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Ecology and Human Impact

Ecosystem Structure​

1. Components of Ecosystem​

Biotic (Jीवीय):

  • Living organisms
  • Producers: Plants (photosynthesis)
  • Consumers: Animals eating other organisms
    • Primary: Herbivores (eat plants)
    • Secondary: Carnivores (eat herbivores)
    • Tertiary: Top predators (eat secondary consumers)
  • Decomposers: Bacteria, fungi (break down dead material)

Abiotic (अजीवीय):

  • Non-living physical factors
  • Climate: Temperature, humidity, rainfall
  • Light: Intensity, duration (photoperiod)
  • Soil: pH, nutrients, texture
  • Water: Availability, salinity
  • Atmosphere: Gases (O₂, CO₂, N₂)

Habitat:

  • Physical place where organism lives
  • Specific conditions required
  • Example: Rainforest, desert, ocean

Niche:

  • Organism's role and function
  • How it uses environment
  • What it eats, where it lives
  • Unique to species

2. Feeding Relationships​

Food Chain (खाद्य श्रृंखला):

  • Linear sequence of organisms
  • Each eats previous
  • Energy flow direction shown
  • Example: Plant → Herbivore → Carnivore → Top Predator

Food Web (खाद्य जाल):

  • Interconnected food chains
  • Shows multiple feeding relationships
  • More realistic
  • Single organism in multiple chains

Trophic Levels:

  • Level 1 (Producers): Green plants (photosynthesis)
  • Level 2 (Primary Consumers): Herbivores
  • Level 3 (Secondary Consumers): Carnivores (eat herbivores)
  • Level 4 (Tertiary Consumers): Top predators

3. Energy Flow Through Ecosystem​

Energy Pyramid (ऊर्जा पिरामिड):

  • Shows energy at each trophic level
  • Decreases at each level
  • ~10% transfer to next level
  • 90% lost as heat, movement, metabolism

Consequence:

  • Limited trophic levels (usually 4-5)
  • Fewer organisms at higher levels
  • Pyramid of Numbers: More plants than herbivores

Efficiency:

  • 100% of energy captured by producers
  • 10% available to primary consumers
  • 1% to secondary consumers
  • 0.1% to tertiary consumers

Pyramid of Biomass:

  • Shows mass of organisms at each level
  • Decreases at each level
  • Reflects energy flow
  • Very rare inverted pyramids (in aquatic systems)

Population and Community Ecology​

1. Population Characteristics​

Population:

  • All organisms of same species in area
  • Can interbreed
  • Share genetic material

Population Density:

  • Number of individuals per unit area
  • Measured in organisms/m²
  • Varies with resources and competition

Population Growth:

  • Birth rate: New organisms
  • Death rate: Loss of organisms
  • Immigration: Individuals entering
  • Emigration: Individuals leaving
  • Change = (Birth - Death) + (Immigration - Emigration)

Age Structure:

  • Proportion at each age
  • Affects growth rate
  • Young population: Rapid growth
  • Old population: Slow growth

2. Population Growth Patterns​

Exponential Growth (चरघातांकीय):

  • Population doubles repeatedly
  • J-shaped curve
  • Limiting factors absent
  • Unsustainable (resources finite)
  • Example: Bacteria in ideal conditions

Logistic Growth (लॉजिस्टिक):

  • S-shaped curve (Sigmoid)
  • Starts exponential
  • Slows as reaches carrying capacity
  • Stabilizes at equilibrium
  • More realistic for natural populations

Carrying Capacity:

  • Maximum population size sustainable
  • Limited by resources
  • Food, water, space availability
  • Varies with environmental conditions

3. Succession (उत्तराधिकार)​

Definition:

  • Gradual change in species composition
  • After disturbance or on bare land
  • Predictable sequence

Primary Succession:

  • On bare rock or new land
  • Lichens establish first
  • Gradual soil development
  • Species slowly increase in complexity

Secondary Succession:

  • After disturbance (fire, clearing)
  • Soil already present
  • Faster than primary
  • Faster return to climax

Climax Community:

  • Final stable community
  • Balanced species composition
  • No net change (if not disturbed)
  • Specific to environment

Nutrient Cycles​

1. Carbon Cycle (कार्बन चक्र)​

Processes:

  • Photosynthesis: Atmospheric CO₂ → Organic carbon in plants
  • Respiration: Organic carbon → CO₂ back to atmosphere
  • Combustion: Fuel burned → CO₂ released
  • Decomposition: Dead organisms → CO₂ via decomposers
  • Fossilization: Organic → Fossil fuels over millions of years

Key Features:

  • Carbon moves between atmosphere and organisms
  • Balanced until industrialization
  • Increased CO₂ from fossil fuel burning
  • Greenhouse gas (global warming)

2. Nitrogen Cycle (नाइट्रोजन चक्र)​

Atmosphere: N₂ (78% of air)

Processes:

Nitrogen Fixation (नाइट्रोजन स्थिरीकरण):

  • N₂ → Ammonia (NH₃)
  • Lightning converts N₂
  • Nitrogen-fixing bacteria in soil
  • Legume root nodules (symbiosis)
  • Industrial (Haber process)

Nitrification (नाइट्रीकरण):

  • NH₃ → Nitrite (NO₂⁻) → Nitrate (NO₃⁻)
  • Nitrosomonas and Nitrobacter bacteria
  • In soil
  • Plants absorb nitrate

Assimilation:

  • Plants take NO₃⁻
  • Synthesize proteins and nucleic acids
  • Animals eat plants

Ammonification:

  • Dead organisms/waste → Ammonia
  • Decomposers break down proteins
  • Ammonia in soil

Denitrification:

  • NO₃⁻ → N₂ (to atmosphere)
  • Anaerobic bacteria
  • Completes cycle

3. Water Cycle (जल चक्र)​

Processes:

Evaporation:

  • Water from oceans/lakes → Vapor
  • Heat energy needed
  • Increases with temperature

Transpiration (वाष्पोत्सर्जन):

  • Water from plants → Vapor
  • Through leaves (stomata)
  • Combined with evaporation = evapotranspiration

Condensation:

  • Water vapor → Liquid droplets
  • In atmosphere
  • Forms clouds

Precipitation:

  • Water falls as rain/snow
  • Returns to land and sea

Infiltration:

  • Water soaks into soil
  • Groundwater
  • Plant uptake or to underground reservoirs

Run-off:

  • Water flowing downhill
  • To streams and rivers
  • Back to oceans

Percolation:

  • Water through soil layers
  • Deep underground
  • Slow movement

Human Impact on Ecosystems​

1. Habitat Destruction (आवास विनाश)​

Causes:

  • Deforestation (logging, clearing for agriculture)
  • Urban development (cities, roads)
  • Wetland drainage
  • Coral reef damage

Consequences:

  • Species loss
  • Reduced biodiversity
  • Fragmented habitats
  • Edge effects increase

2. Pollution (प्रदूषण)​

Air Pollution:

  • Combustion products (CO₂, NOₓ, SO₂)
  • Particulate matter
  • Acid rain
  • Photochemical smog

Water Pollution:

  • Agricultural runoff (fertilizers, pesticides)
  • Industrial waste
  • Sewage
  • Heavy metals
  • Plastic accumulation

Soil Pollution:

  • Pesticide residues
  • Heavy metals
  • Industrial waste
  • Affects plant growth

Bioaccumulation and Biomagnification:

  • Toxic substances concentrated in organisms
  • Predators have highest concentrations
  • Increases along food chain
  • Example: DDT pesticide

3. Overexploitation (अत्यधिक दोहन)​

Definition:

  • Harvesting faster than reproduction
  • Depletes populations
  • Example: Overfishing, hunting

Consequences:

  • Population collapse
  • Extinction risk
  • Ecosystem imbalance

4. Climate Change​

Causes:

  • Greenhouse gas emissions (CO₂, CH₄, N₂O)
  • Fossil fuel combustion
  • Deforestation
  • Industrial agriculture

Effects:

  • Global temperature increase
  • Extreme weather events
  • Sea level rise
  • Species range shifts
  • Breeding time changes
  • Food web disruption
  • Coral bleaching

Conservation​

1. In Situ and Ex Situ Conservation​

In Situ (में स्थान पर):

  • Protect organisms in natural habitat
  • Protected areas (national parks, reserves)
  • Habitat preservation
  • Allows natural processes

Ex Situ:

  • Protect outside natural habitat
  • Zoos, botanical gardens, seed banks
  • Breeding programs
  • Last resort when in situ fails

2. Conservation Strategies​

Protected Areas:

  • National parks
  • Wildlife reserves
  • Marine protected areas
  • Reduces hunting and habitat loss

Sustainable Use:

  • Harvest at or below reproduction rate
  • Fishing quotas
  • Selective logging
  • Maintains population

Captive Breeding:

  • Breed endangered species in captivity
  • Increase numbers
  • Reintroduce to wild
  • Example: Arabian oryx

Environmental Education:

  • Teach conservation importance
  • Change attitudes and behaviors
  • Community involvement
  • Long-term impact

International Cooperation:

  • Treaties (CITES, Ramsar)
  • Protect endangered species
  • Wetland conservation
  • Shared responsibility

Summary​

Ecology encompasses:

  • Ecosystems: Components and relationships
  • Energy Flow: From producers to decomposers
  • Nutrient Cycles: Carbon, nitrogen, water cycling
  • Populations: Growth, succession, characteristics
  • Human Impact: Habitat loss, pollution, climate change
  • Conservation: Protecting biodiversity and ecosystems

Understanding ecology essential for sustainable environmental management.