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Class 7 Science Chapter 7 | Soil | Extra Questions

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Here are expected questions from NCERT Class 7 Science Chapter 9 Soil.

1. What provides anchorage to the plants and supplies water and nutrients?

Soil

2. What are the uses of soil?

  • Soil is useful in many ways. Some of them are:
  • It provides anchorage to the plants and supplies water and nutrients.
  • It is the home for many organisms.
  • Soil is essential for agriculture. Agriculture provides food, clothing and shelter for all. Without soil life on earth is impossible.

3. Polythene bags and plastics pollute the soil and kill the organisms in the soil. True/false

True

4. Explain the layers of soil with the help of an experiment.

Take a little soil. Break the clumps with the hand and powder it. Now take a glass tumbler and fill three fourth of the tumbler with water. Add a handful of soil to the water and stir it well until it dissolves in the water, now wait for some time and leave the soil dissolved water undisturbed. Now we can see layers of particles of different sizes in the glass tumbler. We can also see some dead rotting leaves or animal remains floating on the water. The rotting dead matter in the soil is called the humus. The vertical that we can see now in the glass tumbler is called the soil profile. Each layer differs in texture, colour, depth and chemical composition.

5. What is weathering?

The soil is formed by the breaking of the rocks by the action of wind, waves, and climate. This process is called weathering.

6. What is soil profile?

A vertical section through different layers of the soil is called the soil profile.

7. What are horizons?

Each layer of the soil differs in feel, colour, depth and chemical composition. These layers are known as horizons.

8. Explain soil profile in detail?

The soil is divided into 4 layers. They are:

A horizon: The upper most layer of the soil is called the A horizon or top soil. The upper most horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to the growing plants. This layer is generally soft, porous and can retain more water. It provides shelter for many organisms like worms, moles, rodents and so on. The roots of small plants are embedded entirely in the top soil.

B horizon: The layer under the top soil is called the B-horizon or the middle layer. It has a relatively less amount of humus than the top soil but it has more minerals. This layer is generally harder and more compact.

C horizon: It is situated under the middle layer and it is the third layer. It is made up of small lumps of rocks with cracks and crevices.

Bed rock: It is situated under the C horizon. It is so hard and difficult to dig with a spade. It consists of many big hard rocks.

9. A horizon is also known as …………………………..

topsoil

10. B horizon is also known as ………………………..

middle layer

11. Under the C horizon which layer is situated ………………………………

bed rock

12. Which layer is dark in colour and rich in humus?

Topsoil

13. Which layer has more minerals in it?

B horizon

14. The layer which has big rocks in it and is very hard to dig with a spade.

Bed rock

15. The nature of any soil does not depend upon the rocks from which it has been formed and the type of vegetation that grows in it. True/false

False

16. The relative amount of sand and clay depends upon the rock from which the particles were formed, that is the ………………………………..

parent rock

17. What is soil?

The mixture of rock particles and humus is called the soil.

18. The soil is classified on the basis of the proportion of particles of various sizes. True/false

True

19. What is sandy soil?

Soil that contains a greater proportion of big particles is called sandy soil.

20. What is clayey soil?

If the proportion of fine particles in the soil is relatively higher, it called clayey soil.

21. What is loamy soil?

Soil that has the same proportion of large and fine particles is called loamy soil.

22. What are the three types of soil?

Sandy soil, clayey soil and loamy soil

23. Why is sandy soil light and well aerated?

Sand particles are large and cannot fit close together, so there are large spaces between them. These spaces are filled with air. Hence, sandy soil is light and well aerated.

24. Why is clayey soil heavier than sandy soil?

The particles of clayey soil are smaller and pack closely together. Hence, there is little space for air in clayey soil. At the same time, clayey soil retains water in the tiny gaps between the particles of clay. So, clayey soil is heavier and hold more water than sandy soil.

25. The best soil for growing plants is ……………………………..

loamy soil

26. Loamy soil is a mixture of ……………………………, ………………………. and ……………………….

sand, clay and silt

27. What type of soil is suitable for growing wheat and gram?

Clayey and loamy soil

28. Which soil is used for the cultivation of rice?

Clayey soil

29. Which soil is suitable for growing cotton?

Sandy-loam or loam soil is suitable for growing cotton.

30. The rate of percolation is highest in …………………………. soil and lowest in ………………………… soil.

sandy, clayey

31. What is erosion?

The removal of top soil by water, wind or rice is known as erosion.

32. How deforestation causes soil erosion?

The roots of plants firmly bind the soil and prevents it from getting eroded. If there are no trees, the soil gets removed easily. Soil erosion is severe in areas with little or no vegetation. By planting more trees soil erosion can be prevented to a great extent.

Class 7 Science Solutions

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