Complete Summary and Solutions for Ecosystem – NCERT Class XII Biology, Chapter 12 – Structure, Function, Productivity, Energy Flow, Pyramids

Comprehensive summary and explanation of Chapter 12 'Ecosystem' from the NCERT Class XII Biology textbook, covering the structure and function of ecosystems, productivity (GPP, NPP), energy flow, food chains, ecological pyramids, decomposition, nutrient cycling, examples of terrestrial and aquatic systems, and detailed textbook questions with answers.

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Categories: NCERT, Class XII, Biology, Chapter 12, Ecosystem, Ecology, Productivity, Energy Flow, Food Chain, Decomposition, Nutrient Cycling, Summary, Questions, Answers

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Ecosystem - Class 12 NCERT Chapter 12 - Ultimate Study Guide, Notes, Questions, Quiz 2025

Full Chapter Summary & Detailed Notes - Ecosystem Class 12 NCERT

Overview & Key Concepts

Chapter Goal: Understand ecosystem as a functional unit, focusing on structure, energy flow, nutrient cycling, and ecological pyramids. Exam Focus: Definitions (GPP/NPP, detritus), diagrams (food chains, pyramids), calculations (10% law), comparisons (GFC vs DFC). 2025 Updates: Emphasis on sustainability, climate impact on productivity. Fun Fact: Oceans cover 70% Earth but contribute only 32% NPP due to nutrient limits. Core Idea: Ecosystems maintain balance via energy input and cycling. Real-World: Coral reefs as biodiversity hotspots. Ties: Links to organism-environment (Ch13), biodiversity (Ch15). Expanded: All subtopics (12.1-12.5) covered point-wise with diagram descriptions, principles, steps, and ecological relevance for visual/conceptual learning.
Wider Scope: From local (pond) to global (biosphere); role in conservation and human impacts.
Expanded Content: Detailed processes, global data, exceptions (inverted pyramids); e.g., 10% energy transfer, decomposition rates.

Fig. 12.1: Diagrammatic representation of decomposition cycle (Description)

Tree → leaves fall → partial consumption by fungi/bacteria → litter → earthworms fragment → leaching into soil → catabolism by microbes → humus formation → mineralization to nutrients → back to plants. Arrows show cycle; visual: Ground layer with detritus breakdown.

12.1 Ecosystem – Structure and Function

Definition: Functional unit of nature with biotic (living) and abiotic (non-living) components interacting; varies from pond to biosphere.
Categories: Terrestrial (forest, grassland, desert); Aquatic (pond, lake, river, estuary); Man-made (crop fields, aquarium).
Components: Abiotic (water, soil, climate); Biotic (producers, consumers, decomposers).
Species Composition: Enumeration of plants/animals; Stratification: Vertical layers (e.g., forest: trees top, shrubs middle, herbs bottom).
Functional Aspects: Productivity, decomposition, energy flow, nutrient cycling; illustrated via pond ecosystem (phytoplankton autotrophs, zooplankton consumers, bacteria decomposers).
Pond Example: Shallow water body; abiotic: water/minerals/soil; solar input regulates; unidirectional energy flow with heat loss.
Biotech Relevance: Models for sustainable agriculture, pollution impact studies.

Fig. 12.2: Diagrammatic representation of trophic levels (Description)

Producers (phytoplankton/grass/trees) at base → Primary consumers (zooplankton/herbivores like cow) → Secondary (carnivores like birds/fish) → Tertiary (top carnivores like man/lion). Arrows show energy flow upward.

12.2 Productivity

Primary Production: Biomass/organic matter by plants via photosynthesis; units: g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹.
Gross Primary Productivity (GPP): Total photosynthesis rate; some used in plant respiration.
Net Primary Productivity (NPP): GPP - R (respiration) = biomass for consumers/decomposers.
Secondary Productivity: Rate of new biomass by consumers (herbivores/carnivores).
Factors Affecting: Plant species, environmental (light, temp, water), nutrients (N, P, Fe limiting in oceans), photosynthetic capacity.
Global Values: Biosphere NPP ~170 billion tons (dry); oceans 55 billion tons (32%) despite 70% area; land higher due to nutrients.
Ocean Low Productivity Reason: Light penetration limits, nutrient scarcity in surface waters.
Applications: Assess ecosystem health, agriculture yield.

12.3 Decomposition

Detritus: Dead plant/animal remains (leaves, feces); raw material for decomposers.
Steps: Fragmentation (detritivores like earthworms break), Leaching (water-soluble nutrients precipitate), Catabolism (bacterial/fungal enzymes degrade to inorganics), Humification (dark humus formation, nutrient reservoir), Mineralisation (microbes release inorganics like CO₂, nutrients).
Decomposers: Fungi, bacteria; oxygen-dependent process.
Factors: Chemical (lignin/chitin slow, sugars/N fast); Climatic (warm/moist favor, low temp/anaerobic inhibit, build-up detritus).
Importance: Recycles nutrients, prevents waste accumulation; earthworms as 'farmer's friend'.
Applications: Composting, soil fertility management.

Fig. 12.3: Energy flow through different trophic levels (Description)

Sun → Producers (10% capture) → Herbivores (10% transfer) → Carnivores → Top carnivores; each level loses 90% as heat. Pyramid shape with decreasing bars upward.

12.4 Energy Flow

Source: Sun (99.9%); <50% PAR (photosynthetically active); plants capture 2-10% PAR.
Unidirectional: Sun → Producers → Consumers; follows 1st/2nd thermodynamics (constant input counters entropy).
Trophic Levels: Producers (1st), Herbivores (2nd/primary consumers), Carnivores (3rd/secondary), Top carnivores (4th).
Food Chains: Grazing (GFC: grass → goat → man); Detritus (DFC: dead matter → decomposers → detritivores); aquatic GFC dominant, terrestrial DFC larger fraction.
Food Web: Interconnected chains; omnivores link GFC/DFC.
10% Law: 10% energy transfer per level; limits trophic levels (3-4 max).
Standing Crop: Biomass/number at time; dry weight accurate (water varies).
Applications: Energy budgeting, pollution biomagnification.

Fig. 12.4 (a-d): Ecological Pyramids (Description)

(a) Number: Grassland upright, millions plants support few top carnivores. (b) Biomass: Upright sharp decrease. (c) Inverted biomass: Sea, small phytoplankton support large zooplankton/fish. (d) Energy: Always upright, 1% sunlight to NPP, 10% transfers.

12.5 Ecological Pyramids

Types: Number (individuals), Biomass (dry weight), Energy (kcal); base producers, apex top consumers.
Upright: Most ecosystems; producers > herbivores > carnivores (e.g., grassland numbers/biomass).
Inverted: Number (tree-insects-birds); Biomass (sea: phytoplankton < fish).
Energy Pyramid: Always upright (energy loss as heat); no inversion possible.
Limitations: Ignores species multi-levels, assumes simple chain (not web), excludes saprophytes.
Paradox: Sea inverted biomass due to rapid phytoplankton turnover vs. slow fish growth.
Applications: Assess stability, pollution effects.

Summary

Ecosystems integrate abiotic/biotic for energy/nutrient balance; productivity/decomposition sustain life; unidirectional energy, cyclic nutrients; pyramids visualize flows.
Interlinks: To environmental issues (Ch16), biodiversity conservation.

Why This Guide Stands Out

Ecology-focused: Step-wise cycles, visuals, global data. Free 2025 with mnemonics, conservation links for retention.

Key Themes & Tips

Aspects: Unidirectional vs. cyclic, upright/inverted, 10% rule applications.
Tip: Draw pyramids; memorize GPP-R=NPP.

Exam Case Studies

Forest degradation on productivity; ocean acidification on pyramids.

Project & Group Ideas

Map local pond trophic levels.
Debate: Human impact on energy flow.
Research: Wetland restoration.

Key Definitions & Terms - Complete Glossary

All terms from chapter; detailed with examples, relevance. Expanded: 40+ terms grouped by subtopic; added advanced like stratification, 10% law for depth/easy flashcards.

Ecosystem

Functional unit of biotic/abiotic interactions. Ex: Pond. Relevance: Models nature balance.

Stratification

Vertical species distribution. Ex: Forest layers. Relevance: Niche diversity.

Productivity

Biomass production rate. Ex: NPP forests high. Relevance: Energy base.

GPP

Total photosynthesis. Ex: Minus R = NPP. Relevance: Gross output.

NPP

GPP - Respiration. Ex: Available to consumers. Relevance: Net yield.

Detritus

Dead organic matter. Ex: Fallen leaves. Relevance: Decomposer input.

Humification

Humus formation. Ex: Dark soil reservoir. Relevance: Nutrient storage.

Mineralisation

Inorganic release. Ex: Nutrients for plants. Relevance: Cycling.

PAR

Photosynthetically active radiation. Ex: 2-10% captured. Relevance: Light limit.

Trophic Level

Feeding position. Ex: Producers 1st. Relevance: Energy pyramid.

GFC

Grazing food chain. Ex: Grass-goat-man. Relevance: Aquatic dominant.

DFC

Detritus food chain. Ex: Dead matter-decomposers. Relevance: Terrestrial major.

Food Web

Interlinked chains. Ex: Omnivores connect. Relevance: Stability.

10% Law

Energy transfer efficiency. Ex: Limits levels. Relevance: Loss as heat.

Standing Crop

Biomass at time. Ex: Dry weight accurate. Relevance: Measure levels.

Pyramid of Number

Individuals per level. Ex: Grassland upright. Relevance: Population dynamics.

Pyramid of Biomass

Dry weight per level. Ex: Sea inverted. Relevance: Productivity paradox.

Pyramid of Energy

Energy flow. Ex: Always upright. Relevance: Thermodynamics.

Nutrient Cycling

Repeated use. Ex: Gaseous (C), sedimentary (P). Relevance: Sustainability.

Autotrophs

Self-feeders. Ex: Phytoplankton. Relevance: Base producers.

Heterotrophs

Other-feeders. Ex: Zooplankton. Relevance: Consumers.

Saprotrophs

Decomposers. Ex: Fungi. Relevance: Recycling.

Detritivores

Fragmenters. Ex: Earthworms. Relevance: Breakdown start.

Leaching

Soluble nutrient downflow. Ex: Rain in soil. Relevance: Availability.

Catabolism

Enzyme degradation. Ex: Bacterial action. Relevance: Inorganic conversion.

Primary Carnivores

Herbivore eaters. Ex: Frogs. Relevance: Secondary consumers.

Secondary Carnivores

Carnivore eaters. Ex: Snakes. Relevance: Tertiary consumers.

Omnivores

Mixed feeders. Ex: Humans. Relevance: Web connectors.

Ecological Efficiency

10% transfer. Ex: Energy budget. Relevance: Trophic limit.

Saprophytes

Dead matter feeders. Ex: Mushrooms. Relevance: Pyramid omission.

Biomagnification

Pollutant increase up levels. Ex: DDT in eagles. Relevance: Energy flow risk.

Limiting Factor

Productivity controller. Ex: Light in oceans. Relevance: Liebig's law.

Humus

Resistant organic colloid. Ex: Soil fertility. Relevance: Slow decomposition.

Anaerobiosis

Oxygen lack. Ex: Slow decay. Relevance: Detritus build-up.

Trophic Dynamics

Level interactions. Ex: Predator-prey. Relevance: Stability models.

Ecological Services

Benefits like purification. Ex: Forests clean air. Relevance: Conservation value.

Sedimentary Cycle

Crust reservoir. Ex: Phosphorus. Relevance: Slow replenishment.

Gaseous Cycle

Atmosphere reservoir. Ex: Carbon. Relevance: Global mixing.

Ecotone

Transition zone. Ex: Mangrove. Relevance: High diversity.

Succ succession

Community change. Ex: Pioneer lichens. Relevance: Maturity.

Keystone Species

Disproportionate impact. Ex: Sea otter. Relevance: Stability.

Tip: Group by section; examples for recall. Depth: Principles tie to energy laws. Errors: Confuse GPP/NPP. Historical: Tansley ecosystem 1935. Interlinks: Ch13 pollution. Advanced: Lindeman pyramid. Real-Life: Amazon NPP. Graphs: Pyramid shapes. Coherent: Structure → Function → Balance. For easy learning: Flashcard per term with diagram/app.

60+ Questions & Answers - NCERT Based (Class 12) - From Exercises & Variations

Based on chapter + expansions. Part A: 10 (1 mark, one line), Part B: 10 (4 marks, five lines), Part C: 10 (6 marks, eight lines). Answers point-wise in black text. Easy: Structured for marks.

Part A: 1 Mark Questions (10 Qs - Short)

1. What is an ecosystem defined as?

1 Mark Answer: A functional unit of nature comprising biotic and abiotic components interacting together.

2. Name two categories of ecosystems.

1 Mark Answer: Terrestrial and aquatic ecosystems.

3. What is stratification in an ecosystem?

1 Mark Answer: Vertical distribution of species in different layers.

4. Define gross primary productivity (GPP).

1 Mark Answer: Rate of organic matter production during photosynthesis.

5. What is net primary productivity (NPP)?

1 Mark Answer: GPP minus respiration losses.

6. Name the process where detritus is broken into smaller particles.

1 Mark Answer: Fragmentation by detritivores.

7. What is the percentage of PAR captured by plants?

1 Mark Answer: 2-10%.

8. Define trophic level.

1 Mark Answer: Position of an organism in a food chain based on feeding.

9. What is the 10% law in energy flow?

1 Mark Answer: Only 10% energy transfers to next trophic level.

10. Name a type of ecological pyramid that is always upright.

1 Mark Answer: Pyramid of energy.

Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)

1. Describe the structure of an ecosystem with an example.

4 Marks Answer:

An ecosystem has abiotic (non-living like water, soil) and biotic (living) components.
Biotic includes producers (plants), consumers (animals), decomposers (fungi/bacteria).
Species composition lists plants/animals; stratification shows vertical layers.
Example: Pond - abiotic: water/minerals; biotic: phytoplankton producers, zooplankton consumers.
Interactions result in energy flow and nutrient cycling.

2. Explain primary productivity and its types.

4 Marks Answer:

Primary productivity is biomass produced by autotrophs via photosynthesis.
Gross Primary Productivity (GPP): Total rate of production.
Net Primary Productivity (NPP): GPP - plant respiration, available to heterotrophs.
Units: g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹; global NPP 170 billion tons.
Factors: Light, nutrients; oceans low due to limiting factors.

3. Outline the steps in decomposition.

4 Marks Answer:

Fragmentation: Detritivores break detritus into particles.
Leaching: Water-soluble nutrients enter soil.
Catabolism: Microbes degrade to simpler compounds.
Humification: Forms resistant humus, nutrient reservoir.
Mineralisation: Releases inorganics for reuse.

4. Differentiate GFC and DFC.

4 Marks Answer:

Grazing Food Chain (GFC): Starts with living plants; producers → herbivores → carnivores.
Detritus Food Chain (DFC): Starts with dead matter; detritus → decomposers → detritivores.
GFC dominant in aquatic; DFC larger in terrestrial energy flow.
Linked by omnivores forming food web.
Both unidirectional, 10% transfer.

5. What is energy flow in ecosystems? Explain with 10% law.

4 Marks Answer:

Unidirectional from sun to producers to consumers, lost as heat.
Follows thermodynamics; constant input needed.
10% law: Only 10% energy transfers per trophic level.
Limits levels to 3-4; rest dissipated.
Example: 1000J sun → 100J producers → 10J herbivores.

6. Describe pyramid of numbers with example.

4 Marks Answer:

Graphical representation of individuals per trophic level.
Upright in grassland: Millions grass support few lions.
Inverted in forest: One tree supports thousands insects.
Base producers, apex top consumers.
Limitations: Ignores size differences.

7. Explain factors affecting decomposition rate.

4 Marks Answer:

Chemical: Lignin/chitin slow, sugars/N fast.
Climatic: Temperature/moisture favor microbes.
Warm/moist accelerate; cold/anaerobic inhibit.
Oxygen required for aerobic process.
Build-up in low O₂ areas like wetlands.

8. What is food web? How does it differ from food chain?

4 Marks Answer:

Food web: Interconnected food chains forming network.
Food chain: Linear sequence of eat-or-be-eaten.
Web more stable, accounts omnivores.
Example: Chains grass-rabbit-fox, grass-deer-man link via omnivores.
Reflects real complexity.

9. Describe pyramid of biomass in sea ecosystem.

4 Marks Answer:

Inverted: Phytoplankton biomass small, zooplankton/fish large.
Paradox: Rapid producer turnover sustains slow-growing consumers.
Upright on land: Producers > herbivores.
Measures standing crop dry weight.
Indicates productivity dynamics.

10. Explain nutrient cycling types.

4 Marks Answer:

Gaseous: Reservoir atmosphere/hydrosphere (e.g., carbon cycle).
Sedimentary: Reservoir earth's crust (e.g., phosphorus).
Repeated use via producers-consumers-decomposers.
Essential for sustainability.
Human disruption: Pollution affects gaseous.

Part C: 6 Marks Questions (10 Qs - Long, Exactly 8 Lines Each)

1. Describe ecosystem components and functions with pond example.

6 Marks Answer:

Abiotic: Non-living (water, minerals, light, temp); regulate rates.
Biotic: Producers (phytoplankton, marginal plants), consumers (zooplankton, fish), decomposers (bacteria, fungi).
Structure: Species composition, stratification (surface to bottom).
Functions: Productivity (NPP biomass), decomposition (nutrient release), energy flow (unidirectional), cycling (repeated use).
Pond: Shallow; solar input cycles temp/day; autotrophs convert inorganics; heterotrophs consume; decomposers mineralize dead matter.
Energy: Sun → producers → consumers → heat loss; maintains self-sustainability.
Relevance: Models biosphere interactions.
Human impact: Pollution disrupts balance.

2. Explain primary and secondary productivity with global data.

6 Marks Answer:

Primary: Autotroph biomass; GPP total photosynthesis, NPP = GPP - R for consumers.
Secondary: Consumer new biomass formation rate.
Factors: Environmental (light/water), nutrients (N/P limiting), species capacity.
Global NPP: 170 billion tons dry; oceans 55 billion (32%) despite 70% area.
Ocean low: Surface nutrients scarce, light limits depth.
Land high: Rich soils, diverse plants.
Units: g m⁻² yr⁻¹; compares ecosystems.
Applications: Crop yield, conservation planning.

3. Detail decomposition process and controlling factors.

6 Marks Answer:

Detritus: Dead remains; steps simultaneous.
Fragmentation: Earthworms reduce size.
Leaching: Solubles precipitate in soil.
Catabolism: Enzymes to inorganics.
Humification: Amorphous humus reservoir.
Mineralisation: Inorganic nutrients release.
Factors: Chemical (lignin slow, N fast); climatic (warm/moist favor, anaerobic inhibit).
Importance: Nutrient recycling, soil health.

4. Describe energy flow, trophic levels, and 10% law.

6 Marks Answer:

Source: Sun PAR 2-10% captured by producers.
Unidirectional: Producers → consumers; no backward.
Levels: 1st producers, 2nd herbivores, 3rd carnivores, 4th top.
10% law: 10% transfer, 90% heat loss.
Limits 3-4 levels; standing crop decreases upward.
Example: 10000J sun → 1000J producers → 100J herbivores.
Thermodynamics: Constant input counters entropy.
Relevance: Explains low top predator biomass.

5. Differentiate food chain, web, and explain GFC/DFC.

6 Marks Answer:

Food chain: Linear feeding sequence.
Food web: Branched interconnected chains.
GFC: Living primary producers start; aquatic major.
DFC: Detritus/dead start; terrestrial 50-90% energy.
Linked by omnivores (crows); forms web stability.
Example: GFC grass-rabbit-fox; DFC leaf-fungi-earthworm.
Both 10% transfer, unidirectional.
Web reflects reality, prevents single failure.

6. Explain ecological pyramids with types and examples.

6 Marks Answer:

Graphical trophic representations: Number, biomass, energy.
Number: Upright grassland, inverted tree-insects.
Biomass: Upright forest, inverted sea (phytoplankton turnover).
Energy: Always upright, decreases 10% steps.
Base producers, apex top consumers.
Example: Grassland numbers: 6M plants → 3 lions.
Limitations: Multi-level species, no saprophytes.
Assesses stability, pollution biomagnification.

7. Discuss factors limiting productivity in ecosystems.

6 Marks Answer:

Environmental: Light (PAR), temperature, water availability.
Nutrients: N, P, Fe; Liebig's limiting factor.
Plant species: Photosynthetic efficiency varies.
Oceans: Surface nutrients sink, light limits depth; 55B tons NPP.
Land: Rich soils, but deserts low water.
Global: 170B tons total, oceans 32% despite 70% area.
Human: Deforestation reduces, eutrophication increases.
Management: Fertilizers boost agriculture.

8. Explain nutrient cycling and its types.

6 Marks Answer:

Cycling: Nutrient reuse via producers-consumers-decomposers.
Gaseous: Atmosphere reservoir, fast mixing (carbon, nitrogen).
Sedimentary: Crust reservoir, slow (phosphorus, sulfur).
Processes: Uptake, transfer, mineralization.
Example: Carbon: Photosynthesis → respiration → CO₂.
Importance: Prevents depletion, sustains life.
Disruption: Mining exhausts sedimentary.
Services: Forests purify via cycling.

9. Describe inverted pyramids and their explanations.

6 Marks Answer:

Number inverted: Few producers support many consumers (tree-insects-birds).
Biomass inverted: Sea - small phytoplankton (fast turnover) support large fish.
Energy never inverted: Loss at each step.
Paradox resolution: Producers renew quickly, consumers accumulate slowly.
Example: Forest numbers: 1 oak → 1000 caterpillars → 100 birds.
Upright typical: Grassland biomass decreases upward.
Limitations: Static snapshot, ignores dynamics.
Relevance: Informs fishery management.

10. Give an account of energy flow and its ecological significance.

6 Marks Answer:

Source: Sun → PAR captured by chlorophyll.
Flow: Unidirectional trophic transfer, 10% efficiency.
Pyramid: Decreasing energy upward, heat dissipation.
Significance: Limits biomass, explains rarity of top carnivores.
Thermodynamics: 1st conservation, 2nd entropy increase.
Example: 1% sunlight to NPP, cascading losses.
Implications: Pollution accumulates (biomagnification).
Conservation: Protect producers for flow sustenance.

Tip: Diagrams for pyramids; practice steps. Additional 30 Qs: Variations on cycling, ocean productivity.

Key Concepts - In-Depth Exploration

Core ideas with examples, pitfalls, interlinks. Expanded: All 12.1-12.5 with steps/examples/pitfalls for easy learning. Depth: Calculations (e.g., NPP), troubleshooting.

Ecosystem Structure

Steps: 1. Identify abiotic (climate/soil), 2. List biotic (producers/consumers/decomposers), 3. Note stratification. Ex: Forest layers support diversity. Pitfall: Ignore interactions. Interlink: Affects productivity. Depth: Pond self-sustain via cycling.

Productivity (Primary)

Steps: 1. GPP measure total, 2. Subtract R for NPP. Ex: Forest 2000 g m⁻² yr⁻¹. Pitfall: Confuse gross/net. Interlink: Base for energy flow. Depth: Ocean limit = nutrients; calc NPP = GPP(1000) - R(400) = 600.

Decomposition Cycle

Steps: 1. Fragment/leach, 2. Catabolize, 3. Humify/mineralize. Ex: Leaf litter to soil N. Pitfall: Overlook simultaneous steps. Interlink: Nutrient input. Depth: Anaerobic slow, methane produce.

Energy Flow & 10% Law

Steps: 1. Sun PAR capture, 2. Transfer 10% per level. Ex: 1000J → 100J herbivores. Pitfall: Assume cyclic energy. Interlink: Pyramids visualize. Depth: Lindeman efficiency; heat loss = respiration + undigested.

Trophic Levels & Food Chains

Steps: 1. Assign levels, 2. Map chains/web. Ex: GFC aquatic 60% energy. Pitfall: Overlook DFC terrestrial dominance. Interlink: Omnivores stabilize. Depth: Standing crop dry wt; human multi-level.

Ecological Pyramids

Steps: 1. Plot number/biomass/energy, 2. Interpret upright/inverted. Ex: Sea biomass paradox - turnover. Pitfall: Static, ignore webs. Interlink: Assess health. Depth: Energy always upright per 2nd law.

Nutrient Cycling

Steps: 1. Uptake producers, 2. Transfer consumers, 3. Release decomposers. Ex: C gaseous fast, P sedimentary slow. Pitfall: Forget reservoirs. Interlink: Decomposition key. Depth: Eutrophication excess P.

Limiting Factors

Steps: 1. Identify (light/nutrients), 2. Assess impact. Ex: Ocean Fe limits phytoplankton. Pitfall: Single factor assumption. Interlink: Productivity. Depth: Liebig's minimum law.

Food Web Stability

Steps: 1. Link chains, 2. Note omnivores. Ex: Forest web prevents collapse. Pitfall: Simplify to chain. Interlink: Biodiversity. Depth: Keystone species maintain.

Ecological Services

Steps: 1. List (purification, pollination), 2. Value economically. Ex: Wetlands flood control. Pitfall: Undervalue. Interlink: Conservation. Depth: Forests C sink, air clean.

Advanced: Calc 10% cascades, pyramid exceptions. Pitfalls: Biomass wet vs dry. Interlinks: Ch16 pollution biomagnification. Real: Amazon deforestation NPP drop. Depth: 5 concepts details. Examples: Pond full cycle. Graphs: Energy pyramids. Errors: GFC/DFC mix. Tips: Steps for flows; compare tables.

Solved Examples - From Text with Simple Explanations

Expanded with protocols, calcs; focus on cycles, pyramids. Added NPP calc, pyramid plot.

Example 1: NPP Calculation

Simple Explanation: Net biomass after plant use.

Step 1: GPP = 1500 g m⁻² yr⁻¹.
Step 2: Respiration R = 500 g m⁻² yr⁻¹.
Step 3: NPP = GPP - R = 1000 g m⁻² yr⁻¹.
Step 4: Available to herbivores.
Simple Way: Total minus plant breathing.

Example 2: Energy Flow 10% Law

Simple Explanation: Transfer losses.

Step 1: Sun 10000 J to producers 1000 J (10%).
Step 2: Producers to herbivores 100 J.
Step 3: Herbivores to carnivores 10 J.
Step 4: 90% heat each step.
Simple Way: 1/10 passes up pyramid.

Example 3: Pyramid of Numbers Plot

Simple Explanation: Individuals decrease.

Step 1: Producers 4M, primary 300k, secondary 5k, tertiary 100.
Step 2: Plot bars decreasing upward.
Step 3: Upright shape.
Step 4: Interpret support ratio.
Simple Way: Base wide, top narrow.

Example 4: Decomposition Rate Factors

Simple Explanation: Speed controllers.

Step 1: High N/sugars = fast (tropical leaves).
Step 2: Lignin/chitin = slow (wood).
Step 3: Warm/moist = accelerate microbes.
Step 4: Cold/anaerobic = inhibit, peat forms.
Simple Way: Easy food + good weather = quick breakdown.

Example 5: Food Web Construction

Simple Explanation: Link chains.

Step 1: Chains: Grass-rabbit-fox, grass-deer-man.
Step 2: Link via crow (eats both).
Step 3: Omnivore connects GFC/DFC.
Step 4: Web shows alternatives.
Simple Way: Chains as threads in net.

Example 6: Inverted Biomass Explanation

Simple Explanation: Turnover paradox.

Step 1: Phytoplankton small standing crop, rapid reproduction.
Step 2: Zooplankton/fish large, slow growth.
Step 3: Constant supply sustains.
Step 4: Upright energy despite.
Simple Way: Fast makers feed slow accumulators.

Tip: Calc practice; troubleshoot (e.g., low NPP= nutrient limit). Added for cycling (C steps), pyramids (plot).

Key Terms & Processes - All Key

Expanded table 40+ rows; quick ref. Added advanced (e.g., humus, PAR).

Term/Process	Description	Example	Usage
Ecosystem	Biotic/abiotic unit	Pond	Balance study
Stratification	Vertical layers	Forest strata	Diversity
GPP	Total production	Photosynthesis rate	Gross yield
NPP	Net after respiration	Consumer available	Net biomass
Detritus	Dead matter	Leaves/feces	Decomp input
Fragmentation	Size reduction	Earthworm action	Breakdown start
Leaching	Soluble nutrient flow	Rain soil entry	Precipitation
Catabolism	Microbe degradation	Enzyme to inorganics	Simplification
Humification	Humus formation	Dark soil reserve	Storage
Mineralisation	Inorganic release	Nutrients for plants	Reuse
PAR	Active radiation	400-700nm light	Photosynth input
Trophic Level	Feeding position	Producers 1st	Energy step
GFC	Grazing chain	Grass-herbivore	Aquatic flow
DFC	Detritus chain	Dead-decomposer	Terrestrial flow
Food Web	Interlinked chains	Omnivore network	Stability
10% Law	Transfer efficiency	Energy cascade	Level limit
Standing Crop	Biomass at time	Dry weight measure	Level assess
Pyramid Number	Individuals plot	Grassland upright	Population
Pyramid Biomass	Weight plot	Sea inverted	Productivity
Pyramid Energy	Flow plot	Always upright	Loss visualize
Nutrient Cycling	Reuse loop	Carbon gaseous	Sustain
Autotroph	Self-producer	Algae	Base
Heterotroph	Consumer	Herbivore	Energy user
Saprotroph	Decomposer	Fungus	Recycler
Detritivore	Fragmenter	Worm	Processor
Primary Consumer	Herbivore	Rabbit	2nd level
Secondary Consumer	Carnivore	Fox	3rd level
Omnivore	Mixed feeder	Human	Linker
Biomagnification	Pollutant increase	DDT eagles	Risk
Limiting Factor	Productivity control	Light ocean	Constraint
Humus	Organic colloid	Soil dark	Fertility
Anaerobiosis	Low oxygen	Wetland slow	Inhibit
Gaseous Cycle	Atm res	Nitrogen	Fast
Sedimentary Cycle	Crust res	Phosphorus	Slow
Ecotone	Transition	River-lake	Diverse
Succession	Change sequence	Bare rock lichen	Maturity
Keystone Species	High impact	Otter kelp	Balance
Ecological Efficiency	Transfer %	10 energy	Dynamics
Svedberg Unit	Sed rate	70S ribosome	Size
Liebig's Law	Limiting nutrient	P in lakes	Yield
Biome	Climatic region	Tundra	Global