Ecology & Environmental Science 🌦️

Lindeman's 10% law (1942) states that only 10% of energy is transferred from one trophic level to the next — the remaining 90% is lost as heat through respiration and metabolic processes. For example, if producers (plants) capture 1,000 kcal of solar energy, primary consumers (herbivores) receive 100 kcal, secondary consumers (carnivores) receive 10 kcal, and tertiary consumers receive 1 kcal. This explains why food chains rarely exceed 4–5 trophic levels and why a vegetarian diet is more energy-efficient.

The four major biogeochemical cycles: (1) Carbon cycle — CO₂ fixation by photosynthesis, release by respiration/decomposition; greenhouse gas concern (CO₂, CH₄); (2) Nitrogen cycle — N₂ fixation (Rhizobium, Azotobacter, lightning), nitrification, denitrification; basis for biofertilizer use; (3) Phosphorus cycle — weathering of rocks, no gaseous phase, major limiting nutrient in freshwater systems; (4) Water cycle — evapotranspiration, precipitation, runoff, groundwater recharge. Understanding N cycle is critical for fertilizer management and reducing nitrous oxide emissions.

Biodiversity has three levels: genetic, species, and ecosystem diversity. India has 4 of the world's 36 biodiversity hotspots: (1) Western Ghats + Sri Lanka; (2) Himalaya; (3) Indo-Burma (NE India, Myanmar); (4) Sundaland (Nicobar Islands). India hosts 7–8% of global species on 2.4% of geographic area. In-situ conservation: biosphere reserves (18), national parks (106), wildlife sanctuaries (567). Ex-situ: gene banks, botanical gardens, zoological parks.

Key environmental legislation: (1) Wildlife Protection Act 1972 — schedules animals for protection, establishes sanctuaries and national parks; (2) Forest Conservation Act 1980 — requires Central Government approval for diversion of forest land; (3) Environment Protection Act 1986 — umbrella legislation, established after Bhopal gas tragedy; (4) Biological Diversity Act 2002 — regulates access to biological resources, establishes NBA (National Biodiversity Authority); (5) Water Prevention and Control of Pollution Act 1974; (6) Air Prevention and Control of Pollution Act 1981.

Climate change refers to long-term shifts in global temperatures and weather patterns, primarily caused by anthropogenic greenhouse gas emissions (CO₂, CH₄, N₂O, HFCs). Under the Paris Agreement (2015), India committed to: (1) reduce emission intensity of GDP by 45% by 2030 (vs 2005 baseline); (2) achieve 50% cumulative electric power from non-fossil sources by 2030; (3) create additional carbon sink of 2.5–3 billion tonnes through forest and tree cover by 2030. India updated its NDC (Nationally Determined Contribution) in 2022.

Ecology and Environmental Science is tested in ICAR JRF (all disciplines — a mandatory section), IBPS AFO (Professional Knowledge — 3–5 questions on environmental laws and biodiversity), NABARD Grade A/B (environment section in Agriculture paper), and state PSC Agriculture Officer exams. Lindeman's 10% law, ecological pyramids, biodiversity hotspots, and Indian environmental legislation years are the most frequently tested topics.