Variation is one of the most important concepts in Biology. According to NCERT, variation refers to the differences in characteristics among individuals of the same species. These differences may appear in body structure, colour, size, behaviour, physiology, and many other features.
Variation plays an essential role in survival, adaptation, and evolution of living organisms.
Table of Contents
- Introduction to Variation
- Definition of Variation
- Characteristics of Variation
- Causes of Variation
- Types of Variation
- Importance of Variation
- Sources of Variation in Organisms
- Examples of Variation
- Variation and Evolution
- Difference Between Variation and Adaptation
- NCERT Summary
- Practice Questions
- Fill in the Blanks
- MCQs with Answers
Variation : introduction and importance
No two living organisms are exactly identical, even if they belong to the same species.
For example:
- Human beings have different heights.
- Leaves of plants differ in shape.
- Dogs of the same breed may have different colours.
These differences are called variations.
Variation allows populations to adjust to environmental changes and helps species continue to survive over long periods.
Definition of Variation
Variation is the occurrence of differences in traits or characteristics among individuals of the same species.
Examples:
- Different eye colours in humans
- Different flower colours in plants
- Difference in height and weight
- Different blood groups
Characteristics of Variation
- Occurs naturally in living organisms.
- May be inherited or acquired.
- Can be visible or internal.
- Increases biodiversity.
- Provides raw material for evolution.
Causes of Variation
Variation develops due to several biological processes.
| Cause | Explanation |
|---|---|
| Genetic Changes | Changes in genes produce new traits |
| Sexual Reproduction | Mixing of parental genes |
| Mutation | Sudden changes in DNA |
| Environmental Factors | Climate, food, lifestyle affect traits |
Explanation
1. Genetic Variation
Occurs because offspring receive genes from both parents.
2. Mutation
Sudden changes in genetic material can create new characteristics.
3. Environmental Variation
External factors influence growth and appearance.
Example:
Two identical plants may grow differently under different conditions.
Types of Variation
Variation is mainly divided into two categories.
| Type | Definition | Example |
|---|---|---|
| Inherited Variation | Passed from parents to offspring | Eye colour |
| Acquired Variation | Developed during lifetime | Muscular body due to exercise |
A. Inherited Variation
- Controlled by genes.
- Transferable to next generation.
- Important for evolution.
Examples:
- Hair texture
- Skin colour
- Blood group
B. Acquired Variation
- Not inherited.
- Develops because of environment or habits.
Examples:
- Language spoken
- Body fitness
Sources of Variation in Organisms
1. Sexual Reproduction
During reproduction:
- Genes from both parents combine.
- New combinations appear.
2. Mutation
- Produces sudden genetic changes.
- May create useful or harmful traits.
3. Genetic Recombination
- Exchange of genetic material during reproduction.
4. Environmental Influence
Examples:
- Temperature
- Nutrition
- Habitat
Importance of Variation
Variation is important because it:
Helps Survival
Different individuals survive different environmental conditions.
Leads to Evolution
Useful variations are selected over generations.
Increases Biodiversity
Creates diversity within populations.
Improves Adaptation
Organisms adjust better to changing environments.
Examples of Variation in Daily Life
Human Variation
- Height differences
- Fingerprints
- Hair texture
Plant Variation
- Flower colour
- Fruit size
- Leaf shape
Animal Variation
- Fur patterns
- Body size
- Feeding behaviour
Variation and Evolution
Variation provides the basic material for evolution.
Process:
Variation
↓
Natural Selection
↓
Survival of Suitable Organisms
↓
Evolution
Without variation, organisms would not adapt to environmental changes.
Difference Between Variation and Adaptation
| Variation | Adaptation |
|---|---|
| Differences among individuals | Special features helping survival |
| May or may not help survival | Always improves survival |
| Produced naturally | Develops through selection |
NCERT Quick Summary
- Variation means differences among organisms.
- Variations may be inherited or acquired.
- Sexual reproduction increases variation.
- Variation helps survival and evolution.
- Environmental and genetic factors create variation.
Practice Questions with Answers
1. What is variation?
Answer:
Variation refers to differences in characteristics among individuals of the same species.
2. Why is variation important?
Answer:
Variation helps organisms survive environmental changes and supports evolution.
3. Name two causes of variation.
Answer:
- Genetic changes
- Environmental factors
4. Which variation is inherited?
Answer:
Inherited variation passes from parents to offspring through genes.
5. Does acquired variation pass to offspring?
Answer:
No, acquired variation is generally not inherited.
Fill in the Blanks
- Variation means differences among ________.
Answer: organisms - Variation helps in ________.
Answer: evolution - Traits passed through genes are called ________ variation.
Answer: inherited - Sudden genetic change is called ________.
Answer: mutation - Environmental conditions may produce ________ variation.
Answer: acquired
10 MCQs with Answers
1. Variation refers to:
A. Similarities
B. Differences
C. Growth
D. Respiration
Answer: B
2. Variation is important for:
A. Digestion
B. Evolution
C. Photosynthesis
D. Movement
Answer: B
3. Variation inherited from parents is:
A. Acquired
B. Environmental
C. Genetic
D. Temporary
Answer: C
4. Which process increases variation?
A. Sexual reproduction
B. Breathing
C. Digestion
D. Excretion
Answer: A
5. Mutation means:
A. Cell division
B. Genetic change
C. Growth
D. Nutrition
Answer: B
6. Acquired traits are:
A. Inherited
B. Not inherited
C. Permanent
D. Genetic
Answer: B
7. Variation helps:
A. Survival
B. Extinction
C. Sleep
D. Rest
Answer: A
8. Different flower colours show:
A. Respiration
B. Variation
C. Nutrition
D. Digestion
Answer: B
9. Environmental variation depends on:
A. Surroundings
B. Genes only
C. Cells only
D. Bones
Answer: A
10. Variation provides the basis for:
A. Evolution
B. Digestion
C. Excretion
D. Circulation
Answer: A
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