Flatworms are soft-bodied worms that have flattened bodies which consist of tissues and organ systems. They are lacking a coelom, which is a fluid-filled cavity, that lies between their tissues. Most of them are parasitic and some are free-living.

**Flatworms** are organisms under Phylum Platyhelminthes. They are characterized as soft, flattened organisms that has simplest embryonic germ layers, and shows bilateral symmetry and cephalization. There are three known groups of flatworms and they are **turberllarians, flukes,** and **tapeworms**.

**Tubellarians** are free-living, bottom dwellers flatworms that are located usually in marine or freshwater environments. These species show a variety of colors, shapes, and sizes. One of the most known flatworms is the *cross-eyed* planarians.

**Flukes** are parasitic flatworms that usually infect the internal organs of their host organism. They can suck different nutrients or fluids from the host, thus causing serious infection. One of the known examples of this species is the blood fluke named *Schistosoma mansoni*. This organism causes the infection named **schistosomiasis**

**Tapeworms** are flatworms that are characterized by having a long, flat body and are adapted and used to live inside the intestine of their host organism. They do not have any digestive tract and the only source of their nutrition is through the absorption of nutrients from the intestinal walls of their host. Their body is composed of segments named *proglottids*. One example of this species is the *Taenia solium* (pig tapeworm)

Flatworms are organisms under Phylum Platyhelminthes. They are characterized as soft, flattened organisms that have the simplest embryonic germ layers, and show bilateral symmetry and cephalization. Flatworms can be parasitic or free-living.

The feeding mechanism of parasitic flatworms and free-living flatworms are different in a way because parasitic flatworms attach to the host’s body and slowly suck the blood to obtain their nutrients while free-living flatworms get their nutrients by capturing and digesting small aquatic organisms.

**Flukes** are parasitic flatworms that usually infect the internal organs of their host organism. They can suck different nutrients or fluids from the host, thus causing serious infection. One of the known examples of this species is the blood fluke named *Schistosoma mansoni*. This organism causes the infection named schistosomiasis

The life cycle of *Schistosoma mansoni* involves the use of two host organisms: snails and humans. Let us discuss below how this organism survives and thrive in its hosts.

1. Matured fluke species reproduce sexually inside the blood vessels of the human intestines, and the egg that they produce can be passed out from the alimentary canal through excretion. Humans are known to be their primary host.

2. The egg will then enter the water environment and develop a ciliated larva that may infect the next host with is the snail. The snail acts as an intermediate host.
3. In the snail, the organism will reproduce asexually and the resulting tailed larva will eventually be released into the water environment and the cycle continues as it infects another human host through skin exposure.

**Tubellarians** are free-living, bottom dwellers flatworms that are located usually in marine or freshwater environments. These species show a variety of colors, shapes, and sizes. One of the most known flatworms is the cross-eyed planarians.

Turbellarians’ head has several **ganglia** that control their nervous system. These ganglia function as their brain. Moreover, they also contain specialized cells that detect external stimuli like chemicals, food, and light. The information gathered from these cells is used by them to hunt and locate food, and thrive in dark environments.