Environmental Science – Quick Theory Capsule

Environmental Science is the interdisciplinary study of the physical, chemical & biological processes that sustain life on Earth. For railway exams, focus on ecosystems, pollution types, climate change, biodiversity hotspots, renewable & non-renewable resources, and Indian environmental laws (Wildlife Protection Act 1972, Environment Protection Act 1986, National Green Tribunal 2010). Remember the 3 R’s—Reduce, Reuse, Recycle—and key summits/conferences (Rio 1992, Kyoto 1997, Paris 2015).

The carbon cycle, nitrogen cycle, food chain/web, and energy pyramid are favourite RRB topics. Biomagnification (increase in pollutant concentration up the food chain) and eutrophication (nutrient overload in water bodies) often appear as application-based MCQs. UN agencies—UNEP, IPCC, UNESCO—and Indian organisations—MoEFCC, CPCB, SPCB—must be on your fingertips. Link every pollution source to its primary standard (NAAQS) and every species to its IUCN status; railways love factual pairing questions.

Practice MCQs

1. [Easy] The main source of oxygen in the Earth’s atmosphere is
   A. Volcanic eruptions
   B. Photosynthesis by green plants
   C. Respiration by animals
   D. Evaporation of water

   Answer

   Correct: Option B. Photosynthesis releases O₂ as a by-product.

2. [Easy] Which of the following is a renewable resource?
   A. Coal
   B. Natural gas
   C. Solar energy
   D. Petroleum

   Answer

   Correct: Option C. Solar energy is inexhaustible on human timescale.

3. [Easy] The term “BOD” is related to
   A. Sound pollution
   B. Water pollution
   C. Soil pollution
   D. Air pollution

   Answer

   Correct: Option B. BOD = Biochemical Oxygen Demand, indicator of organic load in water.

4. [Easy] Which gas is the major contributor to global warming?
   A. Ozone
   B. CO₂
   C. SO₂
   D. N₂

   Answer

   Correct: Option B. CO₂ is the principal anthropogenic greenhouse gas.

5. [Easy] The 3 R principle does NOT include
   A. Reuse
   B. Recycle
   C. Reduce
   D. Regenerate

   Answer

   Correct: Option D. Regenerate is not part of the 3 R mantra.

6. [Medium] Which layer of the atmosphere contains the ozone shield?
   A. Troposphere
   B. Stratosphere
   C. Mesosphere
   D. Thermosphere

   Answer

   Correct: Option B. Ozone layer lies 15–35 km high in the stratosphere.

7. [Medium] The first National Park of India is
   A. Kaziranga
   B. Jim Corbett
   C. Gir
   D. Ranthambore

   Answer

   Correct: Option B. Jim Corbett (1936) originally named Hailey National Park.

8. [Medium] Which pollutant is responsible for Minamata disease?
   A. Lead
   B. Mercury
   C. Cadmium
   D. Arsenic

   Answer

   Correct: Option B. Methyl-mercury poisoning in Japan.

9. [Medium] The concept of “Carbon Credit” originated from which protocol?
   A. Montreal Protocol
   B. Kyoto Protocol
   C. Ramsar Convention
   D. Basel Convention

   Answer

   Correct: Option B. Kyoto introduced market-based emissions trading.

10. [Medium] Which of the following is a secondary pollutant?
    A. CO
    B. SO₂
    C. O₃
    D. NO

    Answer

    Correct: Option C. Ground-level ozone forms by photochemical reactions.

11. [Medium] Silent Valley is famous for
    A. Lion conservation
    B. Rhododendron forests
    C. Tropical evergreen forest & lion-tailed macaque
    D. Mangrove ecosystem

    Answer

    Correct: Option C. Located in Kerala, core of Nilgiri Biosphere Reserve.

12. [Medium] The National Green Tribunal was established in
    A. 1972
    B. 1986
    C. 2002
    D. 2010

    Answer

    Correct: Option D. NGT Act 2010, operational from Oct 2010.

13. [Medium] Which schedule of Wildlife Protection Act lists critically endangered species?
    A. Schedule I
    B. Schedule II
    C. Schedule III
    D. Schedule V

    Answer

    Correct: Option A. Schedule I gives highest protection.

14. [Medium] The term “Chipko Movement” is associated with
    A. Appiko, Karnataka
    B. Bishnoi, Rajasthan
    C. Gaura Devi, Uttarakhand
    D. Medha Patkar, Narmada

    Answer

    Correct: Option C. 1973, Chamoli district, hugging trees to stop felling.

15. [Medium] Which greenhouse gas has the highest global warming potential (GWP) per molecule?
    A. CO₂
    B. CH₄
    C. N₂O
    D. SF₆

    Answer

    Correct: Option D. Sulphur hexafluoride GWP > 23 000 (100-yr).

16. [Hard] In an energy pyramid, the second trophic level is always occupied by
    A. Producers
    B. Primary consumers
    C. Secondary consumers
    D. Decomposers

    Answer

    Correct: Option B. Herbivores that eat producers.

17. [Hard] The “polluter pays principle” was first articulated in
    A. Brundtland Report 1987
    B. Rio Declaration 1992
    C. Stockholm Conference 1972
    D. Paris Agreement 2015

    Answer

    Correct: Option B. Principle 16 of Rio Declaration.

18. [Hard] Which Indian Biosphere Reserve is included in UNESCO’s World Network since 2021?
    A. Panna
    B. Achanakmar-Amarkantak
    C. Pachmarhi
    D. Kanchenjunga

    Answer

    Correct: Option B. A-A BR added in 2021 (Man & Biosphere programme).

19. [Hard] The permissible limit of PM2.5 (annual average) as per NAAQS 2009 is
    A. 60 µg/m³
    B. 40 µg/m³
    C. 100 µg/m³
    D. 120 µg/m³

    Answer

    Correct: Option B. 40 µg/m³ for PM2.5 annual mean.

20. [Hard] Which method is used for removal of both SO₂ & particulates from flue gas simultaneously?
    A. Electrostatic precipitator
    B. Cyclone separator
    C. Limestone scrubbing (FGD)
    D. catalytic converter

    Answer

    Correct: Option C. Flue-gas desulphurization captures SO₂ + some particulates.

21. [Hard] The “Nitrogen cascade” concept relates to
    A. successive trophic transfers
    B. multi-media transport & sequential effects of reactive N
    C. denitrification steps
    D. Haber-Bosch recycling

    Answer

    Correct: Option B. One atom of Nr can cause a chain of impacts across air, water, soil.

22. [Hard] Which species is an indicator of clean water due to its intolerance to pollution?
    A. Tubifex worm
    B. E. coli
    C. Stone-fly nymph
    D. Chironomid larva

    Answer

    Correct: Option C. Stone-fly requires high dissolved oxygen.

23. [Hard] The “Extended Producer Responsibility” rule in India first applied to which waste?
    A. e-waste
    B. plastic
    C. tyres
    D. batteries

    Answer

    Correct: Option A. E-waste Rules 2011 introduced EPR.

24. [Hard] Match the convention with the year:
    A. Ramsar – 1971
    B. CITES – 1973
    C. CBD – 1992
    D. All correct

    Answer

    Correct: Option D. All pairings are accurate.

25. [Hard] If the ecological efficiency between trophic levels is 10 %, how much energy (kcal) from 5000 kcal of producers will reach a secondary carnivore?
    A. 50
    B. 500
    C. 5
    D. 0.5

    Answer

    Correct: Option C. 5000 → 500 (herbivore) → 50 (primary carnivore) → 5 (secondary carnivore).

Quick Shortcuts & Tips

1. Mnemonic for greenhouse gases: “C–M–N–O–F” → CO₂, CH₄, N₂O, O₃, Fluoro-gases.
2. Schedule trick: Wildlife Act – I (critically end.), II (hunted), III (small game), IV (vermin), V (plants).
3. Pollution colour codes: SO₂ – yellow smoke; NO₂ – brown haze; CO – colourless deadly.
4. Conference chronology: Stockholm (72) → Rio (92) → Kyoto (97) → Johannesburg (02) → Paris (15).
5. Indian agencies: MoEFCC (policy), CPCB (standards), NGT (judicial) – remember “MCN”.
6. Ozone facts: Good ozone = stratosphere (UV-B shield); bad ozone = troposphere (photochemical smog).
7. BOD vs COD: BOD ≤ COD always; high ratio = biodegradable waste, low ratio = toxic/recalcitrant.
8. Pyramid rule: energy ↓, number/biomass can invert (aquatic ecosystems).
9. GWP order: SF₆ > N₂O > CH₄ > CO₂ – think “SFN-C” for high to low.
10. Eliminate extremes: in limits/standards, extremes (very high or zero) are usually wrong; go for middle value.

Keep revising these pearls; environment questions are high-scoring because they are factual and repetitive in every RRB exam.