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Consider the following statements regarding Ecological Succession:
Primary succession begins on a previously barren area without any soil.
Secondary succession proceeds faster than primary succession.
Lichens are often pioneer species in primary succession.
Secondary succession never occurs after forest fires.
Which of the statements given above are correct?
- A
1 and 2 only
- B
2 and 3 only
- C
1, 2 and 3 only
- D
1, 2, 3 and 4
Explanation
Answer:
✅ C. 1, 2 and 3 only
Explanation
Statement 1 – Correct
Primary succession starts where no previous ecosystem existed, such as:
Newly formed volcanic islands
Bare rocks after glacial retreat
Sand dunes
Since soil is absent, organisms capable of surviving harsh conditions colonize first.
Statement 2 – Correct
Secondary succession is much faster because:
Soil already exists.
Seeds remain in soil.
Microorganisms survive.
Nutrients are already available.
Examples:
Forest fire
Flood
Agricultural land abandoned
Statement 3 – Correct
Lichens are pioneer species because:
They can grow directly on rocks.
They produce acids that weather rocks.
Gradually help in soil formation.
After lichens:
Mosses → Herbs → Shrubs → Trees.
Statement 4 – Incorrect
Forest fires usually leave soil intact.
Hence forests regenerate through secondary succession.
Q7. Which of the following pollutants is mainly responsible for Acid Rain?
- A
CO₂
- B
SO₂ and NOx
- C
Methane
- D
Ozone
Explanation
Answer
✅ B
Explanation
Acid rain forms when sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) react with atmospheric water to form sulfuric and nitric acids.
Effects:
Soil acidification
Damage to forests
Acidification of lakes
Corrosion of monuments
Revise
Acid rain
Smog
Ozone depletion
PM2.5
AQI
Which of the following statements regarding Ecotones is/are correct?
Ecotones are transition zones between two ecosystems.
They generally exhibit high species diversity.
Edge effect is associated with ecotones.
- A
1 only
- B
1 and 2 only
- C
2 and 3 only
- D
1, 2 and 3
Explanation
Answer
✅ D
Explanation
An ecotone is a transition area between two ecosystems (e.g., forest–grassland). It often contains species from both adjoining ecosystems as well as unique species, resulting in high biodiversity. The edge effect is a characteristic ecological phenomenon observed in ecotones.
Which one is NOT an ecosystem service?
- A
Pollination
- B
Nutrient cycling
- C
Plastic production
- D
Water purification
Explanation
Answer
✅ C
Explanation
Ecosystem services include:
Provisioning (food, timber)
Regulating (climate regulation, pollination)
Supporting (nutrient cycling, soil formation)
Cultural (recreation, spiritual values)
Plastic production is an industrial activity.
Which of the following is a validated achievement of the Namami Gange programme (2017-2024)?
- A
Reduction of effluent discharge from 10.75 TDP to zero
- B
Reduction of Biochemical Oxygen Demand (BOD) from 26 TPD to 10.75 TPD
- C
pH levels in the Ganga now exceed industrial effluent standards at all locations
- D
Total elimination of all sewage treatment capacity to favor natural filtration.
Explanation
The source explicitly cites the BOD reduction from 26 TPD in 2017 to 10.75 TPD in 2024 as a key indicator of the program's success.
As of May 2026, what progress has been recorded under the Jal Jeevan Mission (JJM) regarding rural tap water connections?
- A
Coverage increased from 17% at launch to over 81%
- B
100% coverage was achieved across all districts.
- C
Focus shifted entirely to "Jal Sanchay Jan Bhagidari" instead of tap connections
- D
Coverage reached 50%, with the remainder moved to SBM-Grameen 2.0.
Explanation
Correct Ans: A Explanation: The source states JJM coverage moved from 17% (3.23 crore households) to over 81% (15.8 crore households). The target for 100% coverage is 2028.
Q2. Which one of the following ecosystems has the highest Net Primary Productivity (NPP)?
- A
desert
- B
open ocean
- C
tropical Rainforest
- D
Tundra
Explanation
Answer
✅ C. Tropical Rainforest
Explanation
Net Primary Productivity (NPP)
NPP = Gross Primary Productivity − Plant Respiration
Higher NPP means plants store more biomass.
Comparison:
Ecosystem | Productivity |
|---|---|
Tropical rainforest | Very High |
Estuary | Very High |
Coral reefs | High |
Temperate forest | Moderate |
Open ocean | Low |
Desert | Very Low |
Tundra | Very Low |
Tropical rainforests receive:
Heavy rainfall
Warm temperature
Continuous sunlight
Hence productivity remains highest.
Q5. Which gas contributes the maximum to the enhanced greenhouse effect?
- A
methane
- B
CO2
- C
Nitrous oxide
- D
ozone
Explanation
Answer
✅ B. Carbon dioxide
Explanation
Although methane is much stronger molecule-for-molecule, CO₂ contributes the largest share because its atmospheric concentration is far higher and it persists for long periods.
Approximate contribution:
CO₂ ≈ largest share
CH₄ ≈ second
N₂O ≈ smaller but potent
Fluorinated gases ≈ small share but very high warming potential
Revise
Global Warming Potential (GWP)
Carbon budget
Carbon sink
Blue carbon
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