Introduction

An ecosystem is a functional unit of nature where biotic (living) and abiotic (non-living) components interact. Understanding ecosystems is crucial for NEET, as questions often involve energy flow, food chains, pyramids, and nutrient cycles.

Ecology studies interactions between organisms and their environment. NEET exams emphasize ecosystem structure, functions, and dynamics, including formulas, cycles, and diagrams.

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♦ The Living World ⇒ Download Now

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♦ Strategies for Enhancement in Food Production ⇒ Download Now

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♦ Organisms and Populations ⇒ Download Now

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1. Components of an Ecosystem

A. Biotic Components (Living):

• Producers (Autotrophs): Make their own food through photosynthesis → Plants, algae

• Consumers (Heterotrophs): Feed on other organisms

  • Primary → Herbivores (cows, deer)

  • Secondary → Carnivores (fox, snake)

  • Tertiary → Top carnivores (lion, eagle)

• Decomposers (Saprotrophs): Break down dead matter → Bacteria, fungi

B. Abiotic Components (Non-living):

• Soil, water, sunlight, temperature, nutrients, climate

NEET Tip:

• Biotic + Abiotic = Functional ecosystem

2. Food Chain and Food Web

A. Food Chain:

• Linear transfer of energy from producers → consumers → decomposers

• Example: Grass → Grasshopper → Frog → Snake → Hawk

B. Food Web:

• Interconnected food chains forming complex energy flow

NEET Formula / Fact:

• Energy transfer efficiency: ~10% from one trophic level to next

• Rule of 10%: Only 10% of energy passes → Rest lost as heat

NEET Tip:

• Draw food chain + web diagrams for better recall

3. Ecological Pyramids

Definition: Graphical representation of trophic levels

Types:

1. Pyramid of Numbers: Number of organisms at each trophic level

2. Pyramid of Biomass: Total biomass at each trophic level

3. Pyramid of Energy: Energy content at each level → Always upright

NEET Tip:

• Pyramid of energy → Always upright

• Pyramid of biomass → May be inverted in aquatic ecosystems

4. Energy Flow in Ecosystem

• Primary productivity: Rate of biomass production by producers

  • Gross Primary Productivity (GPP): Total energy captured

  • Net Primary Productivity (NPP): GPP – Respiration

  • Formula: NPP = GPP – R

• Secondary productivity: Biomass produced by consumers

NEET Tip:

• NPP and GPP → Important for numerical questions

5. Biogeochemical Cycles

A. Carbon Cycle:

• Photosynthesis → CO₂ fixed

• Respiration, combustion → CO₂ released

• Human activities → Enhance CO₂ (fossil fuels)

B. Nitrogen Cycle:

• Nitrogen fixation → N₂ → NH₄⁺ (Rhizobium, Azotobacter)

• Nitrification → NH₄⁺ → NO₂⁻ → NO₃⁻

• Denitrification → NO₃⁻ → N₂

C. Phosphorus Cycle:

• Weathering of rocks → Phosphate in soil

• Uptake by plants → Movement through food chain

• No atmospheric phase

D. Water Cycle:

• Evaporation → Condensation → Precipitation → Runoff → Transpiration

NEET Tip:

• Memorize steps, microbes, and transformations in cycles

6. Ecosystem Types

A. Terrestrial Ecosystems:

• Forests → Tropical, temperate, boreal

• Grasslands → Savanna, temperate

• Deserts → Extreme temperature, low rainfall

B. Aquatic Ecosystems:

• Freshwater → Lakes, ponds, rivers

• Marine → Oceans, estuaries, coral reefs

NEET Tip:

• Ecosystem examples frequently asked in MCQs and diagrams

7. Ecological Succession

Definition:

• Gradual, sequential replacement of species in a community

Types:

• Primary succession: No previous life → Pioneer species colonize

• Secondary succession: Previously inhabited → Recovery after disturbance

NEET Tip:

• Remember pioneer species (lichens, moss) for primary succession

8. Human Impact on Ecosystems

• Deforestation → Habitat loss, decreased biodiversity

• Pollution → Air, water, soil contamination

• Global warming → Climate change impacts

• Conservation strategies → Protected areas, afforestation, sustainable use

NEET Tip:

• Questions often involve causes, effects, and mitigation strategies

9. NEET Important Formulas / Memory Aids

1. Energy transfer efficiency: 10% per trophic level

2. Net Primary Productivity: NPP = GPP – R

3. Population density in ecosystems: D = N / Area

4. Carbon cycle key transformations: CO₂ ↔ Organic carbon ↔ CO₂

5. Nitrogen cycle key microbes: Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter

Mnemonic for biogeochemical cycles:
“C-Wa-N-P” → Carbon, Water, Nitrogen, Phosphorus

10. NEET Exam Tips

• Memorize food chain → energy flow → pyramid formulas

• Diagram-based questions → Food web, pyramids, biogeochemical cycles

• Focus on producers, consumers, decomposers, and human impacts

• Be familiar with types of ecosystems and succession

Conclusion

Ecosystem is a high-yield NEET topic. Mastery of components, energy flow, food chains, pyramids, biogeochemical cycles, succession, and human impacts is essential for scoring in MCQs, diagram-based, and conceptual questions.

With this StudentBro.in guide, students can efficiently revise ecosystem formulas, diagrams, and examples, enhancing speed and accuracy during NEET exams.

Remember: Ecosystem = Producers + Consumers + Decomposers + Energy Flow + Nutrient Cycles + Human Impact → Core for ecology questions.