Question

Of the four major groups of Platyhelminthes, which are free living and which are symbiotic parasites?

Answer 1

Platyhelminthes are divided into four major groups, with Turbellaria being free-living and Monogenea, Trematoda, and Cestoda being symbiotic parasites.

Step-by-step explanation:

Platyhelminthes, or flatworms, are divided into four major groups: Turbellaria, Monogenea, Trematoda, and Cestoda. Among these groups, the Turbellaria are largely free-living, and include polycladid marine worms and tricladid freshwater species. On the other hand, the Monogenea, Trematoda, and Cestoda are all symbiotic parasites. Monogenea are ectoparasitic, mainly found on the external surface of their hosts, while Trematoda and Cestoda are endoparasitic, living inside their hosts. Trematoda have complex life cycles involving a molluscan secondary host, while Cestoda, also known as tapeworms, infect the digestive systems of their primary vertebrate hosts.