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Variation

Variation means differences among individuals of the same species.

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Student-friendly explanation

Variation is the reason siblings are not exactly alike. Some differences are inherited from parents, while others are caused by environment such as nutrition, light, or climate. Variation is important because it gives a population a chance to survive if conditions change, and it also provides the raw material for evolution.

How to write this in exams

  1. 1

    Start with the exact idea

    Variation means differences among individuals of the same species.

  2. 2

    Then show how to use it

    1. Identify the group being compared. 2. Note the differences between individuals. 3. Decide whether the difference is inherited, environmental, or both. 4. State the role of variation in survival and evolution. 5. Give a suitable example.

  3. 3

    Add one concrete example

    Two brothers may have different heights, skin tones, or hair textures. In plants, two seedlings of the same species may grow to different sizes because of different light or water supply.

  4. 4

    Avoid this incomplete answer

    A common wrong answer is to say variation is only caused by environment. That ignores inherited differences passed through genes.

Definition

Variation means differences among individuals of the same species.

Example

Two brothers may have different heights, skin tones, or hair textures. In plants, two seedlings of the same species may grow to different sizes because of different light or water supply.

Rule to remember

Variation may be inherited, environmental, or a combination of both.

Memory hook

Variation means same species, different features.

Examples and method

Worked example

Two children of the same family may both inherit the same general face shape from their parents, but one may be taller because of better nutrition. This shows that variation can come from heredity and environment together.

Method to apply

1. Identify the group being compared. 2. Note the differences between individuals. 3. Decide whether the difference is inherited, environmental, or both. 4. State the role of variation in survival and evolution. 5. Give a suitable example.

Diagram support

A side-by-side comparison chart of two siblings or two plants helps show variation clearly.

How CBSE asks it

Define variation, or explain why members of the same species are not identical.

Avoid common mistakes

Common confusion

Students often think all differences are due to heredity alone. In reality, both genes and environment can produce variation.

Common wrong answer

A common wrong answer is to say variation is only caused by environment. That ignores inherited differences passed through genes.

Exam tip

When answering, separate inherited variation from environmental variation. This makes your answer more complete and more accurate.

Quick check

Why do siblings of the same parents still look different in some ways?

Siblings look different because variation exists among individuals of the same species. Some differences come from inherited genes, and some come from environmental factors such as food, climate, and sunlight.

Answer writing and exam use

1-mark answer

Variation means differences among individuals of the same species.

2-mark answer

Variation means differences among individuals of the same species. Variation may be inherited, environmental, or a combination of both. Two brothers may have different heights, skin tones, or hair textures. In plants, two seedlings of the same species may grow to different sizes because of different light or water supply.

3-mark answer

Variation is the reason siblings are not exactly alike. Some differences are inherited from parents, while others are caused by environment such as nutrition, light, or climate. Variation is important because it gives a population a chance to survive if conditions change, and it also provides the raw material for evolution. Variation may be inherited, environmental, or a combination of both. Two children of the same family may both inherit the same general face shape from their parents, but one may be taller because of better nutrition. This shows that variation can come from heredity and environment together. Define variation, or explain why members of the same species are not identical. A common wrong answer is to say variation is only caused by environment. That ignores inherited differences passed through genes.
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