Basic Science Solutions for Class 7 Science Chapter 14 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 Basic Science Book of class 7 Science Chapter 14 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class 7 Science are prepared by experts and are 100% accurate.

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The oxygen present in the air oxidises the chemicals present in the rocks. These oxidised chemicals then break the rocks, thus increasing their surface area and speeding up the process of soil formation.

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Rocks, on getting exposed to temperature, contract and expand due to the decrease and increase in temperature, respectively. This weakens the rocks and helps in weathering.

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The following are the components of the soil:
(a) organic matter
(b) water
(c) air
(d) minerals
(e) biota (living organisms)

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Loamy soil is considered to be the best soil for the growth of plants.

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Clayey soil has a greater water-holding capacity.

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Rainwater carries small pieces of rocks along with it, which roll against the ground and against each other, and further break apart. These rock pieces are carried away by flowing water and it deposits them on a plainer land when it slows down. Rainwater enters the cracks of rocks. When it freezes and expands, it breaks apart the rocks. Thus, rainwater helps in speeding up the weathering process by erosion and by facilitating chemical reactions.

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The following characteristics of soil play an important role in the survival and growth of plants:
(i) The amount of water in the soil determines the kind of plants that would survive better in the soil.
(ii) The air in the soil is important for the respiration of roots.
(iii) Microbes play a vital role in nutrient-cycling in the soil, thereby contributing to the growth of plants.
(iv) Soil rich in organic content is better suited for plant growth.

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The A horizon of soil, i.e. the top soil, supports the growth of plants. The A horizon has most of the nutrients in an absorbable form and it is also rich in organic material, i.e. humus, which is important for the growth of plants as it provides them with nutrients. The soil particles of this layer are fine and hold the adequate amount of water and air required for plant growth.

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Substratum (C horizon) is the lowermost layer of the soil just above the parent rock layer. Although substratum contributes to the formation of the top soil, the top soil can be a mixture of soil from different regions as wind, water and other media carry soil along with them and deposit it over an area. Thus, the top soil is not completely formed by substratum.

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The water that seeps through the top soil finally settles down in the substratum or the C horizon of the soil. Water cannot penetrate the layer of bed rock or the parent material beneath the substratum. So, the substratum forms the store of groundwater, one of the major sources of freshwater.



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Advantages of sandy soil:
(a) It is rich in sand particles, the largest of all the types of soil particles.
(b) It is richly ventilated and can be easily ploughed as it is loose.

Disadvantages of sandy soil:
(a) It cannot hold much water as its particles have huge pores.
(b) It easily gets eroded as its particles are loosely bound.

Advantages of clayey soil:
(a) It cannot be easily eroded as its particles are tightly bound to each other.
(b) It can hold a large amount of water.

Disadvantages of clayey soil:
(a) It has very small air-filled pores that makes it poorly ventilated.
(b) Due to high water-holding capacity, it sometimes leads to water logging and suffocation of the plant roots.

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The organisms inhabiting the soil are referred to as the soil biota. The soil biota constitute animals such as worms, microbes and small insects. Earthworm is the most important of the soil biota and for this reason, it is called the friend of farmers.

Earthworm and similar organisms ingest the organic matter in the soil, digest it and excrete it in the form of worm castings. These worm castings are full of nutrients. These nutrients contribute to the growth of plants.

These animals move through the soil by burrowing through it. This helps in the aeration of the soil, making it adequately ventilated and better suited for plant growth.

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1. The breaking down of rocks into smaller particles is called weathering of rocks.
2. The decaying organic matter present in soil is called humus.
3. Water seeps more through sandy soil than through clayey soil.
4. Black soil is good for the cultivation of cotton.
5. Lateritic soil is found in tropical countries.

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(a) clay
Clay particles are the smallest particles in the soil.

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(c) alluvial soil
Alluvial soil is found in the fertile plains of Punjab and Uttar Pradesh.

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(c) bedrock
The hard layer of rocks below the C horizon is called bedrock.

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(a) transported soil
Soil carried from elsewhere and deposited over the substratum is called transported soil.

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(b) B horizon
Rainwater, while seeping through the topsoil, carries nutrients with it and deposits them in the B horizon or the subsoil.

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1. Alluvial Soil C. Very fertile
E. Rich in humus
o. Deposited by rivers
q. Northern plains, costal plains
2. Red Soil D. Low in humus
A. Not very fertile
m. Iron oxide gives the colour
3. Black Soil F. Mineral rich
K. Good for cotton, sugar cane
G. Clayey
t. From volcanic rocks
4. Lateritic Soil D. Low in humus
J. Good for tea, coffee, coconut
n. Western and Eastern Ghats
5. Desert Soil F. Mineral rich
H. Sandy
D. Low in humus
r. Rajasthan, Gujarat, Ladakh
6. Mountain Soil I. Acidic
B. Quite fertile
G. Clayey
p. The Himalayan region



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