Mnemonics: Ecosystem

1. Upright vs. Inverted Pyramids

 Mnemonic: "Energy Never Inverts, Biomass Sometimes, Numbers Rarely."

• Energy Never Inverts: The energy pyramid is always upright because energy decreases from one trophic level to the next due to metabolic losses and inefficiencies.
• Biomass Sometimes: The biomass pyramid can be inverted in ecosystems where producers have very low standing biomass but high productivity (for example, aquatic ecosystems with phytoplankton).
• Numbers Rarely: The number pyramid may be inverted in cases such as a single large tree (one producer) supporting many herbivores and associated consumers.

Examples:

• Grassland: Upright number and biomass pyramids; upright energy pyramid.
• Forest (tree-based): Number pyramid can be inverted because one tree (producer) supports many herbivores (insects); biomass pyramid usually upright.
• Aquatic (phytoplankton-zooplankton): Biomass pyramid may be inverted because phytoplankton reproduce rapidly and support larger zooplankton biomass despite low standing phytoplankton biomass.

2. Steps of Decomposition

Mnemonic: "Fragmented Leach Can Humid Minerals."

• Fragmented → Fragmentation: Detritivores (earthworms, termites, many arthropods) and physical processes break detritus into smaller particles, increasing surface area for microbial attack.
• Leach→ Leaching: Water-soluble organic and inorganic substances are washed out from decomposing matter into the soil, making soluble nutrients available in the soil solution.
• Can → Catabolism: Enzymes produced by microbes (bacteria, fungi) chemically break down complex organic molecules (proteins, carbohydrates, lipids) into simpler compounds.
• Humid→ Humification: Some degradation products are transformed into complex, resistant organic matter called humus; humus improves soil structure and acts as a reservoir of nutrients.
• Minerals→ Mineralisation: Microorganisms convert organic compounds into inorganic forms (e.g., NH4+, NO3-, PO43-), releasing nutrients that plants can absorb.

3. Detritus Food Chain (DFC)

Mnemonic: "Dead Matter Decomposers Degradation gives Nutrient Return." 

• Dead Matter: Detritus such as fallen leaves, dead animals, faeces and other organic residues form the starting point of the DFC.
• Decomposers: Fungi, bacteria and saprophytic microbes, along with detritivorous animals (earthworms, termites, some insects), act on detritus.
•  Degradation: Organic matter is degraded into simpler organic molecules and inorganic nutrients through enzymatic action and physical breakdown.
• Nutrient Return: Nutrients released during decomposition are returned to the soil or water and become available to producers.

4. Grazing Food Chain (GFC)

Mnemonic: "Producers let feed 1°,2°,3° Consumers."

• Producers: Green plants and algae that synthesise organic matter via photosynthesis.
• Primary Consumers: Herbivores that feed on producers (for example, goats, rabbits, many insects).
• Secondary Consumers: Carnivores that feed on primary consumers (for example, frogs, small snakes, insectivorous birds).
• Tertiary Consumers: Top carnivores that feed on secondary consumers (for example, large snakes, predatory birds, big cats).

Tips to Remember

• GFC starts with Green (living plants) - producers are the first trophic level in the grazing food chain.
• DFC starts with Dead (non-living organic matter) - decomposers and detritivores drive the detritus food chain.