Environment & Ecosystem

Environment वह surrounding है जो living organisms को influence करती है और उनसे interact करती है। इसमें physical, chemical, biological और social factors शामिल हैं।

Key Definitions:

• Environment (Physical): All external conditions affecting an organism — air, water, land, temperature, etc.
• Environment (Ecological): The sum total of all living (biotic) and non-living (abiotic) factors.

Types of Environment:

• Natural Environment: Forests, rivers, mountains, atmosphere (created by nature)
• Human-made Environment: Buildings, roads, industries (modified by humans)
• Social Environment: Culture, traditions, economic conditions

• Physical Environment — भौतिक पर्यावरण:
  • Lithosphere (land/earth)
  • Hydrosphere (water bodies)
  • Atmosphere (air/gases)
• Biological Environment — जैविक पर्यावरण:
  • Plants (flora)
  • Animals (fauna)
  • Microorganisms
• Social/Cultural Environment — सामाजिक पर्यावरण:
  • Population, culture, economy, technology, institutions

• Biotic Components — जैविक घटक (Living): All living organisms in an ecosystem.
  • Producers (Autotrophs): Plants, algae, cyanobacteria — make their own food
  • Consumers (Heterotrophs): Animals — depend on others for food
    • Primary Consumers: Herbivores (deer, rabbit)
    • Secondary Consumers: Carnivores (fox, frog)
    • Tertiary Consumers: Top carnivores (lion, eagle)
  • Decomposers (Saprotrophs): Bacteria, fungi — break down dead organic matter
• Abiotic Components — अजैविक घटक (Non-living):
  • Physical: Sunlight, temperature, rainfall, wind, water, soil, topography
  • Chemical: Oxygen, carbon dioxide, nitrogen, minerals, pH, salinity

Ecosystem living organisms (biotic) और non-living environment (abiotic) का functional unit है जो energy flow और nutrient cycling के माध्यम से interact करते हैं।

Key Points:

• Coined by A.G. Tansley (1935)
• Ecosystem = Community + Environment
• Ecosystems can be natural (forest, pond) or artificial (crop field, aquarium)

Types of Ecosystems:

• Terrestrial: Forest, grassland, desert, tundra
• Aquatic: Freshwater (pond, river, lake), Marine (ocean, sea), Estuarine

• Biotic Structure — जैविक संरचना:
  • Producers (Autotrophs): Primary producers — plants, algae
  • Consumers (Heterotrophs): Primary, Secondary, Tertiary
  • Decomposers: Bacteria, fungi
• Abiotic Structure — अजैविक संरचना:
  • Physical factors: Sunlight, temperature, humidity, water, soil
  • Chemical factors: Oxygen, CO₂, nitrogen, minerals
• Functional Aspects — कार्यात्मक पहलू:
  • Energy Flow: Sun → Producers → Consumers → Decomposers
  • Nutrient Cycling: Biogeochemical cycles (C, N, O, P, Water)
  • Food Chain & Food Web: Feeding relationships

Food Chain organisms का एक linear sequence है जिसमें energy और nutrients एक organism से दूसरे में transfer होते हैं — जब एक organism दूसरे को eats करता है।

Example:

• Grassland: Sun → Grass → Deer → Lion
• Pond: Sun → Algae → Fish → Heron
• Forest: Sun → Tree → Caterpillar → Bird → Eagle

Trophic Levels — पोषण स्तर:

• T₁ (Producers): Plants, algae
• T₂ (Primary Consumers): Herbivores
• T₃ (Secondary Consumers): Carnivores eating herbivores
• T₄ (Tertiary Consumers): Top carnivores
• Decomposers: Bacteria, fungi

Food Web interconnected food chains का network है — एक organism कई organisms को eat कर सकता है और कई organisms द्वारा eat किया जा सकता है।

Key Points:

• More complex and realistic than food chain
• Shows multiple feeding relationships
• Provides stability to the ecosystem
• If one species is removed, others can still survive

Example:

• Grass → Grasshopper → Frog → Snake → Eagle
• Grass → Rabbit → Fox
• Seeds → Mouse → Snake → Hawk
• These interconnected chains form a food web

Ecological Pyramids trophic levels में organisms के number, biomass या energy को graphically represent करते हैं।

Types:

• Pyramid of Numbers — संख्या पिरामिड: Number of individuals at each trophic level
• Pyramid of Biomass — बायोमास पिरामिड: Total dry weight of organisms at each trophic level
• Pyramid of Energy — ऊर्जा पिरामिड: Amount of energy at each trophic level

Key Point: Energy pyramid is always upright (10% law — only 10% energy transferred to next level).

• Pyramid of Numbers:
  • Upright: Grassland ecosystem (grass → rabbit → fox)
  • Inverted: Tree ecosystem (one tree → many insects → many birds)
• Pyramid of Biomass:
  • Upright: Most terrestrial ecosystems (plants have max biomass)
  • Inverted: Aquatic ecosystems (phytoplankton → zooplankton → fish — phytoplankton biomass less but more productive)
• Pyramid of Energy:
  • Always upright (energy decreases at each trophic level due to 10% law)

Energy Flow ecosystem में energy का one-way movement है — sun से producers तक, फिर consumers और decomposers तक।

Key Points:

• Energy enters through photosynthesis (sun → producers)
• Energy flows in a single direction (not recycled)
• 10% Law (Lindeman): Only 10% of energy passes to next trophic level
• 90% energy is lost as heat (respiration, metabolism, etc.)

Energy Flow vs Nutrient Cycling:

• Energy Flow: One-way, not recycled
• Nutrient Cycling: Cyclic, recycled (C, N, O, P, Water)

Biogeochemical Cycles nutrients का movement and recycling है — between biotic (living) and abiotic (non-living) components of the ecosystem.

Types:

• Gaseous Cycles — गैसीय चक्र: Carbon, Nitrogen, Oxygen, Water
• Sedimentary Cycles — तलछटी चक्र: Phosphorus, Sulphur, Calcium

Carbon Cycle carbon के atmosphere, organisms, oceans, soil, rocks के बीच movement को दर्शाता है।

• Sources of CO₂: Respiration, decomposition, combustion (fossil fuels, forests), volcanic activity
• Sinks (Removal): Photosynthesis (plants absorb CO₂), oceans (dissolve CO₂), fossil fuel formation
• Human Impact: Burning fossil fuels increases atmospheric CO₂ → global warming

Nitrogen Cycle nitrogen का atmosphere, soil, organisms के बीच conversion और movement है।

• Nitrogen Fixation — नाइट्रोजन स्थिरीकरण: Atmospheric N₂ → ammonia (NH₃) by bacteria (Rhizobium), lightning, industrial
• Nitrification — नाइट्रीकरण: Ammonia (NH₃) → Nitrites (NO₂⁻) → Nitrates (NO₃⁻) (by bacteria: Nitrosomonas, Nitrobacter)
• Assimilation — आत्मसात: Plants absorb nitrates; animals eat plants
• Ammonification — अमोनीकरण: Dead organisms → ammonia (NH₃) (by decomposers)
• Denitrification — विनाइट्रीकरण: Nitrates → N₂ gas (by bacteria: Pseudomonas)

Water Cycle (Hydrological Cycle) water का atmosphere, land, oceans के बीच continuous movement है।

• Evaporation — वाष्पीकरण: Water changes from liquid to vapour (oceans, lakes, rivers)
• Transpiration — वाष्पोत्सर्जन: Water loss from plants through leaves
• Condensation — संघनन: Water vapour → clouds (liquid droplets)
• Precipitation — वर्षण: Rain, snow, hail (water returns to earth)
• Runoff — अपवाह: Water flows over land surface
• Infiltration — अंतःस्रावण: Water seeps into soil/groundwater

Oxygen Cycle oxygen का atmosphere, organisms, water के बीच movement है।

• Photosynthesis: Plants release O₂ (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂)
• Respiration: Organisms consume O₂ and release CO₂
• Decomposition: Decomposers use O₂ during decomposition
• Combustion: Burning of fossil fuels uses O₂

• Trap 1: Ecosystem = only biotic components → ❌ Ecosystem = Biotic + Abiotic + Interaction
• Trap 2: Food chain = food web → ❌ Food chain is linear; food web is complex network
• Trap 3: Energy pyramid can be inverted → ❌ Energy pyramid is always upright (10% law)
• Trap 4: Energy is recycled in ecosystem → ❌ Energy flows one-way; nutrients are recycled
• Trap 5: Carbon cycle = only photosynthesis → ❌ Includes respiration, decomposition, combustion, etc.
• Trap 6: Nitrogen fixation = only industrial → ❌ Biological fixation (Rhizobium) is major
• Trap 7: Pyramid of numbers is always upright → ❌ Can be inverted in tree ecosystems

Which of the following is an abiotic component of an ecosystem?

• A. Plants
• B. Animals
• C. Bacteria
• D. Sunlight

Explanation: Sunlight is a non-living (abiotic) component. Plants, animals, and bacteria are biotic components.

In a food chain, grass → deer → lion, the deer is a:

• A. Producer
• B. Primary consumer
• C. Secondary consumer
• D. Decomposer

Explanation: Deer is a herbivore (primary consumer) eating grass (producer). Lion is the secondary/tertiary consumer.

The pyramid of energy in an ecosystem is always:

• A. Inverted
• B. Upright
• C. Spindle-shaped
• D. Irregular

Explanation: The pyramid of energy is always upright because energy decreases at each trophic level (10% law).

Which bacteria is responsible for nitrogen fixation in root nodules of legumes?

• A. Nitrosomonas
• B. Rhizobium
• C. Nitrobacter
• D. Pseudomonas

Explanation: Rhizobium is the nitrogen-fixing bacteria found in root nodules of legumes. Nitrosomonas and Nitrobacter are nitrifying bacteria; Pseudomonas is denitrifying.

Which of the following is NOT a biogeochemical cycle?

• A. Carbon cycle
• B. Nitrogen cycle
• C. Energy cycle
• D. Water cycle

Explanation: Energy flows one-way and is not recycled. Carbon, Nitrogen, and Water are biogeochemical cycles where nutrients are recycled.

The term 'ecosystem' was coined by:

• A. Charles Darwin
• B. A.G. Tansley
• C. E.P. Odum
• D. John Muir

Explanation: A.G. Tansley coined the term 'ecosystem' in 1935.

Biotic Components:

• Producers (Autotrophs), Consumers (Heterotrophs), Decomposers (Saprotrophs)

Abiotic Components:

• Physical: Sunlight, temperature, water, soil
• Chemical: O₂, CO₂, N₂, minerals

Food Chain & Food Web:

• Food Chain = Linear (single path)
• Food Web = Network (multiple paths)

Ecological Pyramids:

• Numbers (can be upright/inverted)
• Biomass (upright in terrestrial; inverted in aquatic)
• Energy (always upright — 10% law)

Energy Flow:

• One-way (Sun → Producers → Consumers → Decomposers)
• 10% Law: Only 10% energy transferred to next trophic level

Biogeochemical Cycles:

• Gaseous: Carbon, Nitrogen, Oxygen, Water
• Sedimentary: Phosphorus, Sulphur

Exam Formula:

UGC NET में Environment & Ecosystem के questions components, trophic levels, pyramids, cycles, and energy flow पर based होते हैं।