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Practice 5 important Class 7 Science MCQs on Soil. Revise concepts such as humus, soil horizons, soil erosion, and water-holding capacity with exam-focused explanations.
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Chapter Information
- Class: 7
- Subject: Science
- Chapter: Soil
- Quiz Type: Multiple Choice Questions
- Total Questions: 5
Introduction
Soil is an important natural resource that supports plant growth and many living organisms. It contains rock particles, minerals, organic matter, water, and air. Different types of soil have different properties, which makes them suitable for different purposes.
This quiz focuses on important concepts related to soil composition, humus, soil horizons, soil erosion, and water-holding capacity.
What You Will Learn
- What soil is made of
- Meaning and importance of humus
- Different soil horizons
- Causes of soil erosion
- Water-holding capacity of different soils
Q1. The mixture of rock particles and humus is called:
A) Gravel
B) Soil
C) Clay
D) Silt
Answer: B) Soil
Description for Exam:
Soil is a natural mixture containing rock particles, minerals, organic matter such as humus, water, and air. Its composition can vary from one place to another.
Soil (Mixture of Rock Particles and Humus)
Soil is formed from a mixture of small rock particles, minerals, air, water, and humus.
How soil is formed:
Rocks break down slowly due to wind, water, and temperature changes. Dead plants and animals mix with these particles to form soil.
Main components of soil:
- Rock particles
- Humus
- Water
- Air
- Minerals
Importance of soil:
Soil supports plant growth and provides nutrients to plants.
Example:
Farmers use fertile soil for growing crops.
Q2. Which soil layer is rich in humus and minerals?
A) B-horizon
B) A-horizon
C) Bedrock
D) C-horizon
Answer: B) A-horizon
Description for Exam:
The A-horizon, also called topsoil, generally contains a good amount of humus and minerals. It is an important layer for the growth of plants.
A-Horizon (Topsoil)
The A-horizon is the uppermost layer of soil, also called topsoil.
Features of A-horizon:
- Rich in humus and minerals
- Dark in colour
- Contains roots and living organisms
Importance:
This layer is most suitable for plant growth because it contains nutrients and moisture.
Other layers:
- B-horizon → contains less humus
- C-horizon → contains weathered rocks
- Bedrock → hard solid rock layer
Example:
Most crops grow well in nutrient-rich topsoil.
Q3. The rotting dead matter in the soil is called:
A) Clay
B) Sand
C) Minerals
D) Humus
Answer: D) Humus
Description for Exam:
Humus is the dark organic matter formed when dead plants and animals decompose. It improves soil quality and supplies nutrients that support plant growth.
Humus (Rotting Dead Matter)
Humus is the dark organic material formed from the decomposition of dead plants and animals.
Formation of humus:
Micro-organisms break down dead matter into simpler substances.
Benefits of humus:
- Increases soil fertility
- Improves water-holding capacity
- Provides nutrients to plants
Importance:
Humus makes soil healthy and suitable for farming.
Example:
Forest soil is rich in humus because of fallen leaves and dead plants.
Q4. Which type of soil has the highest water-holding capacity?
A) Desert soil
B) Loamy soil
C) Sandy soil
D) Clayey soil
Answer: D) Clayey soil
Description for Exam:
Clayey soil contains very fine particles with small spaces between them. These particles allow clayey soil to retain more water than sandy soil.
Clayey Soil (Highest Water-Holding Capacity)
Clayey soil can hold the maximum amount of water among different soil types.
Reason:
Its particles are very small and closely packed, leaving less space for water to escape.
Characteristics:
- Retains water for a long time
- Rich in nutrients
- Sticky when wet
Disadvantage:
Poor air circulation for plant roots.
Example:
Rice crops grow well in clayey soil because they need more water.
Q5. Soil erosion is caused by:
A) Manure
B) Planting trees
C) Wind and Water
D) Humus
Answer: C) Wind and Water
Description for Exam:
Soil erosion is the removal or carrying away of the upper layer of soil. Wind and flowing water can transport soil particles from one place to another. Vegetation helps reduce soil erosion.
Soil Erosion (Caused by Wind and Water)
Soil erosion is the removal of the top fertile layer of soil by natural forces like wind and water.
Causes of soil erosion:
- Strong winds
- Heavy rainfall
- Deforestation
- Overgrazing
Effects:
- Loss of fertile soil
- Reduced crop production
- Environmental imbalance
Prevention methods:
- Planting trees
- Terrace farming
- Using barriers to reduce water flow
Example:
Floods often wash away fertile topsoil from fields.
Important Concepts
- Soil: Contains rock particles, minerals, organic matter, water, and air.
- Humus: Decomposed organic matter present in soil.
- A-horizon: Topsoil, generally rich in humus and minerals.
- Soil erosion: Removal of soil by agents such as wind and water.
- Clayey soil: Has a high water-holding capacity.
Exam Tips
- Remember: Humus = decomposed organic matter.
- A-horizon = topsoil.
- Wind and water are major agents of soil erosion.
- Clayey soil generally holds the most water among the soil types listed.
Quick Revision
Rock particles + humus + other components → Soil
Decomposed organic matter → Humus
Topsoil → A-horizon
Major causes of erosion → Wind and water
Highest water-holding capacity → Clayey soil
Common Mistakes
- Humus is not the same as minerals.
- A-horizon should not be confused with the C-horizon or bedrock.
- Sandy soil generally allows water to pass through quickly, whereas clayey soil retains more water.
FAQs
Q1. What is humus?
Humus is decomposed organic matter formed from dead plant and animal material.
Q2. Which horizon is called topsoil?
The A-horizon.
Q3. What causes soil erosion?
Agents such as wind and water can cause soil erosion.
Q4. Which soil retains the most water?
Clayey soil generally has the highest water-holding capacity among the options given.
Key Takeaway
Soil is a valuable natural resource made up of several components. Humus, soil horizons, erosion, and water-holding capacity are important concepts for understanding soil and its role in plant growth.
NCERT Reference
This quiz is originally written and paraphrased for educational practice using concepts from the NCERT Class 7 Science chapter “Soil.” The explanations are independently written and do not reproduce textbook passages verbatim.
Related links
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- Class 7 Maths Chapter 3 Data Handling part-7
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- Class 7 Social Science Chapter 1 Tracing Changes Through a Thousand Years part-6
- Class 7 Science Chapter 1 Nutrition in Plants part-5
- Class 7 Maths Chapter 3 Data Handling part-6
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- Class 7 Maths Chapter 3 Data Handling part-5
- Class 7 Science Chapter 1 Nutrition in Plants part-4
- Class 7 English Chapter 1 The Rainbow part-2
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