Question

**Please do not write in cursive**

Q: How are the parasitic types of flatworms different in what body organs they have and how they go about reproduction and development compared to free-living (non-parasitic) flatworms?

Answer 1

The flatworms or platyhelminthes represent a class of worms in which maximum represenatives are parasitic in nature. These parastici worms have different set of adaptations as compared to their non-parasitic counterparts as discussed below:

1. The parasitic flatworms have hookers and suckers in their oral cavities unlike the free-living forms. These structures help them to bind themselves on the walls of the host intestine so that they might not get washed away with the food/fluids.
2. These parasitic flatworms altogether lack a digestive system in them unlike their free-living counterparts. This ensures that they could maximize the body cavity to store the liquid nutritious food sucked from the host intestine.
3. These parasites also lack a well-defined nervous system. This ensures that they can conserve their total body energy and utilize it for other important functions, such as reproduction.

Thus, these are some of the unique adaptations shown by parasitic platyhelminthes as compared to non-parasitic platyhelminthes.

As compared to they free-living counterparts, the parasitic flat worms tend to form spore-like structures which are the infectious spores of the worm. These spores are ejected out of the body along with un-digested food and spreaded in the environment by non-biotic factors such as air, water, soil etc or are uptaken by other vertebrate/non-vertebrate hosts. As these spores reach the body of next host, they complete either vegetative/reproductive phase of their life cycle (depending upon the species of the worm) and finally cause infections.