Ecology Basics
Geography · पारिस्थितिकी की मूल बातें
📋Quick Overview
Ecology is the study of interactions between organisms and their environment. An ecosystem consists of biotic (living) and abiotic (non-living) components interacting together. Key concepts include food chains, food webs, ecological pyramids, trophic levels, biogeochemical cycles, and biodiversity. India is one of the 17 mega-diverse countries and has 4 biodiversity hotspots.
10% Law (Lindeman's Law): Only 10% of energy is transferred from one trophic level to the next. Rest 90% is lost as heat.
📝Ecosystem Components
- •Biotic Components (Living): Producers (plants), Consumers (herbivores, carnivores, omnivores), Decomposers (bacteria, fungi)
- •Abiotic Components (Non-living): Sunlight, temperature, water, soil, air, minerals
- •The term 'Ecosystem' was coined by A.G. Tansley (1935)
- •The term 'Ecology' was coined by Ernst Haeckel (1866)
📖Trophic Levels & Food Chain
| Trophic Level | Category | Examples | Role |
|---|---|---|---|
| T1 | Producers (Autotrophs) | Plants, Algae, Phytoplankton | Make food via photosynthesis, base of food chain |
| T2 | Primary Consumers (Herbivores) | Deer, Rabbit, Grasshopper, Cow | Eat producers directly |
| T3 | Secondary Consumers (Small Carnivores) | Frog, Snake, Fox | Eat primary consumers |
| T4 | Tertiary Consumers (Top Predators) | Tiger, Eagle, Shark | Apex predators, top of food chain |
Food Chain = single linear pathway of energy (Grass → Deer → Tiger). Food Web = interconnected network of multiple food chains in an ecosystem.
📖Ecological Pyramids
| Pyramid Type | Measures | Shape | Exception |
|---|---|---|---|
| Pyramid of Number | Count of organisms at each level | Usually upright; inverted in Tree ecosystem (1 tree → many insects → more parasites) | Tree ecosystem = inverted |
| Pyramid of Biomass | Total weight/mass at each level | Upright in terrestrial; INVERTED in aquatic (phytoplankton weigh less than fish) | Aquatic/Pond ecosystem = inverted |
| Pyramid of Energy | Energy flow at each level | ALWAYS upright (10% law) — never inverted | NO exception — always upright |
📝Biogeochemical Cycles
- •Carbon Cycle: CO2 absorbed by plants (photosynthesis) → eaten by animals → released by respiration, decomposition, burning fossil fuels. Oceans are the largest carbon sink.
- •Nitrogen Cycle: N2 (78% of atmosphere) fixed by Rhizobium bacteria in legume roots → used by plants → returned to soil by decomposers → denitrification releases N2 back to air
- •Water Cycle (Hydrological): Evaporation → Condensation → Precipitation → Collection. Sun drives the water cycle.
- •Oxygen Cycle: Produced by photosynthesis, consumed by respiration and combustion
📖Biodiversity & Hotspots
| Type of Biodiversity | Definition | Example |
|---|---|---|
| Genetic Diversity | Variation in genes within a species | Different varieties of rice, wheat, mango |
| Species Diversity | Variety of different species in an area | Number of plant/animal species in Western Ghats |
| Ecosystem Diversity | Variety of ecosystems in a region | Forests, wetlands, deserts, coral reefs in India |
Biodiversity Hotspot = area with at least 1,500 endemic plant species AND has lost 70%+ of its original habitat. World has 36 hotspots. India has 4 hotspots.
| # | India's Biodiversity Hotspot | Region |
|---|---|---|
| 1 | Western Ghats | Kerala, TN, Karnataka, Goa, Maharashtra |
| 2 | Eastern Himalayas | NE India, Nepal, Bhutan |
| 3 | Indo-Burma | NE India, Myanmar, Thailand, Vietnam |
| 4 | Sundaland | Nicobar Islands (India), Malaysia, Indonesia |
📝IUCN Red List Categories
- •Extinct (EX) — No living individual exists (e.g., Dodo, Dinosaurs)
- •Extinct in Wild (EW) — Only in captivity (e.g., Hawaiian crow)
- •Critically Endangered (CR) — Extremely high risk (e.g., Great Indian Bustard, Gharial)
- •Endangered (EN) — High risk of extinction (e.g., Bengal Tiger, Asian Elephant, Snow Leopard)
- •Vulnerable (VU) — Moderate risk (e.g., One-horned Rhino, Ganges River Dolphin)
- •Near Threatened (NT) → Least Concern (LC) — Lower risk categories