Question

As their name implies, flatworms in the phylum Acoela lack:

Options:

A) Respiratory system
B) Digestive system
C) Nervous system
D) Body symmetry
E) Coelom

Answer 1

Flatworms lack a coelom(e) and rely on diffusion for gas exchange due to the absence of respiratory and circulatory systems. They have an incomplete digestive system, bilateral symmetry, and a nervous system with cephalization.

Step-by-step explanation:

Flatworms in the phylum Acoela lack a coelom (e). These creatures, also known as acoelomates, do have a digestive system, although it is incomplete, with only one opening for both ingestion and egestion. Despite not having a coelom, flatworms do have a distinct head region, cephalization, bilateral symmetry, and a ladder-like nervous system. Moreover, they lack circulatory and respiratory systems, instead relying on diffusion across their flat body structures to exchange gases and nutrients. Flatworms also exhibit an advanced feature of having three embryonic layers, one of which is the mesoderm, allowing the development of various organ systems like the muscular and excretory systems.