Question 1

Which of the following gases is primarily responsible for the greenhouse effect and contributes most to global warming?

Accepted Answer

Carbon dioxide (CO₂) is the primary greenhouse gas responsible for global warming. It accounts for approximately 75% of global greenhouse gas emissions and has a long atmospheric lifetime of 300-1000 years, making it the most significant driver of climate change.

Question 2

Which of the following is the primary cause of ozone layer depletion in the stratosphere?

Accepted Answer

Chlorofluorocarbons (CFCs) are the primary cause of ozone layer depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms that catalytically destroy ozone molecules. One chlorine atom can destroy up to 100,000 ozone molecules.

Question 3

The process by which plants convert sunlight into chemical energy stored in glucose is called:

Accepted Answer

Photosynthesis is the biochemical process in which plants, algae, and some bacteria use sunlight, water, and carbon dioxide to produce glucose and oxygen. The simplified equation is: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Question 4

Which of the following is an example of a renewable energy source?

Accepted Answer

Solar energy is a renewable energy source derived from the sun's radiation. It can be harnessed using photovoltaic cells or solar thermal systems and is inexhaustible on human timescales, unlike fossil fuels which are finite.

Question 5

Which of the following best describes the process of photosynthesis?

Accepted Answer

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy (from the sun) into chemical energy stored in glucose, using carbon dioxide and water, and releasing oxygen as a byproduct.

Question 6

The layer of the Earth's atmosphere closest to the surface where weather occurs is called:

Accepted Answer

The troposphere is the lowest layer of Earth's atmosphere, extending approximately 8-18 km above the surface (lower at poles, higher at equator). It contains 80% of atmospheric mass and is where all weather phenomena occur, including clouds, rain, and wind.

Question 7

The term 'biodiversity' refers to:

Accepted Answer

Biodiversity refers to the variety of all living organisms and ecosystems on Earth, encompassing genetic diversity (within species), species diversity (different species), and ecosystem diversity (different habitats and ecological communities).

Question 8

Which of the following is an example of a biodegradable waste?

Accepted Answer

Food waste (vegetable peels, fruit scraps, leftover food) is biodegradable waste that can be decomposed by microorganisms into simpler substances within a reasonable time period (weeks to months). Other examples include paper, wood, and plant matter.

Question 9

Which of the following is the primary greenhouse gas responsible for global warming, and what is its approximate concentration in the Earth's atmosphere as of 2024?

Accepted Answer

Carbon dioxide (CO₂) is the primary anthropogenic greenhouse gas driving climate change. Its atmospheric concentration has exceeded 420 ppm as of 2024, up from pre-industrial levels of ~280 ppm. While methane and nitrous oxide are also greenhouse gases, CO₂ is the most abundant and persistent, making it the primary driver of long-term global warming.

Question 10

Which of the following is a renewable source of energy?

Accepted Answer

Renewable energy sources are those that can be replenished naturally and sustainably. Solar, wind, hydroelectric, geothermal, and biomass are renewable sources, while coal, petroleum, and natural gas are non-renewable fossil fuels.

Question 11

Which of the following is the primary cause of acid rain?

Accepted Answer

Acid rain is primarily caused by the emission of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) from burning fossil fuels. These gases react with water vapor in the atmosphere to form sulfuric and nitric acids.

Question 12

Which of the following gases is primarily responsible for the greenhouse effect and contributes most to global warming?

Accepted Answer

Carbon dioxide (CO₂) is the primary greenhouse gas responsible for global warming. It accounts for approximately 75% of total greenhouse gas emissions and has a long atmospheric lifetime of 300-1000 years, making it the most significant driver of climate change.

Question 13

The process by which plants convert sunlight into chemical energy stored in glucose is called:

Accepted Answer

Photosynthesis is the biochemical process in which plants, algae, and some bacteria use sunlight, water, and carbon dioxide to produce glucose and oxygen. The equation is: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Question 14

Which of the following is a renewable source of energy?

Accepted Answer

Solar energy is a renewable source because the sun continuously provides energy through radiation, and this resource will not be depleted for billions of years. Other renewable sources include wind, hydroelectric, geothermal, and biomass energy.

Question 15

What is the term used to describe the variety of all living organisms and their genetic diversity within a given ecosystem?

Accepted Answer

Biodiversity refers to the variety of all living organisms (plants, animals, microorganisms) and their genetic diversity within ecosystems. It encompasses species diversity, genetic diversity, and ecosystem diversity.

Question 16

Which of the following is the primary cause of acid rain in industrial regions?

Accepted Answer

Sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) from fossil fuel combustion are the primary causes of acid rain. SO₂ is released from coal and oil burning in power plants and industries. These gases dissolve in atmospheric water vapor to form sulfuric and nitric acids, with pH often <4.0.

Question 17

Which of the following gases is primarily responsible for the depletion of the ozone layer in the Earth's stratosphere?

Accepted Answer

Chlorofluorocarbons (CFCs) are the primary culprits in ozone layer depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms that catalytically destroy ozone molecules. One chlorine atom can destroy up to 100,000 ozone molecules.

Question 18

Which of the following is the primary source of nitrogen fixation in terrestrial ecosystems?

Accepted Answer

Nitrogen-fixing bacteria, particularly those in the genus Rhizobium (found in root nodules of legumes) and free-living bacteria like Azotobacter, are the primary sources of nitrogen fixation. These bacteria convert atmospheric N₂ into ammonia (NH₃), making nitrogen available to plants.

Question 19

Which of the following is the primary cause of eutrophication in freshwater lakes and water bodies?

Accepted Answer

Eutrophication is primarily caused by excess nutrients, particularly nitrogen and phosphorus, from agricultural runoff, sewage discharge, and detergents. These nutrients trigger excessive algal growth (algal bloom), which depletes oxygen and creates dead zones.

Question 20

Which of the following international agreements is specifically focused on protecting the ozone layer?

Accepted Answer

The Montreal Protocol (1987) is the international treaty designed to protect the ozone layer by phasing out ozone-depleting substances (CFCs, halons, etc.). It is considered one of the most successful environmental agreements, with near-universal ratification.

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