One of these is used for excretion in earthworm

Analyze the question: The question asks which structure earthworms use to get rid of metabolic waste (excretion).

Explain the concept: Different animals use different excretory structures:

| Structure | Found in | |---|---| | Contractile vacuole | Protozoans such as Amoeba and Paramecium (osmoregulation and some waste removal) | | Flame cells | Flatworms such as planaria and tapeworm | | Malpighian tubules | Insects such as grasshopper and cockroach | | Nephridia | Annelids such as earthworm | | Kidneys | Vertebrates |

Step-by-step solution:

1. The earthworm is an annelid (phylum Annelida), a segmented worm.
2. Annelids have coiled tubular excretory organs called nephridia (singular: nephridium). Most body segments contain a pair of them.
3. Each nephridium collects waste fluid from the coelom through a funnel-shaped opening called the nephrostome. The waste passes along the coiled tube and leaves the body through a pore called the nephridiopore. In earthworms, the waste is mainly urea and ammonia.
4. Checking the other options: • A: Contractile vacuole belongs to single-celled organisms. • B: Flame cells belong to flatworms. • C: Malpighian tubules belong to insects (arthropods).

Answer: D. Nephridium

Exam tip: Match the animal to its organ with this memory aid:

• Amoeba → Contractile vacuole
• Flatworm → Flame cell
• Insect → Malpighian tubule
• Earthworm → Nephridium (think "Earthworm Needs Nephridia")

JAMB often repeats this kind of "organism and organ" matching, so it is worth learning the whole list.