Human Activities and the Environment Questions in English

(N/A) To become more environment-friendly,we can adopt the following habits:
$1$. Switch off electrical appliances like lights and fans when not in use to conserve energy.
$2$. Avoid wasting water and food. Always close the tap tightly after use.
$3$. Practice the $3R$ principle: Reduce,Reuse,and Recycle.
$4$. Segregate waste properly. Dispose of plastic,paper,and glass in designated recycling bins instead of mixing them with biodegradable waste.
$5$. Avoid using single-use plastics,as they are non-biodegradable and cause soil and environmental pollution.
$6$. Dispose of waste safely in dustbins rather than littering in public places.

(N/A) Changes that can be undertaken in our homes to be environment-friendly are listed below:
$(i)$ Switch off the electrical appliances when not in use.
$(ii)$ Turn the taps off while brushing or bathing and repair the leaking taps.
$(iii)$ Throw biodegradable and non-biodegradable waste into separate bins.
$(iv)$ Construct composting pits.
$(v)$ Food items such as jam,pickles,etc.,come packed in plastic bottles. These bottles can later be used for storing things in the kitchen.

(N/A) Changes that can be undertaken in our schools to make them environment-friendly are listed below:
$(i)$ Electricity can be saved by switching off lights and fans when not required.
$(ii)$ Turn the taps off when not in use to prevent water wastage.
$(iii)$ Biodegradable and non-biodegradable wastes should be disposed of in separate bins to facilitate proper waste management and recycling.

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$ into the atmosphere.
These gases are released during the combustion of fossil fuels such as coal,oil,and natural gas in power plants,industries,and vehicles.
When these gases react with water vapor,oxygen,and other chemicals in the atmosphere,they form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the ground with rain,snow,or fog,resulting in acid rain.

(A) The depletion of the ozone layer is primarily caused by chlorofluorocarbons $(CFCs)$.
$CFCs$ are synthetic chemical compounds that contain chlorine,fluorine,and carbon. When released into the atmosphere,they rise to the stratosphere where they are broken down by ultraviolet radiation,releasing chlorine atoms.
These chlorine atoms act as catalysts to break down ozone molecules $(O_3)$ into oxygen $(O_2)$ and atomic oxygen $(O)$,thereby thinning the ozone layer.
$CFCs$ are commonly used in refrigerators,air conditioners,and aerosol sprays.

(C) Excessive exposure to $UV$-rays (ultraviolet radiation) has harmful effects on human health.
$(i)$ $UV$-rays can suppress the immune system,making the body more susceptible to infections.
$(ii)$ $UV$-rays primarily affect the skin and eyes; they do not cause direct damage to the lungs.
$(iii)$ $UV$-rays are a known carcinogen and prolonged exposure leads to $DNA$ damage in skin cells,resulting in skin cancer.
$(iv)$ Peptic ulcers are typically caused by bacterial infections (like $H. pylori$) or excessive use of NSAIDs,not by $UV$-rays.
Therefore,the correct effects are $(i)$ and $(iii)$.

(D) Non-biodegradable substances are those that cannot be broken down by biological processes (microorganisms).
$(i)$ Wood,paper,and leather are biodegradable.
$(ii)$ Polythene,detergent,and $PVC$ are non-biodegradable.
$(iii)$ Plastic and detergent are non-biodegradable,but grass is biodegradable.
$(iv)$ Plastic,bakelite,and $DDT$ are non-biodegradable.
Therefore,groups $(ii)$ and $(iv)$ contain only non-biodegradable items.

(A) Disposable plastic plates are made of synthetic polymers that are non-biodegradable.
This means they cannot be broken down by biological processes or microorganisms into simpler,harmless substances.
As a result,they persist in the environment for a very long time,leading to pollution and ecological damage.
Therefore,the correct reason is that they are made of non-biodegradable materials.

(D) Improper disposal of waste is considered a curse because it leads to the accumulation of non-biodegradable materials in the ecosystem.
It causes severe pollution of air,water,and soil,which degrades the quality of natural resources.
Furthermore,it poses significant health risks to all living organisms by introducing toxic substances into the food chain.

(D) Cloth bags offer several advantages over plastic bags:
$(a)$ Durability: Cloth bags are stronger and capable of carrying more items compared to plastic bags.
$(b)$ Biodegradability: Cloth is made from natural fibers like cotton or jute,which are biodegradable and do not persist in the environment.
$(c)$ Environmental Impact: Unlike plastic,which takes hundreds of years to decompose and releases toxic chemicals,cloth bags do not pollute the environment.
$(d)$ Reusability: Cloth bags can be washed and reused multiple times,reducing the need for single-use bags.

(N/A) $(i)$ Separation of biodegradable and non-biodegradable waste.
$(ii)$ Gardening and planting trees.
$(iii)$ Use of cloth bags or paper bags instead of polythene or plastic bags.
$(iv)$ Use of organic compost and vermicompost instead of chemical fertilizers.
$(v)$ Harvesting rainwater to conserve water resources.

(N/A) The wastes generated in a house daily include:
$(a)$ Kitchen wastes (leftover food,vegetable/fruit peels).
$(b)$ Paper wastes (newspapers,bags,envelopes).
$(c)$ Plastic bags and packaging materials.
$(d)$ Dust and sweepings.
Measures for disposal:
$(a)$ Segregation: Separate waste into biodegradable (kitchen waste,peels) and non-biodegradable (plastic,glass) categories.
$(b)$ Composting: Prepare a compost pit for biodegradable kitchen wastes to convert them into manure.
$(c)$ Recycling: Send paper wastes and recyclable plastics to recycling centers.
$(d)$ Reuse: Reuse plastic bags and containers whenever possible.
$(e)$ Proper Disposal: Dispose of non-recyclable waste in designated municipal bins.

(N/A) The waste management in fertiliser industries involves the following mechanisms:
$1$. Control of air pollution: Installation of scrubbers and electrostatic precipitators to remove harmful gases and particulate matter from industrial emissions.
$2$. Effluent treatment: Industrial wastewater must be treated in an Effluent Treatment Plant $(ETP)$ to neutralize chemicals and remove toxic pollutants before discharging it into the surrounding environment.

(N/A) The by-products of fertiliser industries primarily include harmful gases such as sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$.
These gases are released into the atmosphere,leading to severe air pollution.
When these gases react with water vapor in the atmosphere,they form sulfuric acid and nitric acid,which fall to the Earth as acid rain.
Acid rain damages soil fertility,harms aquatic life in water bodies,and causes corrosion to buildings and monuments.

(N/A) Excessive use of fertilisers changes the chemistry of soil and kills useful microbes.
$(b)$ Excessive use of non-biodegradable chemical pesticides leads to biological magnification.
$(c)$ Extensive cropping causes loss of soil fertility.
$(d)$ Excess use of groundwater for agriculture lowers the water table.
$(e)$ Damage to natural ecosystems and habitats.

(N/A) The accumulation of harmful chemicals in our bodies,a process known as biological magnification,can be prevented by minimizing the use of pesticides and chemical fertilizers in agriculture. Instead,adopting organic farming practices and using natural pest control methods helps reduce the entry of these toxic substances into the food chain.

(B) The process described is known as eutrophication.
$1$. Excessive fertilizers (rich in nitrates and phosphates) enter the pond,leading to an overgrowth of algae (algal bloom).
$2$. When these algae die,decomposers consume large amounts of dissolved oxygen in the water to break them down.
$3$. This leads to a significant decrease in the dissolved oxygen levels in the pond.
$4$. Consequently,the fish population will decrease in the long run due to the lack of oxygen required for their survival.

(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 case of the river Ganga,the disposal of unburnt corpses into the water is a major source of organic pollution,which leads to the proliferation of coliform bacteria.
While other activities like washing clothes or immersion of ashes contribute to pollution,the decomposition of organic matter from corpses provides a significant nutrient source for these bacteria.

(N/A) The excessive use of fertilisers in the fields led to the runoff of nutrients into the lake during rains.
These fertilisers are rich in phosphates and nitrates,which act as nutrients for aquatic plants,leading to their rapid and excessive growth,a process known as $Eutrophication$.
As the surface of the water became completely covered with these plants,it blocked sunlight from reaching deeper layers.
Furthermore,the decomposition of these plants by microorganisms consumed a large amount of dissolved oxygen,leading to its depletion.
This lack of dissolved oxygen and the change in the ecosystem resulted in the mass death of fish.

(N/A) Coliform bacteria are a group of bacteria that are primarily found in the intestines of humans and other warm-blooded animals. Their presence in water is often used as an indicator of fecal contamination.

(N/A) Ideal methods:
$(i)$ Recycling the wastes.
$(ii)$ Reuse after repairing if required.
$(b)$ Traditional methods:
$(i)$ Throwing them in the dustbin and dumping in sanitary landfills.
$(ii)$ Burning or disposing of them in water bodies or rivers.

(N/A) The group of bacteria whose presence confirms the contamination of river water is known as $Coliform$ bacteria. These bacteria are commonly found in the human intestine and their presence in water indicates contamination by sewage or fecal matter.

(N/A) An affluent lifestyle often leads to the excessive consumption of natural resources,which results in the generation of large amounts of waste and contributes significantly to environmental pollution.

(N/A) Substances that can be broken down into simpler components through the process of decomposition by microorganisms are known as biodegradable substances.
Conversely,substances that cannot be decomposed or broken down by the action of microorganisms are referred to as non-biodegradable substances.

(N/A) Biodegradable substances affect the environment in the following two ways:
$(i)$ During the decomposition of biodegradable substances,foul odors are released,which pollute the surrounding air.
$(ii)$ Areas where moist biodegradable waste accumulates become breeding grounds for insects such as mosquitoes and houseflies. These insects act as vectors for pathogens and spread various diseases.

(N/A) Non-biodegradable substances affect the environment in two ways:
$(i)$ They do not decompose naturally. As a result,they accumulate in the ecosystem,leading to environmental pollution and biomagnification,which can be toxic to organisms.
$(ii)$ Substances like insecticides,detergents,and plastics pollute water bodies and soil,disrupting the natural balance of the ecosystem and harming aquatic and terrestrial life.

(N/A) Ozone is a natural gas composed of three atoms of oxygen. Its chemical formula is $O_{3}$. It is blue in colour and has a strong,pungent odour.
The ozone layer acts as a protective shield for the Earth by absorbing harmful ultraviolet $(UV)$ radiation from the sun. These $UV$ radiations are highly damaging to living organisms,as they can cause skin cancer,cataracts,and damage to the $DNA$ of plants and animals,thereby disrupting the balance of the ecosystem.

(N/A) The problem of waste disposal can be reduced in the following ways:
$(1)$ By segregating biodegradable and non-biodegradable waste into separate bins.
$(2)$ By composting biodegradable waste and using it as manure in a kitchen garden.
Two specific methods for effective waste management are as follows:
$(1)$ Recycling: Processing waste materials into new products to reduce the consumption of fresh raw materials.
$(2)$ Production of Biogas: Converting organic biodegradable waste into energy (biogas) and organic fertilizer.

(B) Environment-friendly practices are actions that help in conserving natural resources and reducing pollution.
$1$. Carrying cloth-bags reduces the use of plastic bags, which are non-biodegradable and harmful to the environment.
$2$. Walking to school instead of using a motorized vehicle reduces the emission of greenhouse gases and pollutants.
$3$. Switching off unnecessary lights and fans helps in conserving electricity, which is often generated by burning fossil fuels.
Since all the mentioned options contribute to environmental protection, the correct answer is $All \text{ of the given options}$.

(N/A) The following problems are caused by the non-biodegradable wastes generated by us:
$(i)$ Non-biodegradable waste cannot be decomposed into simpler forms by biological processes; therefore,it accumulates in the environment in its original form and causes pollution.
$(ii)$ The accumulation of such waste leads to the spread of various diseases and epidemics.
$(iii)$ It leads to the phenomenon of biomagnification,where toxic substances increase in concentration at each successive trophic level in a food chain.

(B) Even if all waste generated is biodegradable,it can still impact the environment if not managed properly.
$1$. Large quantities of biodegradable waste accumulating in one place can lead to the production of foul odors and the breeding of disease-carrying vectors like flies and mosquitoes.
$2$. If biodegradable waste is dumped into water bodies,it can lead to eutrophication,where the decomposition process consumes dissolved oxygen,harming aquatic life.
$3$. Therefore,while biodegradable waste is easier to manage through composting,it is not entirely harmless if left unmanaged or disposed of incorrectly.

(N/A) The ozone layer in the stratosphere protects living organisms on Earth from the harmful ultraviolet $(UV)$ radiation of the sun.
Damage or depletion of the ozone layer is a cause for concern because it allows more $UV$ radiation to reach the Earth's surface,which can cause serious health issues such as skin cancer,cataracts,and damage to the immune system in humans,as well as harm to plants and marine ecosystems.
To limit this damage,the United Nations Environment Programme $(UNEP)$ has taken significant steps.
$UNEP$ succeeded in forging an international agreement known as the Montreal Protocol,which mandates that all signatory countries freeze the production and consumption of chlorofluorocarbons $(CFCs)$ and other ozone-depleting substances at $1986$ levels to prevent further depletion of the ozone layer.

(B) 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.
The confinement of these heat radiations by the Earth's atmosphere,which prevents them from escaping into space,thereby raising the global temperature,is called the greenhouse effect.

(N/A) Our affluent lifestyle leads to the excessive consumption of natural resources and the generation of large amounts of waste,which results in environmental pollution and the degradation of ecosystems.

(N/A) The gases that have replaced $CFCs$ (Chlorofluorocarbons) due to their ozone-depleting potential include:
$(i)$ Hydrofluorocarbons $(HFCs)$
$(ii)$ Perfluorocarbons $(PFCs)$
$(iii)$ Isobutane
Any two of these can be considered as correct answers.

(N/A) The chemical commonly used in fire extinguishers,particularly in the past,is Chlorofluorocarbons $(CFCs)$ or Halons.
$CFCs$ are harmful because they are responsible for the depletion of the ozone layer in the stratosphere.
When these chemicals reach the upper atmosphere,they are broken down by ultraviolet radiation,releasing chlorine atoms.
These chlorine atoms react with ozone $(O_3)$ molecules,breaking them down into oxygen $(O_2)$,thereby thinning the protective ozone layer that shields the Earth from harmful ultraviolet radiation.

(A) The depletion of the ozone layer is primarily caused by the release of certain chemical compounds into the atmosphere:
$(i)$ Chlorofluorocarbons (CFCs) and fluorocarbons: These are widely used in refrigerators and air conditioners.
$(ii)$ Free chlorine atoms: Released from CFCs upon exposure to ultraviolet radiation,these atoms react with ozone $(O_3)$ to break it down into oxygen $(O_2)$.
$(iii)$ Aerosols: Certain propellants used in aerosol sprays also contribute to ozone depletion.

(A) The full form of $CFC$ is Chlorofluorocarbon.
These are organic compounds that contain carbon,chlorine,and fluorine,produced as a volatile derivative of methane,ethane,and propane.

(N/A) Ozone $(O_3)$ is a gas that is highly toxic to living organisms if inhaled directly. However,it performs a vital function by forming the ozone layer in the upper atmosphere (stratosphere). This layer acts as a protective shield that absorbs harmful $UV$ (ultraviolet) radiation from the sun,preventing it from reaching the Earth's surface. Without this layer,$UV$ rays would cause severe damage to living organisms,including skin cancer and cataracts in humans.

(N/A) Plastics are considered non-biodegradable because they are synthetic polymers composed of long,complex chains of molecules.
These chemical structures are highly stable and resistant to natural degradation processes.
Microorganisms,such as bacteria and fungi,lack the specific enzymes required to break down the strong carbon-carbon bonds in plastic molecules.
Consequently,plastics persist in the environment for hundreds of years without being decomposed by biological agents.

(C) Non-biodegradable waste refers to substances that cannot be broken down or decomposed by biological processes (such as the action of bacteria or other saprophytes).
Among the given items:
$1$. Empty packet of chips (Plastic/Aluminium foil) - Non-biodegradable.
$2$. Empty plastic bottle of mineral water - Non-biodegradable.
$3$. Empty paper box of sweets - Biodegradable (made of cellulose/plant material).
$4$. Empty tin of a cold drink - Non-biodegradable.
Therefore,the biodegradable waste is the empty paper box of sweets.

(A) In the first step of ozone formation,high-energy $UV$ radiation breaks down the diatomic oxygen molecule $(O_2)$ into two individual oxygen atoms $(O + O)$.

(B) Microbial enzymes are highly specific in their action. They have evolved to break down natural organic materials found in the environment. Man-made substances,such as plastics,synthetic polymers,and certain pesticides,have chemical structures that do not match the active sites of these enzymes. Consequently,microbes cannot catalyze the decomposition of these non-biodegradable materials.

(N/A) Cloth bags are biodegradable,meaning they can be broken down by the action of bacteria or other saprophytes. In contrast,polythene bags are non-biodegradable and persist in the environment for a long time,causing significant harm to the ecosystem.

(N/A) Soil: Pesticides are used to protect crops from pests. When sprayed on plants,they eventually settle into the soil particles.
Groundwater: Through the process of irrigation and rainwater runoff,these pesticides present in the soil leach into the lower layers of the earth and contaminate the groundwater.
Water bodies: Pesticides reach water bodies like rivers,canals,and ponds through surface runoff from agricultural fields,or when contaminated agricultural waste and wastewater are discharged into these water sources.

(N/A) Accumulation of harmful chemicals in our body can be avoided by taking the following steps:
$(1)$ Wash vegetables and fruits thoroughly with clean water to remove surface pesticides and chemicals.
$(2)$ Soak vegetables and fruits in salt water for a few minutes before cooking to help leach out residual chemicals.
$(3)$ Boil vegetables where possible,as heat can help break down or remove certain pesticide residues.
$(4)$ Promote and use organic farming products,as they are grown without the use of synthetic chemical fertilizers and pesticides.

(N/A) $1$. Reduce the use of non-biodegradable materials: For example,use paper or cloth bags instead of plastic bags to carry items.
$2$. Recycling: Non-biodegradable wastes like plastic,metal,and glass should be sent to factories for recycling so they can be processed into new products.

(N/A) $(i)$ Using improved seeds which are capable of resisting pests.
$(ii)$ Using specific herbs such as $Neem$ during the storage of food grains to prevent pest infestation.

(N/A) Two causes of the depletion of the ozone layer are:
$(i)$ Use of $CFCs$ (Chlorofluorocarbons) in refrigeration.
$(ii)$ Use of $CFCs$ in fire extinguishers and aerosol sprayers.
The harmful effects of the depletion of the ozone layer are:
$(i)$ Due to the depletion of the ozone layer,$UV$ radiations reach the Earth. These $UV$ radiations cause skin cancer,damage to eyes,and harm the immune system.
$(ii)$ This depletion of the ozone layer may also lead to variations in global rainfall,ecological disturbances,and a decrease in global food supplies.

(N/A) $(i)$ The ozone layer is located at a height of approximately $10$ to $16 \, km$ from the equator.
$(ii)$ The ozone layer provides protection against harmful $UV$ (ultraviolet) rays.
$(iii)$ One major effect of the depletion of the ozone layer is an increase in the risk of skin cancer and cataracts in humans due to increased exposure to $UV$ radiation.