Question

Phylum Annelida includes
A) Unsegmented triploblastic coelomates
B) Unsegmented triploblastic acoelomates
C) Segmented triploblastic coelomates
D) Segmented triploblastic acoelomates

Answer 1

Annelids are considered as ringworms. They have three layers of germ cells and have a body cavity between the gut and the outer body wall.

Complete answer:
- The animals of Phylum Annelida are present in marine, terrestrial and freshwater environments, but the presence of moisture or humidity, particularly in terrestrial habitats, is a significant factor in their survival.
- The phylum name is derived from the word annellus in Latin , meaning a little ring. Commensal and parasitic symbioses are demonstrated by animals in this phylum with other individuals in their habitat. In the phylum Annelida, roughly 16,500 species have been described. Polychaete worms, Earthworms, and leeches are members of the phylum.

Now, let us find the solution from the options-
- Annelids are often referred to as "segmented worms" because of their main metamerism or true segmentation feature. In each body segment, the internal and external morphological characteristics are repeated. Metamerism encourages animals by adding "compartments" to become larger while making their movement more effective. From these we came to know that option (A) and (B) are incorrect.
- The coelomic fluid is filled in the coelom. In annelid worms, this coelomic fluid can perform the following functions such as keeping all the organs of the body moist, it will cause the alimentary channel to peristalsis, it acts like a fluid skeleton which provides the body with turgidity. Due to the presence of coelom, they are said to be coelomate. Thus, the option (D) is incorrect.
- Phylum annelida are said to be triploblastic because their embryo has three germ layers and they are mesoderm, ectoderm, and endoderm.

Thus, the correct answer is option (C) Segmented triploblastic coelomates.

Note: Protostomes are annelids. These animals have neuronal and digestive systems that are well established. A specialised band of segments called clitellum is carried by certain animals. The appearance of multiple chitinous projections called chaetae is seen in Annelids, and parapodia are possessed by polychaetes. The suckers are seen in the Hirudinea order. Sexual dimorphism, serial hermaphroditism, and hermaphroditism include reproductive strategies. In class Hirudinea, internal segmentation is missing.