🌿 Ecosystem Dynamics & Energy Flow

An ecosystem is a functional, self-sustaining thermodynamic unit where biotic biological communities interact with abiotic physical components through energy flow and nutrient cycling.

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1. ⚡ Primary & Secondary Productivity

$$\text{Gross Primary Productivity (GPP)}\mathbf{-}\text{Respiration Loss (R)}\mathbf{=}\text{Net Primary Productivity (NPP)}$$

• Gross Primary Productivity (GPP): Total rate of photosynthetic organic matter production by autotrophs per unit area per time (${\text{g/m}}^2/\text{yr}$ or ${\text{kcal/m}}^2/\text{yr}$).
• Net Primary Productivity (NPP): Biomass available for consumption by primary heterotrophs/herbivores.
• Global Biosphere NPP: $\mathbf{170}\text{ Billion Tons (Dry Weight)}\mathbf{/}\text{year}$ (Oceans cover $70\text{\%}$ of Earth's surface but contribute only $\mathbf{55}\text{ Billion Tons}$, whereas terrestrial ecosystems contribute $\mathbf{115}\text{ Billion Tons}$ due to light/nutrient limitation in deep oceans).

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2. 🔺 Ecological Pyramids & Lindeman's 10% Energy Law

  [TERTIARY CONSUMERS]     10 J  (Top carnivore)
           ▲
           │ [10% Transferred; 90% Lost as Heat/Respiration]
  [SECONDARY CONSUMERS]   100 J  (Small carnivore)
           ▲
           │
  [PRIMARY CONSUMERS]    1000 J  (Herbivores)
           ▲
           │
  [PRIMARY PRODUCERS]   10000 J  (Phytoplankton / Grasses)

$$\text{mathbf{text{Lindeman's 10text{\%} Law (1942):} quad text{Energy at Trophic Level } n+1 = 10text{\%} times text{Energy at Trophic Level } n}}$$

2.1 Upright vs Inverted Ecological Pyramids:

1. Pyramid of Energy: ALWAYS UPRIGHT in all ecosystems without exception (Second law of thermodynamics: energy dissipates as heat at each transfer).
2. Pyramid of Biomass in Grassland / Forest: Upright (Producers biomass $>$ Herbivores $>$ Carnivores).
3. Pyramid of Biomass in Aquatic / Sea Ecosystem: INVERTED! (Biomass of fishes far exceeds the standing crop of short-lived phytoplankton).
4. Pyramid of Numbers in Single Tree Ecosystem: INVERTED / Spindle-shaped (1 Oak Tree $⟶$ 1000 Herbivorous Birds $⟶100,000$ Parasitic Lice).

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3. 🌲 Ecological Succession Stages

$$\text{Primary Succession (Slow: Bare Rock/Lava)}\text{vs}\text{Secondary Succession (Faster: Abandoned Farmland/Burned Forest)}$$

• Hydrarch Succession (In Water $\to$ Mesic):$$\text{Phytoplankton}\to \text{Submerged}\to \text{Submerged Floating}\to \text{Reed-swamp}\to \text{Marsh-meadow}\to \text{Scrub}\to \text{Climax Forest}$$
• Xerarch Succession (On Bare Rock $\to$ Mesic):$$\text{Crustose Lichens (Pioneers)}\to \text{Foliose Lichens}\to \text{Mosses}\to \text{Annual Herbs}\to \text{Perennial Grasses}\to \text{Shrubs}\to \text{Climax Forest}$$