RBSE Solutions Class 11 Biology Chapter 42 Global Environmental Change

Rbse Class 11 Biology Chapter 42 Multiple Choice Objective Questions

 

Question 1. Percentage of \( \text{CO}_2 \) in the air
(a) 0.3%
(b) 0.03%
(c) 0.003%
(d) 3.3%
Answer: (b) 0.03%
In simple words: The correct amount of carbon dioxide present in the Earth's atmosphere is a very small percentage, specifically 0.03%.

🎯 Exam Tip: Remember precise percentages for atmospheric gases like \( \text{CO}_2 \), Nitrogen, and Oxygen, as they are often tested.

 

Question 2. The main green house gas is
(a) Freon
(b) Methane
(c) \( \text{CO}_2 \)
(d) \( \text{O}_2 \)
Answer: (c) \( \text{CO}_2 \)
In simple words: Carbon dioxide is considered the most important greenhouse gas because it traps heat in the atmosphere, leading to global warming.

🎯 Exam Tip: Identify the primary greenhouse gases and their relative contributions to the greenhouse effect.

 

Question 4. The meaning of Ozone hole is
(a) Hole in the Ozone layer
(b) Less Ozone in the troposphere
(c) Increased Ozone thickness in the troposphere
(d) Reduced Ozone concentration is the stratosphere.
Answer: (d) Reduced Ozone concentration is the stratosphere.
In simple words: An ozone hole doesn't mean a literal gap, but rather an area where the amount of ozone in the stratosphere becomes much thinner than normal.

🎯 Exam Tip: Understand that the "ozone hole" refers to a thinning, not an actual physical hole, and its location in the stratosphere.

 

Question 5. Excess of which causes acid rain
(a) \( \text{O}_2 \)
(b) \( \text{CO}_2 \) and CO
(c) \( \text{SO}_3 \) and CO
(d) \( \text{SO}_2 \)
Answer: (d) \( \text{SO}_2 \)
In simple words: Too much sulfur dioxide in the air is a major cause of acid rain because it reacts with water to form sulfuric acid.

🎯 Exam Tip: Focus on the key atmospheric pollutants like sulfur dioxide and nitrogen oxides that are responsible for acid rain formation.

Rbse Class 11 Biology Chapter 42 Very Short Answer Questions

 

Question 1. Give the chemical symbol of Ozone.
Answer: The chemical symbol for Ozone is \( \text{O}_3 \). It is a molecule made of three oxygen atoms.
In simple words: Ozone is written as \( \text{O}_3 \).

🎯 Exam Tip: Know the chemical symbols for important environmental gases like oxygen (\( \text{O}_2 \)) and ozone (\( \text{O}_3 \)).

 

Question 2. Which is the most affected country because of Ozone hole?
Answer: Australia is considered the country most affected by the ozone hole, leading to increased radiation and related health issues.
In simple words: Australia is the country most impacted by the ozone hole.

🎯 Exam Tip: Remember specific examples or regions that are significantly impacted by environmental issues like ozone depletion.

 

Question 4. Name the green house gases.
Answer: The main greenhouse gases include \( \text{CO}_2 \), \( \text{CH}_4 \), CFCs (Chlorofluorocarbons), \( \text{O}_3 \), and \( \text{N}_2\text{O} \). These gases trap heat in the Earth's atmosphere.
In simple words: Carbon dioxide, methane, CFCs, ozone, and nitrous oxide are some greenhouse gases.

🎯 Exam Tip: List at least four major greenhouse gases by their chemical formulas and common names.

 

Question 5. What will happen due to excessive green house effect.
Answer: Excessive greenhouse effect leads to global warming. This means the Earth's average temperature increases too much.
In simple words: Too much greenhouse effect causes global warming.

🎯 Exam Tip: Clearly link the excessive greenhouse effect to global warming and understand its basic meaning.

 

Question 6. Give one prime measure to prevent green house effect.
Answer: One main way to prevent the greenhouse effect is to reduce the production of greenhouse gases. This involves using less fossil fuels.
In simple words: Reducing how many greenhouse gases we make is a key way to stop the greenhouse effect.

🎯 Exam Tip: When asked for prevention, focus on the root cause; for greenhouse effect, it's reducing greenhouse gas emissions.

 

Question 7. What is Global warming?
Answer: Global warming refers to the increase in the Earth's average atmospheric temperature. This rise is mainly due to the enhanced greenhouse effect.
In simple words: Global warming is when the Earth's air gets hotter because of extra greenhouse gases.

🎯 Exam Tip: Define global warming simply as the rise in average global temperature, emphasizing its link to the greenhouse effect.

 

Question 8. What is El Nino effect?
Answer: El-Nino effect is a significant weather phenomenon that impacts global climate patterns. It describes changes in ocean temperatures.
In simple words: El-Nino is a weather event that changes global weather.

🎯 Exam Tip: For basic definitions, keep it concise, stating what the phenomenon is (a weather pattern) and its general impact.

 

Question 9. What is the role of Ozone layer?
Answer: The ozone layer plays a crucial role in protecting life on Earth. It absorbs harmful cosmic rays and ultraviolet (UV) rays from the sun, preventing them from reaching the surface.
In simple words: The ozone layer stops bad rays from the sun, like UV rays, from hurting us.

🎯 Exam Tip: Highlight the protective function of the ozone layer, specifically mentioning UV radiation absorption.

 

Question 11. In which industries, CFC is used?
Answer: CFCs (Chlorofluorocarbons) are primarily used in the refrigeration industry. They were common as coolants in fridges and air conditioners.
In simple words: CFCs are used in cooling machines like refrigerators.

🎯 Exam Tip: Connect CFCs directly to their historical use in refrigeration and aerosols, understanding why they became problematic.

 

Question 12. The height of troposphere from the sea level.
Answer: The troposphere extends from the sea level up to a height of approximately 0 to 12 km. This is where most of Earth's weather occurs.
In simple words: The troposphere goes from sea level up to about 12 kilometers high.

🎯 Exam Tip: Know the approximate height ranges for different layers of the atmosphere, especially the troposphere and stratosphere.

 

Question 13. In which part of year, the El-Nino effects occurs.
Answer: The El-Nino effects typically occur during the last part of the year. Historically, they are noted around December, near Christmas.
In simple words: El-Nino usually happens towards the end of the year.

🎯 Exam Tip: Recall the typical season or period during which El-Nino events are observed.

 

Question 14. Define acid rain.
Answer: Acid rain is rainwater that has become acidic due to pollutants in the atmosphere. These pollutants, like sulfuric acid \( (\text{H}_2\text{SO}_4) \) and nitric acid \( (\text{HNO}_3) \), mix with the rain.
In simple words: Acid rain is rain mixed with harmful acids like sulfuric acid and nitric acid from air pollution.

🎯 Exam Tip: Define acid rain by mentioning its cause (air pollutants) and the main acidic components it contains.

 

Question 15. Write harmful effect of Ozone depletion.
Answer: Ozone depletion leads to several harmful effects, including an increased risk of skin cancer, cataracts in the eyes, and reduced production of crops like rice. It allows more harmful UV radiation to reach Earth.
In simple words: When the ozone layer gets thinner, it can cause skin cancer, eye problems like cataracts, and harm crop growth.

🎯 Exam Tip: List key health and environmental impacts of increased UV radiation due to ozone depletion.

Rbse Class 11 Biology Chapter 42 Short Answer Questions

 

Question 1. What do you mean by green house effect?
Answer: The greenhouse effect is a natural process where the Earth's atmosphere traps some of the sun's heat. Certain gases in the atmosphere, called greenhouse gases (like \( \text{CO}_2 \), Methane, \( \text{N}_2\text{O} \), and water vapor), act like a glass wall. They absorb infrared heat radiation from the Earth's surface, which warms the atmosphere. This process is essential for keeping the Earth warm enough to support life, but too much of it can lead to global warming.
In simple words: The greenhouse effect is how Earth's atmosphere traps heat from the sun using certain gases, keeping our planet warm.

🎯 Exam Tip: Clearly define the greenhouse effect as a natural process and mention the role of greenhouse gases in trapping heat.

 

Question 2. What are the main causes of green house effect?
Answer: The main causes of the increased greenhouse effect are:

• Deforestation: Green plants absorb \( \text{CO}_2 \) during photosynthesis. When forests are cut down rapidly, less \( \text{CO}_2 \) is removed from the atmosphere, leading to its increase.
• Burning of fossil fuels: Burning coal, wood, and petroleum releases large amounts of \( \text{CO}_2 \) into the air.
• Industrialization and vehicles: Factories and motor vehicles release many greenhouse gases, including \( \text{CO}_2 \), as a result of burning fuels.

In simple words: Cutting down trees, burning fuels like coal and wood, and pollution from factories and cars are the main things that make the greenhouse effect stronger.

🎯 Exam Tip: Focus on human activities like deforestation and the burning of fossil fuels as the primary drivers of an enhanced greenhouse effect.

 

Question 3. How green house effect can be controlled?
Answer: The greenhouse effect can be controlled by reducing the amount of greenhouse gases released into the atmosphere. This includes lowering emissions of \( \text{CO}_2 \), Methane, and Tropospheric Ozone (\( \text{O}_3 \)). This can be done by using cleaner energy and planting more trees.
In simple words: We can control the greenhouse effect by making and releasing fewer greenhouse gases like carbon dioxide and methane.

🎯 Exam Tip: Suggest practical actions to reduce greenhouse gas emissions, such as using renewable energy and reforestation.

 

Question 4. what is atmosphere?
Answer: The atmosphere is the layer of air that surrounds the Earth, extending up to about 800 to 1000 km in height. The air in the lower part of the atmosphere is heavy and dense, while the air in the upper layers is lighter and thinner.
In simple words: The atmosphere is the blanket of air around Earth, which is thick at the bottom and thin higher up.

🎯 Exam Tip: Define the atmosphere as the gaseous envelope around Earth and briefly describe how its density changes with height.

 

Question 5. Define Ozone layer.
Answer: The ozone layer is a region within the stratosphere, located at a height of about 15 to 30 km above Earth's surface. Approximately 90% of the Earth's atmospheric ozone (\( \text{O}_3 \)) is found in this layer, where it absorbs most of the sun's harmful ultraviolet (UV) radiation.
In simple words: The ozone layer is a protective shield of ozone gas \( (\text{O}_3) \) high up in the sky, between 15 to 30 km, that stops harmful sun rays.

🎯 Exam Tip: State the location (stratosphere) and primary function (UV absorption) of the ozone layer clearly.

 

Question 6. What are the adverse effects of green house effect?
Answer: The adverse effects of the greenhouse effect, mainly global warming, include:

• Increase in global temperature: This leads to extreme weather events.
• Melting of polar ice: Rising temperatures cause glaciers and ice caps to melt, increasing sea levels.
• Flooding of coastal regions: Higher sea levels can submerge low-lying coastal areas and islands.
• Impact on agriculture and fisheries: Changes in climate can reduce crop production and harm fish populations.

In simple words: The bad effects of the greenhouse effect are warmer global temperatures, melting ice, floods in coastal areas, and harm to farms and fishing.

🎯 Exam Tip: List various consequences of global warming, covering environmental, economic, and social impacts.

 

Question 7. Define stratosphere.
Answer: The stratosphere is the second layer of Earth's atmosphere, located directly above the troposphere. It extends from about 12 km up to 50 km above sea level and contains the vital ozone layer, which protects life from UV radiation.
In simple words: The stratosphere is the atmosphere layer above the troposphere, from 12 to 50 km high, where the ozone layer is found.

🎯 Exam Tip: Specify the position of the stratosphere relative to other atmospheric layers and mention its approximate altitude range.

 

Question 8. How Ozone layer protects from the U-V rays of Sun.
Answer: The ozone layer protects Earth by absorbing harmful cosmic rays and ultraviolet (UV) rays from the Sun. This absorption prevents these dangerous radiations from reaching the planet's surface, thus safeguarding animals, humans, and plants from their damaging effects.
In simple words: The ozone layer soaks up harmful UV rays and cosmic rays from the sun, keeping living things on Earth safe.

🎯 Exam Tip: Explain the mechanism of protection: the ozone layer's ability to absorb specific types of harmful radiation.

 

Question 9. Explain in brief the El-Nino effect.
Answer: The El-Nino effect is a natural weather phenomenon that causes changes in global weather patterns. It was named "The little boy" or "Christ Child" by South American fishermen in 1960 because it often occurs around December. During an El-Nino event, the normal trade winds in the Pacific Ocean weaken, causing warm surface water to move eastward. This shift in warm water affects ocean currents and temperatures, leading to significant changes in rainfall (like increased rain in some areas and droughts in others) and impacting marine life by reducing nutrients in certain waters.
In simple words: El-Nino is a weather change where warm ocean water shifts in the Pacific, affecting rain and marine life around the world, usually near Christmas.

🎯 Exam Tip: Provide a concise explanation of El-Nino, including its origin, key characteristics (warm water shift, weakened trade winds), and general impacts on weather and marine ecosystems.

 

Question 10. Write the Main factors causing Ozone depletion.
Answer: The main factors causing ozone depletion are:

• Chlorofluorocarbons (CFCs): Compounds like CFCs (Chloro Fluoro Carbon), CBC (Chloro Bromo Carbon), and BFC (Bromo Fluoro Carbon) are used in refrigeration, aerosols, and industrial cleaning. They release chlorine radicals that destroy ozone molecules.
• Jet Aeroplanes: Jet planes flying in the stratosphere release pollutants that harm the ozone layer.
• Nuclear Blasts: Explosions from nuclear weapons can also damage the ozone.
• Deforestation: While less direct, deforestation can also contribute to climate change which indirectly affects atmospheric chemistry.
• Sulphur Oxides: Gases like \( \text{SO}_2 \) and \( \text{SO}_3 \) and Hydrochloric acid \( (\text{HCl}) \) can also contribute to ozone destruction.
• Fertilizers: Agricultural fertilizers can release compounds that deplete ozone.

In simple words: Ozone depletion is mainly caused by CFCs from fridges and sprays, pollution from jet planes, nuclear blasts, deforestation, and certain industrial gases and fertilizers.

🎯 Exam Tip: Focus on CFCs as the primary cause of ozone depletion and include other contributing factors like jet emissions and industrial chemicals.

 

Question 11. Define El-Nino effect.
Answer: The El-Nino effect refers to a significant change in sea currents that affects the environment. It is caused by the warming of the Pacific Ocean near the equator, off the coast of South America. This warming impacts global weather patterns, leading to altered rainfall and temperature distribution worldwide.
In simple words: El-Nino is when the Pacific Ocean near the equator gets warmer, changing sea currents and affecting weather around the world.

🎯 Exam Tip: When defining El-Nino, include the location (equatorial Pacific), the change (ocean warming), and its broad environmental impact.

 

Question 12. What are the main reasons of atmospheric heating?
Answer: The main reason for atmospheric heating is the increase of \( \text{CO}_2 \) and other greenhouse gases in the atmosphere. These gases trap heat, leading to an enhanced greenhouse effect. This ultimately results in an increase in the Earth's average atmospheric temperature, a phenomenon known as global warming.
In simple words: The atmosphere gets warmer mainly because more carbon dioxide and other greenhouse gases trap heat, causing global warming.

🎯 Exam Tip: Link atmospheric heating directly to the increased concentration of greenhouse gases, especially \( \text{CO}_2 \), and the resulting global warming.

Rbse Class 11 Biology Chapter 42 Essay Type Questions

 

Question 1. Define green house effect. Write its adverse effects and how to control it?
Answer: The greenhouse effect is a natural process where the Earth's atmosphere traps some of the Sun's energy, keeping our planet warm enough to sustain life. It functions like a greenhouse, where glass walls allow sunlight in but prevent heat from escaping. Certain atmospheric gases, known as greenhouse gases (including \( \text{CO}_2 \), methane \( (\text{CH}_4) \), nitrous oxide \( (\text{N}_2\text{O}) \), chlorofluorocarbons (CFCs), and water vapor), absorb infrared radiation emitted by the Earth's surface, thereby warming the lower atmosphere.

Causes of Green House Effect:The main reasons for the increasing greenhouse effect include:

• Deforestation: Green plants absorb \( \text{CO}_2 \). Rapid deforestation reduces this absorption, causing \( \text{CO}_2 \) levels to rise.
• Burning of fossil fuels: Burning coal, wood, and other fuels for energy releases significant amounts of \( \text{CO}_2 \).
• Industrialization and vehicles: Industries and motor vehicles are major sources of greenhouse gas emissions.

Adverse Effects of Green House Effect (Global Warming):The increased greenhouse effect leads to global warming, which has serious consequences:

1. Increased global temperature: This causes heavy rainfall and floods in coastal areas and droughts in others. Extreme weather events like cyclones and hurricanes become more frequent.
2. Reduced agricultural and fish production: Climate change negatively impacts farming and fishing, threatening food security.
3. Rising sea levels: Melting polar ice caps due to higher temperatures cause sea levels to rise, submerging coastal regions and islands.

How to Control Green House Effect:To control the greenhouse effect and mitigate global warming, measures include:

• Reducing greenhouse gas emissions: This involves decreasing the production of gases like \( \text{CO}_2 \), methane, and \( \text{N}_2\text{O} \) by transitioning to renewable energy sources and improving energy efficiency.
• Afforestation and reforestation: Planting more trees helps absorb \( \text{CO}_2 \) from the atmosphere.
• Promoting sustainable practices: Encouraging eco-friendly transportation, reducing industrial pollution, and managing waste effectively.

In simple words: The greenhouse effect is when gases in our air trap heat, warming the Earth. This happens mostly because we cut down trees and burn fuels, making Earth too hot. To fix it, we need to make fewer gases and plant more trees.

🎯 Exam Tip: When discussing the greenhouse effect, ensure your answer covers its definition, natural function, human-caused enhancement, specific adverse effects (global warming), and actionable control measures.

 

Question 2. Write the adverse effects of depletion in Ozone and how it can be controlled?
Answer: The ozone layer, primarily located in the stratosphere (15-30 km above Earth), protects life by absorbing harmful cosmic and ultraviolet (UV) rays from the Sun. Ozone depletion refers to the thinning of this layer, notably observed as the "ozone hole" over Antarctica. This thinning is mainly due to increased environmental pollution.
Factors Causing Ozone Depletion:

1. Chlorofluorocarbons (CFCs): These highly volatile organic compounds (including CBC and BFC) are used in refrigeration, aerosols, foam production, and industrial cleaning. When exposed to radiation, CFCs release chlorine radicals that catalytically destroy ozone.
   \( \text{CFCl}_3 \xrightarrow{\text{Radiation}} \text{CFCl}_2 + \text{Cl} \)
   \( \text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2 \)
   \( \text{ClO} + \text{O}_3 \rightarrow 2\text{O}_2 + \text{Cl} \) One chlorine radical can destroy about one lakh (100,000) ozone molecules.
2. Jet Aeroplanes: Aircraft flying in or near the stratosphere release pollutants that harm the ozone layer.
3. Nuclear Blasts: Nuclear explosions can also contribute to ozone destruction.
4. Deforestation: This leads to climate changes that indirectly affect the ozone layer.
5. Sulphur oxides and Hydrochloric acid: Chemicals like \( (\text{SO}_3.\text{SO}_3) \) and \( (\text{HCl}) \) can also deplete ozone.
6. Fertilizers: Agricultural fertilizers release compounds that contribute to ozone layer degradation.

Adverse Effects of Ozone Depletion:

• Health Impacts: Increased exposure to UV radiation can lead to higher rates of skin cancer and cataracts in the eyes.
• Agricultural Impact: It causes a reduction in the production of staple crops like paddy (rice) and other cereals.
• Marine Ecosystem Disturbance: Harmful UV rays can disrupt marine food chains, affecting plankton and other aquatic life.

How Ozone Depletion Can Be Controlled:Controlling ozone depletion requires reducing the emission of ozone-depleting substances (ODS):

• Phasing out CFCs: International agreements, like the Montreal Protocol, have led to the ban and gradual phasing out of CFCs and other ODS in industries.
• Developing alternatives: Using ozone-friendly refrigerants and aerosol propellants instead of CFCs.
• Reducing industrial emissions: Implementing stricter controls on chemical industries to minimize the release of harmful substances.
• Sustainable agricultural practices: Managing fertilizer use to reduce emissions of ozone-depleting compounds.

In simple words: The ozone layer protects us from bad sun rays. It gets thin because of chemicals like CFCs from old fridges and sprays, and pollution from planes and factories. This thinning causes skin cancer, eye problems, and harms plants and marine life. We can control it by stopping the use of these harmful chemicals and finding safer alternatives.

🎯 Exam Tip: For a comprehensive answer, define ozone depletion, list the primary chemicals involved (CFCs) with their reactions, explain the specific adverse effects on health and environment, and outline control measures (e.g., international protocols, alternative chemicals).

 

Question 3. Write about global warming.
Answer: Global warming refers to the long-term increase in Earth's average atmospheric temperature, primarily due to the enhanced greenhouse effect. This phenomenon occurs when increased concentrations of greenhouse gases, such as \( \text{CO}_2 \), methane, and \( \text{N}_2\text{O} \), trap more heat in the atmosphere.
The rise in global temperature leads to various severe problems:

• Melting glaciers and ice caps: This causes sea levels to rise significantly, threatening low-lying coastal areas and islands with submergence.
• Changes in rainfall and vegetation patterns: Some regions experience heavy floods and excessive rain, while others suffer from prolonged droughts. This affects agriculture and water availability.
• Extreme weather events: The frequency and intensity of cyclones, hurricanes, and heatwaves increase.
• Ecosystem disruption: Many species face extinction as their habitats change too rapidly for them to adapt.

To prevent or slow down global warming, it is crucial to control the increase in \( \text{CO}_2 \) and other greenhouse gases. This involves global efforts to reduce emissions, transition to renewable energy sources, improve energy efficiency, and promote reforestation.
In simple words: Global warming means Earth's temperature is rising because too many gases like carbon dioxide trap heat. This causes ice to melt, sea levels to go up, weird weather, and hurts animals and plants. We need to cut down on these gases to stop it.

🎯 Exam Tip: Define global warming, explaining its link to greenhouse gases. Describe at least three major environmental and societal impacts, and suggest general mitigation strategies to control it.

 

Question 4. Explain El-Nino effect.
Answer: The El-Nino effect is a complex climate pattern characterized by the warming of surface waters in the equatorial Pacific Ocean, off the coast of South America. This phenomenon, which typically occurs in the latter part of the year (around December), was named "El Niño" (meaning "The little boy" or "Christ Child") by Peruvian fishermen due to its timing.
During an El-Nino event, the normal east-to-west trade winds in the Pacific weaken or reverse. This allows warm water from the western Pacific to move eastward, replacing the typically cold, nutrient-rich waters along the South American coast. This shift in ocean temperatures and currents has profound global impacts:

• Weather changes: It leads to increased rainfall and flooding in some parts of the world (like Peru and Ecuador) and severe droughts in others (like Australia and parts of Asia).
• Marine life disruption: The warmer waters and reduced upwelling of nutrients negatively affect marine ecosystems, leading to a decline in fish populations.
• Economic impact: It can cause significant economic losses due to agricultural failures and fishing industry declines, and even contribute to natural disasters like bushfires.

In simple words: El-Nino is a climate event where the Pacific Ocean near the equator gets warmer, changing how winds blow and causing floods in some places and droughts in others, affecting marine life and weather worldwide.

🎯 Exam Tip: Explain El-Nino by detailing the changes in ocean temperature and trade winds, and describe its varied global impacts on rainfall, marine ecosystems, and human activities.

RBSE Class 11 Biology Chapter 42 Multiple Choice Objective Questions

 

Question 1. Percentage of CO2 in the air
(a) 0.3%
(b) 0.03%
(c) 0.003%
(d) 3.3%
Answer: (b) 0.03%
In simple words: The amount of carbon dioxide gas in the air is a very small percentage, which is 0.03%.

🎯 Exam Tip: Remember the exact percentage of key atmospheric gases like CO2, O2, and N2, as they are often asked in MCQs.

 

Question 2. The main green house gas is
(a) Freon
(b) Methane
(c) CO2
(d) O2
Answer: (c) CO2
In simple words: Carbon dioxide is the most important gas that traps heat in the Earth's atmosphere, leading to the greenhouse effect.

🎯 Exam Tip: While many gases contribute to the greenhouse effect, CO2 is generally considered the primary one due to its abundance and impact from human activities.

 

Question 4. The meaning of Ozone hole is
(a) Hole in the Ozone layer
(b) Less Ozone in the troposphere
(c) Increased Ozone thickness in the troposphere
(d) Reduced Ozone concentration is the stratosphere.
Answer: (d) Reduced Ozone concentration is the stratosphere.
In simple words: The "ozone hole" does not mean an actual hole, but rather a significant thinning or decrease in the amount of ozone gas in the stratosphere layer of the Earth's atmosphere.

🎯 Exam Tip: Understand that an 'ozone hole' is a reduction in concentration, not a physical opening. Knowing the location (stratosphere) is also crucial.

 

Question 5. Excess of which causes acid rain
(a) O2
(b) CO2 and CO
(c) SO3 and CO
(d) SO2
Answer: (d) SO2
In simple words: Too much sulfur dioxide gas in the air is the main reason why acid rain occurs. When it mixes with water, it forms acidic compounds.

🎯 Exam Tip: Sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary pollutants leading to acid rain. Focus on these chemical culprits.

RBSE Class 11 Biology Chapter 42 Very Short Answer Questions

 

Question 1. Give the chemical symbol of Ozone.
Answer: The chemical symbol for Ozone is \( O_3 \).
In simple words: Ozone is a gas made of three oxygen atoms joined together.

🎯 Exam Tip: Always write chemical symbols correctly with the right element and subscript numbers.

 

Question 2. Which is the most affected country because of Ozone hole?
Answer: Australia is the most affected country due to the ozone hole.
In simple words: The country most impacted by the ozone hole is Australia.

🎯 Exam Tip: Relate the ozone hole's effects to geographical regions most impacted by increased UV radiation.

 

Question 4. Name the green house gases.
Answer: The main greenhouse gases are carbon dioxide \( (CO_2) \), methane \( (CH_4) \), chlorofluorocarbons (CFCs), ozone \( (O_3) \), and nitrous oxide \( (N_2O) \).
In simple words: Gases like carbon dioxide, methane, CFCs, ozone, and nitrous oxide trap heat and are called greenhouse gases.

🎯 Exam Tip: Remember the full list of major greenhouse gases and their chemical formulas for questions asking for their names.

 

Question 5. What will happen due to excessive green house effect.
Answer: Excessive greenhouse effect leads to global warming.
In simple words: Too much greenhouse effect causes the Earth to get hotter, which is called global warming.

🎯 Exam Tip: Clearly link the cause (excessive greenhouse effect) to its main consequence (global warming).

 

Question 6. Give one prime measure to prevent green house effect.
Answer: One main way to prevent the greenhouse effect is to reduce the production of greenhouse gases.
In simple words: To stop the greenhouse effect, we must make fewer greenhouse gases.

🎯 Exam Tip: Focus on the core action: reducing emissions of the gases causing the effect.

 

Question 7. What is Global warming?
Answer: Global warming is the increase in the atmospheric temperature caused by the greenhouse effect.
In simple words: Global warming means the Earth's air is getting hotter because of too much greenhouse effect.

🎯 Exam Tip: Define global warming by clearly stating it's an increase in average temperature due to the greenhouse effect.

 

Question 8. What is El Nino effect?
Answer: The El Nino effect is a significant weather phenomenon that affects global climate patterns.
In simple words: El Nino is a major weather event that changes global weather.

🎯 Exam Tip: Remember that El Nino refers to a large-scale climate pattern, not just a local weather event.

 

Question 9. What is the role of Ozone layer?
Answer: The ozone layer protects Earth by absorbing harmful cosmic rays and ultraviolet (UV) rays from the Sun.
In simple words: The ozone layer stops dangerous rays from the sun, keeping Earth safe.

🎯 Exam Tip: Highlight the protective function of the ozone layer and specify the types of radiation it blocks.

 

Question 11. In which industries, CFC is used?
Answer: Chlorofluorocarbons (CFCs) are widely used in the refrigeration industry.
In simple words: CFCs are used in refrigerators and air conditioners.

🎯 Exam Tip: Associate CFCs primarily with cooling systems and aerosols as their main historical uses.

 

Question 12. The height of troposphere from the sea level.
Answer: The troposphere extends from sea level up to a height of approximately 0 to 12 km.
In simple words: The troposphere is the lowest layer of the atmosphere, reaching up to about 12 kilometers from the ground.

🎯 Exam Tip: Be precise about the approximate height range of the troposphere, as layer boundaries are common questions.

 

Question 13. In which part of year, the El-Nino effects occurs.
Answer: The El-Nino effects typically occur during the last part of the year, around December.
In simple words: El Nino usually happens towards the end of the year, often in December.

🎯 Exam Tip: Remember the seasonal timing of El Nino events, which relates to its historical naming.

 

Question 14. Define acid rain.
Answer: Acid rain is precipitation that contains high levels of acidic components, such as sulfuric acid \( (H_2SO_4) \) and nitric acid \( (HNO_3) \), which form when pollutants mix with water in the atmosphere.
In simple words: Acid rain is when rain mixes with pollution like acid from chemicals and becomes harmful.

🎯 Exam Tip: When defining acid rain, mention the key acidic compounds (sulfuric and nitric acid) that contribute to its formation.

 

Question 15. Write harmful effect of Ozone depletion.
Answer: Harmful effects of ozone depletion include an increased risk of skin cancer, cataracts in the eyes, and reduced production of crops like rice.
In simple words: Less ozone means more skin cancer, eye problems like cataracts, and less food from farms.

🎯 Exam Tip: List both human health impacts (skin cancer, cataracts) and ecological/agricultural impacts when asked about ozone depletion effects.

RBSE Class 11 Biology Chapter 42 Short Answer Questions

 

Question 1. What do you mean by green house effect?
Answer: The greenhouse effect is a natural process where the Earth's atmosphere traps some of the sun's heat. Certain gases in the atmosphere, called greenhouse gases, act like a glass wall in a greenhouse. They absorb heat radiation, warming the Earth's surface and maintaining a temperature suitable for life. If this effect becomes too strong due to increased greenhouse gases, it can lead to global warming.
In simple words: The greenhouse effect is how Earth's air traps heat, like a blanket, keeping our planet warm enough to live.

🎯 Exam Tip: Explain the greenhouse effect as a natural phenomenon and then mention how human activities intensify it, leading to global warming.

 

Question 2. What are the main causes of green house effect?
Answer: The main causes of an increased greenhouse effect are:

• **Deforestation**: Green plants absorb carbon dioxide during photosynthesis. With forests being cut down rapidly, less \( CO_2 \) is removed from the air, causing its levels to rise.
• **Burning of Fossil Fuels**: Burning things like coke, wood, and other fossil fuels releases a lot of \( CO_2 \) into the atmosphere.
• **Industrialization and Vehicles**: Factories and cars release many greenhouse gases, including \( CO_2 \), as industries grow and more vehicles are used.

In simple words: The main reasons for more greenhouse effect are cutting down trees, burning fuels like coal and wood, and pollution from factories and cars.

🎯 Exam Tip: Categorize the causes into deforestation, burning fossil fuels, and industrial/vehicular emissions for a structured answer.

 

Question 3. How green house effect can be controlled?
Answer: The greenhouse effect can be controlled by reducing the amount of greenhouse gases released into the atmosphere. This includes decreasing the production of gases like carbon dioxide \( (CO_2) \), methane \( (CH_4) \), and tropospheric ozone \( (O_3) \). Using cleaner energy sources, planting more trees, and improving energy efficiency can help achieve this.
In simple words: We can control the greenhouse effect by making less harmful gases like \( CO_2 \) and \( CH_4 \), using clean energy, and planting more trees.

🎯 Exam Tip: Focus on key actions like reducing emissions, promoting renewable energy, and afforestation as methods to control the greenhouse effect.

 

Question 4. what is atmosphere?
Answer: The atmosphere is the layer of air that surrounds the Earth, extending up to about 800 to 1000 km in height. It consists of various gases. The air in the lower part of the atmosphere is heavy and dense, while the air in the upper layers becomes lighter.
In simple words: The atmosphere is the blanket of air around Earth, made of different gases, with heavier air near the ground and lighter air higher up.

🎯 Exam Tip: Define the atmosphere by its composition (air/gases) and its general vertical structure (density variation).

 

Question 5. Define Ozone layer.
Answer: The ozone layer is a region within the Earth's stratosphere, located at a height of about 15 to 30 km (or 12 to 35 km). Approximately 90% of the atmospheric ozone \( (O_3) \) resides in this layer. It is vital for protecting life on Earth by absorbing harmful ultraviolet (UV) radiation from the Sun.
In simple words: The ozone layer is a part of the air high above Earth that stops dangerous sun rays from reaching us.

🎯 Exam Tip: State the location (stratosphere), key component (ozone, \( O_3 \)), and primary function (UV protection) when defining the ozone layer.

 

Question 6. What are the adverse effects of green house effect?
Answer: The adverse effects of an intensified greenhouse effect, leading to global warming, include:

• **Global Temperature Increase**: The overall temperature of the Earth will rise significantly.
• **Extreme Weather**: This will cause more heavy rains and floods in coastal areas and severe droughts in regions that usually get average rainfall.
• **Sea Level Rise**: Polar ice will melt, leading to an increase in sea level, which could submerge coastal regions.
• **Impact on Agriculture and Fisheries**: There will be a decrease in the production of crops and fish, especially in countries like India and other developing nations.

In simple words: Bad effects of the greenhouse effect include hotter temperatures, more floods and droughts, rising sea levels, and less food from farming and fishing.

🎯 Exam Tip: When discussing adverse effects, remember to cover climate-related changes (temperature, rainfall, sea level) and their consequences on ecosystems and human activities.

 

Question 7. Define stratosphere.
Answer: The stratosphere is the second lowest layer of Earth's atmosphere, situated above the troposphere and extending roughly from 12 km to 50 km in height. The troposphere and stratosphere are separated by a boundary called the tropopause. The stratosphere is important because it contains the ozone layer, which protects life on Earth from harmful ultraviolet radiation.
In simple words: The stratosphere is the second layer of Earth's air, found above the troposphere, and it contains the ozone layer.

🎯 Exam Tip: Key points for defining the stratosphere are its position relative to the troposphere, its height range, and the presence of the ozone layer.

 

Question 8. How Ozone layer protects from the U-V rays of Sun.
Answer: The ozone layer protects Earth by absorbing dangerous cosmic rays and ultraviolet (UV) rays from the Sun. This absorption prevents these harmful radiations from reaching the Earth's surface, thereby protecting the lives of animals, humans, and plants.
In simple words: The ozone layer stops harmful cosmic and UV rays from the sun, which keeps living things on Earth safe from radiation damage.

🎯 Exam Tip: Explain the protection mechanism: the ozone layer *absorbs* (not reflects) harmful UV and cosmic rays.

 

Question 9. Explain in brief the El-Nino effect.
Answer: The El-Nino effect is a natural weather phenomenon first named by South American fishermen in 1960. The name "El Nino" is Spanish for "The little boy" or "Christ Child," chosen because these warm water events often occur around December, near Christmas. It involves unusual warming of ocean surface waters in the eastern Pacific Ocean, off the coast of South America, which affects global weather patterns.
In simple words: El Nino is when the ocean water near South America gets unusually warm around Christmas time, changing weather around the world.

🎯 Exam Tip: Include the origin of the name, its timing, and the specific geographical area (eastern Pacific) affected by warm ocean waters.

 

Question 10. Write the Main factors causing Ozone depletion.
Answer: The main factors causing ozone depletion are:

• **CFCs and Related Compounds**: Chlorofluorocarbons (CFCs), Chlorobromocarbons (CBCs), and Bromofluorocarbons (BFCs), collectively known as Freons, are highly volatile organic compounds. They are used in refrigeration, aerosols, foam production, and cleaning industrial machines. These compounds release chlorine radicals that destroy many ozone molecules. For example:
  \( CFCl_3 \xrightarrow{Radiation} CFCl_2 + Cl \)
  \( Cl + O_3 \implies ClO + O_2 \)
  \( ClO + O_3 \implies 2O_2 + Cl \)
• **Jet Aeroplanes**: Jet planes flying high in the stratosphere release air and other pollutants that harm the ozone.
• **Nuclear Blasts**: Nuclear explosions also contribute to ozone damage.
• **Deforestation**: Reduced forest cover contributes to \( CO_2 \) increase, which can indirectly affect stratospheric conditions.
• **Sulfur Oxides and Hydrochloric Acid**: Pollutants like sulfur oxides \( (SO_2, SO_3) \) and hydrochloric acid \( (HCl) \) can also destroy ozone.

In simple words: Ozone gets thinner mainly because of chemicals like CFCs from fridges and sprays, pollution from jet planes, nuclear blasts, cutting down trees, and other harmful acids in the air.

🎯 Exam Tip: Focus on CFCs and their breakdown products (chlorine radicals) as the primary chemical culprits, and also mention other major contributors like jet emissions and deforestation.

 

Question 11. Define El-Nino effect.
Answer: The El Nino effect refers to the unusual warming of sea currents in the Pacific Ocean near the equator, off the coast of South America. This phenomenon occurs when the normal trade winds weaken, allowing warm surface water to flow towards the east. This shift in ocean temperature greatly affects the environment and global weather patterns.
In simple words: El Nino is when the ocean water near the equator in the Pacific gets warmer than usual, changing sea currents and affecting weather around the world.

🎯 Exam Tip: Emphasize the warming of equatorial Pacific waters and the weakening of trade winds as the defining characteristics of El Nino.

 

Question 12. What are the main reasons of atmospheric heating?
Answer: The main reason for atmospheric heating is the increase in carbon dioxide \( (CO_2) \) in the atmosphere, which intensifies the greenhouse effect. As a result, the average temperature of the atmosphere rises, a phenomenon known as global warming. This excess trapping of heat leads to an overall warming of our planet.
In simple words: The air gets hotter mainly because more carbon dioxide in the atmosphere traps too much heat, causing global warming.

🎯 Exam Tip: Directly link atmospheric heating to the increased concentration of greenhouse gases, especially CO2, and the resulting enhanced greenhouse effect.

RBSE Class 11 Biology Chapter 42 Essay Type Questions

 

Question 1. Define green house effect. Write its adverse effects and how to control it?
Answer:
**Definition of Greenhouse Effect:**
A greenhouse is a structure, often made of glass, where plants are grown, and its inside stays warmer than the outside air due to trapped sunlight. Similarly, the Earth's atmosphere acts like a natural greenhouse. It contains various gases, such as Carbon Dioxide \( (CO_2) \), Methane \( (CH_4) \), Nitrous Oxide \( (N_2O) \), Chlorofluorocarbons (CFCs), and water vapor. These "greenhouse gases" absorb heat radiation emitted from the Earth's surface after it's warmed by the sun. This process traps heat, leading to a specific atmospheric temperature that keeps our planet warm enough to support life. This natural warming phenomenon is called the greenhouse effect.

The Earth's atmosphere extends up to 800-1000 km, but a dense covering up to 30 km is most relevant. The atmosphere is a mixture of gases, primarily 78% Nitrogen and 21% Oxygen.

**Causes of Enhanced Greenhouse Effect:**
The continuous increase in greenhouse gases, especially \( CO_2 \) (which contributes about 60% to the greenhouse effect), is mainly due to:

• **Deforestation**: Green plants use \( CO_2 \) for photosynthesis. Rapid cutting down of forests means less \( CO_2 \) is removed from the air, causing its levels to increase. Combustion of forests also adds to \( CO_2 \) emissions.
• **Burning of Fossil Fuels**: Burning coal, wood, and other fossil fuels releases large amounts of \( CO_2 \).
• **Industrialization and Vehicles**: Growing industries and the increasing number of motor vehicles are major sources of \( CO_2 \) and other greenhouse gases.

**Adverse Effects of Greenhouse Effect (Global Warming):**
An increase in atmospheric \( CO_2 \) leads to a rise in the Earth's average temperature, known as global warming. This has several serious negative effects:

• **Temperature Rise**: The global temperature will continue to increase, potentially by 3.6°C by 2100.
• **Extreme Weather Events**: This leads to more intense rainfall and floods in coastal areas, and severe droughts in regions that typically receive moderate rainfall. It can also cause cyclones and hurricanes.
• **Melting Glaciers and Sea Level Rise**: Significant melting of glaciers will cause sea levels to rise, submerging low-lying cities, marshlands, and islands.
• **Impact on Agriculture and Fisheries**: Agricultural productivity, especially rice, and fish production will decrease, affecting food security, particularly in developing countries.
• **Health Issues**: Rising temperatures can lead to epidemics.
• **Ecological Imbalance**: There will be changes in rainfall and vegetation patterns, severely disrupting ecosystems.

**How to Control the Greenhouse Effect:**
Controlling the greenhouse effect primarily involves reducing the release of greenhouse gases. Key measures include:

• Reducing the production and use of fossil fuels.
• Promoting renewable energy sources like solar and wind power.
• Increasing forest cover through extensive tree-planting (afforestation).
• Improving energy efficiency in homes, industries, and transportation.
• Developing technologies that capture carbon emissions.

In simple words: The greenhouse effect is when certain gases in the air trap the sun's heat, keeping Earth warm. But too many of these gases, mainly from cutting trees and burning fuels, make Earth too hot (global warming). This causes big problems like floods, droughts, and melting ice. To fix it, we need to use less harmful gases and plant more trees.

🎯 Exam Tip: For essay questions, provide a clear definition, list distinct causes, detail the adverse effects, and suggest control measures. Use bullet points for clarity and include a relevant diagram if applicable.

 

Question 2. Write the adverse effects of depletion in Ozone and how it can be controlled?
Answer:
**Ozone Layer and Depletion:**
Ozone \( (O_3) \) is a gas found mainly in the stratosphere, about 15 to 30 km above Earth. This ozone layer is crucial because it absorbs harmful cosmic and ultraviolet (UV) radiation from the sun, protecting life on Earth. However, the ozone layer is getting thinner in many places, a process called ozone depletion. This thinning is sometimes called an "ozone hole," which means a big drop in ozone concentration, not an actual hole. For example, a significant depletion of 70% was reported over Antarctica in 1985, leading to the "Ozone hole" there.

**Factors Responsible for Ozone Depletion:**
The primary factors causing ozone depletion are:

• **Chlorofluorocarbons (CFCs)**: These are highly volatile chemicals used in refrigerators, aerosols, foam-making, and industrial cleaning. CFCs release chlorine radicals when exposed to radiation. These radicals then react with and destroy ozone molecules in a chain reaction:
  \( CFCl_3 \xrightarrow{Radiation} CFCl_2 + Cl \)
  \( Cl + O_3 \implies ClO + O_2 \)
  \( ClO + O_3 \implies 2O_2 + Cl \)
• **Other Harmful Chemicals**: Chlorobromocarbons (CBCs) and Bromofluorocarbons (BFCs) also contribute to ozone destruction.
• **Jet Aeroplanes**: Jet aircraft flying in the stratosphere release pollutants that harm the ozone.
• **Nuclear Blasts**: Nuclear explosions can also damage the ozone layer.
• **Sulfur Oxides and Hydrochloric Acid**: Industrial emissions like sulfur oxides \( (SO_2, SO_3) \) and hydrochloric acid \( (HCl) \) contribute to ozone destruction.

**Adverse Effects of Ozone Depletion:**
The thinning of the ozone layer allows more harmful UV radiation to reach Earth, causing severe problems:

• **Health Impacts**: Increases the risk of skin cancer and cataracts (clouding of the eye lens) in humans and animals.
• **Agricultural Damage**: Reduces the production of vital crops, such as rice, impacting food supplies.
• **Marine Ecosystems**: Disrupts marine food chains by harming small organisms like phytoplankton, which are the base of the food web.
• **Immune System Damage**: Weakens the immune systems of living organisms.

**How to Control Ozone Depletion:**
Controlling ozone depletion involves global efforts to reduce the release of ozone-destroying substances:

• **Phasing out CFCs and Halons**: Completely stop the production and use of CFCs, halons, and other ozone-depleting substances (ODS) in all industries.
• **Developing Alternatives**: Use ozone-friendly alternatives in refrigeration, aerosols, and fire suppression.
• **International Agreements**: Implement and strengthen international agreements like the Montreal Protocol, which aims to reduce ODS emissions.
• **Public Awareness**: Educate people about the dangers of ozone depletion and how they can contribute to protecting the ozone layer.

In simple words: The ozone layer protects us from bad sun rays, but chemicals like CFCs and pollution are making it thin. This causes skin cancer, eye problems, and harms plants and sea life. To control it, we must stop using these harmful chemicals and protect the atmosphere.

🎯 Exam Tip: Clearly define ozone depletion, list specific chemical and physical causes, outline adverse health and environmental effects, and suggest concrete control measures like phasing out CFCs.

 

Question 3. Write about global warming.
Answer: Global warming refers to the long-term heating of Earth's climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere. The primary reason for this atmospheric heating is the continuous increase of carbon dioxide \( (CO_2) \) and other greenhouse gases, which enhance the natural greenhouse effect. As a result, the average temperature of the atmosphere rises significantly.

**Impacts of Global Warming:**
This increase in temperature causes many problems globally:

• **Melting Ice and Sea Level Rise**: A key impact is the significant melting of glaciers and polar ice caps. The water from this melting flows into the oceans, causing sea levels to rise. This threatens to submerge low-lying coastal areas, wetlands, and islands.
• **Changes in Rainfall Patterns**: Global warming alters the distribution of rainfall. Some regions may experience heavier rains and more floods, while others face prolonged droughts, impacting agriculture and water availability.
• **Extreme Weather Events**: It leads to more frequent and intense heatwaves, storms, and other extreme weather phenomena.
• **Ecosystem Disruption**: Changes in temperature and climate patterns disrupt ecosystems, affecting plant growth and animal habitats, and potentially leading to species extinction.

Controlling the increase in \( CO_2 \) and other greenhouse gases is essential to prevent further global temperature increases and avoid very serious and negative environmental effects.
In simple words: Global warming means the Earth is getting hotter because too much carbon dioxide and other gases trap heat. This causes ice to melt, sea levels to rise, and weather patterns to change, leading to floods, droughts, and harm to nature. We must reduce these gases to stop it.

🎯 Exam Tip: Explain global warming as a rise in Earth's average temperature due to greenhouse gas increase. Describe its major impacts (ice melt, sea level rise, extreme weather) and the urgent need for control.

 

Question 4. Explain El-Nino effect.
Answer: The El Nino effect is a significant weather phenomenon characterized by the unusual warming of sea surface temperatures in the central and eastern tropical Pacific Ocean. This event was first named by South American fishermen in 1960. The term "El Nino" is Spanish for "The little boy" or "Christ Child," chosen because these warm water events often appear around December, close to Christmas.

**How El Nino Occurs and Its Effects:**
Normally, strong trade winds blow warm surface water westward across the Pacific. However, during an El Nino, these trade winds weaken. This allows the warm water in the western Pacific to move eastward, creating unusually warm ocean conditions off the coast of South America.

This shift in ocean temperatures profoundly affects global weather patterns and ecosystems:

• **Rainfall Changes**: Regions that usually receive regular rainfall might experience droughts, while areas typically dry may see increased rainfall and floods. For example, during April to October, regions affected by El Nino often experience increased rainfall.
• **Marine Life Impact**: The warmer water during El Nino years lacks the nutrients found in cooler waters. This nutrient-poor water starves the bottom of the marine food chain, leading to a decline in fish populations and affecting larger marine animals.
• **Droughts and Bushfires**: El Nino can cause severe droughts in regions like the western Pacific (e.g., Australia), which can lead to dangerous bushfires.

In simple words: El Nino is when the ocean water in the Pacific near the equator gets much warmer than usual, often around Christmas. This happens because the normal winds get weak. It changes weather worldwide, causing floods, droughts, and harming ocean life.

🎯 Exam Tip: Explain El Nino by describing the warming of Pacific waters and the weakening of trade winds. Detail its environmental impacts, focusing on climate shifts and effects on marine ecosystems.