Question

Which phylum of animals is also called flatworms?

Answer 1

Hint: Flatworms are the organisms which are straight dorsoventrally stretching from head to tail. They have a smooth dorsoventrally flattened body. These organisms are triploblastic because they have three germ layers, namely, exoderm, endoderm and mesoderm.

Complete answer:
Flatworms is the other name for platyhelminthes, they are also called tapeworms. They are classified under invertebrates as they are devoid of vertebral columns. These organisms live as parasites on other organisms including humans. There are around 20,000 different species of these organisms. Certain animals which are a part of this phylum are considered to cause specific diseases in humans. For instance, Schistosomiasis, which is an infection caused by parasitic forms of platyhelminthes. There is a specific family known as Schistosomatidae which causes these types of infections.
Though they contain three germ layers and are called triploblastic, they are devoid of any body cavity so they are called acoelomate animals. One of the exclusive features of this type of animal is that they have bilateral symmetry because of their dorsiventral flattened body.
Some free living animals are also a part of this phylum, for example turbellarians. The free living forms of this phylum are predators. The creatures belonging to this family may differ in their sizes. They are bisexual organisms which means they have both male and female sexual organs in one organism.

Note:
Platyhelminthes are invertebrates due to the fact that they are devoid of vertebral columns. They are known as flatworms because they are flat in body structure. They have an unsegmented body which is very delicate.