Q.To sustain themselves, earthworms must guide their way through the soil using their powerful muscles. They gather nutrients by ingesting organic matter and soil, absorbing what they need into their bodies. True or False: The two ends of the earthworm can equally ingest soil.

Step 1. The earthworm's alimentary canal is a straight, one-way tube: soil and organic matter are taken in only through the mouth, located at the anterior end in the first segment (the peristomium).

Step 2. This ingested material travels the length of the body - through the buccal cavity, pharynx, oesophagus, gizzard and intestine - being ground and digested along the way.

Step 3. The undigested residue is expelled only at the opposite, posterior end, through the anus, as worm castings (vermicasts); the anus is an exit for waste, not an entry point for fresh soil.

Step 4. Since ingestion happens exclusively at the anterior mouth end and egestion happens exclusively at the posterior anal end, the two ends of the earthworm do not equally ingest soil.

Trace the one-way direction of the gut tube - ingestion only at the mouth end, egestion only at the anus end.

• Assuming a straight tube-shaped gut can take in material from either end since it runs from front to back.
• Confusing the regular egestion of castings at the anus with an ability of that end to also ingest soil.