Mix Example - NATURAL RESOURCES Questions in English

(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) - Water is capable of dissolving a large number of substances.
- Water flows through or over rocks containing soluble minerals.
- Some of these minerals dissolve in the water.
- Consequently,rivers carry many nutrients from the land to the sea.
- These minerals are essential for the survival and growth of marine organisms.
$(b)$ - The biosphere is characterized by a constant interaction between biotic (living) and abiotic (non-living) components.
- These interactions involve the continuous transfer of matter and energy between the different components of the biosphere.
- This cycle of matter and energy flow maintains the balance of the ecosystem,making it a dynamic yet stable system.

(N/A) The three primary processes in which oxygen is used are:
$1$. Combustion: Oxygen is essential for the burning of fuels.
$2$. Respiration: Living organisms use oxygen to break down glucose and release energy.
$3$. Formation of oxides of nitrogen: Oxygen reacts with nitrogen during high-temperature processes (like lightning or internal combustion engines) to form nitrogen oxides.

(N/A) $(i)$ Some bacteria are poisoned by elemental oxygen.
$(ii)$ The process of nitrogen fixation by bacteria,such as the enzyme nitrogenase,is inhibited by the presence of oxygen.

(N/A) The carbon cycle is essential for maintaining a constant level of $CO_{2}$ in the Earth's atmosphere. This balance is crucial for regulating the Earth's temperature through the greenhouse effect,which keeps the planet habitable for life.

(N/A) $(i)$ In the atmosphere,oxygen is found in the elemental form to the extent of $21 \%$.
$(ii)$ In combined form,it occurs as $CO_{2}$ both in the earth's crust as well as in the air.
$(iii)$ In the crust,it is found as the oxides of most metals and silicon,and also as carbonate,sulphate,nitrate,and other minerals.
$(iv)$ It is also an essential component of most biological molecules like carbohydrates,proteins,nucleic acids,and fats (or lipids).

(N/A) The three ways by which $CO_{2}$ is returned back into the atmosphere are:
$(i)$ By the decomposition of dead organic matter by microorganisms.
$(ii)$ As a byproduct of cellular respiration by both plants and animals.
$(iii)$ As a gaseous waste product formed by the combustion of fossil fuels like coal,wood,petrol,and natural gas.

(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.

(N/A) $(i)$ Nitrogen-fixing bacteria,$e.g.$,$Rhizobium$,$Azotobacter$.
$(ii)$ Bacteria that convert complex nitrogenous organic compounds (proteins) into ammonia,$e.g.$,$Actinomyces$.
$(iii)$ Nitrifying bacteria that convert ammonia into nitrates,$e.g.$,$Nitrosomonas$ and $Nitrobacter$.
$(iv)$ Denitrifying bacteria,$e.g.$,$Pseudomonas$.

(B) Greenhouse gases are gases in the Earth's atmosphere that trap heat. They allow sunlight to pass through the atmosphere but prevent the heat that the sunlight brings from leaving the atmosphere.
Common greenhouse gases include carbon dioxide $(CO_{2})$,methane $(CH_{4})$,nitrous oxide $(N_{2}O)$,and water vapor.
Oxygen $(O_{2})$ is not a greenhouse gas because it does not absorb infrared radiation emitted from the Earth's surface.
Therefore,the correct option is $B$.

(C) Many animals,particularly those that are ectothermic or have specific reproductive strategies,lay eggs that are highly sensitive to environmental temperature fluctuations. If the temperature deviates from the optimal range,the development of the embryo inside the egg can be severely hindered or stopped. Similarly,larvae (the immature form of many animals) are often soft-bodied and lack the complex thermoregulatory mechanisms of adults,making them extremely vulnerable to changes in temperature. Therefore,eggs and larvae are the most susceptible stages to temperature changes.

(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.

(B) Deforestation refers to the large-scale removal of forest cover.
$1$. Loss of biodiversity: Forests are habitats for millions of species; their destruction leads to the extinction of flora and fauna.
$2$. Global warming: Trees absorb $CO_2$ through photosynthesis. Fewer trees mean more $CO_2$ in the atmosphere,which enhances the greenhouse effect and leads to global warming.
$3$. Soil erosion: Tree roots bind the soil together. Without trees,the topsoil is easily washed away by rain or blown away by wind.
Since all these consequences are direct results of deforestation,the correct option is $B$.

(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.

(A) All living organisms are composed of organic molecules that form the structural and functional basis of life.
These essential biomolecules include proteins,carbohydrates,fats (lipids),nucleic acids ($DNA$ and $RNA$),and vitamins.
While carbon dioxide,carbonates,and hydrogen carbonates are carbon-containing compounds,they are generally considered inorganic and are not the fundamental building blocks of life forms in the same way as organic macromolecules.
Therefore,the correct group of carbon-containing molecules found in all life forms is proteins,carbohydrates,fats,nucleic acids,and vitamins.

(B) Carbon exists in nature in two primary states: combined forms and elemental forms.
In combined forms,it is found as carbon dioxide,carbonates,and hydrogen carbonates.
In elemental forms,carbon exists as allotropes,which include diamond and graphite.
Therefore,the correct option is $B$.

(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 $C$.

(D) Nitrogen fixation is the process by which atmospheric nitrogen $(N_2)$ is converted into ammonia or other nitrogenous compounds like nitrates and nitrites.
This process is primarily carried out by nitrogen-fixing bacteria,such as $Rhizobium$,which live in the root nodules of leguminous plants or freely in the soil.
These bacteria possess the enzyme nitrogenase,which facilitates the conversion of inert atmospheric nitrogen into forms that plants can assimilate.
Therefore,the correct mechanism is a biological process involving nitrogen-fixing bacteria present in the soil.

(A) The water cycle is the continuous movement of water on,above,and below the surface of the Earth.
Key processes involved in the water cycle include:
$1$. Evaporation: Water changes from liquid to gas (water vapor) due to heat from the sun.
$2$. Transpiration: Plants release water vapor into the atmosphere through their leaves.
$3$. Precipitation: Water falls back to the Earth's surface in the form of rain,snow,or hail.
$4$. Condensation: Water vapor cools and turns back into liquid water droplets,forming clouds.
Photosynthesis is a biological process used by plants to convert light energy into chemical energy (glucose) using water and carbon dioxide. While water is consumed in this process,it is not a stage of the global water cycle.

(B) Water pollution is defined as the contamination of water bodies (e.g., lakes, rivers, oceans, aquifers, and groundwater) usually as a result of human activities.
$1$. The addition of undesirable substances (pollutants) like toxic chemicals, sewage, or industrial waste makes water unfit for use.
$2$. The removal of desirable substances (like dissolved oxygen) disrupts the aquatic ecosystem.
$3$. $A$ change in temperature (thermal pollution) affects the metabolic rates and survival of aquatic organisms.
$4$. $A$ change in pressure is a physical property related to depth and does not constitute water pollution.

(C) Soil erosion is the removal of the top layer of soil by natural forces like wind and water.
Raising forests (afforestation) is an effective method to prevent soil erosion because the roots of trees bind the soil particles together,preventing them from being washed or blown away.
Deforestation and overgrazing remove the protective vegetation cover,making the soil more susceptible to erosion.
Excessive use of fertilizers can degrade soil quality but does not directly prevent physical erosion.

(D) When rain falls on soil without vegetational cover,there are no roots to hold the soil particles together.
As a result,the force of the falling raindrops and the flow of water wash away the top layer of the soil,which is rich in nutrients.
This process is known as soil erosion,leading to the loss of fertile surface soil.

(A) Nitrogen-fixing bacteria,such as $Rhizobium$ and $Azotobacter$,possess an enzyme called nitrogenase which is responsible for the fixation of atmospheric nitrogen into ammonia. This enzyme is highly sensitive to oxygen and is irreversibly inactivated by it. Therefore,these bacteria require an anaerobic (oxygen-free) environment to function effectively. In contrast,ferns,$Chara$ (an algae),and mango trees are aerobic organisms that require oxygen for cellular respiration.

(B) The Earth's atmosphere is primarily heated through a process involving solar radiation and terrestrial radiation.
$1$. The sun emits short-wave radiation that passes through the atmosphere and reaches the Earth's surface.
$2$. The Earth's surface (land and water bodies) absorbs this energy and gets heated.
$3$. The heated surface then re-radiates this energy back into the atmosphere in the form of long-wave infrared radiation.
$4$. Greenhouse gases in the atmosphere trap this re-radiated heat,thereby warming the atmosphere.
Therefore,the atmosphere is mainly heated by the energy re-radiated by land and water.

(C) The atmosphere acts as a blanket for the Earth. It traps heat during the day through the greenhouse effect and prevents it from escaping rapidly into space at night.
If there were no atmosphere,the Earth would receive intense solar radiation during the day,causing the temperature to rise significantly.
Conversely,at night,all the heat would radiate back into space,causing the temperature to drop drastically.
Therefore,the temperature would increase during the day and decrease during the night.

(D) Soil is formed through the process of weathering of rocks over a long period of time.
During this process,the large rocks are broken down into smaller particles by physical,chemical,and biological factors.
Since minerals are inherent components of rocks,the parent rock serves as the primary and major source of minerals found in the soil.
Therefore,the correct option is $D$.

(A) The Earth is often referred to as the 'Blue Planet' because a significant portion of its surface is covered by water.
Scientific estimates indicate that approximately $71 \%$ to $75 \%$ of the Earth's surface is covered by oceans,seas,and other water bodies.
Among the given options,$75 \%$ is the most accurate representation of the water coverage on Earth's surface.

(B) The topsoil is the uppermost layer of the soil.
It is rich in humus,which is the organic matter formed by the decomposition of dead plants and animals.
It also contains various living organisms (such as bacteria,fungi,earthworms,and insects) and soil particles (sand,silt,and clay).
Therefore,topsoil is a mixture of humus,living organisms,and soil particles.

(D) The carbon cycle describes the movement of carbon through the biosphere.
$1$. Plants take up $CO_{2}$ from the atmosphere through photosynthesis to produce organic carbon (glucose).
$2$. Animals consume these plants, incorporating the organic carbon into their own tissues.
$3$. When animals die, decomposers break down the organic matter.
$4$. During decomposition and respiration, carbon is released back into the atmosphere as $CO_{2}$, which can then be used again by plants.
Therefore, the sequence $Organic carbon in animals \rightarrow decomposers \rightarrow CO_{2} in atmosphere \rightarrow organic carbon in plants$ represents a correct cycle.

(D) The process of biological nitrogen fixation is carried out by the enzyme nitrogenase.
This enzyme is highly sensitive to oxygen and is inactivated in its presence.
Therefore,nitrogen-fixing bacteria,such as Rhizobium,require an anaerobic (oxygen-free) environment to function effectively.
In root nodules of leguminous plants,this environment is maintained by the protein leghemoglobin,which acts as an oxygen scavenger.

(A) Rainfall patterns are primarily determined by the prevailing wind patterns and the presence of water bodies in an area.
Water bodies,such as oceans,lakes,and rivers,provide the moisture necessary for cloud formation through evaporation.
When moisture-laden air moves over land,it cools down and condenses to form rain.
Therefore,the proximity and number of water bodies significantly influence the amount and frequency of rainfall in a specific region.

(B) The use of large amounts of fertilizers and pesticides has several negative impacts on the environment and agriculture.
$1$. They destroy the soil fertility by altering the chemical composition of the soil.
$2$. They adversely affect the useful microorganisms and components present in the soil,which are essential for maintaining soil health.
$3$. Over time,the excessive use of these chemicals can lead to the degradation of land,eventually turning the fields barren.
$4$. Therefore,stating that they are 'eco-friendly' is incorrect,as they cause pollution and harm the ecosystem.

(C) The process of ecological succession on barren rocks (lithosere) begins with the colonization of pioneer species,which are Lichens.
Lichens secrete acids that help in the weathering of rocks,leading to the formation of a thin layer of soil.
Once a thin layer of soil is formed,the environment becomes suitable for the growth of bryophytes,specifically Mosses.
Mosses further contribute to soil formation and moisture retention,eventually paving the way for larger plants like ferns and higher vegetation.

(D) Aquatic organisms are adapted to a specific range of temperatures.
Marked changes in water temperature can disrupt the biological processes of these organisms.
Specifically,temperature fluctuations significantly affect the breeding cycles of aquatic animals,as many species rely on specific temperature cues to initiate spawning or reproduction.
While other factors like nutrient availability and digestion can be indirectly influenced,the most direct and critical impact of significant temperature change in an aquatic ecosystem is on the breeding and reproductive success of the animals.

(A) The biosphere consists of both biotic (living) and abiotic (non-living) components.
Biotic components include all living organisms such as producers (plants),consumers (animals),and decomposers (bacteria and fungi).
Abiotic components include non-living factors such as air,water,soil,sunlight,and temperature.
Since air is a non-living factor,it is an abiotic component,not a biotic one.

(B) Carbon dioxide $(CO_2)$ is a greenhouse gas. An increase in its concentration leads to the trapping of more heat,resulting in global warming ($A$ and $C$).
$CO_2$ is a raw material for photosynthesis,so an increase in its concentration can enhance the rate of photosynthesis in many plants $(D)$.
However,an increase in $CO_2$ does not directly cause an abundance of desert plants. Desert plants are adapted to arid conditions,and their distribution is primarily limited by water availability,not by the concentration of $CO_2$ in the atmosphere. Therefore,option $B$ is the correct answer.

(C) Oxygen $(O_2)$ is essential for the respiration of aerobic organisms,which is necessary for their survival.
Ozone $(O_3)$ is a highly reactive and toxic gas at ground level.
If all the oxygen in the environment were converted into ozone,two major consequences would occur:
$1$. Living organisms would die due to the lack of oxygen required for cellular respiration.
$2$. Ozone itself is poisonous to living tissues when present in high concentrations,leading to immediate toxicity.
Therefore,the conversion of all oxygen to ozone would result in the death of living forms due to both the absence of life-sustaining oxygen and the toxic nature of ozone.

(D) Soil formation is a slow process involving the weathering of rocks.
$1$. The sun causes rocks to expand and contract,leading to cracks.
$2$. Water enters these cracks,freezes,and expands,breaking the rocks into smaller pieces.
$3$. Wind carries abrasive particles that wear down rocks over time.
$4$. Polythene bags are non-biodegradable synthetic materials that do not contribute to the natural weathering of rocks or the formation of soil; instead,they pollute the soil and hinder its natural processes.

(A) Oxygen is present in the atmosphere in two primary forms:
$1$. Diatomic oxygen $(O_2)$: This is the form of oxygen that is essential for the respiration of most living organisms.
$2$. Ozone $(O_3)$: This is a triatomic form of oxygen found in the upper layers of the atmosphere (stratosphere),which protects the Earth from harmful ultraviolet $(UV)$ radiation from the Sun.
Therefore,the correct option is $A$.

(B) The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere,pedosphere,geosphere,hydrosphere,and atmosphere of the Earth.
Photosynthesis involves the uptake of $CO_2$ by plants to produce organic compounds.
Respiration involves the release of $CO_2$ by living organisms back into the atmosphere.
Burning of fossil fuels releases stored carbon back into the atmosphere as $CO_2$.
Transpiration is the process of water movement through a plant and its evaporation from aerial parts,such as leaves,stems,and flowers. It is a part of the water cycle,not the carbon cycle.

(C) The term '$Ozone-hole$' does not refer to an actual physical hole or a gap in the atmosphere.
Instead, it refers to the significant depletion or '$thinning$' of the ozone layer in the stratosphere, particularly over the Antarctic region.
This depletion is primarily caused by the release of chemicals like chlorofluorocarbons $(CFCs)$ into the atmosphere, which break down ozone $(O_3)$ molecules.

(D) The depletion of the ozone layer is primarily caused by the release of Chlorofluorocarbons $(CFCs)$ into the atmosphere.
These are man-made compounds that contain both fluorine and chlorine.
When $CFCs$ reach the stratosphere,they are broken down by ultraviolet radiation,releasing chlorine atoms.
These chlorine atoms act as catalysts in the destruction of ozone $(O_3)$ molecules,converting them into oxygen $(O_2)$,which leads to the thinning of the ozone layer.

(A) Photosynthesis is the biological process by which green plants,algae,and certain bacteria convert light energy into chemical energy.
During this process,carbon dioxide and water are consumed to produce glucose,and oxygen is released as a byproduct into the atmosphere.
This process is the primary source of atmospheric oxygen,which is essential for the survival of aerobic organisms.

(B) During cold weather,the temperature is low,which causes water vapor in the air to condense around dust particles or smoke particles (such as unburnt carbon particles or hydrocarbons) released from combustion processes.
This mixture of smoke and fog is known as smog.
The suspended particles scatter light,which significantly reduces visibility in the atmosphere.

(C) Environmental problems like $Ozone$ layer depletion,$Greenhouse$ effect,and $Global$ warming are all significant issues that have gained prominence due to human activities in the recent past.
$1$. $Ozone$ layer depletion is caused by the release of $CFCs$ (chlorofluorocarbons).
$2$. $Greenhouse$ effect is the trapping of heat by gases like $CO_2$ and $CH_4$.
$3$. $Global$ warming is the gradual increase in the Earth's average temperature.
Since all these phenomena are contemporary environmental concerns,the correct option is $C$.

(D) The air we breathe contains approximately $78\%$ nitrogen and $21\%$ oxygen.
While oxygen is essential for cellular respiration and is absorbed into the blood through the alveoli in the lungs,nitrogen is an inert gas in the context of human metabolism.
Because nitrogen does not participate in any metabolic reactions within the body,it is not absorbed by the blood or cells.
Therefore,the nitrogen that enters the lungs during inhalation simply remains in the air passages and is expelled from the body along with $CO_2$ during the process of exhalation.