Levels of Organization
Flatworms have an organ level of organization.
The development of directional movement is correlated with cephalization. In some flatworms, the process of cephalization has included the development in the head region of light-sensitive organs called ocelli.
Their Body Cavity and Thier Unique Circulatory System and Respiratory System
Flatworms are aceolomates that also have no circulatory system and no respiratory system in the sense that they have organs to move oxygen and nutrients through the body, flatworms actually process those things with diffusion.
The digestive cavity has only one opening for both the intake of nutrients and the removal of undigested wastes; as a result, the food cannot be processed continuously.
In all platyhelminths, the nervous system is concentrated at the anterior end of the body. This is least marked in the acoels, which have nerve nets rather like those found in cnidarians and ctenophores, but densest around the head. Other platyhelminths have rings of ganglia in the head and main nerve trunks running along their bodies
Flatworms can reproduce sexually and asexually, they are also both male and female so when ever they meet another flatworm they can reproduce.
The excretory system consists of protonephridia.
Flatworms are unsegmented.
The space between the skin and gut is filled with mesenchyme, a connective tissue made of cells and reinforced by collagen fibers that act as a type of skeleton, providing attachment points for muscles.
Wikipedia - Flatworms
Encyclopedia Britannica - Flatworms
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