Download Photosynthesis

Day length
Plants
making food 1.
Joe lives for basketball.
He plays basketball every morning.
He eats breakfast after playing, then goes to school.
His mum says he needs the energy the food provides.
At school he wrote down the food he had for breakfast.
With the help of his teacher,
he wrote down where the food came from.
Here is what he wrote.
Milk
Butter
Cow
Grass
Sun
Egg
Chicken
Corn
Sun
Wheat
Sun
Bread
EXPLAIN in your own words where the energy Joe uses comes from.
© KCL/PENTECH/WCED 2000
Day length
Plants
making food 2.
Joe is still confused about how plants make food.
Joe’s teacher says food with sugar and starch gives you a lot of energy.
She shows Joe an experiment to test for starch.
1
2
30 seconds
boiling
water
3 minutes
green
leaf
white
leaf
hot alcohol
in tube
green plant
4
3
30 seconds
5
boiling
water
in beaker
6
leaf turns black
warm water
yellow
iodine solution
DESCRIBE in your own words how to carry out the experiment.
© KCL/PENTECH/WCED 2000
Day length
Plants
making food 3.
Joe’s teacher shows him plants that have been kept in different conditions.
clear
plastic
box
black
plastic
box
Carbon dioxide
removed
And then they do the starch test together with these results.
black leaf
yellow leaf
EXPLAIN what the results of the starch test show.
© KCL/PENTECH/WCED 2000
yellow leaf
Day length
Plants
making food 4.
Joe found this in a book at the library
Photosynthesis literally means ‘light building’.
Biologists talk of photosynthesis occuring in plants.
Plants can absorb the energy in light using their green pigment called chlorophyll.
Plants also absorb carbon dioxide from the air into their leaves
and water from the soil through their roots.
Plants use light energy to combine the carbon dioxide and water to make glucose.
The glucose is used to make the sweet sugar found in nectar, fruits and stem (sugar cane).
Some of the glucose is turned into starch and stored in different parts of the plant such as
the leaves themselves, roots, seeds and stems.
Plants absorb minerals, like nitrates and phosphates, from the soil through their roots.
These chemicals are used to build protein which is stored in seeds
and is needed for plant growth.
During photosynthesis oxygen is produced and released into the air.
DRAW a diagram to illustrate the process of photosynthesis.
© KCL/PENTECH/WCED 2000
Day length
Plants
making food 5.
Joe said he could not see the oxygen coming out from leaves on plants and trees.
His teacher set up an experiment to show the oxygen.
evening
morning
oxygen
bubbles
pond
weed
water
COUNT the bubbles at different times of the day.
DRAW a histogram for your results on the axes below.
Number of
bubbles
6am
9am
12 noon
3pm
6pm
9pm
Time of day
Make a CONCLUSION
Hint: which environmental factors will have changed over the course of the day
to cause this effect on the rate of photosynthesis.
© KCL/PENTECH/WCED 2000