Question

Which set of characters belongs to the same phylum?

• A. First true coelomates and nephridia as the excretory structures.
• B. Pseudocoelomates and flame cells as the excretory structures.
• C. Acoelomates and metanephridia cells as the excretory structures.
• D. Eucoelomates and flame cells as the excretory structures.

Answer 1

Answer: (A)

Annelida exhibit an organ-system level of body organization and bilateral symmetry. They are triploblastic, metamerically segmented, and coelomate animals. Their body surface is distinctly marked out into segments or metameres and, hence, the phylum name Annelida (Latin, annulus : little ring). They possess longitudinal and circular muscles that help in locomotion. Aquatic annelids like Nereis possess lateral appendages, parapodia, which help in swimming. A closed circulatory system is present. Nephridia (sing. nephridium) helps in osmoregulation and excretion. The neural system consists of paired ganglia (sing. ganglion) connected by lateral nerves to a double ventral nerve cord. Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious. Reproduction is sexual.
Examples: Nereis, Pheretima (Earthworm), and Hirudinaria (Bloodsucking leech).