Our Environment Class 10 Notes – Ecosystem, Food Chains & Environmental Issues

Understanding our environment is crucial not just for exams, but for life. This chapter explores how living organisms interact with each other and their surroundings, forming complex ecosystems. These Class 10 Our Environment notes cover everything from food chains to waste management, aligned with the latest CBSE curriculum.

Introduction to Environment and Ecosystem

What is Environment?

Environment refers to everything that surrounds an organism and influences its life the physical and biological world in which one lives.

The environment consists of three important parts:

1. Living organisms: Plants, animals, human beings, and microorganisms
2. Physical surroundings: Land, water bodies, and air
3. Meteorological factors: Sunlight, temperature, rainfall, and humidity

What is an Ecosystem?

An ecosystem is a structural and functional unit of the biosphere consisting of living beings and the physical environment, which interact with each other and maintain a balance in nature.

In an ecosystem, energy and matter are continuously exchanged between living and non-living components.

Types of Ecosystems

Ecosystems can be broadly classified into:

Natural Ecosystems:

• Aquatic: Freshwater (ponds, lakes, rivers, streams) and Marine (oceans, coastal areas)
• Terrestrial: Grassland, Desert, and Forest

Artificial Ecosystems:

• Aquarium and Cropland

Components of Ecosystem

Ecosystems have two main components:

A. Abiotic (Non-living) Components

These include the non-living physico-chemical factors that affect the distribution, structure, behavior, and interrelationships of organisms.

Types of Abiotic Factors:

1. Inorganic substances: Carbon, nitrogen, oxygen, calcium, phosphorus, water, carbon dioxide
2. Organic substances: Carbohydrates, proteins, lipids, nucleic acids (present in living organisms and dead organic matter)
3. Climatic factors: Light, temperature, humidity, wind, rainfall, water
4. Edaphic factors: Soil, substrate, topography, minerals, pH

B. Biotic (Living) Components

The living organisms present in an ecosystem form the biotic component. Based on their mode of nutrition, they are classified as:

(i) Producers (Autotrophs)

• Include all green plants and blue-green algae
• Prepare their own food through photosynthesis
• Convert solar energy into chemical energy
• Also called photoautotrophs

Photosynthesis equation:

6 CO₂ + 6 H₂O --[Sunlight/Chlorophyll]--> C₆H₁₂O₆ + 6 O₂(Carbon dioxide + Water → Glucose + Oxygen)

(ii) Consumers (Heterotrophs)

Unable to synthesize their own food, they depend on producers or other organisms.

Types of consumers:

• Primary consumers (Herbivores): Eat plants or plant products
  • Examples: Cattle, deer, goat, rabbit, grasshoppers (terrestrial); snails, tadpoles (aquatic)
• Secondary consumers (Carnivores): Feed on herbivores
  • Examples: Cats, dogs, foxes (terrestrial); water bugs, frogs, small fish (aquatic)
• Tertiary consumers: Larger carnivores feeding on secondary consumers
  • Examples: Wolves, snakes (terrestrial); large fish, water birds (aquatic)
• Quaternary consumers (Top carnivores): Largest carnivores, not eaten by other animals
  • Examples: Tigers, lions (terrestrial); dolphins, whales (aquatic)
• Omnivores: Eat both plants and animals
  • Examples: Humans, bears, crows, dogs
• Parasites: Live on or inside other organisms
  • Examples: Bacteria, protozoans, tapeworms

(iii) Decomposers (Saprotrophs)

• Obtain food from dead organic matter
• Break down dead remains into simple substances
• Release nutrients back to the environment
• Examples: Bacteria and fungi

Importance of Decomposers:

1. Act as cleansing agents by decomposing dead bodies
2. Return nutrients to soil, air, and water for reuse
3. Maintain soil fertility
4. Enable recycling of materials in the biosphere

Food Chain and Food Web

Food Chain

A food chain is a sequential interlinking of organisms involving the transfer of food energy from producers through a series of organisms with repeated eating and being eaten.

Examples of Food Chains

Terrestrial (Grassland/Forest):

Grass → Deer → Lion(Producer → Herbivore → Carnivore)

Aquatic (Pond/Lake):

Algae → Zooplankton → Small Fish → Big Fish(Producer → Herbivore → Small carnivore → Big carnivore)

Complex aquatic chain:

Algae → Protozoan → Fish → Squid → Seal(Phytoplankton → Zooplankton → Carnivore I → Carnivore II → Top carnivore)

Characteristics of Food Chain

1. Involves nutritive interaction between living organisms
2. Always proceeds in a straight, progressive line
3. Unidirectional flow of energy from sun to producers to consumers
4. Usually consists of 3-4 trophic levels (maximum 5)
5. Omnivores occupy different positions in different food chains
6. At each transfer, 80-90% of energy is lost as heat
7. Only 10% of energy transfers to the next trophic level

Types of Food Chains

1. Grazing Food Chain

Begins with green plants (producers)

Examples:

2. Detritus Food Chain

Begins with dead organic matter (detritus)

Food Web

A food web is a network of interconnected food chains at various trophic levels, forming multiple feeding connections among different organisms in a biotic community.

In nature, food chains don't operate in isolation. Each organism may be eaten by multiple species and may itself consume multiple species, creating an interlocking pattern.

Characteristics of Food Web

1. Formed by interlinking of multiple food chains
2. Provides alternative food pathways
3. Makes ecosystems more stable
4. Helps control overpopulation of species
5. Aids in ecosystem development
6. Organisms may operate at multiple trophic levels simultaneously

Importance: If one species is affected by disease or reduction in numbers, the ecosystem doesn't collapse because alternative food sources are available through the web structure.

Trophic Levels and Energy Flow

What are Trophic Levels?

Trophic levels are the distinct sequential steps in a food chain where transfer of energy occurs.

Trophic level hierarchy:

1. First trophic level: Producers (green plants) – autotrophs
2. Second trophic level: Primary consumers (herbivores)
3. Third trophic level: Secondary consumers (small carnivores)
4. Fourth trophic level: Tertiary consumers (large carnivores)
5. Fifth trophic level (rare): Quaternary consumers (top carnivores)

Trophic levels can be represented as an ecological pyramid.

Flow of Energy in an Ecosystem

Energy flow in ecosystems follows the laws of thermodynamics:

1. Source: About 1% of sun's energy falling on leaves is used by plants in photosynthesis
2. Transfer: Energy moves from one trophic level to the next as chemical energy in food
3. Utilization: At each level, organisms use energy for metabolic activities (respiration, growth)
4. Loss: Energy is lost at each transfer (as heat), remaining unutilized
5. Decomposers: Part of energy at each level is used by decomposers

Flow of energy is unidirectional – energy lost as heat from living organisms cannot be reused by plants in photosynthesis.

Flow of material: Unlike energy, materials in ecosystems follow a cyclic pattern through biogeochemical cycles.

The 10% Law (Lindeman's Law, 1942)

According to the ten percent law, only 10% of the total energy entering a particular trophic level is available for transfer to the next trophic level.

Example:

• Sun provides 1000 J of energy
• Plants capture 1% = 10 J (the remaining 990 J is lost)
• Herbivores receive 10% of 10 J = 1 J (9 J is lost)
• Carnivores receive 10% of 1 J = 0.1 J (0.9 J is lost)

This explains why:

• Food chains are typically short (3-4 steps)
• Biomass decreases at higher trophic levels
• Vegetarian food habits are more energy-efficient
• Large carnivores are relatively rare in ecosystems

Biological Magnification (Biomagnification)

Biological magnification is the increase in concentration of harmful chemical substances in the body of living organisms at each successive trophic level of a food chain.

How It Happens

1. Non-biodegradable chemicals (pesticides like DDT, heavy metals like mercury, arsenic) enter ecosystems
2. These chemicals are absorbed by organisms but cannot be broken down or excreted
3. As one organism eats another, these chemicals accumulate
4. Concentration increases progressively at each trophic level
5. Humans, occupying the highest trophic level, accumulate maximum concentrations

Example: DDT in Aquatic Ecosystem

Health Effects

• Mercury accumulation: Minamata disease
• Fluorine accumulation: Knee-knock syndrome
• DDT effects: Thinning of eggshells in birds, reproductive issues
• General effects: Cancer, neurological disorders, immune system damage

Prevention

1. Minimize use of non-biodegradable pesticides
2. Develop biodegradable alternatives
3. Implement integrated pest management
4. Monitor and regulate industrial discharge
5. Promote organic farming practices

Waste Management

Types of Waste

Biodegradable Wastes

Substances that can be broken down by natural processes (action of bacteria, fungi) into simpler, harmless substances.

Examples:

• Urine and fecal matter
• Sewage
• Paper
• Vegetable and fruit peels
• Agricultural residues
• Wood and cloth

Harmful effects (when accumulated in large quantities):

1. Produce foul smell during decomposition
2. Breeding ground for flies (spread diarrhea, typhoid, cholera)
3. Create stagnant water pools (mosquito breeding → malaria, dengue)
4. Reduce soil fertility when industrial organic waste is dumped

Non-Biodegradable Wastes

Substances that cannot be degraded by natural biological processes; only physical processes (heat, pressure) can affect them.

Examples:

• Plastics and polythene
• Metals (aluminum, iron)
• Glass
• Pesticides (DDT, BHC)
• Heavy metals (mercury, lead, arsenic)
• Radioactive substances (uranium, plutonium)

Harmful effects:

1. Enter food chains and cause biomagnification
2. Persist in environment for long periods
3. Affect soil fertility
4. Make soil acidic or alkaline
5. Cannot enter biogeochemical cycles

Comparison

Modes of Waste Disposal

1. Landfills

• Solid wastes buried in low-lying areas to level uneven surfaces
• Used primarily in urban areas
• Simple but requires large land areas

2. Recycling

• Paper → Recycled into new paper at mills
• Plastic → Melted and remolded at processing factories
• Metals → Sent to metal industries
• Industrial wastes → Treated in special plants
• Most effective method for resource conservation

3. Composting

• Household organic waste (peels, leftover food, dead leaves) converted to compost
• Used as manure in gardens and fields
• Natural, eco-friendly method
• Enriches soil with nutrients

4. Incineration (Burning at High Temperature)

• Burning substances at very high temperature (>1000°C)
• Converts waste into ashes
• Used for: household waste, chemical waste, hospital waste
• Generates CO₂ and water vapor (escape into atmosphere)
• Remaining ash disposed by landfills
• Effective for bulk waste removal

5. Biogas Production

• Biodegradable wastes used in biogas plants
• Generates biogas (cheap fuel)
• Produces manure (cheap fertilizer)
• Dual benefit: energy + fertilizer

Environmental Problems

A. Ozone Layer Depletion

What is Ozone?

• Ozone (O₃) is a form of oxygen with three oxygen atoms
• Forms a layer in the stratosphere (18-50 km above Earth)
• Acts as a shield protecting life from harmful UV radiation

Formation and Breakdown

Formation:

O₂ --[UV radiation]--> O + O (free oxygen atoms)O₂ + O --> O₃ (ozone)

Natural breakdown:

O₃ --[UV radiation]--> O₂ + OO + O₂ --> O₃

These reactions maintain equilibrium.

Ozone Depletion

Causes:

1. Chlorofluorocarbons (CFCs): From refrigerators, air conditioners, aerosol sprayers
2. Methane (CH₄): From paddy fields, cattle sheds, biogas plants
3. Nitrous oxides (N₂O): From fertilizers, automobiles

Mechanism:

• CFCs release active chlorine (Cl and ClO radicals) under UV radiation
• These radicals destroy ozone through chain reactions
• Convert ozone back to oxygen

Ozone Hole

• First discovered over Antarctica in 1985
• Represents areas where ozone layer has thinned significantly
• Not an actual "hole" but a region of severe depletion

Effects of Ozone Depletion

1. Skin cancer: Increased UV radiation damages DNA
2. Eye damage: Cataracts, other eye diseases
3. Immune system damage: Lowered resistance to diseases
4. Crop damage: Affects plant growth
5. Marine ecosystem damage: Affects phytoplankton

Prevention

• Montreal Protocol (1987): International agreement to phase out CFCs
• UNEP (United Nations Environment Programme): Works to freeze CFC production
• Use CFC-free alternatives in refrigeration and aerosols
• Develop ozone-friendly technologies

B. Greenhouse Effect and Global Warming

Greenhouse Effect

The greenhouse effect is the trapping of heat in Earth's atmosphere by greenhouse gases, similar to how glass traps heat in a greenhouse.

Process:

1. Sunlight enters Earth's atmosphere
2. Earth's surface absorbs energy and heats up
3. Earth radiates energy back (infrared radiation)
4. Greenhouse gases trap this outgoing radiation
5. Trapped heat warms the atmosphere

Greenhouse Gases:

1. Carbon dioxide (CO₂): From fossil fuel burning, deforestation
2. Methane (CH₄): From marshes, paddy fields, cattle
3. Nitrous oxides (N₂O₅): From fertilizers, bacterial action
4. Chlorofluorocarbons (CFCs): From refrigerators, air conditioners

Global Warming

Global warming is the gradual increase in Earth's average temperature due to increased greenhouse gas concentrations.

Observed change: Temperature increased by 0.6°C in the 20th century

Effects:

1. Melting of glaciers and polar ice: Sea level rise
2. Climate change: Altered precipitation patterns
3. Heat-related diseases: Increased mortality
4. Pest proliferation: More parasites and agricultural pests
5. Soil moisture decrease: Desertification
6. Species extinction: Inability of some species to adapt
7. Extreme weather events: More hurricanes, floods, droughts

Prevention of Global Warming

1. Minimize fossil fuel use: Switch to renewable energy
2. Energy-efficient devices: Reduce energy consumption
3. Recycling and reusing: Use recyclable, reusable products
4. Afforestation: Plant more trees (absorb CO₂)
5. Reduce waste: Recycle newsprint, cardboard, home waste
6. Public transportation: Reduce vehicle emissions
7. Sustainable practices: Promote eco-friendly technologies

C. Acid Rain

What is Acid Rain?

Acid rain is precipitation (rain, snow, fog) with a pH lower than normal (pH < 5.6) due to atmospheric pollution.

Formation:

1. Sulphur oxides (SO₂, SO₃) and nitrogen oxides (NO, NO₂) released from:
   • Power stations
   • Factories
   • Smelters
   • Automobile exhausts
2. These gases rise and react with water vapor in clouds
3. Form sulphuric acid (H₂SO₄) and nitric acid (HNO₃)
4. Fall as acid rain

Effects of Acid Rain

1. Plant damage: Leaf damage, growth inhibition
2. Soil degradation: Alters chemical balance, pH
3. Aquatic life damage: Acidifies water bodies, kills fish
4. Heritage buildings: Corrodes marble, limestone (e.g., Taj Mahal)
5. Metal corrosion: Damages metal structures
6. Human health: Respiratory problems

Prevention

1. Use cleaner fuels (low sulfur content)
2. Install scrubbers in factory chimneys
3. Use catalytic converters in vehicles
4. Shift to renewable energy sources
5. International cooperation to reduce emissions

Important Definitions to Remember

Formulas and Concepts 

Practice Questions and Answers

Set A: Very Short Answer Questions (1 Mark)

Q1. What is an ecosystem?

Ecosystem is the functional unit of the environment consisting of various interactions among its physical and biological components. Examples: garden, pond, forest.

Q2. Why are green plants called producers?

Green plants are called producers because they convert solar energy into chemical energy during photosynthesis and produce their own organic food from inorganic compounds.

Q3. Name two biodegradable wastes.

Vegetable peels, paper, wood, cotton cloth, agricultural residues, cow dung.

Q4. Name two non-biodegradable wastes.

Plastics, polythene, metals, glass, DDT, radioactive substances.

Q5. What is the significance of the ozone layer?

Ozone layer absorbs harmful ultraviolet (UV) radiations from the sun and protects life on Earth from their harmful effects like skin cancer and eye damage.

Q6. Define trophic level.

Each step or level of the food chain where transfer of energy occurs is called a trophic level.

Q7. What is biological magnification?

Biological magnification is the progressive increase in concentration of harmful non-biodegradable chemicals at successive trophic levels in a food chain.

Q8. What percentage of solar energy is captured by plants?

About 1% of the sun's energy falling on leaves is captured by plants for photosynthesis.

Q9. What are omnivores? Give one example.

Omnivores are organisms that feed on both plants and animals. Example: humans, bears, crows.

Q10. What causes acid rain?

Acid rain is caused by emissions of sulphur oxides (SO₂) and nitrogen oxides (NO₂) from industries and vehicles, which react with water vapor in the atmosphere to form acids.

Set B: Short Answer Questions (2-3 Marks)

Q11. Why is the flow of energy in an ecosystem unidirectional?

The flow of energy in an ecosystem is unidirectional because:

1. Energy flows from the sun to producers, then to various levels of consumers
2. At each transfer, energy is used for metabolic activities (respiration, movement, growth)
3. A large amount of energy (90%) is lost as heat at each trophic level
4. The energy lost as heat cannot be reused by plants for photosynthesis
5. Energy does not return to the sun or previous trophic levels

Q12. Explain the 10% law with an example.

The 10% law states that only 10% of energy from one trophic level is transferred to the next level.

Example:

• Sun provides 1000 J of energy
• Plants capture 1% = 10 J (990 J lost to environment)
• Herbivores get 10% of 10 J = 1 J (9 J lost)
• Carnivores get 10% of 1 J = 0.1 J (0.9 J lost)

This explains why food chains are short and why there are fewer organisms at higher trophic levels.

Q13. What are decomposers? Why are they essential for the ecosystem?

Decomposers are microorganisms (bacteria and fungi) that break down dead organic matter into simpler substances.

Importance:

1. Cleansing agents: Decompose dead bodies of plants and animals
2. Nutrient recycling: Return nutrients (carbon, nitrogen) to soil, air, and water for reuse by producers
3. Maintain soil fertility: Keep soil rich in nutrients
4. Enable material recycling: Allow biogeochemical cycles to continue
5. Prevent accumulation: Stop buildup of dead organic matter

Q14. Differentiate between biodegradable and non-biodegradable wastes.

Q15. What is a food web? How is it different from a food chain?

Food Web: A network of interconnected food chains at various trophic levels, forming multiple feeding connections.

Differences:

Importance of food web:

• Provides alternative food sources
• Makes ecosystem more stable
• Controls overpopulation
• Supports ecosystem development

Q16. Explain biological magnification with an example.

Biological magnification is the increase in concentration of harmful non-biodegradable chemicals at each successive trophic level.

Example: DDT in aquatic food chain:

• Water: 0.02 ppm
• Phytoplankton: 5 ppm (250× increase)
• Zooplankton: 5 ppm
• Small fish: 240 ppm (48× increase)
• Large fish: 240 ppm
• Fish-eating birds: 1,600 ppm (6.7× increase)

Why it happens:

1. Chemicals enter through water/food
2. Organisms cannot break down these chemicals
3. Chemicals accumulate in body tissues
4. Concentration multiplies at each level
5. Humans at top level get maximum concentration

Q17. What are the harmful effects of ozone layer depletion?

1. Skin cancer: Increased UV radiation damages DNA in skin cells
2. Eye damage: Cataracts and other eye diseases due to UV exposure
3. Immune system damage: Weakens body's defense against diseases
4. Crop damage: Affects photosynthesis and plant growth
5. Marine ecosystem damage: Kills phytoplankton, affecting entire food chain
6. Material damage: Degrades plastics and other materials

Q18. What is the greenhouse effect? Name four greenhouse gases.

Greenhouse effect: The trapping of heat in Earth's atmosphere by certain gases, preventing it from escaping to space, similar to glass in a greenhouse.

Process:

1. Sunlight reaches Earth
2. Earth absorbs energy and heats up
3. Earth radiates heat back (infrared radiation)
4. Greenhouse gases trap this outgoing heat
5. Trapped heat warms the atmosphere

Four greenhouse gases:

1. Carbon dioxide (CO₂)
2. Methane (CH₄)
3. Nitrous oxides (N₂O)
4. Chlorofluorocarbons (CFCs)

Q19. Why is vegetarian food habit more energy efficient?

Vegetarian food habit is more energy efficient because:

1. Shorter food chain: Vegetarians are primary consumers, directly eating producers
2. More energy available: Receive 10% of plant energy directly
3. Less energy loss: Non-vegetarians receive only 10% of 10% = 1% of plant energy
4. Example:
   • Plant energy: 1000 J
   • Vegetarian gets: 100 J (10%)
   • Non-vegetarian (via herbivore): Gets only 10 J (1%)

Therefore, vegetarian diet can support more people with the same amount of plant production.

Q20. Suggest any four methods to reduce waste generation.

1. Recycle and reuse: Separate waste for recycling (paper, plastic, metals)
2. Use cloth bags: Avoid single-use plastic bags while shopping
3. Compost organic waste: Convert kitchen waste into compost for plants
4. Minimize packaging: Choose products with less packaging
5. Donate/repair: Give away or repair items instead of discarding
6. Reduce consumption: Buy only what you need

Set C: Long Answer Questions (5 Marks)

Q21. Draw a neat diagram of a food chain consisting of at least four trophic levels. Explain energy flow through this food chain using the 10% law.

Explanation:

1. First Trophic Level (Producers - Grass):
   • Sun provides 10,000 J of energy
   • Grass captures only 1% = 100 J through photosynthesis
   • Remaining 9,900 J is lost as heat
2. Second Trophic Level (Primary Consumers - Deer):
   • Deer eats grass and gets 100 J
   • Only 10% is converted to deer's body mass = 10 J
   • Remaining 90 J (90%) is lost through:
     • Respiration (heat energy)
     • Movement and metabolic activities
     • Undigested food
3. Third Trophic Level (Secondary Consumers - Wolf):
   • Wolf eats deer and gets 10 J
   • Only 10% is stored = 1 J
   • 9 J (90%) is lost as heat and metabolic activities
4. Fourth Trophic Level (Tertiary Consumers - Eagle):
   • Eagle gets 1 J from wolf
   • Only 10% is stored = 0.1 J
   • 0.9 J is lost

Significance:

• Explains why food chains are short (3-4 levels)
• Explains why top carnivores are fewer in number
• Demonstrates inefficiency of energy transfer
• Shows why ecosystems need continuous solar energy input

Q22. What are the different components of an ecosystem? Explain with examples.

Ecosystem components are divided into two main categories:

A. Abiotic (Non-living) Components

These are physico-chemical factors that affect organism distribution and behavior.

1. Inorganic substances:

• Carbon, nitrogen, oxygen, calcium, phosphorus
• Compounds: water (H₂O), carbon dioxide (CO₂)
• Present in air, water, or dissolved in soil

2. Organic substances:

• Carbohydrates, proteins, lipids, nucleic acids
• Present in living organisms and dead matter
• Decomposed by bacteria and fungi

3. Climatic factors:

• Light, temperature, humidity, wind, rainfall
• Affect growth, reproduction, distribution

4. Edaphic factors:

• Soil type, pH, minerals, topography
• Influence plant and organism distribution

B. Biotic (Living) Components

Classified by mode of nutrition:

1. Producers (Autotrophs):

• All green plants and blue-green algae
• Prepare food through photosynthesis
• Convert solar energy to chemical energy
• Examples: Grass, trees, phytoplankton

2. Consumers (Heterotrophs):

• Cannot make their own food
• Depend on producers or other organisms

Types:

• Primary (Herbivores): Deer, rabbit, grasshopper
• Secondary (Small carnivores): Frog, small fish, snakes
• Tertiary (Large carnivores): Wolves, large fish
• Quaternary (Top carnivores): Lions, eagles, sharks
• Omnivores: Humans, bears, crows
• Parasites: Tapeworms, bacteria

3. Decomposers (Saprotrophs):

• Break down dead organic matter
• Release nutrients back to environment
• Examples: Bacteria, fungi

Interaction: All components interact to maintain ecosystem balance through nutrient cycling and energy flow.

Q23. Explain the greenhouse effect and global warming. What are their causes and effects?

Greenhouse Effect

The trapping of heat in Earth's atmosphere by greenhouse gases, preventing it from escaping to space.

Process:

1. Sunlight enters Earth's atmosphere
2. Earth's surface absorbs energy and heats up
3. Earth radiates infrared (heat) radiation back
4. Greenhouse gases absorb and trap this heat
5. Trapped heat warms the atmosphere

Natural vs. Enhanced:

• Natural greenhouse effect is essential for life (without it, Earth would be -18°C)
• Enhanced greenhouse effect due to human activities causes problems

Global Warming

The gradual increase in Earth's average temperature due to increased concentration of greenhouse gases.

Observed change: Temperature increased by 0.6°C in the 20th century

Causes

Greenhouse gases and their sources:

1. Carbon dioxide (CO₂):
   • Burning fossil fuels (coal, petroleum, natural gas)
   • Deforestation
   • Industrial processes
2. Methane (CH₄):
   • Paddy fields (waterlogged rice cultivation)
   • Cattle sheds (ruminant digestion)
   • Biogas plants
   • Marshes and wetlands
3. Nitrous oxides (N₂O):
   • Excessive fertilizer use
   • Bacterial action in soil
   • Automobile exhausts
4. Chlorofluorocarbons (CFCs):
   • Refrigerators and air conditioners
   • Aerosol sprayers
   • Fire extinguishers

Effects

Environmental:

1. Melting glaciers and ice caps: Leading to sea level rise
2. Coastal flooding: Low-lying areas submerged
3. Climate change: Altered rainfall patterns
4. Extreme weather: More hurricanes, droughts, floods
5. Desertification: Decreased soil moisture

Biological:

1. Species extinction: Inability to adapt to rapid changes
2. Coral bleaching: Death of coral reefs
3. Pest proliferation: More agricultural pests
4. Disease spread: Expansion of disease vectors

Human impacts:

1. Heat-related diseases: Increased mortality
2. Food security: Reduced crop yields
3. Water scarcity: Changed precipitation patterns
4. Economic losses: Damage to infrastructure

Prevention

1. Reduce fossil fuel consumption
2. Use renewable energy (solar, wind, hydroelectric)
3. Energy-efficient appliances and practices
4. Afforestation and reforestation
5. Sustainable transportation
6. Recycling and waste reduction
7. International cooperation (Paris Agreement)

Q24. Describe various methods of waste disposal. Which method is most eco-friendly and why?

Methods of Waste Disposal

1. Landfills

• Process: Solid wastes buried in low-lying areas
• Use: Levels uneven surfaces
• Advantages: Simple, inexpensive
• Disadvantages:
  • Requires large land area
  • Groundwater contamination risk
  • Methane production (greenhouse gas)
  • Land becomes unusable for years

2. Incineration

• Process: Burning waste at high temperature (>1000°C)
• Products: Ash, CO₂, water vapor
• Advantages:
  • Reduces volume significantly
  • Generates energy (heat)
• Disadvantages:
  • Air pollution
  • Produces toxic gases if not controlled
  • Expensive equipment
  • Cannot burn all types of waste

3. Recycling

• Process: Converting waste materials into new products
• Materials: Paper, plastic, metals, glass
• Advantages:
  • Conserves natural resources
  • Saves energy
  • Reduces landfill burden
  • Creates employment
• Disadvantages:
  • Requires segregation
  • Some materials lose quality
  • Transportation costs

4. Composting

• Process: Biological decomposition of organic waste
• Product: Nutrient-rich compost (manure)
• Suitable for: Kitchen waste, garden waste, agricultural residues
• Advantages:
  • Completely natural process
  • Produces valuable fertilizer
  • Enriches soil
  • No harmful emissions
  • Can be done at household level
• Disadvantages:
  • Takes time (weeks to months)
  • Requires space
  • May attract pests if not managed properly

5. Biogas Production

• Process: Anaerobic decomposition of biodegradable waste
• Products: Biogas (fuel) and slurry (manure)
• Advantages:
  • Dual benefit: energy + fertilizer
  • Reduces dependence on fossil fuels
  • Reduces waste volume
• Disadvantages:
  • Requires initial investment
  • Needs regular maintenance
  • Suitable only for organic waste

Most Eco-Friendly Method: Composting

Reasons:

1. Natural process: Uses natural decomposition by microorganisms
2. Zero pollution: No harmful gases or chemicals released
3. Closes nutrient cycle: Returns nutrients to soil
4. Sustainable: Can be continued indefinitely
5. Low cost: Minimal infrastructure needed
6. Household level: Can be done by anyone
7. Dual benefit: Reduces waste + produces fertilizer
8. Improves soil: Enhances soil structure and water retention
9. No energy required: Works naturally
10. Complete disposal: Organic matter completely decomposed

Best overall approach: Combine methods

• Reduce waste generation
• Reuse items when possible
• Recycle paper, plastic, metals
• Compost organic waste
• Incinerate hazardous waste (with proper controls)
• Landfill only as last resort

Waste hierarchy: Reduce > Reuse > Recycle > Recover energy > Landfill

Q25. What is biological magnification? Explain with a suitable example. Why is it dangerous for humans?

Biological magnification (biomagnification) is the process by which the concentration of harmful, non-biodegradable chemicals increases progressively at each successive trophic level in a food chain.

Mechanism

1. Entry: Harmful chemicals enter ecosystems through:
   • Agricultural runoff (pesticides)
   • Industrial discharge (heavy metals)
   • Atmospheric deposition
2. Absorption: Producers (plants/phytoplankton) absorb these chemicals from water/soil
3. Non-biodegradability: Organisms cannot break down or excrete these chemicals
4. Accumulation: Chemicals accumulate in body tissues (fat, organs)
5. Magnification: When one organism eats another, chemicals concentrate
6. Progressive increase: Concentration multiplies at each trophic level

Example: DDT in Aquatic Ecosystem

Food chain: Water → Phytoplankton → Zooplankton → Small fish → Large fish → Fish-eating birds

Overall magnification: From 0.02 ppm to 1,600 ppm = 80,000 times increase

Real-world Example

Minamata Disease (Japan, 1956):

• Industrial mercury discharged into Minamata Bay
• Accumulated in fish
• Humans eating fish developed severe neurological disorders
• Symptoms: Numbness, muscle weakness, vision/hearing loss, paralysis
• Over 2,000 people affected, hundreds died

Why Dangerous for Humans

1. Top position: Humans occupy the highest trophic level, receiving maximum concentration

2. Multiple food chains: Humans eat from various sources, accumulating chemicals from multiple pathways

3. Long-term accumulation: Chemicals persist in human body for years

4. Health effects:

Immediate:

• Nausea, vomiting
• Skin rashes
• Headaches

Long-term:

• Cancer: DDT, heavy metals are carcinogenic
• Neurological damage: Mercury affects brain and nervous system
• Reproductive issues: Reduced fertility, birth defects
• Immune suppression: Weakened disease resistance
• Organ damage: Liver, kidney, heart damage
• Hormonal disruption: Endocrine system affected

5. Bioaccumulation: Even small daily exposures add up over lifetime

6. Fat solubility: Chemicals like DDT dissolve in fat, stored in adipose tissue

7. Breast milk transmission: Nursing mothers pass chemicals to infants

8. No antidote: Most chemicals cannot be easily removed from body

Common Biomagnifying Substances

1. Pesticides: DDT, BHC, aldrin, dieldrin
2. Heavy metals: Mercury, lead, cadmium, arsenic
3. Industrial chemicals: PCBs, dioxins
4. Radioactive substances: Strontium-90, cesium-137

Prevention

1. Ban harmful chemicals: International agreements (Stockholm Convention)
2. Use alternatives: Biodegradable pesticides, integrated pest management
3. Regulate discharge: Strict industrial waste treatment
4. Monitoring: Regular testing of water, food
5. Organic farming: Avoid synthetic pesticides
6. Awareness: Educate public about risks

Conclusion: Biological magnification demonstrates how human activities can have far-reaching consequences through ecosystems, ultimately affecting human health. It emphasizes the need for sustainable practices and careful chemical management.

Mnemonic Tips to Remember

1. Components of Ecosystem: "ABPC"

• A - Abiotic (non-living)
• B - Biotic (living)
• P - Producers
• C - Consumers

2. Types of Consumers: "HCOT"

• H - Herbivores (Primary)
• C - Carnivores (Secondary)
• O - Omnivores
• T - Top carnivores (Quaternary)

3. Greenhouse Gases: "COCONUT"

• CO - Carbon dioxide (CO₂)
• CO - Carbon monoxide
• N - Nitrous oxide (N₂O)
• U - UV-trapping gases
• T - Trace gases (CFCs, Methane)

Alternative: "Can Men Never Catch"

• C - Carbon dioxide (CO₂)
• M - Methane (CH₄)
• N - Nitrous oxide (N₂O)
• C - CFCs

4. Ozone Depletion Causes: "COMMON"

• C - CFCs (Chlorofluorocarbons)
• O - Oxides of nitrogen
• M - Methane
• M - Man-made chemicals
• O - Other aerosols
• N - NOₓ from vehicles

5. Effects of Ozone Depletion: "SCIMP"

• S - Skin cancer
• C - Cataract (eye damage)
• I - Immune system damage
• M - Marine ecosystem affected
• P - Plant growth reduced

6. Trophic Levels: "Please Call Some Taxis"

• P - Producers (1st level)
• C - Consumers - Primary (2nd level)
• S - Secondary consumers (3rd level)
• T - Tertiary consumers (4th level)

7. Waste Disposal Methods: "CRIB-L"

• C - Composting
• R - Recycling
• I - Incineration
• B - Biogas production
• L - Landfills

8. Biodegradable Items: "PAPER"

• P - Paper
• A - Agricultural waste
• P - Plant parts (leaves, peels)
• E - Edible wastes
• R - Rags (cloth)

9. Non-biodegradable Items: "PGMD"

• P - Plastics
• G - Glass
• M - Metals
• D - DDT (pesticides)

10. 10% Energy Rule: "Ten Percent Passes"

• At each trophic level, only Ten Percent of energy Passes to the next level
• Alternative: Think "90% Lost, 10% Most" (90% lost, 10% reaches next level)

11. Decomposer Functions: "RNFC"

• R - Recycle nutrients
• N - Nutrient release
• F - Fertility maintenance
• C - Cleansing agents

12. Global Warming Effects: "MCHEFS"

• M - Melting ice caps
• C - Climate change
• H - Heat waves
• E - Extreme weather
• F - Flooding
• S - Species extinction

13. Food Chain Direction: "Sun Plants Herbivores Carnivores Top"

• Always remember: Energy flows from Sun → Plants → Herbivores → Carnivores → Top carnivores
• Simple: SPHCT

14. Biological Magnification Example: "Water Phyto Zoo Small Big Birds"

• Water → Phytoplankton → Zooplankton → Small fish → Big fish → Birds
• Concentration increases at each step

15. Abiotic Factors: "SWAT-C"

• S - Soil
• W - Water
• A - Air
• T - Temperature
• C - Climatic factors (light, humidity)

One-Page Summary: Our Environment

• Environment: Everything surrounding an organism—living and non-living factors
• Ecosystem: Functional unit where living organisms interact with physical environment
• Food Chain: Linear sequence of organisms transferring energy through feeding
• Food Web: Interconnected network of food chains
• Trophic Level: Each step in a food chain
• Biological Magnification: Increase in toxic chemical concentration at successive trophic levels

Ecosystem Components

Abiotic (Non-living):

• Physical: Air, water, soil
• Climatic: Temperature, light, humidity, rainfall

Biotic (Living):

• Producers (Autotrophs): Green plants, algae—make own food via photosynthesis
• Consumers (Heterotrophs):
  • Primary (herbivores): Eat plants
  • Secondary (carnivores): Eat herbivores
  • Tertiary/Quaternary: Top carnivores
• Decomposers: Bacteria, fungi—break down dead matter, recycle nutrients

Food Chain & Energy Flow

Structure: Sun → Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers

10% Law (Lindeman):

• Only 10% of energy transfers to next trophic level
• 90% lost as heat and metabolic activities
• Explains short food chains (3-4 levels maximum)

Example:

• Sun (1000 J) → Plants (10 J) → Herbivores (1 J) → Carnivores (0.1 J)

Energy Flow: Unidirectional (cannot return to previous levels)

Material Flow: Cyclic (through biogeochemical cycles)

Food Web

• Multiple interconnected food chains
• Provides alternative feeding pathways
• Increases ecosystem stability
• Prevents collapse if one species affected

Ecological Pyramids

1. Pyramid of Numbers: Number of organisms at each level
2. Pyramid of Biomass: Total dry weight at each level
3. Pyramid of Energy: Energy content at each level (always upright)

Biological Magnification

• Non-biodegradable toxins (DDT, mercury, heavy metals) accumulate
• Concentration increases at higher trophic levels
• Example: Water (0.02 ppm) → Fish (240 ppm) → Birds (1600 ppm)
• Effects: Cancer, neurological damage, reproductive issues
• Humans most affected (top of food chain)

Waste Management

Biodegradable: Can be broken down by microorganisms

• Examples: Food waste, paper, wood, plant matter
• Disposal: Composting, biogas production

Non-biodegradable: Cannot be broken down naturally

• Examples: Plastics, metals, glass, DDT
• Disposal: Recycling, reuse (not landfill/burning)

Disposal Methods:

1. Composting ✓ (Most eco-friendly)
2. Recycling ✓
3. Biogas production ✓
4. Incineration (Controlled)
5. Landfills (Last resort)

Environmental Problems

1. Ozone Layer Depletion

Location: Stratosphere (18-50 km above Earth)

Function: Absorbs harmful UV radiation

Causes: CFCs (from ACs, refrigerators), methane, nitrogen oxides

Effects:

• Skin cancer
• Cataracts
• Immune system damage
• Crop damage

Solution: Montreal Protocol (ban CFCs)

2. Greenhouse Effect & Global Warming

Greenhouse Gases: CO₂, CH₄, N₂O, CFCs

Sources:

• Fossil fuel burning
• Deforestation
• Industries, vehicles
• Agriculture (methane)

Effects:

• Temperature rise (0.6°C in 20th century)
• Melting glaciers → sea level rise
• Extreme weather events
• Species extinction
• Droughts, floods

Solutions:

• Renewable energy
• Afforestation
• Energy efficiency
• Reduce fossil fuel use

3. Acid Rain

Causes: SO₂ and NO₂ from industries/vehicles react with water

Effects:

• Plant/soil damage
• Aquatic life death
• Building corrosion (Taj Mahal)

Important Points to Remember

1. Only 1% of solar energy captured by plants
2. 10% energy transfer between trophic levels
3. Food chains typically 3-4 levels long
4. Decomposers are essential for nutrient recycling
5. Energy flow is unidirectional
6. Material flow is cyclic
7. Food webs are more stable than food chains
8. Humans occupy highest trophic level → maximum toxin accumulation
9. Vegetarian diet more energy-efficient than non-vegetarian
10. Composting is most eco-friendly waste disposal

Conclusion

Learn Our Environment is not just about scoring marks it's about becoming environmentally conscious citizens. This chapter teaches us how delicately balanced our ecosystems are and how human activities can disrupt this balance.