Question

Alimentary canal is absent in
A) Taenia and Schistosoma
B) Ascaris and Fasciola
C) Taenia and Echinococcus
D) Tricuris and Fasciola

Answer 1

Hint: Alimentary canal is the part of the digestive system. The food is broken down and absorbed in the alimentary canal. The organisms which live as endoparasites do not have alimentary canal as they absorb the nutrients from the host. Example tapeworm, enteric bacteria etc.

Complete answer:
The alimentary canal is the part of the body which begins in mouth and ends at the anus. Through the mouth the organisms ingest food and excrete the undigested food through the anus. In the alimentary canal the food is broken down by the help of the digestive enzymes and absorbed for the growth and development. The organisms which live parasitic mode of life do not have an alimentary canal as they directly suck and absorb the nutrient from the host in which they are living. For example- Tapeworm and Echinococcus.

The Taenia is a parasite which infects pig. This organism enters the human body through the infected pork and lives in the intestine of humans where they absorb the nutrition and divide. In case of Echinococcus which is also a kind of tape worm which infects the livestock and humans. They cause disease echinococcosis.

Schistosoma- It is a parasite. These organisms have a blind ended digestive system having mouth, oesophagus and caeca. Their excretory system comprises of flame cells.

Ascaris and Fasciola-They both are parasites and suck blood. Ascaris possess a proper alimentary canal which begins with mouth and ends at anus. In case of Fasciola, the alimentary canal begins with mouth but do not end with anus.

Tricuris- It is a nematode which has complete digestive system which begins with mouth and ends with the anus. These organisms are responsible for causing Tricuriasis.

Thus the correct answer is option ‘C’.

Note: The alimentary canal is more advanced as compared to gastrointestinal cavity. It performs both intracellular and extracellular digestion. In case of invertebrates, extracellular digestion takes place.