chloride paper pink.
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Copyright © 2025 ZNotes Education & Foundation. All Rights Reserved. This document is
authorised for personal use only by Maita at undefined on 16/03/25.
CAIE Checkpoint
Science
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