The excretory structure in the earthworm is the

1. Analyze the question The question asks which organ removes metabolic waste (excretion) in the earthworm, a member of Phylum Annelida.

2. Explain the concept Different animal groups have different excretory structures:

| Animal group | Excretory structure | |---|---| | Flatworms (e.g., planaria, tapeworm) | Flame cells (protonephridia) | | Annelids (e.g., earthworm) | Nephridia | | Insects (e.g., grasshopper, cockroach) | Malpighian tubules | | Vertebrates (fish, frog, mammals) | Kidneys |

3. Step-by-step solution

• The earthworm is an annelid, with a body made of many segments.
• Nearly every segment has a pair of coiled tubes called nephridia.
• Each nephridium opens into the body cavity (coelom) through a funnel-like structure called the nephrostome. It collects waste, mainly urea and ammonia, and passes it through the tubule. The waste leaves through a small pore (nephridiopore) on the body surface.

Eliminating the other options:

• A. Malpighian tubule: found in insects, not earthworms.
• B. Flame cell: found in flatworms.
• D. Kidney: found in vertebrates.

4. Answer The correct option is C. nephridium.

5. Exam tip Match each animal with its excretory organ using this chain: Flatworm → Flame cell; Annelid → Nephridium; Insect → Malpighian tubule; Vertebrate → Kidney. Remember "Earthworm = Nephridia": both "Earthworm" and "Nephridia" have an "n" sound in them, and each segment has its own pair of nephridia.