Question

Which of the following is not a feature of flatworms?
(A) Endoderm
(B) Ectoderm
(C) Mesoderm
(D) Pseudocoelomate

Answer 1

Hint: Flatworms belong to the phylum platyhelminthes of the animal kingdom. Pseudocoelomate is a condition when the invertebrates have false coelom or false cavity. A true body coelom is always derived from the mesoderm.

Complete answer-
Platyhelminthes consist of mostly parasitic animals that survive by living inside or outside of various animals including humans. These are acoelomates i.e. without a body cavity. The members of this phylum include flatworms which range from micro-organism to 2-3 feet long organisms.
Following are some characteristics of platyhelminthes-
They are either free-living or parasitic.
They are bilaterally symmetrical, acoelomate and triploblastic.
The presence of cilia can be seen on the body that is required for locomotion.
Anus and circulatory system are absent but the presence of the mouth can be seen.
Their body looks like a leaf as there are no segments and is dorsoventrally flattened.
As we have already mentioned above that flatworms are triploblastic that means it has the presence of all the three germ layers i.e. ectoderm the outer layer, endoderm the inner layer and mesoderm the middle layer. So, from all the discussion we had we can conclude that
Option (D) is our right answer.

Note-
Platyhelminthes literally breaks up to ‘platy’ which means flat and ‘helminthes’ which means worm. They prefer the process of diffusion for the movement of oxygen and nutrients throughout the body and so lack a proper circulatory as well as respiratory system. They have only one opening from where the food enters as well as the undigested food comes out and so it’s digestive system is incomplete too.