Class 7 Science · Original EZT practice
Nutrition in Plants (Class 7): original worked practice
Making sugar, absorbing minerals and testing a leaf for starch are not the same thing. Use each question to separate the process from the evidence, then test your explanation against a fresh case.
8 original worked examples, 8 fresh self-check questions and 4 mixed questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 17 October 2026:
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Separate carbon food from mineral nutrients
Choose the method: A green plant can build organic food using light, carbon dioxide and water. It still needs minerals; making sugar does not mean making every required substance from nothing.
EZT practice question
A learner says a healthy green seedling needs no soil minerals because it makes its own food. Identify the mistake.
Show the worked solution
- Photosynthesis supplies organic compounds from simple raw materials using light energy.
- Mineral elements such as nitrogen are needed for other substances, including proteins.
- The source of carbon food and the source of mineral nutrients answer different questions.
Answer: Making organic food does not remove the need for mineral nutrients.
Check: A plant supplied with light and water can still grow poorly if an essential mineral is missing.
Watch for this: Autotroph does not mean independent of air, water, light or minerals.
Now try it yourself
A green cactus has reduced leaves. Can its green stem contribute to making food?
Check your answer
Yes, if its stem has photosynthetic tissue and suitable conditions.
Photosynthesis is not restricted to broad leaves; green stems can contribute.
Read the summary without treating light as matter
Choose the method: Photosynthesis uses carbon dioxide and water to build carbohydrates using light energy. Oxygen is released. The usual school equation is an overall summary.
EZT practice question
A card lists sunlight, carbon dioxide, oxygen and water. Sort the entries into energy input, material inputs and a released product for the school photosynthesis summary.
Show the worked solution
- Sunlight is the energy input, not a chemical substance added as an atom source.
- Carbon dioxide and water are material inputs.
- Oxygen is a released product in the summary.
Answer: Energy: sunlight. Material inputs: carbon dioxide and water. Released product: oxygen.
Check: Carbon in the carbohydrate must come from a carbon-containing input, carbon dioxide.
Watch for this: The summary is not a single-step account of all the reactions inside a chloroplast.
Now try it yourself
A diagram has an arrow from air into a leaf labelled oxygen as the raw material for making carbohydrate. What label needs changing?
Check your answer
Change the photosynthesis material-input label to carbon dioxide.
Plants also use oxygen in respiration, but the diagram asks specifically about the photosynthesis carbon input.
Distinguish a test result from the process
Choose the method: In an appropriate school starch test, iodine can indicate starch. It does not directly measure the rate of photosynthesis or prove the absence of every other food substance.
EZT practice question
A teacher provides two starch-test records: leaf sample A turns blue-black; leaf sample B does not. A learner says B contains no food of any kind. Is that justified?
Show the worked solution
- A positive result supports starch being present in A under the test conditions.
- A negative result in B means starch was not detected, if the test and controls worked.
- The result does not test for every sugar, protein or other substance.
Answer: No. The iodine result concerns detectable starch, not all food substances.
Check: A test cannot establish the absence of materials it is not designed to detect.
Watch for this: This question interprets supplied records; it is not a procedure involving hot water or alcohol.
Now try it yourself
A leaf starch test is negative. Does that measure exactly how much photosynthesis took place that morning?
Check your answer
No.
Stored starch, transport, prior treatment and test sensitivity also affect the result.
Design a fair comparison on paper
Choose the method: To interpret a light-and-starch comparison, control the starting starch and keep other conditions comparable. Use teacher-provided records rather than performing chemical tests from this page.
EZT practice question
A plant leaf already contains starch before one part is shaded. Later both shaded and exposed parts test positive. Does this disprove the role of light?
Show the worked solution
- The starting starch could remain in the shaded part.
- A fair comparison needs suitable prior starch depletion, checked with a control rather than assumed from a fixed number of days.
- Light blocking and the other growing conditions also need to work as intended.
Answer: No. The starting starch makes this comparison inconclusive.
Check: An outcome caused by an uncontrolled starting condition cannot isolate the effect of light.
Watch for this: Three days in darkness is not a universal guarantee: species, reserves, health and conditions matter.
Now try it yourself
In a valid matched comparison with no detectable starting starch, the exposed part later tests positive and the shaded part negative. What does the record support?
Check your answer
It supports a role for light in starch formation under those conditions.
The matched design reduces alternative explanations, but the starch test remains an indirect indicator.
Use chlorophyll evidence carefully
Choose the method: In a suitable variegated leaf comparison, green and non-green regions can differ in detectable starch. Visible leaf colour is not a universal test for absence of chlorophyll.
EZT practice question
A teacher supplies a controlled record: the green region of a variegated leaf has detectable starch after light exposure; the white region does not. What limited conclusion fits?
Show the worked solution
- The result is consistent with chlorophyll-containing tissue making starch through photosynthesis.
- The comparison needs suitable starting-starch and test controls.
- It does not prove every red or purple leaf is unable to photosynthesise: other pigments can mask chlorophyll.
Answer: The record supports the role of chlorophyll in photosynthetic starch formation, with those controls.
Check: A conclusion about the two tested regions must not turn into a rule about every coloured leaf.
Watch for this: Root cells and other non-photosynthetic plant tissues do not all contain chloroplasts.
Now try it yourself
A red leaf contains chlorophyll hidden by other pigments. Must it be unable to photosynthesise?
Check your answer
No.
Visible red colour does not establish that chlorophyll is absent.
A living host is not decaying matter
Choose the method: A parasite obtains resources from a living host. A saprotrophic fungus obtains nutrients by breaking down dead organic material and absorbing products. Fungi are not plants.
EZT practice question
Compare two supplied descriptions: a dodder stem takes resources from a living host; a fungus grows on dead leaf litter. Name the nutrition relationship in each.
Show the worked solution
- The living-host case describes parasitic nutrition.
- The dead-litter case describes saprotrophic nutrition.
- Both use organic material made by other organisms, but the source differs.
Answer: Dodder: parasite. The described litter fungus: saprotroph.
Check: The living versus dead source distinguishes these two descriptions.
Watch for this: Not every fungus is a saprotroph and a mushroom is not a green plant.
Now try it yourself
A learner groups a mushroom with green grass because both grow from the ground. What is wrong?
Check your answer
Growing from the ground does not determine how an organism obtains food.
Grass can photosynthesise; the described mushroom is a fungus that depends on organic material from elsewhere.
Insects supply more than a sugar story
Choose the method: Green insectivorous plants photosynthesise organic carbon compounds. Digested prey can supply mineral nutrients, particularly where those nutrients are scarce.
EZT practice question
A learner says covering a pitcher plant with shade is harmless if plenty of insects are available. Explain the missing requirement.
Show the worked solution
- Its green tissue still uses light for photosynthesis.
- Prey can supplement mineral nutrition, not replace the normal role of photosynthesis in this green plant.
- More prey does not establish that the plant has enough light or suitable water and growing conditions.
Answer: Insects do not remove the plant's need for suitable light for photosynthesis.
Check: The argument confused a mineral supplement with a replacement for photosynthetic food production.
Watch for this: Do not call insect capture proof that the green plant cannot make organic food.
Now try it yourself
Why can a pitcher plant photosynthesise and still benefit from catching insects?
Check your answer
The two processes can meet different needs: photosynthesis supplies organic carbon compounds and prey supplements mineral nutrients.
The nutrient-poor habitat explains why the supplement can be useful.
Locate nitrogen fixation before claiming a soil benefit
Choose the method: Suitable bacteria in legume root nodules can fix atmospheric nitrogen into usable compounds. The bacteria gain resources from the plant. Effects on a later crop depend on residue and soil management.
EZT practice question
A learner says planting a legume instantly releases all the fixed nitrogen into the soil for the next crop. Correct the claim.
Show the worked solution
- Fixation occurs through suitable bacteria associated with root nodules; the fixed nitrogen is first part of the plant-bacteria system.
- A harvested crop can remove nitrogen-containing material.
- Benefits to a later crop depend on retained residues, decomposition and other management conditions.
Answer: A legume rotation can contribute to soil nitrogen, but it is not an instant transfer of all fixed nitrogen to the next crop.
Check: Track where the nitrogen is: some stays in living plant material or leaves the field at harvest.
Watch for this: Plants do not simply absorb atmospheric nitrogen gas through their roots as a ready-to-use mineral nutrient.
Now try it yourself
In a lichen partnership, must the photosynthetic partner always be an alga rather than a bacterium?
Check your answer
No. It can be an alga and/or a cyanobacterium, associated with a fungus.
Cyanobacteria can photosynthesise too; alga plus fungus is a useful simple example, not the only case.
Try a mixed set
Choose a method or explanation before opening each answer.
1. Must every food chain begin with a photosynthesising green plant?
Show answer and reason
No.
Photosynthesis supports many food chains, but some ecosystems depend on organisms using chemical energy rather than sunlight.
2. Does a plant stop all respiration when light becomes available?
Show answer and reason
No.
Respiration continues in living tissues. Net gas exchange depends on the balance of respiration and photosynthesis, not light alone.
3. A negative starch test is obtained, but the positive control also fails. Is the leaf result trustworthy?
Show answer and reason
No; the test is inconclusive.
A failed positive control means the test may not be detecting starch correctly.
4. Why is asking only whether an organism is green a weak way to classify its nutrition?
Show answer and reason
Colour alone can miss the actual food source.
Pigments can mask chlorophyll, some green organisms obtain extra nutrients from prey, and a supplied nutrition relationship needs direct evidence.
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Questions about this practice page
- Is Nutrition in Plants the current Class 7 Chapter 1?
- It is a legacy Chapter 1 title. In the linked current Curiosity sources, Chapter 1 introduces science and Chapter 10 covers plant life processes. Follow the edition your school uses.
- Does an iodine test measure photosynthesis directly?
- No. It indicates detectable starch under suitable test conditions. Starting starch, controls and other conditions matter when using it as evidence about photosynthesis.
- Are mushrooms plants that cannot make food?
- Mushrooms are fungi, not plants. Many familiar mushrooms obtain nutrients from dead organic material, but fungi have several nutrition relationships.
- Does a green pitcher plant need insects instead of light?
- No. It still uses light for photosynthesis. Prey can supplement mineral nutrients; it does not replace the role of photosynthesis in organic food production.
- Are these NCERT exercise answers or practical instructions?
- No. They are original EZT reasoning questions using selected plant-nutrition ideas and hypothetical records. Any school practical needs its own teacher-led safety guidance.