Living Science Solutions for Class 7 Science Chapter 10 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 Living Science Book of class 7 Science Chapter 10 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science Solutions. All Living Science Solutions for class 7 Science are prepared by experts and are 100% accurate.

Page No 106:

Question 1:

Humus and the smallest particles of rock form the

(a) A-horizon
(b) B-horizon
(c) C-horizon
(d) bedrock

Answer:

(a) A-horizon
Humus and the smallest particles of rock form the upper layer of soil called topsoil or A-horizon.

Page No 106:

Question 2:

Which of these has the smallest size of particles?

(a) sand
(b) silt
(c) clay
(d) gravel

Answer:

(c) clay
Clay has the smallest size of particles, less than 0.002 mm in diameter. Single clay particle cannot be seen with a naked eye.

Page No 106:

Question 3:

Which type of soil is best for growing cotton?

(a) sandy
(b) clayey
(c) loamy
(d) sandy-loam

Answer:

(d) sandy loam
Sandy loam soil is best for growing cotton. It can hold air, but water can drain through it easily.

Page No 106:

Question 4:

Which of these does not cause weathering?

(a) clouds
(b) wind
(c) flowing water
(d) freezing of rainwater

Answer:

(a) clouds
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.

Page No 106:

Question 5:

Water percolating into the soil collects over

(a) A-horizon
(b) B-horizon
(c) C-horizon
(d) none of these

Answer:

(d) none of these
Water percolating into the soil collects above the bedrock. This natural level of groundwater is called the water table.

Page No 106:

Question 6:

Water logging can be expected in soil which is rich in

(a) sand
(b) clay
(c) silt
(d) humus

Answer:

(b) clay
Clayey soil absorbs and retains a lot of water. In clayey soil, stagnant water collects above the soil whenever it rains. This is known as water logging.

Page No 106:

Question 7:

Paddy grows best in

(a) clayey soil
(b) loam
(c) sandy soil
(d) sandy-loam

Answer:

(a) clayey soil
Paddy grows best in soils rich in clay and organic matter with a capacity to retain water.

Page No 106:

Question 1:

Breaking down of rock into smaller pieces by natural forces is called___________

Answer:

Breaking down of rock into smaller pieces by natural forces is called weathering.

Page No 106:

Question 2:

Which absorbs more water-sandy soil or clay?

Answer:

Clayey soil absorbs more water than sandy soil and allows less water to percolate.

Page No 106:

Question 3:

The layer of soil that contains the largest rock pieces is called________

Answer:

The layer of soil that contains the largest rock pieces is called C-horizon.

Page No 106:

Question 4:

In general, which is the best topsoil for growing plants?

Answer:

The best topsoil for growing plants is loam. Loam is a mixture of sand, silt, clay and humus. It has the right water-holding capacity for plant growth.

Page No 106:

Question 5:

Water logging occurs in sandy soil. True of false?

Answer:

False.
Water logging occurs in clayey soil, which absorbs and retains a lot of water. Sandy soil cannot absorb much water because of the large spaces between the soil particles.

Page No 106:

Question 6:

Is soil a natural resource?

Answer:

Yes, soil is a natural resource because it comes from the earth and is used by us.

Page No 106:

Question 7:

Since clay holds more water, it is very good for plants as they get plenty of water. True of false?

Answer:

False.
Although clay holds more water, water drains through soil very slowly since the particles are very small and tightly packed. This type of soil is not able to trap enough air for the roots of the plants.

Page No 106:

Question 8:

Humus is formed by the action of insects on soil. True of false?

Answer:

False.
A variety of dead and decaying organisms contribute to the formation of humus.



Page No 107:

Question 1:

What does soil consist of?

Answer:

Soil consists of two components:
(a) Small mineral particles which come from larger rocks. These minerals include salts of iron, calcium, potassium, magnesium, phosphorus, etc.
(b) Humus is dark brown in colour and consists of decaying remains of plants and animals.

Page No 107:

Question 2:

What is weathering?

Answer:

Weathering is a process by which huge pieces of rocks break down into smaller pieces and gradually change into soil. It takes place by the action of natural forces such as water, wind, roots of plants and variations in day and night temperatures.

Page No 107:

Question 3:

Which soil will allow more water to percolate-sandy soil or clayey soil? Why?

Answer:

Sandy soil will allow more water to percolate because it has a lot of sand and water drains quickly through large spaces between the sand particles.

Page No 107:

Question 4:

Which soil will absorb more water-sandy soil or clayey soil? Why?

Answer:

Clayey soil will absorb more water because the soil particles are very small and the water drains very slowly.

Page No 107:

Question 5:

What is humus?

Answer:

Humus is a component of soil which is dark brown in colour and consists of decaying remains of plants and animals. When small plants such as mosses, lichens and ferns die, they mix with the soil and form humus. Humus makes the soil fertile by providing organic nutrients.

Page No 107:

Question 6:

How does large variation between day and night temperatures cause weathering?

Answer:

Due to large variation in day and night temperatures, the rocks expand during the day and contract during the night. This constant expansion and contraction weakens the rocks and they crack and crumble causing weathering.

Page No 107:

Question 7:

What do you mean by 'water table'?

Answer:

The natural level of groundwater is called the water table. Rainwater percolates through the soil and collects above the bedrock to form the water table.

Page No 107:

Question 1:

Explain how water is responsible for the formation of soil.

Answer:

The role of water in the formation of soil is extremely important in the following ways:
(a) Rainwater which enters rock crevices freezes in winter. As a result, it expands. This expansion puts pressure on rocks and breaks the rocks into smaller pieces.
(b) The small pieces of rocks roll down by the force of flowing water. They collide against the ground and against each other. Hence, they break down further and get converted into very fine particles.

Page No 107:

Question 2:

Trees help in soil formation as well as in its protection. Explain.

Answer:

Roots of trees growing through rocks exert great pressure on the rocks. This pressure causes cracks in the rocks, leading to the formation of soil. The roots of trees bind to the soil and prevent soil erosion and provide protection to the soil.

Page No 107:

Question 3:

Name the different layers of soil. What does each layer consist of?

Answer:

The different layers of soil are as follows:
(i) Topsoil (A-horizon):
It consists of humus and the smallest particles of rock.
(ii) Subsoil (B-horizon):
It consists of small pieces of rocks and some nutrients such as soluble minerals and iron oxides.
(iii) Parent rock (C-horizon):
It consists of small pieces of rocks with cracks and crevices.

Page No 107:

Question 4:

Distinguish between clay, silt and sand.

Answer:

Clay Silt Sand
Particle size is smallest. It is less than 0.002 mm in diameter. Particle size is larger than clay. It is between 0.002 mm and 0.2 mm in diameter. Particle size is largest. It is more than 0.2 mm in diameter.
It can hold a large amount of water. It can hold a small amount of water. Water-holding capacity is most poor.

Page No 107:

Question 5:

What is loam? Why is it considered to be the best topsoil for growing plants?

Answer:

Loam is a mixture of sand, silt, clay and humus.
It is considered to be the best topsoil for growing plants because it has the right water-holding capacity for plant growth. It also has adequate spaces between the soil particles to trap air required by the roots of plants.

Page No 107:

Question 6:

Why is soil regarded as our most important natural resource?

Answer:

Soil is considered as our most important natural resource due to the following reasons:
(a) It provides us food, clothing and shelter: By supporting growth of plants, the soil provides us with food and clothing. Plants also provide us with wood, which is used for constructing house.
(b) It provides us minerals: Minerals are dug out from the earth to extract metals such as iron, gold, silver, etc.
(c) It provides us water: Water that seeps into the soil is stored underground as subsoil water. This water is used for drinking and other purposes.

Page No 107:

Question 7:

Why is the earthworm referred to as 'farmer's friend'?

Answer:

Earthworms improve the soil texture. They make the soil loose by burrowing into the soil, thus allowing air to enter into it and water to drain from it. They also form channels in the soil for roots to spread through. Hence, earthworms are referred to as 'farmer's friend'.

Page No 107:

Question 9:

Soil without humus cannot be fertile. True of false?

Answer:

True.
Humus makes the soil fertile by providing organic nutrients.

Page No 107:

Question 10:

Humus if formed by the action of decomposers. True of false?

Answer:

True.
Humus is formed by the action of decomposers such as bacteria and fungi.

Page No 107:

Question 1:

What effect does construction of buildings and roads have on water percolation through the soil? Hence what effect would this have on the water table?

Answer:

The rate of water percolation through the soil decreases as a result of construction of buildings and roads because water cannot percolate into cement. Due to this, the water table will shrink.

Page No 107:

Question 2:

Soil is constantly formed by weathering of rocks. Why then are we so concerned about soil erosion?

Answer:

Topsoil is the most fertile soil because it consists of humus. Soil erosion removes topsoil, thus decreasing soil fertility. The formation of topsoil by the process of weathering takes a very long time. Hence, we are so concerned about soil erosion.

Page No 107:

Question 3:

Why does topsoil have much more humus than subsoil?

Answer:

Humus is formed by the death and decay of plants and animals. When small plants die, they mix with the soil to form humus. These plants and animals are confined to topsoil. Hence, topsoil have much more humus than subsoil.

Page No 107:

Question 4:

What kind of soil is most suitable for making toys and why?

Answer:

Clayey soil is most suitable for making toys because it does not crumble when rolled into a ball.



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