Question
Which one of the following statements about certain given animals is correct? [CBSE AIPMT 2010]
(a) Round worms (Aschelminthes) are pseudocoelomates
(b) Molluscs are acoelomates
(c) Insects are pseudocoelomates
(d) Flatworms (Platyhelminthes) are coelomates
Answer/Explanation
Ans. (a)
Round worms (phylum-Aschelminthes) are pseudocoelomates, false coelom is derived from embryonic blastocoel.
Flat worms (phylum-Platyhelminthes) are acoelomate animals.
Molluscs and insects (phylum-Arthropoda) are coelomate animals.
Question
Which one of the following groups of animals is bilaterally symmetrical and triploblastic? [CBSE AIPMT 2009]
(a) Coelenterates (cnidarians)
(b) Aschelminthes (roundworms)
(c) Ctenophores
(d) Sponges
Answer/Explanation
Ans. (b)
Aschelminthes are bilateral symmetrical and triploblastic animals, e.g. Ascaris.
Coelenterates are radially symmetrical and diploblastic animals, e.g. Obelia.
Ctenophores are radially symmetrical and diploblastic animals, e.g.
Ctenoplana.
Sponges are asymmetrical or radially symmetrical and diploblastic animals, e.g. Sycon.
Question
Ascaris is characterised by [CBSE AIPMT 2008]
(a) absence of true coelom but presence of metamerism
(b) presence of neither true coelom nor metamerism
(c) presence of true coelom but absence of metamerism
(d) presence of true coelom and metamerism (metamerisation)
Answer/Explanation
Ans. (b)
Ascaris is endoparasite of man. It inhabits the small intestine more frequently of children than of adults. The body is elongate, cylindrical and gradually tapering at both ends. There is no metameric segmentation. In Ascaris between body wall and visceral organs is a spacious fluid filled cavity.
This cavity is not true coelom as it is not lined by coelomic epithelium, has no relation with reproductive and excretory organs and develops from blastocoel. This body cavity is referred as pseudocoel.
Question
What is common between Ascaris lumbricoides and Anopheles stephensi? [CBSE AIPMT 2000]
(a) Hibernation
(b) Metamerism
(c) Anaerobic respiration
(d) Sexual dimorphism
Answer/Explanation
Ans. (d)
Both A. lumbricoides and A. stephensi; have different males and females and it is possible to distinguish between them morphologically.
Question
Ascaris larva is called [CBSE AIPMT 1992]
(a)cysticercus
(b) rhabditiform
(c) hexacanth
(d) onchosphere
Answer/Explanation
Ans. (b)
Ascaris larva is called rhabditoid or rhabditiform due to its close resemblance with Rhabditis.
Question
Ascaris lumbricoides infection occurs through [CBSE AIPMT 1991]
(a) sole of uncovered feet
(b) contaminated cooked measly pork
(c) improperly cooked measly pork
(d) from air through inhalation
Answer/Explanation
Ans. (b)
The transmission of infective stage through embryonated egg of Ascaris lumbricoides takes place by contaminated cooked measly pork and contaminated water.