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Autotrophic nutrition and photosynthesis

Autotrophic nutrition is the mode in which organisms make their own food from carbon dioxide and water, usually using sunlight and chlorophyll.

In one line: Green leaf, sunlight, air, and water make the plant's food factory.

Practice This Concept

Understand it

In green plants, photosynthesis occurs mainly in leaves.
Chlorophyll traps light energy.
Carbon dioxide enters through stomata, water comes from roots, and glucose is formed.
Oxygen is released as a by-product.
This process is the base of food supply for most living beings.

Example

A potted plant kept in sunlight makes starch in its leaves.

Rule to remember

Rule: Carbon dioxide + water in the presence of sunlight and chlorophyll → glucose + oxygen.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

If a plant has healthy green leaves but is kept in a dark cupboard for two days, starch formation falls because light energy is not available for photosynthesis.

Method you can reuse

1Take in carbon dioxide through stomata.
2Bring water from roots.
3Trap sunlight in chlorophyll.
4Form glucose.
5Store extra food as starch.
6Release oxygen.

Sketch it in your answer

Draw a leaf with stomata, chloroplasts, sunlight, carbon dioxide entry, water from roots, and oxygen release.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why does a leaf kept in darkness not make starch properly?

Think first, then show answer

A leaf kept in darkness cannot make starch properly because sunlight is needed for photosynthesis, and without light the food-making process slows down or stops.

Common wrong answer

Only water is enough for food formation.

Why it loses marks: Light, chlorophyll, carbon dioxide, and water all work together.

Don't mix this up

Students often forget that sunlight and chlorophyll are both needed, not one alone.

Exam tip

In exam answers, always mention raw materials, chlorophyll, sunlight, and the product glucose or starch.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Explain photosynthesis, identify the role of chlorophyll, or describe how a plant makes food and releases oxygen.

1
Enough for 1 mark
Autotrophic nutrition is the mode in which organisms make their own food from carbon dioxide and water, usually using sunlight and chlorophyll.
2
Add for 2 marks
Example: A potted plant kept in sunlight makes starch in its leaves.
3
Add for 3 marks
In green plants, photosynthesis occurs mainly in leaves.

MCQ Quiz

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