Question

Describe the decomposition cycle in a terrestrial ecosystem with the help of a diagram.

Hint:

Follow detritus through five steps: fragmentation, leaching, catabolism, humification, mineralisation.

Answer 1

Step 1: Understanding the Concept:
Dead plant and animal material does not just disappear, it is broken down step by step by decomposers and physical processes, and its nutrients are returned to the soil so producers can use them again.

Step 2: Describe the stages in order.
Fragmentation is the first step, in which detritivores (such as earthworms) physically break detritus (dead remains) into smaller pieces, increasing the surface area available for further breakdown.
Leaching happens alongside this, where water-soluble inorganic nutrients from the detritus dissolve and move down into the soil, becoming part of the soil layer.
Catabolism is carried out by bacterial and fungal enzymes, which degrade the fragmented detritus into simpler inorganic substances through biochemical breakdown.
Humification runs alongside catabolism, producing a dark-coloured, amorphous substance called humus, which resists further rapid microbial breakdown and is highly colloidal, acting as a nutrient reservoir in the soil.
Mineralisation is the final stage, in which the humus is degraded further, by certain microbes, releasing simple inorganic nutrients back into the soil, ready to be absorbed by plant roots again.

Step 3: Give the diagram flow in words.
Detritus → (fragmentation by detritivores) → smaller particles → (leaching) → soil nutrients, alongside → (catabolism by microbial enzymes) → simple organics → (humification) → humus → (mineralisation) → inorganic nutrients released back to soil → taken up by producers.

Final Answer:
The decomposition cycle moves detritus through fragmentation, leaching, catabolism, humification, and mineralisation, ultimately returning inorganic nutrients to the soil for producers to reuse.