Primary 5 · Science · Systems: Photosynthesis
Systems: Photosynthesis questions for Primary 5 Science
10 questions to work through online, 2 of them written out the way the paper asks. Answer and you get the working straight away, then a score at the end. No sign-up, and you can retake it as often as you like.
- What a plant needs
- What is produced
- Why a leaf is de-starched
- Reading a leaf experiment
- Reading results
- Why photosynthesis matters
- Where it happens
- Naming the food made
- Naming the green substance
- Applying the ideas
| Light given | Bubbles of gas per minute |
|---|---|
| none | 0 |
| dim | 7 |
| bright | 24 |
| very bright | 31 |
Answers and explanations for all 10 questions
Every answer with the reasoning behind it. Worth reading after you have tried the set — or on its own, if you are a parent marking it.
Which two of these does a plant need in order to make its own food?
Answer: A and B only
Photosynthesis uses light, carbon dioxide and water. Oxygen is produced rather than used, and no food is taken from the soil.
Which gas does a plant give out during photosynthesis?
Answer: oxygen
Photosynthesis takes in carbon dioxide and gives out oxygen. That is why a planted aquarium has bubbles rising from the leaves in bright light.
Before testing a leaf for starch, a plant is left in a dark cupboard for two days. Why?
Answer: so that any starch already in the leaves is used up before the test begins
If starch were already there, a positive result would prove nothing. Emptying the leaf first means any starch found afterwards must have been made during the experiment.
After the day, both leaves were tested with iodine. What result would be expected for leaf B in the set-up above?
Answer: Only the uncovered half turned blue-black.
Iodine turns blue-black where there is starch. Only the half that received light could make any, so only that half changes colour.
Based on the table above, which conclusion is correct?
Answer: The brighter the light, the faster the plant photosynthesises.
As the light goes from none to very bright, the bubbles rise 0, 7, 24, 31. More light means faster photosynthesis and more oxygen given off.
Which two of these does photosynthesis provide for animals?
Answer: A and B only
Plants release the oxygen animals breathe and make the food that every food chain begins with. Without photosynthesis, animals would have neither.
In which part of a plant does most photosynthesis take place?
Answer: the leaves
Leaves are broad, thin and full of chloroplasts, and they are held out where the light is. That is what makes them the place photosynthesis happens.
When a leaf is tested with iodine after a day in the light, it turns blue-black. Which substance does that show the leaf has made?
Answer: starch
Iodine turning blue-black shows that the leaf contains starch.
The green substance inside the chloroplasts traps the light a plant needs. What is it called?
Answer: chlorophyll
The green substance that traps light is chlorophyll.
Why does a lawn under a garden bench turn yellow and thin after a few weeks?
Answer: The bench blocks the light, so the grass beneath cannot make food.
Without light the grass cannot photosynthesise. It uses up its food store, loses its green colouring and thins out — which is why the pale patch matches the shadow.