Important Questions for CBSE Class 7 Science Chapter 9 - Soil

Very Short Answer Questions: (1 Marks)

Define the Following Terms:

1. Soil

Ans: Soil is the dark brown to the black upper layer of the ground that contains a mixture of humus and stony particles and is where plants thrive.

2. Soil Profile

Ans: The soil profile is a vertical segment of the soil that represents all of the layers.

3. Weathering

Ans: Weathering is the progressive disintegration of rocks and minerals into smaller soil particles as a result of environmental influences such as wind, water, and temperature.

4. Humus

Ans: The dead and decaying plant materials that make up the organic element of the topsoil. It is created when plant matter decomposes under the influence of soil microbes.

5. Erosion

Ans: Erosion is the progressive wearing down and loss of the land's surface caused by wind, water, and other factors.

Short Answer Questions: (3 Marks)

6. What are the factors that cause soil erosion?

Ans: Erosion is the progressive wearing down and loss of the land's surface caused by wind, water, and other factors. Erosion can be induced by both natural and man-made environmental conditions.

1. Wind: When soil is exposed to the wind on a regular basis, the finer topsoil particles are swept away by the wind, resulting in erosion.

2. Water: As water flows above land, it eliminates the top layers of soil, causing erosion.

3. Cattle Overgrazing and Deforestation: Cattle overgrazing and deforestation both deplete plant roots in the soil. These roots are unable to hold on to soil particles as a result. Soil deteriorates as it becomes loose and degraded.

7. What is the percolation rate of the soil?

Ans: The passage of water through the soil is known as percolation. The rate at which water moves through the soil is referred to as the percolation rate. The amount of water percolated per minute can be calculated. The percolation rate is a measure of the soil's ability to retain water. Water retention capacity decreases as water percolates faster through the soil, and vice versa. The highest percolation rate is found in sandy soil, whereas the lowest is found in clayey soil.

8. What is meant by water retention of the soil?

Ans: Water retention refers to the amount of water retained by the soil. After the rest of the water has percolated, this is the water that stays in the soil. This is a measurement of how much water will be available to plants and other organisms in the soil. It is calculated by subtracting the percolated water from the total water added to the soil. The amount of water per kilogramme of soil can be calculated. Clayey soil holds the most water, whereas sandy soil holds the least.

9. How can we prevent soil erosion?

Ans: Soil erosion can be controlled and prevented in the following ways: 

1. Planting/Vegetation: Planting vegetation can control and prevent soil erosion by holding on to soil particles and preventing them from being eroded.

2. Fertilizer Use: Fertilizers can stop soil from eroding by adding an extra layer of protection.

3. Retaining Walls: Constructing retaining walls around places where soil erosion is a problem can help to reduce the amount of soil eroded.

Permeable fabric materials, such as coir, can be used to strengthen the soil and prevent erosion.

10. How is soil important for plant growth?

Ans: Plants cannot grow without soil.

1. Soil gives a surface for plant roots to anchor to and helps them stand upright.

2. The soil offers essential minerals for plant growth.

3. Soil is a vital source of water for plant growth.

4. Humus and essential bacteria in the soil aid in nitrogen fixation and availability to plants.

Long Answer Questions: (5 Marks)

11. Explain the soil profile with a diagram.

Ans:

The vertical part of a soil profile represents the many layers of soil on the planet.

The colour, texture, depth, and chemical makeup of each layer vary. Horizons are the names given to these levels.

O Horizon: The humus layer on topsoil is known as the O horizon. Because microbes decompose plant stuff, it is high in organic matter. It has a dark colour and a velvety texture. It contributes to the soil's fertility.

A Horizon: The topsoil is the topmost layer on the land surface and is referred to as A horizon. The surface of the A-horizon, or topsoil, is known as the humus or O horizon. A horizon is more permeable and made up of fine soil particles. Microorganisms and other organisms such as worms, rodents, moles, and beetles live there because it holds more water. The little plants' roots are completely encased in topsoil.

B Horizon: It's smaller and deeper than A horizon. It has a lower proportion of organic stuff and a higher proportion of hard mineral components.

C Horizon: It's made up of little rock chunks with fractures and crevices.

Bedrock: The soil's deepest layer. It is made up of bigger rock fragments. Digging is extremely difficult and time-consuming.

12. Compare the Different Types of Soil.

Ans: The differences between types of soil are:

13. Explain How Soil is Formed.

Ans: Weathering is the process that creates soil. Weathering is the progressive disintegration of rocks and minerals into smaller soil particles as a result of environmental influences such as wind, water, and temperature. Initially, there were enormous tracts of rocky ground. These massive rocks were exposed to extremes of temperature, rain, wind, and river flow, among other things. The surface of the rock slowly and gradually breaks down to smaller rock particles on the surface due to the constant and combined effect of all these forces. The C-horizon is thus produced from the bedrock. Further weathering of the smaller rock particles results in the formation of the B horizon, which consists of smaller rock particles packed more compactly. The weathering of the B horizon continues until the formation of the A horizon. The soil particles in a horizon are finer and softer. Microbial breakdown adds organic humus to the mix. Soil formation is a slow and gradual process that might take up to a million years.

Why are Important Questions for Class 7 Science Chapter 9 - Soil Necessary?

• Vedantu’s Important Questions for Class 7 Science Chapter 9 - Soil are the finest material to understand and practice the topics in the best way.

• The material carries all the information in detail and pointwise.

• All the cases of the material are solved in the simplest way which explains the term clearly.

• Vedantu’s Important Questions for Class 7 Science Chapter 9 - Soil provides all the main topics so that the student can focus on it and prepare for the exam. 

Conclusion

Exploring the essential questions from CBSE Class 7 Science Chapter 9, 'Soil,' leads to a deeper understanding of this vital natural resource. These questions delve into soil formation, its composition, and the crucial role it plays in sustaining life. Understanding these aspects enables students to appreciate soil's significance in agriculture, ecology, and the environment. Mastering these questions fosters a holistic understanding of soil science, empowering students to become responsible stewards of our Earth.