Man and His Environment

Environment: Everything around an organism (Living and Non-living factors).

Ecology: Study of interactions between organisms and their environment.

Levels of Organization:

• Biosphere: Part of Earth where life exists (approx. 20km thick).
• Ecosystem: Self-sufficient unit where organisms interact with non-living environment (e.g., Pond, Forest).
• Community: All interacting populations in an area.
• Population: Members of same species in an area at a specific time.
• Organism: Individual living thing.

Biotic Components (Living):

• Producers (Autotrophs): Plants, Algae. Produce food via photosynthesis.
• Consumers (Heterotrophs): Animals, Fungi. Depend on others for food. Types: Herbivores (eat plants), Carnivores (eat animals), Omnivores (eat both).
• Decomposers (Reducers): Bacteria, Fungi. Break down dead matter and recycle nutrients.

Abiotic Components (Non-living): Light, Water, Air, Soil, Temperature.

Energy Flow: Non-cyclic (Uni-directional). Sun -> Producers -> Consumers -> Heat (lost). Energy reduces at each trophic level (10% law).

Material Flow: Cyclic. Nutrients circulate between biotic and abiotic components (Biogeochemical cycles).

Food Chain: Linear sequence of transfer of food energy. (e.g., Grass -> Grasshopper -> Frog -> Snake -> Hawk).

Food Web: Network of interconnected food chains. More stable than a single chain.

Trophic Levels: Feeding levels (Producers = T1, Primary Consumers = T2, etc.).

Graphical representation of trophic levels.

• Pyramid of Numbers: Number of organisms at each level.
• Pyramid of Biomass: Total mass of living matter at each level.
• Pyramid of Energy: Energy content at each level. Always upright.

Carbon Cycle: Movement of Carbon via Photosynthesis, Respiration, Decomposition, Combustion.

Nitrogen Cycle: Essential for proteins/DNA. Stages:

• Nitrogen Fixation: N2 gas -> Ammonia/Nitrates (by bacteria/lightning).
• Nitrification: Ammonium -> Nitrites -> Nitrates (by Nitrosomonas/Nitrobacter).
• Assimilation: Plants absorb nitrates.
• Ammonification: Decomposers release Ammonia from dead bodies.
• Denitrification: Nitrates -> Nitrogen gas (by bacteria).

Intra-specific Interactions: Between members of the same species.

Inter-specific Interactions: Between members of different species.

Types of Interactions:

• Competition: Organisms compete for limited resources (food, space). Maintains balance.
• Predation: Predator kills and eats Prey (e.g., Lion vs Zebra).
• Symbiosis: Close relationship between two species.
  • Parasitism: One benefits (Parasite), other is harmed (Host). (e.g., Lice, Tapeworm, Cuscuta plant).
  • Mutualism: Both benefit. (e.g., Lichens, Nitrogen-fixing bacteria in roots, Termites & protozoa).
  • Commensalism: One benefits, other unaffected. (e.g., Epiphytes on trees, Sucker fish on shark).

Ecosystem Balance: Natural stability where interactions and cycles run smoothly. Disturbed by human activities.

Global Warming: Rise in Earth's average temperature due to Greenhouse Effect (trapping of heat by CO2, Methane). Causes: Burning fossil fuels, Deforestation. Effects: Melting glaciers, Floods, Climate change.

Acid Rain: Rain with low pH (<5.6) due to Oxides of Nitrogen and Sulphur (from factories/vehicles) forming HNO3 and H2SO4. Effects: Kills aquatic life, damages buildings (Taj Mahal), destroys forests.

Deforestation: Clearing of forests. Causes: Agriculture, Urbanization, Lumber. Effects: Soil erosion, More CO2 (Global warming), Loss of habitat.

Overpopulation: Population exceeding available resources. Causes: High birth rate, low death rate (medical advances). Effects: Resource depletion, pollution, poverty.

Urbanization: Expansion of cities. Migration from rural to urban areas. Effects: Pollution, Overcrowding, Loss of agricultural land.

Definition: Harmful change in environment affecting life.

• Air Pollution: Contamination of air. Pollutants: CO, SO2, NOx, CFCs. Effects: Smog, Acid Rain, Ozone Depletion, Respiratory diseases.
• Water Pollution: Contamination of water bodies. Causes: Industrial waste, Sewage, Fertilizers/Pesticides, Oil spills. Effects: Eutrophication (algal bloom), Waterborne diseases (Cholera, Typhoid).
• Land Pollution: Degradation of soil quality. Causes: Solid waste, Trash, chemicals. Effects: Poor plant growth, diseases. Control: Landfills, Incineration.

Saving natural resources.

• Renewable Resources: Regenerated naturally (Trees, Air, Water).
• Non-renewable Resources: Cannot be regenerated quickly (Coal, Oil, Gas).
• 3R Strategy:
  • Reduce: Use less resources.
  • Reuse: Use things again (e.g., Cloth bags).
  • Recycle: Remake products from waste (Paper, Plastic, Glass).

Efforts in Pakistan: Ministry of Environment, EPA (Environmental Protection Agency), WWF-Pakistan projects (Conservation of Snow Leopard, Indus Dolphin).