Human Activities and the Environment Questions in English

(N/A) The ozone layer in the upper atmosphere acts as a shield by protecting living organisms from harmful $UV$ radiations.
Formation of ozone layer:
Ozone at higher levels of the atmosphere is formed by the action of $UV$ radiations on oxygen $(O_2)$ molecules. High-energy $UV$ radiations split molecular oxygen $(O_2)$ into free oxygen $(O)$ atoms. These atoms then combine with molecular oxygen to form ozone $(O_3)$:
$O_2 \xrightarrow{UV} O + O$
$O + O_2 \longrightarrow O_3$
Compounds responsible for depletion:
Chlorofluorocarbons $(CFCs)$ are the primary compounds responsible for the depletion of the ozone layer.
Entry into the atmosphere:
These compounds enter the atmosphere through human-made sources such as aerosol sprays,refrigerants in refrigerators,air conditioners,and fire extinguishers that utilize $CFCs$.

(N/A)

Biodegradable substances	Non-biodegradable substances
$1$. Substances that are broken down by biological processes are called biodegradable.	$1$. Substances that are not broken down by biological processes are called non-biodegradable.
$2$. These substances are naturally recycled and do not accumulate in the environment.	$2$. These substances persist in the environment for a long time and require large dumping sites.

Effects of biodegradable substances:
$(1)$ During decomposition,they may release foul-smelling gases like methane and hydrogen sulphide.
$(2)$ If not managed properly,they can become breeding grounds for disease-causing microorganisms.
Effects of non-biodegradable substances:
$(1)$ They persist in the environment for a long time,leading to bioaccumulation and biomagnification in the food chain.
$(2)$ They cause long-term pollution of soil,air,and water,and occupy significant land space for disposal.

(N/A) The two primary chemicals responsible for the thinning of the ozone layer are:
$(i)$ Chlorofluorocarbons $(CFCs)$
$(ii)$ Hydrochlorofluorocarbons $(HCFCs)$
Other substances like Hydrobromofluorocarbons $(HBFCs)$ and Halons also contribute to ozone depletion.

(B) Biodegradable wastes are organic materials that can be broken down by microorganisms into simpler substances,which can then be converted into manure or compost.
Non-biodegradable wastes,such as plastics,glass,and metals,do not decompose easily and persist in the environment for a long time,causing pollution.
Separating these wastes at the source ensures that biodegradable waste can be recycled into organic fertilizer,while non-biodegradable waste can be processed through appropriate recycling methods,thereby reducing environmental harm.

(N/A) To raise awareness among residents regarding the harmful effects of improper waste disposal,the following methods can be adopted:
$(a)$ Organizing street plays to demonstrate the impact of waste accumulation on public health.
$(b)$ Distributing pamphlets that explain the importance of hygiene and proper waste management.
$(c)$ Conducting meetings with the residents' welfare association to discuss sustainable waste disposal strategies.
$(d)$ Encouraging the segregation of waste at the source into biodegradable and non-biodegradable categories to facilitate recycling and composting.

(N/A) $(i)$ Plastic bags are non-biodegradable and,therefore,require large dumping sites.
$(ii)$ When dumped into the ground,they damage soil fertility and block water drainage.
$(iii)$ They can be ingested by stray animals,causing choking or internal injuries.
$(iv)$ Burning plastic bags releases toxic gases into the atmosphere,causing air pollution.
Alternatives: Use bags made of jute,cotton,or paper.

(N/A) The aims of the "Ganga Action Plan" are:
$(i)$ To improve the quality of the river water.
$(ii)$ To check the growth of disease-causing microorganisms.
$(iii)$ To prevent the contamination of river water due to the discharge of industrial waste and sewage.
Values that can be learnt from the "Ganga Action Plan" are:
$(i)$ Conservation of water resources.
$(ii)$ Preservation of cultural and environmental heritage.
$(iii)$ Developing a sense of responsibility towards cleanliness and environmental hygiene.

(N/A) Biodegradable substances are materials that can be broken down into simpler substances by biological processes,such as the action of decomposers,bacteria,or saprophytes.
Example: Vegetable peels,fruit waste,or human excreta.
Non-biodegradable substances are materials that cannot be broken down into simpler substances by biological processes or decomposers.
Example: Plastic,glass,or metal cans.
Changes in habits to dispose of non-biodegradable waste:
$1$. Segregation of waste at the source by using separate dustbins for biodegradable and non-biodegradable waste.
$2$. Adopting the $3R$ principle (Reduce,Reuse,and Recycle) by reusing items like plastic containers and recycling materials like glass and metal.

(B) Coliform bacteria are a large group of bacteria found in the intestines of warm-blooded animals,including humans.
Their presence in water indicates contamination by human fecal matter.
Since these bacteria are associated with waterborne diseases such as cholera,typhoid,and diarrhoea,their presence in the Ganga river serves as a reliable indicator of the level of water pollution and potential health risks.

(N/A) $(i)$ Proper treatment of sewage and industrial waste before it is discharged into water bodies to prevent water pollution.
$(ii)$ Increasing the plantation of trees,as they act as natural filters and help in reducing air pollution.
$(iii)$ Strictly enforcing regulations on vehicle emissions to ensure that only vehicles meeting non-polluting norms are used.

(B) The total coliform count is a standard indicator of water quality. Coliform bacteria are a group of bacteria found in the intestines of warm-blooded animals. Their presence in water indicates contamination by fecal matter,which suggests that the water is contaminated by disease-causing microorganisms.

(A) No,this practice is not environmental-friendly because it results in the wastage of fossil fuels and contributes to air pollution due to increased carbon emissions.
Suggestion: The teachers should adopt car-pooling or use public transport.
Justification: By sharing a vehicle,the total number of cars on the road decreases,which directly reduces fuel consumption and the amount of pollutants released into the atmosphere.
$(b)$ Two other ways to become environmental-friendly are:
$(i)$ Using public transport instead of private vehicles to reduce traffic and emissions.
$(ii)$ Using fuel-efficient modes of transport or switching to electric vehicles to minimize the carbon footprint.

(N/A) Different disposal strategies are required to manage biodegradable and non-biodegradable wastes effectively. Segregation ensures that biodegradable waste can be processed naturally,while non-biodegradable waste can be recycled or disposed of safely.
$(b)$ Biodegradable waste can be processed in a biogas plant to produce energy or can be used to produce manure and compost through the process of composting.

(N/A) The two gases considered to be better alternatives to $CFCs$ (Chlorofluorocarbons) due to their lower ozone depletion potential are:
$(i)$ Hydrofluorocarbons $(HFCs)$: These compounds contain hydrogen,fluorine,and carbon. They do not contain chlorine,which is the primary element responsible for ozone destruction in $CFCs$.
$(ii)$ Perfluorocarbons $(PFCs)$: These are compounds consisting only of carbon and fluorine atoms. They are chemically inert and have a significantly lower impact on the ozone layer compared to $CFCs$.

(B) The ozone layer in the stratosphere acts as a shield by absorbing harmful ultraviolet $(UV)$ radiation from the sun.
Depletion of this layer allows these high-energy $UV$ rays to penetrate the Earth's atmosphere and reach the surface.
Exposure to these rays causes serious health hazards in human beings,such as skin cancer,cataracts,and damage to the immune system.

(B) Yes,there is an effect of heat and pressure on non-biodegradable materials.
Although they do not break down through microbial action,prolonged exposure to heat and pressure under the soil can cause physical and chemical degradation.
This process often leads to the leaching of toxic chemicals and additives present in these materials into the surrounding soil and groundwater.
Consequently,this results in soil pollution and potential contamination of the water table.

(N/A) There is a need to dispose of waste in a proper manner because:
$(i)$ To stop pollution: Waste should be disposed of properly to prevent land and water pollution.
$(ii)$ To prevent diseases: If waste is disposed of improperly,it may cause diseases like cholera,dengue,typhoid,pneumonia,etc. To prevent such diseases,we need to dispose of waste in a proper way.

(N/A) Harmful chemicals enter our bodies through the food chain. When these chemicals are sprayed in agricultural fields,they are often non-biodegradable,meaning they persist in the environment and may wash into water bodies. When human beings consume agricultural products or aquatic organisms such as fish or prawns,these chemicals are transferred and accumulate in their bodies at higher concentrations.
This phenomenon is called 'biological magnification' or 'biomagnification'.

(N/A) Devices like refrigerators and $ACs$ affect the environment in the following ways:
$1$. They release chlorofluorocarbons $(CFCs)$,which are among the most harmful greenhouse gases and are primarily responsible for ozone layer depletion.
$2$. They consume a significant amount of electricity,which leads to the increased burning of fossil fuels like coal and natural gas,thereby contributing to global warming and resource depletion.

(D) Disposable plastic plates are made of synthetic polymers that are non-biodegradable.
This means they cannot be broken down by microorganisms into simpler,harmless substances in the environment.
As a result,they accumulate in the environment,leading to pollution and posing a threat to ecosystems and wildlife.
Therefore,the correct option is $D$.

(A) The depletion of the ozone layer is primarily caused by the release of chlorofluorocarbons $(CFCs)$ into the atmosphere.
These compounds are used in refrigerators,air conditioners,and aerosol sprays.
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) Biodegradable waste refers to organic materials that can be broken down by microorganisms like bacteria and fungi into simpler substances.
Vegetables and fruit are organic materials derived from plants,which easily decompose in the environment.
Glass,plastic,and metal are non-biodegradable materials because they cannot be broken down by biological processes and persist in the environment for a long time.

(D) Non-biodegradable wastes are those substances that cannot be broken down into simpler,harmless substances by the action of microorganisms (like bacteria or fungi).
Polythene is a synthetic polymer (plastic) that does not decompose naturally in the environment.
In contrast,fruits,vegetables,and paper are biodegradable as they are organic materials that can be decomposed by biological processes.

(B) Chlorine atoms act as catalysts in the depletion of the ozone layer.
One atom of chlorine can destroy approximately $1,00,000$ molecules of ozone $(O_3)$ through a chain reaction process.
In this process,the chlorine atom is not consumed but continues to react with ozone molecules repeatedly.
Therefore,the correct option is $B$.

(C) Chlorofluorocarbons $(CFCs)$ are synthetic compounds used in refrigerators,air conditioners,and aerosol sprays.
When $CFCs$ reach the upper atmosphere,they are broken down by ultraviolet radiation,releasing chlorine atoms.
These chlorine atoms act as catalysts in the destruction of ozone $(O_3)$ molecules.
It is estimated that $CFCs$ are responsible for approximately $80\%$ of the total depletion of the ozone layer.

(D) Coliform bacteria are a group of bacteria found in the human intestine.
Their presence in water indicates contamination by disease-causing microorganisms.
In the river Ganga,the disposal of unburnt corpses and human excreta into the water is the primary source of these bacteria.
Therefore,the disposal of unburnt corpses into water is the main cause for the abundant presence of coliform bacteria.

(A) The statement is $True$. Economic and social development models directly influence how natural resources are utilized. If development prioritizes sustainability and ecological balance,the environment is conserved. Conversely,if development focuses solely on rapid industrialization without considering environmental impact,it leads to the destruction of natural resources and ecosystems.

(B) The statement is False. The Chipko Andolan (movement) originated in the Garhwal Himalayas in the early $1970$s,specifically in the Reni village of Chamoli district,Uttarakhand. The movement in Khejrali village,Rajasthan,which occurred in $1731$ to protect Khejri trees,was led by Amrita Devi Bishnoi and is historically distinct from the modern Chipko Andolan.

(B) The atmosphere is divided into several layers based on temperature and altitude.
The layer closest to the Earth's surface is known as the $Troposphere$.
It extends up to an average height of about $13 \ km$ from the surface and is where most weather phenomena occur.

(C) The Earth's atmosphere is divided into several layers based on temperature and altitude.
$1$. The $Troposphere$ is the lowest layer,extending up to about $10-15 \ km$.
$2$. The $Stratosphere$ lies above the troposphere and extends up to approximately $50 \ km$ from the Earth's surface.
$3$. The $Mesosphere$ lies above the stratosphere.
Therefore,the layer located at an altitude of $50 \ km$ is the $Stratosphere$.

(D) The ozone layer is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet $(UV)$ radiation.
It contains a high concentration of ozone $(O_3)$ in relation to other parts of the atmosphere.
The stratosphere is located approximately $10$ to $50 \ km$ above the Earth's surface.

(B) The ozone layer is located in the stratosphere of the Earth's atmosphere.
It acts as a protective shield by absorbing the harmful $UV$ (ultraviolet) radiations coming from the Sun.
These $UV$ radiations have high energy and can cause skin cancer,cataracts,and damage to the immune system in living organisms.
Therefore,the correct option is $B$.

(B) Ozone is an allotrope of oxygen consisting of three oxygen atoms bonded together.
Its molecular formula is $O_{3}$.

(C) The ozone layer in the stratosphere acts as a shield by absorbing harmful ultraviolet $(UV)$ radiation from the sun.
Specifically,the ozone molecule absorbs $UV$ radiation in the wavelength range of $200$ nm to $310$ nm.
This range covers the most biologically damaging $UV$-$B$ and $UV$-$C$ radiation,preventing them from reaching the Earth's surface.
Therefore,the correct range is $310$ nm to $200$ nm.

(A) The depletion of the ozone layer,commonly referred to as the 'ozone hole',is most pronounced over the South Pole (Antarctica). Scientific observations have recorded a significant thinning of the ozone layer in this region,with depletion levels ranging between $40$ to $60$ percent. This phenomenon is primarily caused by the release of chlorofluorocarbons $(CFCs)$ and other ozone-depleting substances into the atmosphere.

(C) The gradual thinning of the Earth's ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous bromine or chlorine from industries or other human activities is known as ozone depletion. This phenomenon is specifically referred to as ozone depletion,which leads to the formation of an 'ozone hole' in certain regions like Antarctica.

(A) The depletion of the ozone layer is primarily caused by the release of chlorofluorocarbons $(CFCs)$ into the atmosphere.
When these $CFCs$ reach the stratosphere,they are broken down by ultraviolet radiation,releasing chlorine atoms $(Cl)$.
These chlorine atoms act as catalysts in the destruction of ozone $(O_3)$ molecules,converting them into oxygen $(O_2)$.
Therefore,the addition of chlorine $(Cl)$ atoms to the atmosphere is the primary factor responsible for ozone depletion.

(A) The substance commonly used as a refrigerant in refrigerators and air conditioners is $Freon$ (a group of chlorofluorocarbons or $CFCs$).
$Freon$ is a trade name for a group of chlorofluorocarbons that were widely used due to their stability and non-toxic nature,although they are now being phased out because they contribute to the depletion of the ozone layer.

(B) An environmental problem refers to the harmful effects of human activity on the biophysical environment.
$A$. The combination of a free oxygen atom with an oxygen molecule $(O + O_2 \rightarrow O_3)$ is a natural chemical process that forms ozone.
$B$. The depletion of the ozone layer is a significant environmental problem caused by the release of chlorofluorocarbons $(CFCs)$ and other pollutants,which leads to increased $UV$ radiation reaching the Earth's surface.
$C$. Water accumulation is generally a physical phenomenon,not an environmental problem in this context.
$D$. Starvation is a socio-economic issue rather than a direct environmental problem.
Therefore,the correct option is $B$.

(D) According to environmental studies and data regarding urban waste management,it is estimated that an individual living in an urban area generates approximately $0.5 \ kg$ of waste per day.
This waste includes biodegradable materials,plastics,paper,and other household refuse.
Therefore,the correct option is $D$.

(B) The $Red \ Data \ Book$ is a public document created for recording endangered and rare species of animals,plants,and fungi as well as some local subspecies that are present within a particular region or country.
It is maintained by the $International \ Union \ for \ Conservation \ of \ Nature \ (IUCN)$.
Therefore,the correct option is $B$.

(D) Deforestation refers to the large-scale removal of trees and forests.
$1$. It leads to a decrease in rainfall because trees contribute to the water cycle through transpiration.
$2$. It causes an increase in soil erosion as tree roots hold the soil together.
$3$. It leads to an increase in atmospheric $CO_2$ levels because trees act as carbon sinks,and their removal releases stored carbon.
$4$. Population growth is a cause of deforestation,not an effect of it. Therefore,the correct answer is $D$.

(C) The greenhouse effect is a natural process that warms the Earth's surface.
When the Sun's energy reaches the Earth's atmosphere,some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases.
$CO_2$ (Carbon dioxide) is the primary greenhouse gas contributing to global warming.
An increase in the concentration of $CO_2$ due to human activities like burning fossil fuels and deforestation traps more heat in the atmosphere,leading to an enhanced greenhouse effect.

(C) According to the report published in $2010$,there were $88$ National Parks in India. National Parks are protected areas established by the government to conserve wildlife and their natural habitats. Therefore,the correct option is $C$.