Question 1

Which of the following ecosystems is characterized by the presence of mangrove forests and serves as a nursery ground for many marine species?

Accepted Answer

Mangrove ecosystems are found in coastal areas and are characterized by salt-tolerant trees with aerial root systems. They serve as critical nursery grounds for fish, crustaceans, and other marine organisms, and provide protection from storms and coastal erosion.

Question 2

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

Accepted Answer

Photosynthesis is the biochemical process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in glucose (C₆H₁₂O₆). The simplified equation is: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Question 3

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. This is why CFCs were banned under the Montreal Protocol (1987).

Question 4

The Montreal Protocol (1987) was primarily designed to protect the environment by phasing out which harmful substance?

Accepted Answer

The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out chlorofluorocarbons (CFCs) and other ozone-depleting substances. CFCs were commonly used in refrigerants, aerosols, and foam production.

Question 5

Which of the following is an example of a renewable energy source that does not produce greenhouse gas emissions?

Accepted Answer

Solar energy is a renewable energy source derived from the sun's radiation. It does not produce greenhouse gas emissions during operation and is sustainable for long-term use. Other examples include wind, hydroelectric, and geothermal energy.

Question 6

Which of the following is the primary greenhouse gas responsible for climate change, and what is its approximate concentration in the atmosphere as of 2024?

Accepted Answer

Carbon dioxide (CO₂) is the primary anthropogenic greenhouse gas driving climate change. As of 2024, atmospheric CO₂ concentration has exceeded 420 ppm (parts per million), a level not seen in over 800,000 years. This increase is primarily due to fossil fuel combustion and deforestation.

Question 7

Which of the following is classified as a 'keystone species' in ecosystem ecology?

Accepted Answer

A keystone species is an organism whose presence has a disproportionately large effect on its ecosystem relative to its abundance. The removal of a keystone species can lead to significant ecosystem collapse. Sea otters are a classic example—they control sea urchin populations, which prevents overgrazing of kelp forests.

Question 8

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

Accepted Answer

Carbon dioxide (CO₂) is the primary anthropogenic greenhouse gas driving climate change. As of 2024, atmospheric CO₂ concentration has exceeded 420 ppm (parts per million), having risen from pre-industrial levels of ~280 ppm. This increase is primarily due to fossil fuel combustion, deforestation, and industrial processes. While methane and nitrous oxide are potent greenhouse gases, CO₂ is the most abundant and has the longest atmospheric residence time, making it the primary driver of sustained global warming.

Question 9

Which of the following is the primary cause of eutrophication in freshwater ecosystems?

Accepted Answer

Eutrophication is the process of nutrient enrichment (primarily nitrogen and phosphorus) in water bodies, leading to excessive algal growth, oxygen depletion, and ecosystem degradation. The primary causes are agricultural runoff (fertilizers), sewage discharge, and industrial effluents containing high levels of nitrogen and phosphorus.

Question 10

The process by which nitrogen is converted from atmospheric N₂ to ammonia (NH₃) by certain microorganisms is called:

Accepted Answer

Nitrogen fixation is the biochemical process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or other nitrogen compounds that can be utilized by plants and animals. This process is carried out by nitrogen-fixing bacteria (e.g., Rhizobium, Azotobacter) and cyanobacteria.

Question 11

The Montreal Protocol (1987) was primarily designed to address which environmental issue?

Accepted Answer

The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out ozone-depleting substances (ODS) such as chlorofluorocarbons (CFCs), halons, and other chemicals. It is considered one of the most successful environmental agreements globally.

Question 12

Which of the following biogeochemical cycles is primarily driven by bacterial denitrification, converting nitrates back into atmospheric nitrogen?

Accepted Answer

The nitrogen cycle involves multiple stages: nitrogen fixation (N₂ → NH₃), nitrification (NH₃ → NO₃⁻), and denitrification (NO₃⁻ → N₂). Denitrification is the process by which anaerobic bacteria (such as Pseudomonas and Bacillus) reduce nitrates to nitrogen gas, returning it to the atmosphere. This is a critical step that completes the cycle and prevents excessive nitrogen accumulation in soil and water bodies.

Question 13

The Montreal Protocol (1987) was primarily designed to address the depletion of which atmospheric layer and the resulting increase in which type of radiation reaching Earth's surface?

Accepted Answer

The Montreal Protocol was designed to protect the stratospheric ozone layer from depletion caused by chlorofluorocarbons (CFCs) and other ozone-depleting substances. The depletion of the ozone layer results in increased ultraviolet (UV) radiation, specifically UV-B radiation, reaching Earth's surface, which causes skin cancer, cataracts, and immune system damage.

Question 14

The process of eutrophication in aquatic ecosystems is primarily caused by excessive input of which nutrient(s), and what is the immediate ecological consequence?

Accepted Answer

Eutrophication is primarily caused by excessive input of nitrogen (N) and phosphorus (P) from agricultural runoff, sewage, and industrial discharge. The immediate ecological consequence is excessive algal growth (algal bloom), which leads to oxygen depletion (hypoxia) when the algae decompose, creating 'dead zones' where most aquatic life cannot survive.

Question 15

Which of the following is the primary mechanism by which invasive species reduce native biodiversity, and what is the term for the ecological role that a species occupies within its environment?

Accepted Answer

The primary mechanism by which invasive species reduce native biodiversity is through competitive exclusion (outcompeting native species for resources such as food, water, and habitat space). The ecological role that a species occupies is called its 'niche.' Invasive species often have broader niches or superior competitive abilities, allowing them to exclude native species from their ecological niches.

SSC CPO Environment & Ecology

Environment & Ecology— Rules & Concept

Key Points to Remember

Exam-Specific Tips

Environment & Ecology — Practice Questions

60-Second Revision — Environment & Ecology