Our Environment

Introduction

• The environment encompasses all living and non-living components interacting in a given area, maintaining a natural balance.
• This chapter explores ecosystems, their components, energy flow, food chains, and human impacts like ozone depletion and waste management.
• Understanding environmental interactions is crucial for sustainable living.

13.1 Eco-System – What Are Its Components?

• Ecosystem: A system of interacting organisms (biotic) and physical surroundings (abiotic) in an area, maintaining balance.
• Components:
  • Biotic: Living organisms (plants, animals, microorganisms, humans).
  • Abiotic: Non-living factors (temperature, rainfall, wind, soil, minerals).
• Examples:
  • Natural Ecosystems: Forests, ponds, lakes.
  • Artificial Ecosystems: Gardens, crop fields, aquariums.
• Activity 13.1:
  • Design an aquarium: Requires space (jar), water, oxygen (aerator), food.
  • Add aquatic plants/animals for a self-sustaining system (plants produce oxygen, animals consume plants).
  • Aquariums need periodic cleaning to remove waste; natural ponds/lakes are self-cleaned by decomposers and water flow.
• Organism Roles:
  • Producers: Green plants, some bacteria; use sunlight and chlorophyll to produce food (e.g., sugars, starch) via photosynthesis.
  • Consumers: Depend on producers directly/indirectly.
    • Herbivores: Eat plants (e.g., deer, rabbit).
    • Carnivores: Eat animals (e.g., lion, eagle).
    • Omnivores: Eat both (e.g., human, bear).
    • Parasites: Live on/in hosts (e.g., lice, tapeworm).
  • Decomposers: Bacteria, fungi; break down dead organisms/waste into simple inorganic substances for soil replenishment.
• Activity 13.2:
  • Avoid predatory aquatic animals in aquariums to prevent ecosystem collapse.
  • Discuss organism interdependence: Producers support consumers; consumers provide nutrients via waste; decomposers recycle nutrients.
  • Example food chain: Algae → Small fish → Large fish.
  • Primary importance: Producers (base of food chain, energy source); all groups are critical for balance.
• Ecosystems rely on interdependent biotic and abiotic components for stability.

13.1.1 Food Chains and Webs

• Food Chain: Series of organisms where each feeds on the previous one, forming trophic levels (Fig. 13.1).
• Trophic Levels (Fig. 13.2):
  • 1st: Producers (autotrophs, e.g., plants).
  • 2nd: Primary consumers (herbivores, e.g., deer).
  • 3rd: Secondary consumers (small carnivores, e.g., frogs).
  • 4th: Tertiary consumers (large carnivores, e.g., lions).
  

  Figure:Trophic levels
• Energy Flow (Fig. 13.4):
  • Unidirectional: From sun to producers to consumers to decomposers.
  • Producers capture ~1% of sunlight energy, converting it to chemical energy.
  • At each trophic level, ~10% of energy is transferred to the next (rest lost as heat, used in digestion/work).
  • Energy loss limits food chains to 3–4 steps.
  

  Figure:Diagram showing flow of energy in an ecosystem
• Food Web: Network of interconnected food chains; each organism may be eaten by multiple others (Fig. 13.3).

Figure:Food-web
• Biological Magnification:
  • Non-degradable chemicals (e.g., pesticides) accumulate in organisms, increasing in concentration up the food chain.
  • Humans (top trophic level) accumulate the highest concentrations, leading to health risks.
• Activity 13.3:
  • Debate pesticide bans in food items; sources include crops treated with pesticides, absorbed by plants or aquatic organisms.
  • Reduce intake: Wash produce, choose organic foods, support stricter regulations.
• Questions:
  1. Trophic Levels:
     • Steps in a food chain; Example: Grass → Deer → Lion.
     • Levels: Grass (producer, 1st), Deer (primary consumer, 2nd), Lion (secondary consumer, 3rd).
  2. Decomposers’ Role:
     • Break down dead organisms/waste into inorganic substances, recycling nutrients for plants; prevent waste accumulation.
• Food chains and webs illustrate energy flow and chemical accumulation in ecosystems.

13.2 How Do Our Activities Affect the Environment?

• Human Impact: Our activities alter the environment, causing issues like pollution, ozone depletion, and waste accumulation.
• Human actions require careful management to minimize environmental harm.

13.2.1 Ozone Layer and How It Is Getting Depleted

• Ozone (O₃):
  • Molecule of three oxygen atoms; toxic at ground level but vital in the upper atmosphere.
  • Shields Earth from harmful ultraviolet (UV) radiation, which causes skin cancer and ecosystem damage.
• Formation:
  • UV radiation splits O₂ into free oxygen atoms: \( \text{O}_2 \xrightarrow{\text{UV}} \text{O} + \text{O} \).
  • Free oxygen combines with O₂: \( \text{O} + \text{O}_2 \rightarrow \text{O}_3 \).
• Depletion:
  • Sharp decline since the 1980s due to chlorofluorocarbons (CFCs) used in refrigerants and fire extinguishers.
  • CFCs release chlorine, which breaks down ozone molecules.
• Action Taken:
  • 1987 UNEP agreement (Montreal Protocol) froze CFC production at 1986 levels.
  • Mandatory CFC-free refrigerators globally.
• Activity 13.4:
  • Research chemicals (e.g., CFCs, halons) causing ozone depletion.
  • Evaluate regulations’ success; recent data shows reduced ozone hole size due to CFC bans.
• Ozone protection is critical for life, with global efforts reducing depletion.

13.2.2 Managing the Garbage We Produce

• Waste Generation:
  • Daily waste includes kitchen waste, paper, plastics, clothes, footwear.
  • Increased by lifestyle changes, disposable products, and non-biodegradable packaging.
• Biodegradable vs. Non-Biodegradable:
  • Biodegradable: Broken down by biological processes (e.g., food, paper).
  • Non-Biodegradable: Persist in environment (e.g., plastics, metals); broken down only by physical processes (heat, pressure).
• Activity 13.5:
  • Bury household waste under 15 cm soil; observe at 15-day intervals.
  • Biodegradable (e.g., food, paper) decomposes; non-biodegradable (e.g., plastics) persists.
  • Food waste decomposes fastest.
• Activity 13.6:
  • Research biodegradable (e.g., organic matter) and non-biodegradable (e.g., plastics, lifetime: 100–1000 years) substances.
  • Biodegradable plastics exist but may still harm environment during production/decomposition.
• Activity 13.7:
  • Investigate household/classroom waste: Quantity, biodegradability.
  • Check local waste collection/treatment systems for separate biodegradable/non-biodegradable handling.
  • Solutions: Composting, recycling, reducing single-use items.
• Activity 13.8:
  • Study local sewage treatment to prevent water pollution.
  • Investigate industrial waste treatment to avoid soil/water contamination.
• Activity 13.9:
  • E-waste contains hazardous materials (e.g., lead, mercury), harming soil/water if not properly disposed.
  • Plastic recycling reduces waste but may release pollutants during processing.
• Disposable Cups Case Study:
  • Plastic cups replaced reusable glasses for hygiene but caused waste accumulation.
  • Kulhads (clay cups) deplete fertile soil; paper cups are biodegradable, reducing environmental impact.
• Questions:
  1. Biodegradable vs. Non-Biodegradable:
     • Biodegradable substances are broken down by specific enzymes/microorganisms; non-biodegradable lack such pathways, persisting in environment.
  2. Biodegradable Impact:
     • Nutrient recycling supports plant growth; improper disposal (e.g., food waste) attracts pests.
  3. Non-Biodegradable Impact:
     • Pollutes soil/water, harms wildlife (e.g., plastic ingestion), accumulates in environment.
• Effective waste management is essential to mitigate environmental degradation.

Key Questions and Answers

1. Ozone and Ecosystem Impact:
   • Ozone (O₃) in upper atmosphere shields UV radiation; depletion increases UV exposure, causing skin cancer and ecosystem damage.
2. Reducing Waste Disposal Problems:
   • Recycle materials (e.g., paper, plastics); compost biodegradable waste.
3. Biodegradable Items:
   • (a) Grass, flowers, leather; (c) Fruit-peels, cake, lime-juice; (d) Cake, wood, grass are biodegradable. Answer: (a), (c), (d).
4. Food Chain:
   • (b) Grass → Goat → Human represents a food chain. Answer: (b).
5. Environment-Friendly Practices:
   • All listed practices (cloth bags, switching off lights, walking) reduce environmental impact. Answer: (d).
6. Killing All Organisms in a Trophic Level:
   • Disrupts food chain; e.g., no producers stop energy flow, collapsing ecosystem.
7. Impact of Removing Trophic Levels:
   • Impact varies: Removing producers is most disruptive (no energy input); removing higher levels affects fewer organisms but alters balance.
   • No level can be removed without damage due to interdependence.
8. Biological Magnification:
   • Accumulation of non-degradable chemicals up food chain; higher trophic levels (e.g., humans) have greater concentrations, increasing toxicity risks.
9. Non-Biodegradable Waste Problems:
   • Pollution, wildlife harm, long-term environmental persistence.
10. All Biodegradable Waste:
    • Still impacts environment if mismanaged (e.g., methane from decomposing waste, pest attraction).
11. Ozone Layer Damage Concerns:
    • Increased UV radiation harms health and ecosystems.
    • Steps: Montreal Protocol (CFC bans), promoting CFC-free products.