AP BIOLOGY

Detailed explanation-1: -The phylum Platyhelminthes consists of simple worm-like animals called flatworms (Fig. 3.36).

Detailed explanation-2: -Answer: Phylum Platyhelminthes includes triploblastic, acoelomate, bilaterally symmetrical and dorsoventrally compressed flatworms. Phylum Platyhelminthes has following characteristic features: (1) Free-living, commensal or parasitic forms. They are heterotrophic in nature.

Detailed explanation-3: -flatworm, also called platyhelminth, any of the phylum Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates. A number of flatworm species are free-living, but about 80 percent of all flatworms are parasitic-i.e., living on or in another organism and securing nourishment from it.

Detailed explanation-4: -Characteristics of Platyhelminthes They are triploblastic, acoelomate, and bilaterally symmetrical. They may be free-living or parasites. The body has a soft covering with or without cilia. Their body is dorsoventrally flattened without any segments and appears like a leaf.

Detailed explanation-5: -They have a flat body because they do not have a coelom or even a pseudocoelom. They also lack a respiratory system. Instead, their cells exchange gases by diffusion directly with the environment.