NCERT Solutions for Class 7 Science Chapter 9 Soil are provided here with simple step-by-step explanations. These solutions for Soil are extremely popular among Class 7 students for Science Soil Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the NCERT Book of Class 7 Science Chapter 9 are provided here for you for free. You will also love the ad-free experience on Meritnation’s NCERT Solutions. All NCERT Solutions for class Class 7 Science are prepared by experts and are 100% accurate.
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Question 1:
The microorganisms present in the soil require moisture (water) and nutrients for growth and survival. Choose from the options below the habitat (place) where the soil has plenty of water and nutrients.
(a) Desert
(b) Forest
(c) Open field
(d) Cricket ground
Answer:
Roots of trees found in forests hold soil particles and protect top soil (which contains humus) from getting eroded. Humus makes soil fertile and provides nutrients to growing plants. Trees in a forest act as natural absorbers and help the soil to absorb a huge quantity of the rainwater. Therefore, the habitat where the soil has plenty of water and nutrients is a forest.
Hence, the correct answer is option (b).
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Question 2:
Availability of water and minerals in the soil for maximum absorption by roots is in the –
(a) B-horizon
(b) C-horizon
(c) A-horizon
(d) surface of soil
Answer:
A – horizon is top soil, rich in humus which improves the soil texture, increases it water holding capacity as well as provides nutrients to the growing plants. Humus and minerals make the soil fertile and favour plant growth.
Hence, the correct answer is option (c).
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Question 3:
Soil conservation measures are mainly aimed at protecting which of the following?
(a) Plants
(b) Top soil
(c) Sub soil
(d) Soil organisms
Answer:
Top soil is rich in humus which is dark brown in colour and consists of decaying remains of plants and animals. It is the most fertile region and soil conservation measures are mainly aimed at protecting top soil.
Hence, the correct answer is option (b).
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Question 4:
Read the following statements with reference to soil.
(i) Weathering is a very fast process of soil formation.
(ii) Percolation of water is faster in sandy soils.
(iii) Loamy soil contains only sand and clay.
(iv) Top soil contains the maximum amount of humus.
Choose the correct statements from the above.
(a) (ii) and (iv) (b) (i) and (iii)
(c) (ii) and (iii) (d) (i) and (ii)
Answer:
Weathering is the breaking down of huge pieces of rocks into smaller pieces by the action of natural forces such as water, glaciers, wind and roots of plants, etc. It takes hundreds of years to produce a few centimeters of soil. Therefore, it is a very slow process. Percolation of water is faster in sandy soils. Loamy soil is a mixture of sand, silt and clay and also has humus in it. Top soil contains the maximum amount of humus.
Hence, the correct answer is option (a).
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Question 5:
Soil has particles of different sizes. Arrange the words given below in increasing order of their particle size.
Rock, Clay, Sand, Gravel, Silt
Answer:
The increasing order of particles size is given as:
Clay < Silt < Sand < Gravel < Rock
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Question 6:
The components of loamy soil are ______, ______ and ______.
Answer:
The components of loamy soil are sand, silt and clay.
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Question 7:
Read the following statements and give the appropriate terms for each of them.
(a) The process of breakdown of rocks by the action of wind, water, sunlight.
(b) Removal of top soil during heavy rains or strong winds.
(c) Accumulation of wastes in the soil generated by human activity which alter the features of soil.
(d) The process of movement of water into deeper layers of soil.
Answer:
(a) Weathering
(b) Soil erosion
(c) Soil pollution
(d) Percolation
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Question 8:
Unscramble the following jumbled words related to soil.
Answer:
(a) HUMUS
(b) SOIL PROFILE
(c) HORIZON
(d) LOAM
(e) WEATHERING
(f) PERCOLATION
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Question 9:
Which of the following situations – ‘A’ or ‘B’ – is advantageous for absorption of water and minerals? Why?
Situation ‘A’ : Growth and branching of roots in the C-horizon.
Situation ‘B’ : Growth and branching of roots in A and B- horizons.
Answer:
A and B horizons are humus rich regions and humus improves the texture of soil, increases water holding capacity of soil and provides nutrients for the growth of plants. Minerals are also present in A and B horizons. Humus and minerals make soil fertile and help in growth of plants. Therefore, the situation B is advantageous for absorption of water and minerals.
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Question 10:
How can a farmer convert acidic soil to neutral soil?
Answer:
The farmers can convert acidic soil to a neutral soil by adding small quantity of a basic solution such as quick lime solution or slaked lime solution into the soil.
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Question 11:
Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give reason to support your answer.
Answer:
Plants cover the soil surface and their roots bind the soil particles and hold them in place. During strong winds and rains they protect the top soil and thereby prevent soil erosion. Therefore, it is not a good practice to remove grass and small plants growing in an open unused field.
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Question 12:
A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper. He could not dig beyond a depth of 5 feet. Provide a suitable scientific explanation.
Answer:
A man digging a pit found that he could dig with ease initially but digging became difficult as he went deeper because the soil surface has loose top soil which is easier to dig. At deeper layers, partially weathered rocks or bedrocks are present which are hard and make digging difficult.
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Question 13:
Locate the following zones given as boxed items in Figure 9.1 which shows a diagram of soil profile.
| Top soil, | Subsoil, | C-horizon, | Bedrock |
Answer:
The main layers of soil are top soil (A horizon), sub soil (B horizon), parent rock (C horizon) and bedrock which are shown in the given soil profile.
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Question 14:
Rajasthan is a desert state in India. Once while travelling to Rajasthan by train, Boojho observed several streams and rivulets of rain water during the journey but to his surprise he did not see streams of water in the desert region even during rains. Help Boojho find a suitable explanation for this.
Answer:
Deserts are vast stretches of sandy soil. In sandy soil, due to the presence of large spaces between the sand particles, the water drains out quickly. Therefore, sandy soil cannot hold much water and tends to be light and dry. Due to this reason in deserts, the falling rainwater immediately percolates downwards in the spaces between sand particles. That is why, Boojho did not see streams of water in the desert region.
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Question 15:
Match the animals in Column I with their natural place of dwelling (habitat) in Column II.
| Column I | Column II |
| (a) Earthworm | (i) sand and beaches |
| (b) Garden lizard | (ii) burrows in soil |
| (c) Crab | (iii) deep, narrow holes in dry soils |
| (d) Rodents | (iv) surface of soil |
| (e) Scorpion | (v) surface of shaded moist soils |
| (f) Snails and slugs | (vi) a horizon of moist soil |
Answer:
The correct match between column I and column II is given as:
(a) - (vi), (b) - (iv), (c) - (i), (d) - (ii), (e) - (iii), (f) - (v)
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Question 16:
Continuously water-logged soils are disadvantageous for plant growth. Why?
Answer:
Roots absorb oxygen that is present in the spaces between soil particles. But in water-logged soils water occupies the spaces between soil particles and pushes the oxygen out into the atmosphere. Therefore, roots are deprived of oxygen and this affects root and plant growth.
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Question 17:
Why is soil erosion relatively less in dense forests as compared to barren, open fields?
Answer:
In dense forests, the tree cover i.e., canopy prevents rainwater from directly falling on the forest soil. The canopy layer of forests obstructs the flow of raindrops so that rainwater falls on the leaves of trees and then drips slowly onto the forest floor. Thus, forests allow rainwater to seep. The roots of the vegetation bind the soil particles and hold them firmly which protects the top soil and prevents it from getting eroded by wind or water. But in barren, open fields the soil is exposed to the wind and falling rain. The soil particles become loose and easily get carried away by blowing wind or flow of water. Therefore, soil erosion is relatively less in dense forests as compared to open barren fields.
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Question 18:
Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently. Give reasons.
Answer:
Gardeners gently dig up the soil around the roots of garden herbs (plants) frequently because:
(i) It enables easy root growth.
(ii) It makes the percolation of water easy.
(iii) It aerates the soil and allows the air to get deeper into the soil.
(iv) It remove weeds.
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Question 19:
In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages. Give suitable reasons.
Answer:
In towns and cities, generally, the bore wells have to be dug very deep to get water as compared to bore wells dug in villages because excessive use of water in towns and cities depletes the groundwater. Also, due to the asphalted roads and vast areas of concrete soil in towns and cities, rainwater cannot percolate to recharge groundwater and the groundwater level further decreases. Villages have larger areas of open soil surface and fewer asphalated roads and concrete surfaces. Thus, larger soil surface area is available for rainwater to percolate into the soil easily and recharge the groundwater. Therefore, even shallow bore wells yield water in village.
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Question 20:
Several terms related to soil are hidden in the squares given as in the given figure Spot them and make a list.Two examples are given for you.
Answer:
The terms hidden in the squares are:
Profile, Humus, Rock, Silt, Horizon, Weathering, Erosion, Plant, Gravel, Sand, Clay, Percolation, Water and Mineral. This can be represented as:
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