Ecosystem
Definition
An ecosystem is a community of living organisms (biotic factors) interacting with each other and their physical environment (abiotic factors) as a system. It includes energy flow through trophic levels and nutrient cycling. Ecosystems can range from a small pond to an entire forest or ocean.
Key Points for NEET
- 1Includes biotic (living) and abiotic (non-living) components
- 2Energy flows unidirectionally through food chains
- 3Nutrients cycle through biogeochemical cycles
- 4Has producers, consumers, and decomposers
- 510% energy transfer between trophic levels
Example
A pond ecosystem with algae, fish, frogs, birds, and bacteria
Asked in NEET
Common Mistakes to Avoid
- ✗Confusing food chain (linear) with food web (interconnected) — real ecosystems have food webs
- ✗Thinking 10% law means exactly 10% energy transfer — it is an approximation (Lindeman efficiency)
- ✗Forgetting that decomposers act at every trophic level, not just at the end of the food chain
Quick Revision Notes
- ⚡Energy flow: Sun → Producers → Primary consumers → Secondary → Tertiary (unidirectional, non-cyclic)
- ⚡10% rule (Lindeman): only ~10% energy transfers between trophic levels; rest lost as heat
- ⚡Ecological pyramids: energy pyramid always upright; biomass can be inverted (aquatic ecosystem)
- ⚡Biogeochemical cycles: carbon, nitrogen, phosphorus, water — nutrients cycle, energy flows
Related Terms
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More Ecology Definitions
Biodiversity
Biodiversity refers to the variety of life on Earth at all levels, from genes to ecosystems. It includes species diversity (number and variety of species), genetic diversity (variation within species), and ecosystem diversity (variety of habitats). Biodiversity is crucial for ecosystem stability and human welfare.
Nitrogen Fixation
Nitrogen fixation is the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or other usable nitrogen compounds. This can occur biologically (by bacteria like Rhizobium) or abiotically (lightning, industrial processes). It is essential for making nitrogen available to plants.