Question

What is the difference between flatworms and roundworms?

Answer 1

The flatworms belong to the phylum Platyhelminthes and around 80% of flatworms are parasitic in nature. The term Platyhelminthes was given by Gegenbaur. The roundworms belong to the phylum Nemathelminthes or Aschelminthes.

Complete answer:

Flatworms	Roundworms
They have a thin, dorsoventrally flattened body, so called flatworms.	They have a long cylindrical body, vermiform, unsegmented with no lateral appendages.
They do not have a body cavity and thus are acoelomates.	They are pseudocoelomates i.e. they have a body cavity between their mesoderm and endoderm layers.
They have an incomplete alimentary canal.	These are the first animals to have a complete and straight alimentary canal. Intestine is non-muscular and they have a tube within a tube plan.
The excretion and osmoregulation in flatworms occurs by flame cells or solenocytes or protonephridia.	These are ammonotelic in nature and their excretory system is H-shaped and intracellular called a Rennett cell.
They are mostly hermaphrodites.	They are dioecious or unisexual and always show sexual dimorphism.
The examples of Platyhelminthes are:- Taenia solium: It is a digenetic and hermaphroditic tapeworm that is also known as Pork tapeworm.- Fasciola hepatica: It is also called sheep liver fluke as it is an endoparasite of bile duct of sheep.	The examples of Aschelminthes are:- Wuchereria bancrofti: It is also called filarial worm as it causes filariasis.- Trichurus: It is a monogenetic endoparasite of caecum and colon of children. It is also known as whipworm.

Note: Both flatworms and roundworms can be parasitic or free living. But flatworms have hooks and suckers for adhesion on their host. And roundworms are extremely abundant in soil.