Mix Example - NATURAL RESOURCES Questions in English

(A) The heat from the sun reaches the earth and warms the land and water surfaces.
These surfaces then re-radiate the absorbed heat in the form of infrared radiation,which warms the air in the atmosphere.
Therefore,the atmosphere is primarily heated by the radiation re-emitted from the land and water bodies.

(B) The atmosphere acts as a blanket that regulates the temperature of the earth.
During the day,the atmosphere prevents a significant amount of solar radiation from reaching the surface,keeping it from becoming excessively hot.
During the night,the atmosphere traps heat and prevents it from escaping into outer space,keeping the earth warm.
If there were no atmosphere,the earth would experience extreme temperature fluctuations: it would become extremely hot during the day due to direct solar exposure and extremely cold at night due to the rapid loss of heat.

(C) Living organisms require $O_2$ (oxygen) for the process of cellular respiration to generate energy. If all oxygen in the environment were converted to $O_3$ (ozone),there would be no oxygen available for respiration. Consequently,all aerobic living organisms would die due to the lack of oxygen,as ozone is highly reactive and toxic to biological systems.

(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.

(A) Oxygen exists in the atmosphere primarily in two forms: diatomic oxygen $(O_2)$,which is essential for respiration,and ozone $(O_3)$,which is found in the upper atmosphere and protects the Earth from harmful ultraviolet radiation.
Both $O_2$ and $O_3$ are allotropes of the element oxygen.

(B) The enzyme responsible for nitrogen fixation is $Nitrogenase$.
$Nitrogenase$ is highly sensitive to the presence of oxygen $(O_2)$.
Oxygen inactivates the $Nitrogenase$ enzyme,thereby inhibiting the process of biological nitrogen fixation.
Therefore,nitrogen-fixing bacteria,such as $Rhizobium$,create an anaerobic (oxygen-free) environment (often using $Leghemoglobin$) to protect the enzyme and allow the fixation process to occur.

(C) Water bodies provide water for evaporation. Water vapour,formed after evaporation,condenses to cause rainfall. $A$ lack of water bodies in an area reduces humidity in the air and thus adversely affects the rainfall patterns.

(D) The use of large amounts of fertilizers and pesticides leads to the destruction of soil fertility,makes fields barren over time,and harms beneficial soil microorganisms. Therefore,they are not eco-friendly. Thus,option $D$ is the incorrect statement.

(A) Nitrogen fixation is the process of converting atmospheric nitrogen $(N_2)$ into ammonia or other nitrogenous compounds like nitrates and nitrites.
This process is primarily carried out by nitrogen-fixing bacteria (such as $Rhizobium$) present in the soil or in the root nodules of leguminous plants.
Cereal crops themselves do not fix nitrogen; they rely on soil nitrogen.
Industrial processes typically use the Haber-Bosch process,which requires high pressure and temperature,not direct atmospheric nitrogen conversion as described in biological contexts.
Therefore,the correct mechanism is the biological process performed by nitrogen-fixing bacteria in the soil.

(B) The water cycle involves the continuous movement of water on,above,and below the surface of the Earth. Key processes include evaporation,transpiration,condensation,and precipitation.
Photosynthesis is a biological process in which plants use water,carbon dioxide,and sunlight to produce glucose and oxygen. While water is a reactant in photosynthesis,the process itself is primarily a component of the carbon cycle and the energy flow in ecosystems,not a fundamental step of the global water cycle.

(C) Water pollution is defined as the contamination of water bodies by substances that make it harmful for living organisms or unfit for use.
Adding undesirable substances (pollutants) or removing desirable substances (like oxygen) causes pollution.
Thermal pollution (a change in temperature) also negatively impacts aquatic life.
$A$ change in pressure of water bodies is a physical phenomenon that does not constitute pollution.

(C) Greenhouse gases are gases in the Earth's atmosphere that trap heat.
Major greenhouse gases include $CO_2$ (Carbon dioxide),$CH_4$ (Methane),$N_2O$ (Nitrous oxide),and water vapor.
Carbon monoxide $(CO)$ is generally considered a toxic air pollutant rather than a direct greenhouse gas,as it does not significantly absorb infrared radiation compared to the others.
Ammonia $(NH_3)$ is also not classified as a primary greenhouse gas.
However,in the context of standard multiple-choice questions regarding greenhouse gases,$CO$ is the most commonly cited non-greenhouse gas among the options provided.

(A) Transpiration is a process involved in the water cycle,where plants release water vapor into the atmosphere. It is not a part of the carbon cycle. Photosynthesis,respiration,and the burning of fossil fuels are all key processes that regulate the movement of carbon through the biosphere,atmosphere,and geosphere.

(B) The term 'ozone-hole' does not refer to an actual physical hole or gap in the atmosphere.
Instead,it refers to the phenomenon of the depletion or 'thinning' of the ozone layer,primarily caused by the release of chlorofluorocarbons $(CFCs)$.
Therefore,options $A$ and $C$ are incorrect as they imply a physical hole.
Option $D$ is incorrect because the ozone layer is being depleted,not thickened.

(C) Compounds that contain both fluorine and chlorine are known as chlorofluorocarbons $(CFCs)$. These compounds are released into the atmosphere,where they break down to release chlorine atoms. Chlorine atoms react with ozone $(O_3)$ to convert it into oxygen $(O_2)$,thereby leading to the depletion of the ozone layer.

(D) All the problems mentioned,including ozone layer depletion,the greenhouse effect,and global warming,have significantly intensified and originated as major environmental crises following the industrial revolution due to human activities.

(A) Nitrogen is the most abundant gas in the atmosphere, making up about $78\%$ of the air we inhale.
Since the human body does not have any metabolic process to utilize nitrogen gas $(N_2)$, it does not participate in cellular respiration or any other biological function.
Therefore, the nitrogen that enters the lungs during inhalation remains inert and is exhaled back into the atmosphere along with $CO_2$ and other gases during the process of exhalation.

(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.

(C) The carbon cycle involves the movement of carbon through the biosphere.
$1$. $CO_2$ in the atmosphere is absorbed by plants during photosynthesis to form organic carbon compounds.
$2$. These organic compounds are transferred to animals when they consume plants.
$3$. Upon the death of plants and animals,decomposers break down the organic matter,releasing carbon back into the soil as inorganic carbon or into the atmosphere as $CO_2$.

(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.

(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 this coverage.

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

(C) An increase in $CO_2$ levels leads to the greenhouse effect,which causes more heat to be retained by the environment and contributes to global warming.
Increased $CO_2$ can also enhance the rate of photosynthesis in many plants.
However,the abundance of desert plants is primarily limited by the scarcity of water,not by the concentration of $CO_2$.
Even with higher $CO_2$ levels,desert plants cannot thrive without sufficient water,which is a limiting factor in arid ecosystems.

(D) Photosynthesis is a biological process in which green plants,algae,and some bacteria use sunlight,water,and carbon dioxide to produce food (glucose) and release oxygen as a byproduct into the atmosphere.
Respiration,burning of fossil fuels,and decomposition by fungi consume oxygen and release carbon dioxide into the atmosphere.

(A) Low visibility during cold weather is primarily caused by the formation of smog. Smog is a mixture of smoke and fog. When unburnt carbon particles or hydrocarbons from vehicle emissions and industrial processes are suspended in the air,they act as condensation nuclei for water vapor,leading to the formation of thick fog or smog,which significantly reduces visibility.

(B) In the process of primary succession on barren rocks,$Lichens$ are the pioneer species.
$Lichens$ secrete organic acids that help in the weathering of rocks,which leads to the formation of a thin layer of soil.
This soil provides a suitable environment for the growth of bryophytes,specifically $Mosses$.
$Mosses$ further contribute to soil formation and moisture retention,which eventually allows for the colonization of higher plants like ferns and other vegetation.

(C) Aquatic organisms are adapted to a specific range of temperatures.
Marked changes in water temperature can significantly affect the metabolic activities of aquatic organisms,including their reproductive cycles and breeding patterns.
While temperature can influence plant growth and digestion rates,the most direct and critical impact of sudden or marked temperature fluctuations in an aquatic ecosystem is on the breeding and survival of aquatic animals,as many species rely on specific temperature cues for spawning and larval development.

(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.

(B) Nitrogen-fixing bacteria,such as $Rhizobium$,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 inactivated in its presence. Therefore,these bacteria require an anaerobic environment (oxygen-free) to function effectively,often provided by the protein leghemoglobin in root nodules.

(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.

(B) The addition of undesirable substances like pesticides,fertilizers,industrial waste,and domestic sewage into water bodies leads to pollution.
These pollutants are toxic and can kill aquatic organisms or cause various diseases.
Furthermore,the decomposition of organic waste increases the biological oxygen demand,which leads to a reduction in the dissolved oxygen levels in the water.
This decrease in dissolved oxygen adversely affects the survival and health of aquatic organisms.

(B) The water from the surface of a lake continuously undergoes evaporation.
Evaporation is an endothermic process,meaning it absorbs latent heat from the surroundings to change from a liquid state to a gaseous state.
This absorption of heat creates a cooling effect in the immediate environment.
Therefore,when we go near a lake during summer,we feel relief from the heat.

(N/A) During the day,the land heats up faster than the sea. The air above the land gets heated quickly and starts rising,creating a region of low pressure. Consequently,the cooler air over the sea rushes into this low-pressure area,causing a sea breeze.
During the night,the land cools down faster than the sea. The air above the water remains warmer than the air over the land. Therefore,the air moves from the land towards the sea,creating a land breeze.

(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) $C, N, S, P, H$ and $O$ are the fundamental components of various biomolecules. Living organisms are composed of numerous biomolecules.
Most of these elements enter the living world through plants.
$1$. Carbon enters through the process of photosynthesis,where plants fix atmospheric $CO_2$ into organic compounds.
$2$. Nitrogen is fixed in the soil by nitrogen-fixing bacteria,allowing plants to absorb it in the form of nitrates or ammonium compounds.
$3$. Sulphur and phosphorus are present as minerals in the soil and are absorbed by plant roots along with water.
$4$. Hydrogen and oxygen enter plants primarily when they absorb water $(H_2O)$ from the soil.
$5$. Animals obtain these elements by consuming plants or other animals. Additionally,animals obtain hydrogen and oxygen through drinking water,and oxygen is taken up directly from the atmosphere during respiration.

(B) These elements are continuously utilized by living organisms for various metabolic processes.
However,these elements undergo a cyclic process known as the biogeochemical cycle,which ensures they are returned to the atmosphere through various natural processes such as respiration,decomposition,and nitrogen fixation.
Because of this constant recycling,the concentration of gases like oxygen,nitrogen,and carbon dioxide remains balanced and almost constant in the atmosphere.

(B) The moon does not have an atmosphere.
Due to the absence of an atmosphere,there is no mechanism to trap heat or regulate the surface temperature during the daytime,unlike on Earth where the atmosphere acts as a blanket.
Furthermore,the lack of an atmosphere allows all the accumulated heat to escape rapidly into space during the night.
Consequently,the moon experiences extreme temperature fluctuations between day and night.

(N/A) In coastal areas, a $ \text{sea breeze} $ blows during the daytime. This $ \text{sea breeze} $ provides a consistent and ideal wind speed for flying kites. Therefore, people enjoy flying kites near the seashore.

(B) The Mathura refinery releases significant amounts of toxic gases,specifically oxides of sulphur $(SO_2)$ and nitrogen $(NO_x)$.
These gases react with moisture in the atmosphere to form sulphuric acid and nitric acid.
This results in acid rain,which reacts with the calcium carbonate $(CaCO_3)$ present in the marble of the Taj Mahal,leading to its corrosion and yellowing.

(B) Lichens are known as bio-indicators of air pollution,specifically sensitive to sulfur dioxide $(SO_2)$.
Delhi has a very high density of automobiles and industrial activities,which leads to high levels of $SO_2$ in the atmosphere.
This high concentration of $SO_2$ prevents the growth of lichens in Delhi.
In contrast,places like Manali or Darjeeling have cleaner air with significantly lower levels of $SO_2$,allowing lichens to grow abundantly.

(C) Although the Earth is covered by a vast amount of water,most of it is present in oceans as saline water,which is not suitable for human consumption,agriculture,or industrial use.
Fresh water,which is essential for life,is a limited resource.
Furthermore,the distribution of fresh water on Earth is highly uneven,leading to water scarcity in many regions.
Therefore,conservation is necessary to ensure the sustainable availability of fresh water for all living organisms.

(D) The mass mortality of fishes in a pond can be attributed to several environmental factors:
$(i)$ Thermal pollution: An increase in water temperature reduces the concentration of dissolved oxygen,leading to suffocation.
$(ii)$ Addition of poisonous compounds: Toxic substances like mercury or pesticides can cause direct poisoning of aquatic life.
$(iii)$ Blockage of gills: Suspended pollutants or oil spills can physically block the gills,preventing respiration and leading to death.

(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.

(B) Root nodules contain symbiotic nitrogen-fixing bacteria,such as $Rhizobium$.
These bacteria convert atmospheric nitrogen into ammonia,which the plant can use for protein synthesis and growth.
This process is essential for plant nutrition,especially in nitrogen-deficient soils.