Textbook ExpertVerified Tutor
31 Dec 2021
Background and context
The worms of the Platyhelminthes phylum are called flatworms because of their flattened bodies. The word "worm" is not very scientific. But it is a term that informally describes animals (generally invertebrates) that have long bodies without legs or arms. Worms are the first important group of animals to have bilateral symmetry, meaning that the right side of their body mirrors the left.
Molluscs (also known as mollusks) are smooth-bodied, stratified, bilaterally symmetrical, coelomates animals; generally opened with a mantle, ventral leg, anterior head, and visceral dorsal mass. Molluscans are very diverse animals and form an important part of the ecosystem of the world. Phylum Mollusca belongs to some of the animals one is familiar with, like snails, octopus, squid, oysters, clams, etc.
Phylum Annelida is a large phylum. Annelids are also known as segmented worms or ringworms. They are present in a variety of environments including seawater, freshwater, and moist terrestrial regions. Also some species of this phylum display some unique shapes and brilliant colors. Annelids exhibit bilateral symmetry and are invertebrates. They are coelomate and triploblastic. The body is segmented which is the most distinctive characteristic of annelids.
Unlock all Textbook Solutions
Already have an account? Log in