Mineral Riches in the Soil Questions in English

(N/A) The formation of soil takes place through the process of weathering,which involves the following steps:
$1$. Physical weathering: Rocks near the Earth's surface are broken down by the sun's heat,which causes expansion and contraction,leading to cracks and fragmentation.
$2$. Chemical and physical action of water: Water enters the cracks in rocks,freezes,and expands,breaking the rocks apart. Fast-flowing water also causes erosion and mechanical breakdown of rocks.
$3$. Wind action: Strong winds cause erosion and abrasion,breaking down rocks into smaller particles over millions of years.
$4$. Biological weathering: Living organisms like lichens and mosses grow on rock surfaces. They release chemicals that break down the rock and physically penetrate the surface,turning it into a fine powder,which forms a thin layer of soil.

(B) The removal of the top layer of soil is known as soil erosion.
This layer is rich in humus and essential nutrients.
The primary agents causing soil erosion are flowing water and wind.
If this process continues for a long time,the land becomes infertile due to the loss of valuable nutrients.

(N/A) The methods to prevent or reduce soil erosion are as follows:
$1$. Afforestation: Planting more trees helps bind the soil particles with roots,preventing them from being washed away.
$2$. Contour Ploughing: Ploughing along the contours of the land helps in reducing the speed of water flow,thereby minimizing soil erosion.
$3$. Terrace Farming: Creating steps on hilly slopes reduces the velocity of water runoff,allowing soil to settle.
$4$. Soil Cover: Keeping the soil covered with vegetation or crop residues protects it from the direct impact of rain and wind.
$5$. Controlled Grazing: Overgrazing by livestock removes the protective plant cover,exposing the soil; therefore,controlled grazing is essential to maintain soil integrity.

(N/A) Living organisms depend on soil in the following ways:
$1$. Soil provides anchorage to plants by binding their roots. Plants absorb essential nutrients from the soil for their growth and development.
$2$. Soil serves as a natural habitat for various microorganisms like bacteria,fungi,and algae,as well as larger organisms like earthworms. These organisms play a crucial role in maintaining soil fertility.
$3$. Many animals,such as rats and rabbits,use soil to build their burrows or homes.
$4$. Earthworms live and perform their activities within the soil,contributing to its fertility by releasing nitrogen-rich excreta.
Regarding aquatic organisms,they are not totally independent of soil. Aquatic organisms rely on aquatic plants for food and oxygen. These aquatic plants require minerals for their survival,which are transported from the soil to water bodies by rivers,rainwater,and surface runoff. Without the continuous supply of minerals from the soil,aquatic life would not be sustainable.

(D) Soil formation is a natural process involving the weathering of rocks by factors like the sun (temperature changes),water,and wind. Polythene bags are non-biodegradable synthetic materials that do not contribute to soil formation; instead,they contaminate the soil and make it barren.

(B) Top-soil is the uppermost layer of the soil profile. It is rich in organic matter known as humus,which is formed by the decomposition of dead plants and animals. It also contains various living organisms such as bacteria,fungi,earthworms,and insects,along with mineral particles (sand,silt,and clay) that provide the physical structure of the soil. Therefore,top-soil is a complex mixture of humus,living organisms,and soil particles.

(D) Soil is formed through the process of weathering of rocks over a long period of time.
During this process,the physical and chemical breakdown of the parent rock releases various minerals into the soil.
Therefore,the parent rock acts as the primary reservoir and source of minerals found in the soil.
While bacteria,plants,and animals contribute organic matter (humus) to the soil,they are not the primary source of the mineral content.

(D) Soil erosion is the removal of the top layer of soil by natural forces like wind and water.
$A$,$B$,and $C$ are activities that expose the soil or degrade its structure,thereby increasing erosion.
Raising forests $(D)$ helps prevent soil erosion because the roots of trees bind the soil particles together,and the canopy reduces the impact of rain on the ground.

(A) Vegetation plays a crucial role in soil conservation. Plants hold the topsoil in place with their roots. When there is no vegetational cover,the soil is exposed,and the force of falling rain washes away the nutrient-rich topsoil,leading to soil erosion.

(N/A) Water is a universal solvent and is capable of dissolving a large number of substances. As rivers flow over the Earth's surface,they pass over various types of rocks and soil. The water dissolves soluble minerals present in these rocks and soil through the process of weathering and erosion. These dissolved minerals are then transported by the river currents and eventually deposited into the sea,thereby increasing the mineral content of sea water.

(D) The loss of topsoil,also known as soil erosion,can be prevented by the following methods:
$(i)$ Increasing the vegetational cover: Plants and trees hold the soil particles together with their roots,preventing them from being washed away by water or blown away by wind.
$(ii)$ Checking the cutting of trees (deforestation): Trees act as windbreaks and their roots stabilize the soil. Reducing deforestation helps maintain soil integrity.
$(iii)$ Preventing excessive grazing: Overgrazing removes the protective plant cover,leaving the soil exposed to erosion. Regulating grazing allows vegetation to recover and protect the soil.

(A AND B) The organisms that can grow on stones and help in the formation of soil are Lichens $(a)$ and Mosses $(b)$.
Mode of action:
$1$. Lichens grow on the surface of rocks and release certain acids (like lichen acids) that chemically weather the rock surface,causing it to break down into smaller particles.
$2$. Mosses grow on the surface of rocks after lichens have created a thin layer of soil. They further break down the rock surface through mechanical and chemical processes,contributing to the accumulation of organic matter and the formation of soil.

(N/A) Soil formation is a complex process involving various environmental influences:
$1$. Abiotic factors: These are non-living components that contribute to the weathering of rocks. Key examples include the sun (causing thermal expansion and contraction),water (causing erosion and chemical weathering),and wind (causing mechanical abrasion).
$2$. Biotic factors: These are living organisms that contribute to soil development. Key examples include lichens (which secrete acids to break down rock surfaces),mosses (which help retain moisture and create organic matter),and trees (whose roots penetrate rock crevices,causing physical breakdown).

(N/A) Lichens are the first organisms to colonize bare rocks,which is why they are called pioneer species.
They secrete organic acids (such as oxalic acid) that chemically weather the rock surface.
This process breaks down the rock into smaller mineral particles.
Over time,the accumulation of these mineral particles,along with the dead organic matter from the lichens themselves,contributes to the formation of a thin layer of soil,which allows other plants like mosses to grow.

(N/A) Water contributes to the formation of soil in the following ways:
$(i)$ Water causes the 'weathering' or wearing off of rocks over a long period of time.
$(ii)$ Flowing water causes rocks to rub against other rocks, creating small particles that are carried downstream and deposited as soil.
$(iii)$ Water enters the crevices of rocks and expands upon freezing, which exerts pressure and cracks the rocks into smaller pieces.

(D) Fertile soil is rich in microorganisms that decompose dead organic matter,resulting in the formation of humus.
Humus is highly beneficial because it provides essential minerals to the soil.
It also improves the water-holding capacity of the soil.
Furthermore,humus makes the soil porous,which facilitates better aeration and root penetration.

(B) Farms in hills have steep slopes.
There is always a risk of topsoil being washed away by rainwater due to the steep gradient.
Step farming involves cutting the slopes into a series of flat,step-like terraces.
This reduces the velocity of flowing water and allows it to soak into the ground,thereby preventing soil erosion.
Hence,step farming is common in hills.

(N/A) The Sun heats the rocks during the day,causing them to expand. At night,these rocks cool down and contract. Because different components of the rock expand and contract at different rates,this uneven process leads to the development of cracks in the rocks. Over long periods,these cracks widen,causing the rocks to break into smaller particles,which eventually form soil.

(B) Soil erosion is the removal of the top layer of soil. In mountainous regions,the steep slopes and high-velocity water runoff make it extremely difficult to prevent or reverse soil erosion. Once the topsoil is washed away from these slopes,the underlying rock is exposed,making it nearly impossible for vegetation to regrow and for the soil to accumulate again.

(N/A) Two factors that contribute to soil fertility are:
$1$. Humus: The presence of organic matter (decayed plant and animal remains) provides essential nutrients to the soil.
$2$. Microorganisms: Organisms like bacteria,fungi,and earthworms help in the decomposition of organic matter,which enriches the soil with nutrients and improves its structure.

(ROCKS) The major source of minerals in the soil is the weathering of rocks. Over millions of years,various physical,chemical,and biological processes break down large rocks into smaller particles,which eventually form the mineral component of the soil.

(N/A) The various components of soil include:
$1$. Small particles of rock (weathered rock materials).
$2$. Humus (decayed organic matter).
$3$. Living organisms (such as bacteria,fungi,earthworms,and insects).
$4$. Air and water trapped between the soil particles.

(B) The mineral nutrients present in a particular soil are primarily determined by the parent rock from which the soil was formed through the process of weathering. The chemical composition of the parent rock dictates the types of minerals available in the soil.

(N/A) The soil type is primarily determined by the following factors:
$1$. Size of the soil particles (e.g.,sand,silt,or clay).
$2$. Amount of humus present in the soil.
$3$. Type and quantity of microorganisms present in the soil.
$4$. Climate and weathering processes of the parent rock.

(B) Step farming,also known as terrace farming,is common in hilly regions because it helps to reduce the velocity of flowing water.
By creating flat steps on steep slopes,the speed of runoff is decreased,which significantly reduces the washing away of topsoil.
Therefore,it is primarily done to prevent soil erosion and maintain soil fertility.

(N/A) Wind is caused by the movement of air from one region to another due to the uneven heating of the Earth's atmosphere by the Sun.
$(b)$ Two methods of preventing soil erosion are:
$1.$ Afforestation (planting more trees).
$2.$ Terrace farming (or contour ploughing).

(N/A) Sandy soil has large particle size and poor water-holding capacity. Therefore,it is unsuitable for growing vegetables as it cannot retain moisture and nutrients required for plant growth.
$(b)$ He likely added organic manure to the soil. The two advantages are:
$(i)$ It increases the water-holding capacity of the sandy soil.
$(ii)$ Manure enriches the soil with essential nutrients and organic matter,thereby increasing soil fertility.

(N/A) $(i)$ Bio-fertilizers are organisms that enrich the nutrient quality of the soil by fixing atmospheric nitrogen or by dissolving phosphorus.
$(ii)$ $Rhizobium$ bacteria live in the root nodules of leguminous plants. They have a symbiotic relationship with the plants,where they fix atmospheric nitrogen into organic forms that the plants can use,thereby increasing the nitrogen content of the soil.
$(iii)$ Rahila was curious because she possessed a spirit of inquiry,a concern for science,and a scientific temperament.

(N/A) $(i)$ Lichens are the symbiotic life forms that can grow on bare rocks.
$(ii)$ They secrete certain organic acids while growing on the surface of rocks.
$(iii)$ These acids cause the rock surface to weather,creating small cracks and crevices.
$(iv)$ Over time,these cracks widen due to the accumulation of dead organic matter and the action of water and wind,eventually breaking the rock into smaller particles to form soil.

(N/A) $(i)$ Soil is a mixture of small rock particles,bits of decayed living organisms known as humus,and microscopic life forms.
$(ii)$ The type of soil is determined by the average size of the particles found in it,while the quality of the soil is determined by the amount of humus and the microscopic organisms present in it.

(N/A) $(i)$ Soil is formed through the process of weathering,where rocks at or near the Earth's surface are broken down over long periods by physical,chemical,and biological factors.
$(ii)$ Topsoil is the uppermost layer of the soil profile,which is rich in humus,organic matter,and living organisms,along with fine soil particles.
$(iii)$ It is important because it provides essential nutrients for plant growth,supports the biodiversity of the area,and acts as a habitat for various microorganisms.

(N/A) $(i)$ The sun heats up the rocks during the day,causing them to expand.
$(ii)$ At night,the rocks cool down and contract.
$(iii)$ Since different parts of the rock expand and contract at different rates,this unequal stress causes the rocks to crack and break into smaller pieces over time,eventually forming soil.

(N/A) Soil can be conserved through the following methods:
$1.$ Restoration of soil fertility:
$(a)$ By using an optimum amount of fertilizers and manures.
$(b)$ Practicing crop rotation.
$(c)$ Growing leguminous plants to fix nitrogen.
$(d)$ Leaving the field fallow for a period to allow natural recovery.
$2.$ Prevention of soil erosion:
$(a)$ Growing protective vegetation to cover the soil surface,which reduces the impact of rain and wind.
$(b)$ Practicing terrace farming in hilly regions to reduce the speed of water runoff.
$(c)$ Constructing embankments (bandhs) to prevent soil wash-off.

(N/A) Soil formation: It is the process of breaking down rocks into smaller particles through physical,chemical,and biological weathering.
Two factors: $1$. Sun (temperature changes causing expansion/contraction),$2$. Water (flowing water or freezing in cracks).
Soil erosion: It is the process where the top layer of soil is removed or carried away from one place to another.
Two factors: $1$. Deforestation (loss of root binding),$2$. Overgrazing (removal of vegetation cover).

(N/A) Soil formation factors:
$1$. Sun: The heat from the sun causes rocks to expand during the day and contract at night. This uneven expansion and contraction lead to the formation of cracks,eventually breaking the rocks into smaller pieces.
$2$. Water: Water enters the cracks in rocks. During winter,this water freezes and expands,exerting pressure that widens the cracks,eventually breaking the rocks. Additionally,fast-flowing water carries rock particles,causing them to collide and wear down into smaller particles.
$3$. Wind: Strong winds carry sand and rock particles,which rub against larger rocks,causing erosion and breaking them down over time.
$4$. Living Organisms: Lichens growing on rock surfaces release chemicals that powder the rock surface. Mosses and other plant roots grow into the cracks,further breaking the rocks into fine soil particles.
$(b)$ Function of Humus:
Humus makes the soil more porous,which allows water and air to penetrate deep into the ground,facilitating the growth of roots and supporting soil fertility.

(N/A) $(i)$ Strong winds: Wind causes erosion and physical weathering of rocks over time.
$(ii)$ Fast-flowing water: Water flowing over rocks causes abrasion and breaks them into smaller particles.
$(iii)$ Living organisms: Lichens,mosses,and fungi grow on rock surfaces,releasing chemicals that break down the rock and contribute to soil formation.
$(iv)$ Temperature variations: Repeated heating and cooling of rocks due to solar radiation causes expansion and contraction,leading to cracks and eventual disintegration.

(N/A) $(i)$ Lichens grow on the surface of rocks and release certain chemicals that cause the rock surface to powder down,creating a thin layer of soil.
$(ii)$ Mosses then grow on this surface,which further breaks down the rock material.
$(iii)$ The roots of big trees grow into the crevices of rocks,creating cracks and widening them over time,which eventually leads to the formation of soil.

(N/A)
- Soil is an essential resource that determines the biodiversity of an area.
- The topsoil,which is the outermost layer,is rich in minerals and provides necessary nutrients to various life forms.
- It serves as a habitat for numerous microorganisms that assist in the recycling of nutrients.
- It supports vegetation,which in turn provides food and shelter for thousands of animal species.
$(b)$
- No,organisms living in water are not entirely independent of soil.
- The minerals and nutrients required by aquatic life are derived from the soil,which are carried into water bodies by rainwater or surface runoff.

(N/A) Soil pollution is caused by the following factors:
- Dumping of industrial wastes in vacant sites,such as along roads,railway tracks,or in sanitary landfills.
- Accumulation of wastes from residences,cattle sheds,industries,and agricultural fields.
- Excessive and indiscriminate use of chemical fertilizers and pesticides in agriculture.
$(b)$ Three ways to prevent soil pollution are:
$(i)$ Judicious and controlled use of chemical fertilizers and pesticides.
$(ii)$ Proper management and scientific disposal of household and industrial waste.
$(iii)$ Adoption of sustainable agricultural practices such as intensive cropping and terrace farming to maintain soil health.

(N/A) Humus is the dark-coloured,partially decayed organic matter found in the top layer of soil.
Its functions are as follows:
$1$. It makes the soil porous,which increases the soil's water-holding capacity and air content.
$2$. It is rich in nutrients,which promotes the growth of plants.
$3$. It improves soil structure,allowing plant roots to penetrate the soil more easily.

(N/A) The sun plays a crucial role in soil formation through the process of weathering:
- Rocks heat up and expand during the day due to solar radiation.
- At night, these rocks cool down and contract.
- Because different parts of the rock expand and contract at different rates, this uneven heating and cooling causes cracks to develop, eventually breaking the rocks into smaller pieces, which eventually form soil.
$(b)$ Dust is considered a pollutant for the following reasons:
- Inhalation of dust particles can cause respiratory diseases such as asthma, bronchitis, and lung cancer.
- Dust, when combined with smoke and water vapor, forms smog, which reduces visibility and leads to accidents.
- Exposure to specific types of dust, such as cement, asbestos, or coal dust, can trigger severe allergies, sneezing, and chronic conditions like tuberculosis $(TB)$.

(N/A) The loss of topsoil can be prevented by adopting the following measures:
$(i)$ Intensive cropping: This practice ensures the field is not left unused by growing crops continuously.
$(ii)$ Terrace farming: This is practiced in hilly regions where small fields are formed in the shape of steps to grow crops,which reduces soil erosion.
$(iii)$ Afforestation and planting: Sowing grasses or planting trees on barren soil prevents it from being washed away.
$(iv)$ Proper drainage: Constructing drainage canals around the fields helps in the controlled removal of excess rainwater,preventing soil runoff.

(N/A) The Sun: The Sun heats up rocks during the day, causing them to expand, and at night they cool down and contract. This repeated expansion and contraction result in the formation of cracks, and rocks ultimately break into smaller pieces.
Wind: Strong winds cause erosion by rubbing against rocks and carrying rock particles. This abrasive action breaks down large rocks into smaller particles, which eventually contribute to the formation of soil.

(B) Modern farming practices often rely on the excessive use of fertilizers and pesticides.
These chemicals are used to increase crop production and control pests and weeds. However,they have several harmful effects on the soil and the ecosystem:
$(i)$ The excessive use of fertilizers and pesticides alters the soil's natural chemical balance,making it either too acidic or too alkaline,which reduces its overall fertility.
$(ii)$ Many of these chemicals are non-biodegradable. They accumulate in the soil and enter the food chain,leading to biomagnification and adversely affecting the health of animals and humans.
$(iii)$ Long-term use of these chemicals destroys the diversity of beneficial soil microorganisms and organisms that are essential for maintaining soil health,ultimately reducing crop yield.

(N/A) Causes of Soil Erosion :
$(i)$ Wind: Strong winds carry away the fertile topsoil particles.
$(ii)$ Rain: Heavy rainfall washes away unprotected topsoil,especially on slopes.
$(iii)$ Improper Farming: Poor agricultural practices,such as improper tilling or leaving fields fallow for long periods,expose the soil to erosion.
$(iv)$ Flooding: Frequent flooding of rivers removes the topsoil from fields located near river banks.
$(v)$ Deforestation: The removal of trees and vegetation reduces the soil's ability to hold together,leading to increased erosion.

(A) The soil structure is primarily determined by the size of the particles present in the soil.
Soil particles are classified into sand,silt,and clay based on their size.
The proportion of these particles determines the texture and structure of the soil,which in turn affects its water-holding capacity,aeration,and nutrient content.
Therefore,particle size is the major factor in deciding soil structure.

(A) The type of soil is primarily determined by the average size of the particles present in it.
Soil is classified into types like sandy,clayey,or loamy based on the proportion of different-sized particles (sand,silt,and clay).
While moisture,humus,and microorganisms are important components of soil quality and fertility,they do not define the fundamental 'type' of the soil structure itself.

(C) Soil erosion is the process by which the top layer of soil is removed by natural forces like wind and water.
Vegetative cover,such as plants and grass,acts as a protective layer that binds the soil particles together with roots and reduces the impact of rain and wind.
Therefore,soil that is bare of vegetation (lacking any plant cover) is highly susceptible to erosion because it lacks the structural support provided by roots and the protective barrier against environmental forces.
Thus,topsoil that is bare of vegetation is removed very quickly.

(D) Biodiversity in a particular area is primarily determined by the quality of topsoil.
Topsoil contains essential nutrients,organic matter,and microorganisms that support plant growth.
The fertility and composition of the topsoil directly influence the types of vegetation that can grow in an area,which in turn determines the variety of animal life (fauna) that can be supported.
Therefore,the quality of topsoil is a critical factor in sustaining biodiversity.

(C) The endoskeletons and exoskeletons of many animals,such as corals,mollusks,and vertebrates,are primarily composed of carbonate salts,specifically calcium carbonate $(CaCO_3)$.
These salts provide structural support and protection to the organisms.
Therefore,the correct option is $C$.