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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.

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Student-friendly explanation

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.

How to write this in exams

  1. 1

    Start with the exact idea

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

  2. 2

    Then show how to use it

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

  3. 3

    Add one concrete example

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

  4. 4

    Avoid this incomplete answer

    Only water is enough for food formation. This is wrong because light, chlorophyll, carbon dioxide, and water all work together.

Definition

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

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.

Memory hook

Green leaf, sunlight, air, and water make the plant's food factory.

Examples and method

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 to apply

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

Diagram support

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

How CBSE asks it

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

Avoid common mistakes

Common confusion

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

Common wrong answer

Only water is enough for food formation. This is wrong because light, chlorophyll, carbon dioxide, and water all work together.

Exam tip

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

Quick check

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

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.

Answer writing and exam use

1-mark answer

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

2-mark answer

Autotrophic nutrition is the mode in which organisms make their own food from carbon dioxide and water, usually using sunlight and chlorophyll. Rule: Carbon dioxide + water in the presence of sunlight and chlorophyll → glucose + oxygen. A potted plant kept in sunlight makes starch in its leaves.

3-mark answer

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. Rule: Carbon dioxide + water in the presence of sunlight and chlorophyll → glucose + oxygen. 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. Explain photosynthesis, identify the role of chlorophyll, or describe how a plant makes food and releases oxygen. Only water is enough for food formation. This is wrong because light, chlorophyll, carbon dioxide, and water all work together.
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