FYUG Even Semester Exam 2025
EESDSM-252: Ecology and Environmental Science

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UNIT-I: Earth's Atmosphere

Question 1 (a) [2 Marks]

Name the different layers of atmosphere.

The Earth's atmosphere is divided into five main layers based on temperature gradients:

• Troposphere (Lowest layer)
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere (Uppermost layer)

Question 1 (b) [2 Marks]

Write the composition of the earth's atmosphere.

The atmosphere is a mixture of various gases. The dry air composition near the surface is:

• Nitrogen (N₂): 78.08%
• Oxygen (O₂): 20.95%
• Argon (Ar): 0.93%
• Carbon Dioxide (CO₂): 0.04%
• Trace Gases: Neon, Helium, Methane, Krypton, and Water Vapor (variable).

Question 1 (c) [2 Marks]

Write the significance of stratosphere.

The stratosphere is critical for life on Earth primarily because:

The stratosphere contains the Ozone Layer, which absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, protecting living organisms from DNA damage and skin cancer.

It also provides a stable region for commercial jet flights due to its lack of weather turbulence.

Question 2 (a) [10 Marks]

Give an account on the evolution and development of the earth's atmosphere.

The evolution of Earth's atmosphere occurred in three distinct stages over 4.6 billion years:

1. The First Atmosphere (Primordial): Primarily consisted of Hydrogen and Helium. This was lost to space due to Earth's weak gravity and solar winds.
2. The Second Atmosphere (Outgassing): Formed through volcanic activity. Gases released included water vapor (H₂O), CO₂, and Nitrogen (N₂). As the Earth cooled, water vapor condensed to form oceans.
3. The Third Atmosphere (Oxygenation):
   • Life evolved in oceans. Cyanobacteria began performing photosynthesis.
   • CO₂ levels dropped as it was fixed into carbonate rocks and used by plants.
   • Oxygen levels rose significantly (The Great Oxidation Event), leading to the current N₂-O₂ dominated atmosphere.

Question 2 (b) (Option B) [10 Marks]

What are Milankovitch cycles and how do they affect the earth's climate?

Milankovitch cycles refer to the collective effects of changes in Earth's movements on its climate over thousands of years.

• Eccentricity: Changes in the shape of Earth's orbit around the sun (circular vs. elliptical) every 100,000 years.
• Obliquity (Tilt): Changes in the angle of Earth's axis (between 22.1° and 24.5°) every 41,000 years. Higher tilt increases seasonal extremes.
• Precession: The "wobble" of Earth's axis every 26,000 years, affecting the timing of seasons.

Climate Impact: These cycles change the distribution and intensity of solar radiation reaching the Earth, acting as primary drivers for ice ages and interglacial periods.

UNIT-II: Meteorological Parameters

Question 3 (a) [2 Marks]

What are the different types of air masses?

Air masses are classified based on their source region:

• Continental Polar (cP): Cold and dry
• Maritime Polar (mP): Cold and moist
• Continental Tropical (cT): Hot and dry
• Maritime Tropical (mT): Hot and moist

Question 3 (b) [2 Marks]

Distinguish between El Niño and La Niña.

Feature	El Niño	La Niña
Temperature	Abnormal warming of surface waters in Eastern Pacific.	Abnormal cooling of surface waters in Eastern Pacific.
Impact on Monsoon	Often leads to weak monsoons/droughts in India.	Often leads to stronger monsoons/floods in India.

Question 3 (c) [2 Marks]

Define climate.

Climate is the long-term average of weather patterns in a specific region, typically calculated over a period of 30 years.

Question 4 (a) [10 Marks]

Explain the different meteorological parameters.

Meteorological parameters are measurable factors that describe the state of the atmosphere:

• Temperature: Measured in Celsius or Kelvin; determines the energy state of air.
• Atmospheric Pressure: Force exerted by air weight; measured using a barometer (Units: hPa or mb).
• Humidity: The amount of water vapor in the air (Relative vs. Absolute humidity).
• Wind Speed and Direction: Influenced by pressure gradients; measured by anemometers.
• Precipitation: Any form of water falling from the sky (Rain, snow, hail).
• Solar Radiation: The primary energy driver for all weather processes.

Question 4 (b) (Option B) [10 Marks]

What are Western disturbances? Write the impact of climate change on Western disturbances.

Definition: Western Disturbances are extra-tropical storms originating in the Mediterranean region that bring sudden winter rain to the northwestern parts of the Indian subcontinent.

Impact of Climate Change:

• Frequency and Intensity: Rising global temperatures alter the Jet Stream, making these disturbances more erratic.
• Shifting Patterns: They are becoming more frequent in late spring, leading to unseasonal rainfall that destroys rabi crops.
• Glacial Impact: Increased moisture leads to heavy snowfall/avalanches in the Himalayas, affecting water security.

UNIT-III: Global Warming and Sea Level

Question 5 (a) [2 Marks]

Write the major causes of global warming.

• Burning of fossil fuels (Coal, Oil, Gas).
• Deforestation (loss of carbon sinks).
• Industrial emissions and agricultural practices (methane from livestock).

Question 5 (b) [2 Marks]

Name the different greenhouse gases.

• Carbon Dioxide (CO₂)
• Methane (CH₄)
• Nitrous Oxide (N₂O)
• Fluorinated gases (HFCs, CFCs)
• Water Vapor (H₂O)

Question 5 (c) [2 Marks]

What are atmospheric windows?

Atmospheric windows are specific ranges of the electromagnetic spectrum (like the 8–12 micrometer range) where the atmosphere is relatively transparent to outgoing terrestrial infrared radiation, allowing it to escape into space.

Question 6 (a) [10 Marks]

Write the impacts of climate change on agricultural productivity and biological responses with mitigation strategies.

Agricultural Impacts:

• Reduced crop yields due to heat stress and altered rainfall.
• Increased pest and weed infestations.

Biological Responses:

• Phenological shifts: Changes in timing of flowering or migration.
• Range shifts: Species moving toward poles or higher altitudes.

Mitigation Strategies:

• Developing drought-resistant crop varieties.
• Precision farming and improved irrigation techniques.
• Reforestation and soil carbon sequestration.

UNIT-IV: Ozone Layer

Question 7 (a) [2 Marks]

What is ozone layer depletion?

It is the gradual thinning of the Earth's ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities.

Question 7 (b) [2 Marks]

What are ozone depleting substances? Give examples.

Chemicals that destroy the ozone molecules in the stratosphere. Examples: Chlorofluorocarbons (CFCs), Halons, and Carbon tetrachloride.

Question 7 (c) [2 Marks]

Write the importance of ozone layer.

It acts as a shield, absorbing 97-99% of the sun's medium-frequency ultraviolet light (UV-B), which would otherwise cause skin cancer, cataracts, and damage to terrestrial and marine ecosystems.

Question 8 (a) [10 Marks]

Discuss the key perspectives of Chapman cycle.

The Chapman Cycle explains the natural continuous process by which ozone is formed and destroyed in the stratosphere:

1. Photolysis of O₂: O₂ + UV (light) -> O + O
2. Ozone Formation: O + O₂ + M -> O₃ + M (where M is a third body like N₂)
3. Ozone Photolysis: O₃ + UV -> O₂ + O
4. Recombination: O₃ + O -> 2O₂

This steady-state cycle maintains a constant concentration of ozone under natural conditions.

UNIT-V: Policies and Protocols

Question 9 (a) [2 Marks]

What is meant by carbon trading?

A market-based system aimed at reducing greenhouse gas emissions. Companies are given a "cap" or limit on emissions; if they emit less, they can sell their excess "credits" to companies that exceed their limit.

Question 9 (b) [2 Marks]

What is Kyoto Protocol? When and where was it adopted?

An international treaty that committed industrialized nations to reduce GHGs. It was adopted in Kyoto, Japan, on 11 December 1997.

Question 9 (c) [2 Marks]

Write the key objectives of Montreal Protocol.

The primary objective is to protect the ozone layer by phasing out the production and consumption of numerous substances that are responsible for ozone depletion (ODS).

Question 10 (a) [10 Marks]

Give an overview of India's climate change policy.

India's policy is primarily guided by the National Action Plan on Climate Change (NAPCC) launched in 2008, which includes eight core missions:

• National Solar Mission
• National Mission for Enhanced Energy Efficiency
• National Mission on Sustainable Habitat
• National Water Mission
• National Mission for Sustaining the Himalayan Ecosystem
• National Mission for a Green India
• National Mission for Sustainable Agriculture
• National Mission on Strategic Knowledge for Climate Change

India has also committed to Net Zero by 2070 and significant increases in renewable energy capacity under the Paris Agreement.

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