Ecology in India and around World is important part of environment and its syllabus. Previous Year Question (PYQ) papers are invaluable resources for aspirants preparing for competitive exams like the Union Public Service Commission (UPSC) examinations. In this article we present important PYQ on ecology.
PYQ on Ecology
Q- In the case of which of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrients to enter the cycle? (2021)
(a) Carbon cycle
(b) Nitrogen cycle
(c) Phosphorus cycle
(d) Sulphur cycle
Answer- Option C
EXPLANATION
The carbon and nitrogen cycles are categorized as gaseous cycles, with the atmosphere and hydrosphere serving as the primary reservoirs for nutrients. In the sulfur cycle, nutrients are released through processes such as rock weathering, erosional runoff, and organic matter decomposition. While the sulfur cycle is predominantly sedimentary, two of its compounds, hydrogen sulfide (H2S) and sulfur dioxide (SO2), introduce a gaseous component to its typical sedimentary cycle.
As for the phosphorus cycle, nutrients are mainly released through rock weathering since phosphorus primarily exists as a mineral in phosphate rocks. It enters the cycle through erosion and mining activities.
Q- What is blue carbon? (2021)
(a)Carbon captured by oceans and coastal ecosystems
(b) Carbon sequestered in forest biomass and agricultural soils
(c) Carbon contained in petroleum and natural gas
(d) Carbon present in the atmosphere
Answer- Option A
EXPLANATION
Blue Carbon refers to carbon storage in coastal, aquatic, and marine environments, encompassing vegetation, marine organisms, and sediments. Coastal ecosystems like mangroves, tidal marshes, and seagrass meadows accumulate significant carbon deposits over long periods through natural processes. These ecosystems are known to sequester and retain more carbon, often termed “blue carbon,” per unit area compared to terrestrial forests. Due to their capacity to absorb carbon dioxide from the atmosphere, these vegetated ecosystems serve as substantial net carbon sinks and are increasingly acknowledged for their role in mitigating climate change.
Q- Biological Oxygen Demand (BOD) is a standard criteria for (2017)
(a) Measuring oxygen level in blood
(b) Computing oxygen levels in forest ecosystems
(c) Pollution assay in aquatic ecosystem
(d) Assessing oxygen levels in high altitude regions
Answer- Option C
EXPLANATION
Biological Oxygen Demand (BOD) refers to the quantity of dissolved oxygen required by aerobic biological organisms to decompose organic matter in a particular water sample within a specified timeframe and temperature. It serves as a common metric in wastewater treatment facilities and serves as an indicator of the level of organic pollution present in water bodies.
Q- In which of the following regions of India are you most likely to come across the `Great Indian Hornbill’ in its natural habitat? (2016)
(a) Sand deserts of northwest India
(b) Higher Himalayas of Jammu and Kashmir
(c) Salt marshes of western Gujarat
(d) Western Ghats
Answer- Option D
EXPLANATION
The Great Indian hornbill inhabits forested regions across Nepal, India, Mainland Southeast Asia, and Sumatra. This species is categorized as Vulnerable on the IUCN Red List of Threatened Species and is included in Schedule I of the Wildlife Protection Act of India. Additionally, Great Hornbills are present in three distinct areas within South Asia: the Western Ghats, the Himalayan foothills spanning from Uttaranchal to southern Nepal, Bhutan, and northeastern India.
Q- Recently, for the first time in our country, which of the following States has declared a particular butterfly as ‘State Butterfly’? (2016)
(a) Arunachal Pradesh
(b) Himachal Pradesh
(c) Karnataka
(d) Maharashtra
Answer- Option D
EXPLANATION
Maharashtra has become the first state in the country to have a state butterfly, Blue Mormon. Blue Mormon, the second largest butterfly found in India.
Q- Which one of the following is the best description of the term “ecosystem”? (2015)
(a) A community of organisms interacting with one another
(b) That part of the Earth which is inhabited by living organisms
(c) A community of organisms together with the environment in which they live
(d) The flora and fauna of a geographical area
Answer- Option C
EXPLANATION
An ecosystem encompasses the interplay between living and nonliving components within a specific environment. Various types of ecosystems exist, including terrestrial ecosystems, forest ecosystems, grassland ecosystems, desert ecosystems, tundra ecosystems, freshwater ecosystems, and marine ecosystems.
Q- The term ‘Goldilocks Zone’ is often seen in the news in the context of (2015)
(a) the limits of habitable zone above the surface of the Earth
(b) regions inside the Earth-like planets in outer space
(c) search for the Earth-like planets in outer space
(d) search for meteorites containing precious metals
Answer- Option C
EXPLANATION
In astronomy and astrobiology, the circumstellar habitable zone (CHZ), often referred to as the Goldilocks Zone, is the orbital region around a star where conditions are suitable for the existence of liquid water on the surface of planetary-mass objects, given adequate atmospheric pressure.
This zone, also known as the habitable zone, represents a range of distances from a star where temperatures are conducive to maintaining liquid water.
Q- Which of the following phenomena might have influenced the evolution of organisms? (2014)
- Continental drift
- Glacial cycles
Select the correct answer using the code given below.
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- Option C
EXPLANATION
The theory of continental drift pertains to the arrangement of landmasses and oceans. It suggests that all continents were once part of a single supercontinent known as Pangaea, surrounded by a vast ocean called Panthalassa.
Over time, Pangaea split into two major landmasses – Laurasia and Gondwanaland, constituting the northern and southern segments respectively. Subsequent fragmentation led to the formation of smaller continents as observed today. This movement likely facilitated the migration of certain species between continents, influencing their evolutionary paths.
Additionally, glacial cycles could have impacted evolution by causing extinctions among species unable to withstand extreme cold, as well as by altering sea levels due to glacial melt, thereby affecting organisms’ habitats.
Q- Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth? (2014)
- Volcanic action
- Respiration
- Photosynthesis
- Decay of organic matter
Select the correct answer using the code given below.
(a) 1 and 3 only
(b) 2 only
(c) 1, 2 and 4 only
(d) 1, 2,3 and 4
Answer- Option C
EXPLANATION
Photosynthesis is a biological process in which carbon dioxide is absorbed and oxygen is released, thus contributing to the reduction of carbon dioxide in the atmosphere. Therefore, Statement 3 is incorrect.
Volcanic activity releases carbon dioxide into the atmosphere.
Respiration involves the intake of oxygen and the release of carbon dioxide by cells, while decomposition also results in the release of carbon dioxide.
Q- Which one of the following is the process involved in photosynthesis? (2014)
(a) Potential energy is released to form free energy
(b) Free energy is converted into potential energy and stored
(c) Food is oxidized to release carbon dioxide and water.
(d) Oxygen is taken, and carbon dioxide and water vapour are given out
Answer- Option B
EXPLANATION
Photosynthesis is the biological process whereby green plants and certain other organisms harness light energy to convert carbon dioxide and water into glucose and oxygen gas. This process effectively stores light energy in the form of chemical bonds within glucose molecules. When these bonds are broken through cellular respiration, the stored energy is released as kinetic energy. Consequently, options 2, 3, and 4 are clarified.
Q- In the grasslands, trees do not replace the grasses as a part of an ecological succession because of (2013)
(a) insects and fungi
(b) limited sunlight and paucity of nutrients
(c) water limits and fire
(d) None of the above
Answer- Option C
EXPLANATION
Grasses are not replaced by trees in ecological succession because trees demand more water than grasses, potentially causing water scarcity for other species. Additionally, trees are susceptible to catching fire, and such fires can spread rapidly. Consequently, trees do not supplant grasses as part of ecological succession, which refers to the change in species composition within an ecological community over time.
Q- Which one of the following is the correct sequence of ecosystems in the order of decreasing productivity? (2013)
(a) Oceans, lakes, grasslands, mangroves
(b) Mangroves, oceans, grasslands, lakes
(c) Mangroves, grasslands, lakes, oceans
(d) Oceans, mangroves, lakes, grasslands
Answer- Option C
EXPLANATION
The proportion of energy entering an ecosystem in the form of biomass at a specific trophic level is referred to as ecosystem productivity. Ecosystem productivity is classified into two main categories: primary productivity and secondary productivity.
Primary productivity involves the generation of biomass by autotrophs, which include both photoautotrophs and chemoautotrophs. It is further divided into gross primary productivity (GPP) and net primary productivity (NPP), where NPP represents the energy retained after accounting for losses.
Secondary productivity, on the other hand, pertains to the biomass accumulation among heterotrophs, such as herbivores. These organisms obtain biomass from plants and transfer a portion of it to subsequent trophic levels. Productivity is measured as mass per unit volume per unit time.
Ocean productivity averages around 50 grams of carbon per square meter per year, while land productivity averages about 160 grams of carbon per square meter per year. Open ocean productivity is similar to that of desert regions.
Q- With reference to food chains in ecosystems, consider the following statements : (2013)
- A food chain illustrates the order in which a chain of organisms feed upon each other
- Food chains are found within the populations of a species
- A food chain illustrates the numbers of each organism which are eaten by others
Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 2 only
(c) 1, 2 and 3
(d) None
Answer- Option A
EXPLANATION
A food chain represents the transfer of food energy from producers, such as green plants, through a series of organisms that eat and are eaten by each other. Each step in the food chain is termed a trophic level, and it starts with producers and ends with top carnivores. The position an organism occupies in a food chain is its trophic level.
Food chains depict the sequential feeding relationships among organisms. Therefore, statement 1 accurately describes the concept of a food chain. However, statement 2 is incorrect because food chains represent inter-species relationships, not relationships within a single population.
Similarly, statement 3 is inaccurate because food chains illustrate the sequence of organisms being consumed, not the specific quantities consumed, which is depicted in a food web.
Q- Which of the following adds/add nitrogen to the soil? (2013)
- Excretion of urea by animals
- Burning of coal by man
- Death of vegetation
Select the correct answer using the codes given below.
(a) 1 only
(b) 2 and 3 only
(e) 1 and 3 only
(d) 1, 2 and 3
Answer- Option C
EXPLANATION
When coal undergoes combustion, nitrogen contributes to the formation of oxides, which can be released as flue gases, leading to atmospheric pollution. However, nitrogen does not directly add to the soil unless these oxides enter the nitrogen cycle. After coal combustion, what remains is fly ash, which lacks nitrogen content. Therefore, statement 2 is inaccurate.
Conversely, nitrogenous waste products from living organisms, such as urea and uric acid, as well as dead organic matter, are decomposed by bacteria, converting them back into inorganic ammonia. Hence, statements 1 and 3 are correct.
Q- Which one of the following terms describes not only the physical space occupied by an organism but also its functional role in the community of organisms? (2013)
(a) Ecotone
(b) Ecological niche
(c) Habitat
(d) Home range
Answer- Option B
EXPLANATION
An ecological niche pertains to the distinct functional role and position occupied by a species within its habitat or ecosystem. It encompasses the functional attributes exhibited by a species within its environment, commonly known as its “niche.”
Also read about UPSC PYQ on Biodiversity.