Kenia Diaz

level of organization

they have an organ level of organization

Germ layers

they are triploblastic meaning they have three embryonic tissue layers,

  • ectoderm
  • mesoderm
  • endoderm

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flatworms are bilateral


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

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Body Cavity, Circulatory System and Respiratory System

Unlike other bilaterians, they have no body cavity, and no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion
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Digestive System

The digestive cavity has only one opening for both the ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously.

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Nervous System

In all platyhelminths, the nervous system is concentrated at the head end. This is least marked in the acoels, which have nerve nets rather like those of 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

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Reproduction system

They can reproduce both asexually and sexually.

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Excretory system

The excretory system consists of protonephridia

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Flatworms are unsegmented

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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.

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Wikipedia - Flatworms

Encyclopedia Britannica - Flatworms

Discover Life - Platyhelminthes FLATWORMS; TAPEWORMS; FLUKES