Q1. Which of the following best defines an ecosystem?
Environmental and Ecological Changes and Impact Assessment: RAS Prelims MCQs
168 RAS Prelims MCQs on environmental and ecological changes and impact assessment cover ecosystem concepts, pollution, climate and environmental law. Ecotones, decomposers, primary productivity, secondary pollutants, the greenhouse effect, the EIA Notification 2006, the Environment (Protection) Act 1986 and the Aravalli mining ban are asked as definitions, laws and statements.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
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Q2. Which among the following is not classified as an abiotic component of an ecosystem?
Explanation
Abiotic components are the non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Examples include temperature, sunlight, and minerals. In contrast, organisms that break down organic matter are biological entities. These life forms belong to the biotic category, playing a vital role in recycling nutrients by consuming dead plants and animals.
Q3. What is an ecotone in the context of ecosystems?
Explanation
An ecotone serves as a boundary or transition area where two different biological communities meet and integrate. This zone often contains species from both adjacent ecosystems and may even support unique organisms not found in either. Because it acts as a bridge between diverse habitats, it usually exhibits high biodiversity and distinct environmental conditions compared to the surrounding major biomes.
Q4. Which of the following represents a functional aspect of an ecosystem?
Explanation
Functional aspects of an ecosystem describe how the system operates and sustains itself over time. These include processes like productivity, decomposition, and the movement of essential elements through various environmental reservoirs. The circulation of minerals and chemical elements between the biotic and abiotic components ensures that life-sustaining resources remain available for all organisms within the stable biological community.
Q5. Identify the incorrect statement regarding the types of ecosystems.
Explanation
Ecosystems are categorized based on their origin and habitat. Natural ecosystems, such as forests or estuaries, develop without human interference. However, agricultural lands used for growing food are artificial systems because they are created and managed by humans. These man-made terrestrial environments require constant intervention, such as irrigation and fertilization, to maintain their specific biological structure and productivity.
Q6. In an ecosystem, which organisms are primarily responsible for converting complex organic matter into simple inorganic substances?
Explanation
Certain organisms specialize in breaking down complex organic remains of dead plants and animals into simpler inorganic molecules. These biological recyclers, often found in soil or water, perform the critical process of decomposition. By releasing enzymes to digest waste externally and then absorbing the nutrients, they return vital minerals to the environment, allowing producers to reuse them for growth.
Q7. The rate at which organic matter is created by producers in an ecosystem is known as:
Explanation
Primary productivity represents the speed at which autotrophs like plants produce biomass through photosynthesis. The total amount of chemical energy or organic matter generated per unit area over a specific period is defined as the gross value. This total production includes the energy that the plants themselves will eventually use for their own respiration and basic metabolic maintenance needs.
Q8. Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R):
Assertion (A): Energy flow in an ecosystem is always strictly unidirectional.
Reason (R): Energy captured by autotrophs does not revert back to solar input.
Assertion (A): Energy flow in an ecosystem is always strictly unidirectional.
Reason (R): Energy captured by autotrophs does not revert back to solar input.
Explanation
Energy enters an ecosystem primarily through sunlight, which is captured by plants during photosynthesis. This energy then moves through successive trophic levels as organisms consume one another. Since thermodynamic laws dictate that energy is lost as heat at every transfer, it cannot return to the sun. Therefore, the movement of energy remains a one-way path from producers to top consumers.
Q9. Through which biological process do plants release water vapor into the atmosphere?
Explanation
Living vegetation plays a significant role in the local and global climate by moving water from the soil back into the air. Through small openings in their leaves, plants release moisture that has been absorbed by their roots. This biological process not only helps cool the plant but also contributes significantly to the total amount of humidity in the surrounding atmosphere.
Q10. Environmental pollution can be broadly defined as:
Explanation
Pollution occurs when various substances or forms of energy are introduced into the environment at a rate faster than they can be naturally neutralized or dispersed. This imbalance leads to undesirable changes in the physical, chemical, or biological characteristics of the air, water, and soil. Such contamination often harms human health and disrupts the delicate functioning of ecosystems across the entire planet.Answer key for these questions
| Q | Correct answer |
|---|---|
| 1 | (b) Interacting organisms and their physical environment |
| 2 | (a) Decomposers |
| 3 | (c) A zone of transition between diverse ecosystems |
| 4 | (d) Nutrient cycling |
| 5 | (c) Crop fields are considered natural terrestrial ecosystems. |
| 6 | (b) Saprotrophs |
| 7 | (d) Gross primary productivity |
| 8 | (a) Both A and R are true and R is the correct explanation of A. |
| 9 | (d) Transpiration |
| 10 | (a) Adding substances to environment faster than dispersal |
Key facts from Environmental and Ecological Changes and Impact Assessment
- An ecosystem is made of interacting organisms and their physical environment; an ecotone is a zone of transition between ecosystems.
- Saprotrophs convert complex organic matter into simple substances; gross primary productivity is the rate at which producers create organic matter.
- Plants release water vapour through transpiration.
- Ground-level ozone is a secondary pollutant; CO, SO₂ and PM10 are primary pollutants.
- The greenhouse effect is the trapping of heat by atmospheric gases.
- Category B2 projects are exempt from public consultation under the EIA Notification 2006; the Supreme Court banned mining in the Aravalli range in Haryana and Rajasthan.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Environmental and Ecological Changes and Impact Assessment?
This page has 168 practice MCQs on Environmental and Ecological Changes and Impact Assessment (Health, Environment and Agriculture). Each has the correct answer, and most have an explanation.
What is a secondary pollutant?
A pollutant that is not emitted directly but forms in the air from primary pollutants. Ground-level ozone is the standard example, formed when nitrogen oxides and volatile organic compounds react in sunlight.
What is an ecotone?
A zone of transition between two different ecosystems, such as the area between a forest and a grassland. It often has more species than either neighbour because it has species of both.
Which projects are exempt from public consultation under EIA 2006?
Category B2 projects, which have less environmental impact. Category A and B1 projects need public consultation as part of the clearance process, which is the main way local people are heard.