medium difficulty6 min

Variation

Variation means differences among individuals of the same species.

In one line: Variation means same species, different features.

Understand it

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.

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.

See it worked out

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

Worked example

1Two 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.
2This shows that variation can come from heredity and environment together.

Method you can reuse

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

Visual tip

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

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

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

Think first, then show answer

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.

Common wrong answer

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

Don't mix this up

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

Exam tip

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

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

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

1
Enough for 1 mark
Variation means differences among individuals of the same species.
2
Add for 2 marks
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.
3
Add for 3 marks
Variation is the reason siblings are not exactly alike.

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