Q.What are earthworm casts?

Step 1. As soil passes through the earthworm's alimentary canal, digestive enzymes break down the organic matter it contains, and the simpler, useful molecules are absorbed through the intestinal wall.

Step 2. The remaining undigested particles, along with fine soil, are not absorbed and instead continue to the end of the gut.

Step 3. This residue is expelled through the anus and deposited on (or near) the soil surface as small, granular faecal deposits. …

Trace what happens to the undigested fraction of ingested soil after it passes through …

• Confusing casts with the cocoon (which holds eggs and sperm) rather than with faecal waste. …