Chapter 27: Man and his Environment

Non-Renewable Resources: Exhaustible, cannot be replaced once consumed. Examples: Coal, Oil, Natural Gas, Metals.

Renewable Resources: Can be used again and again. Examples: Air, Water, Soil, Wildlife, Forests.

• Air: 78% Nitrogen, 21% Oxygen. Essential for respiration and photosynthesis. Pollutants: CO, Nitrogen oxides, Sulphur dioxide.
• Water: 75% of earth surface. 97% ocean, 3% fresh water (2% ice, 1% available). Essential for life.
• Soil: Upper layer of earth crust. Supports plants. Depleted by erosion and pollution.
• Wildlife: Non-cultivated plants and non-domesticated animals. Source of food and balance in food chain.
• Energy:
  • Inexhaustible: Solar, Hydroelectric, Tidal, Wind, Geothermal.
  • Exhaustible: Fossil fuels (Coal, Oil, Gas).

Befouling of environment by harmful substances (Pollutants).

Air Pollution

Harmful substances in air (SO2, CO, NOx, CFCs, Lead).

• Ozone Depletion: Thinning of Ozone layer (O3) in stratosphere due to CFCs (Chlorofluorocarbons) from refrigerators/ACs. Allows UV rays to reach earth causing skin cancer, cataracts.
• Greenhouse Effect: Trapping of heat by CO2 (acting like glass in greenhouse). Leads to Global Warming (melting of glaciers, floods).
• Acid Rain: SO2 and NO2 combine with water vapor to form H2SO4 and HNO3. pH < 5.6. Kills aquatic life, damages buildings (Taj Mahal), destroys forests.

Water Pollution

Contamination of water bodies.

• Sewage: Causes diseases (Cholera, Typhoid).
• Eutrophication: Enrichment of water with nutrients (Phosphates/Nitrates) causing algal blooms. Decomposers use up oxygen, killing fish.
• Industrial Effluents: Toxic chemicals, heavy metals.
• Agro-chemicals: Fertilizers, Pesticides (Bioaccumulation).

Population Explosion

Rapid increase in human population. Causes: Better medical facilities, lower death rate. Consequences: Shortage of food/space, pollution, deforestation.

Deforestation vs Afforestation

• Deforestation: Cutting down forests for agriculture/urbanization. Causes soil erosion, climate change, loss of biodiversity.
• Afforestation/Reforestation: Planting trees. reforestation is replanting, afforestation is planting new forests. Importance: Timber, Medicine, Soil conservation, Climate regulation (transpiration).