Excretion is a critical physiological function in all organisms, designed to remove metabolic waste and maintain homeostasis. The identification of excretory structures can often reveal the species or group an organism belongs to. Investigating an organism with a funnel-like structure collecting waste, ducts carrying waste to nephrostones, and nephridiopores for waste removal provides insight into its classification.

Key Features Described

• Funnel-like structure (Nephrostome): Ciliated opening that collects coelomic fluid and waste.

• Ducts leading to nephrostones and nephridiopores: Tubular structures transporting waste to exterior openings.

• Nephridiopores: External pores for excretion.

These features are hallmarks of the nephridium-based excretory system, typical of segmented annelids, primarily earthworms.

Earthworm Excretory System Overview

• Earthworms have segmentally arranged paired nephridia in every segment except the first three.

• Each nephridium consists of:

  • Nephrostome: Ciliated funnel opening into the coelom that filters waste-laden fluid.

  • Tubular nephridium: Long coiled tubules involved in selective reabsorption and secretion.

  • Nephridiopore: External opening on the body wall for the removal of waste.

• This system is efficient in managing nitrogenous waste (mostly ammonia) and maintaining osmoregulation.biozoomer+2

Distinguishing Earthworms from Other Options

• Ascaris: A nematode that lacks metanephridia and nephrostomes. Its excretory system is made of a pair of longitudinal excretory canals with pores, lacking funnel structures.

• Snail: Molluscs use nephridia but with different structure lacking nephrostomes and nephrostones as described.

• Spider: Arthropods use Malpighian tubules and coxal glands, which differ structurally from nephridia with nephrostomes.

Conclusion

The described combination of funnel-like nephrostomes, ducts, and nephridiopores for waste excretion is characteristic of earthworms.

Correct Answer: (1) Earthworm