Environment & Ecology Short Notes | Complete Exam-Oriented Guide for Competitive Exams

November 22, 2025

ENVIRONMENT & ECOLOGY – SHORT NOTES

Exam-Oriented | Definitions | Concepts | Processes | One-liners | Frequently Asked Points

ENVIRONMENT & ECOLOGY

1. INTRODUCTION TO ENVIRONMENT

Environment – Definition

The environment refers to all external conditions in which an organism lives. It includes living (biotic) and non-living (abiotic) components.

Components

  1. Biotic: Plants, animals, microorganisms.

  2. Abiotic: Air, water, soil, sunlight, temperature.

Types of Environment

  • Natural environment: Forests, rivers, oceans, atmosphere.

  • Artificial/man-made environment: Buildings, dams, cities.

  • Social environment: Culture, institutions, interactions among humans.

2. ECOLOGY

Definition

Ecology is the scientific study of the interaction between organisms and their environment.

Levels of Organization

  1. Organism – single individual

  2. Population – group of same species

  3. Community – different populations interacting

  4. Ecosystem – community + abiotic factors

  5. Biome – large ecological area (tundra, desert, forest)

  6. Biosphere – all ecosystems on Earth

3. ECOSYSTEM

Definition

An ecosystem is a functional unit of environment where living organisms interact with each other and with physical surroundings.

Components

(A) Biotic Components

  • Producers (Autotrophs): Plants, algae.

  • Consumers (Heterotrophs):

    • Primary consumers – herbivores

    • Secondary consumers – carnivores

    • Tertiary consumers – top carnivores

  • Decomposers: Fungi, bacteria.

(B) Abiotic Components

  • Solar energy, water, minerals, temperature, air.

Types of Ecosystems

  • Natural: Forests, grasslands, deserts, lakes, oceans.

  • Artificial: Aquarium, crop fields, gardens.

Ecosystem Functions

  • Energy flow

  • Nutrient cycling

  • Ecological succession

4. ENERGY FLOW IN ECOSYSTEM

Important Points

  • Energy flows in one direction only – sun → producers → consumers → decomposers.

  • Follows the 10% Law of Energy Transfer (Lindeman):

    • Only 10% of energy is transferred to the next trophic level.

Trophic Levels

  1. Producers

  2. Primary consumers

  3. Secondary consumers

  4. Tertiary consumers

Food Chain

A single direct pathway of energy flow.
Types:

  • Grazing food chain (GFC) – begins with plants.

  • Detritus food chain (DFC) – begins with dead organic matter.

Food Web

Interlinked food chains that increase ecosystem stability.

5. BIOGEOCHEMICAL CYCLES

(1) Carbon Cycle

  • Carbon present as CO₂.

  • Major processes: photosynthesis, respiration, decomposition, combustion.

(2) Nitrogen Cycle

  • Nitrogen fixation by Rhizobium, lightning.

  • Nitrification → Nitrite bacteria (Nitrosomonas), Nitrate bacteria (Nitrobacter).

  • Denitrification → Pseudomonas.

(3) Water Cycle

  • Evaporation → Condensation → Precipitation → Runoff.

(4) Phosphorus Cycle

  • No atmospheric phase.

  • Source = rocks.

  • Important for ATP, DNA, RNA.

6. BIODIVERSITY

Definition

Variety of life forms on Earth at:

  • Genetic level

  • Species level

  • Ecosystem level

Types of Biodiversity

  1. α (Alpha): Within a habitat

  2. β (Beta): Between habitats

  3. γ (Gamma): Entire region

Importance

  • Ecological balance

  • Food, medicines

  • Soil fertility

  • Economic and cultural value

Threats to Biodiversity

  • Habitat destruction

  • Climate change

  • Pollution

  • Invasive species

  • Overexploitation

Biodiversity Hotspots (India)

  1. Himalayas

  2. Western Ghats

  3. Indo-Burma

  4. Sundaland

7. CONSERVATION OF BIODIVERSITY

In-Situ Conservation (On-site)

  • National parks

  • Wildlife sanctuaries

  • Biosphere reserves

  • Sacred groves

Ex-Situ Conservation (Off-site)

  • Zoos

  • Botanical gardens

  • Seed banks

  • Cryopreservation

Important Indian Protected Areas

  • Kaziranga (Rhinoceros)

  • Gir (Asiatic Lion)

  • Corbett (Tiger)

  • Periyar (Elephants)

8. CLIMATE CHANGE

Definition

Long-term changes in temperature and weather patterns due to natural and human factors.

Causes

  • Burning fossil fuels

  • Deforestation

  • Industrial emissions

  • Agriculture (methane)

Greenhouse Gases

  • Carbon dioxide

  • Methane

  • Nitrous oxide

  • Water vapor

  • CFCs

Effects

  • Rising temperature

  • Melting glaciers

  • Sea-level rise

  • Extreme weather

  • Biodiversity loss

International Agreements

  • Kyoto Protocol (1997)

  • Paris Agreement (2015)

  • Montreal Protocol (1987) – ozone protection

9. POLLUTION

Types of Pollution

1. Air Pollution

Major pollutants:

  • CO, SO₂, NOₓ

  • Particulate matter (PM2.5, PM10)

  • Ozone, CFCs

Sources:

  • Vehicles, industries, burning waste.

Effects:

  • Smog, acid rain, respiratory diseases.

Control:

  • Scrubbers, catalytic converters, green fuels.

2. Water Pollution

Sources:

  • Industrial effluents

  • Sewage

  • Agricultural runoff

Effects:

  • Eutrophication

  • Waterborne diseases

Control:

  • Sewage treatment plants

  • Effluent treatment

  • Ban on harmful pesticides

3. Soil Pollution

Sources:

  • Chemical fertilizers

  • Plastics

  • Mining

  • Acid rain

Effects:

  • Loss of fertility, biomagnification.

4. Noise Pollution

Sources:

  • Machines, vehicles, loudspeakers.

Effects:

  • Hearing loss, stress.

Permissible limit:

  • Residential: 55 dB (day), 45 dB (night).

5. Radioactive Pollution

Sources:

  • Nuclear power plants

  • Medical waste

Effects:

  • Genetic mutation, cancer.

10. OZONE LAYER DEPLETION

  • Ozone (O₃) absorbs harmful UV radiation.

  • CFCs and halons destroy ozone.

Effects

  • Skin cancer

  • Cataract

  • Reduced crop yield

Protection

  • Montreal Protocol (1987)

  • Ban on CFCs

11. ENVIRONMENTAL IMPACT ASSESSMENT (EIA)

Definition

EIA is a process to evaluate the environmental impacts of developmental projects before approval.

Objectives

  • Identify negative impacts

  • Suggest mitigation measures

  • Ensure sustainable development

Stages

  1. Screening

  2. Scoping

  3. Impact analysis

  4. Public hearing

  5. Decision making

  6. Monitoring

Projects requiring EIA

  • Dams

  • Mining

  • Highways

  • Thermal power plants

12. NATURAL RESOURCES

Types

  1. Renewable: Solar, wind, biomass, water.

  2. Non-renewable: Coal, petroleum, minerals.

Forest Resources

  • Functions: Oxygen production, habitat, climate regulation.

  • Threats: Deforestation, fires, illegal logging.

Water Resources

  • Issues: Scarcity, pollution, over-extraction.

Mineral Resources

  • Issues: Mining pollution, land degradation.

13. DISASTER MANAGEMENT & ENVIRONMENT

Types of Natural Disasters

  • Earthquakes

  • Floods

  • Cyclones

  • Landslides

  • Droughts

NDMA (National Disaster Management Authority)

  • Established: 2005

  • Chairman: Prime Minister

Goals

  • Preparedness

  • Mitigation

  • Rescue & relief

  • Rehabilitation

14. ENVIRONMENTAL LAWS IN INDIA

Key Acts

  • Environment Protection Act, 1986

  • Air Act, 1981

  • Water Act, 1974

  • Forest Conservation Act, 1980

  • Wildlife Protection Act, 1972

  • Biological Diversity Act, 2002

Institutions

  • MoEFCC – Ministry of Environment

  • CPCB – Central Pollution Control Board

  • SPCB – State Pollution Control Board

15. IMPORTANT INTERNATIONAL ORGANIZATIONS

  • UNEP – United Nations Environment Programme

  • IPCC – Intergovernmental Panel on Climate Change

  • WWF – World Wildlife Fund

  • IUCN – International Union for Conservation of Nature

IUCN Red List Categories

  • Extinct

  • Critically Endangered

  • Endangered

  • Vulnerable

  • Near Threatened

  • Least Concern

16. IMPORTANT ONE-LINERS (HIGH-SCORING)

  • Silent Valley is a tropical rainforest in Kerala.

  • Chipko Movement: Forest conservation movement in Uttarakhand (1973).

  • Biosphere Reserve Example: Nilgiri (India’s first).

  • Ramsar Sites: Wetlands of international importance.

  • Ozone layer is found in: Stratosphere.

  • Minamata disease: Mercury poisoning.

  • Blue baby syndrome: Nitrate pollution.

  • Greenhouse effect discovered by: Joseph Fourier.

  • Acid rain caused by: SO₂ & NOₓ.

  • Bhopal gas tragedy (1984): Methyl Isocyanate (MIC).

  • World Environment Day: 5 June.

✅ Conclusion

Environment & Ecology is one of the highest-scoring sections in competitive exams. Understanding ecology basics, biodiversity, climate change, and pollution control helps in solving 10–15 GS questions in SSC, RRB, PSC, and Banking exams.

Basil

Posted by Basil

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