Question

Which of the following statements are incorrect?
(i) Parapodia are lateral appendages in arthropods used for swimming
(ii) Radula in molluscs are structures involved in excretion
(iii) Aschelminthes are dioecious
(iv) Echinoderm adults show radial symmetry
(v) Ctenophores are diploblastic
(a) (i) and (ii)
(b) (i) and (iii)
(c) (i), (iv), and (v)
(d) (iii) and (iv)
(e) (ii), (iii), and (iv)

Answer 1

The statements are correct except the options where the function of certain parts are correct, but belong to the wrong phylum of animals and where the organ belongs to a correct animal phylum but the function is incorrect.

Complete answer:
Parapodia are lateral appendages present in annelids which help the animal in swimming. They are not present in arthropods.
- Parapodia are paired, lateral appendages extending from the body segments.
- Radula is a rasping organ present in molluscs but is not involved in excretion, instead, they are involved in feeding.
- Radula is a minutely toothed, chitinous ribbon structure.
The Achelminthes phylum has dioecious animals where the sexes are separate i.e. males and females are distinct.
- While the larvae of echinoderms are bilaterally symmetrical, the adults are radially symmetrical.
- Ctenophores are diploblastic with tissue level organization.
- The radula is inaccurately compared to a tongue. It is used for scraping food off rocks or cutting food before it enters the oesophagus.
- An example of Aschelminthes is the giant roundworm. An example of an echinoderm is the starfish. An example of Ctenophores are comb jellies.

So, the correct answer is ‘(a) (i) and (ii).’

Note:
An example of annelids equipped with parapodia is the Nereis, which is a genus of polychaete worms consisting of mostly marine species. They possess setae and parapodia for locomotion.
- The parapodia ends in chitinous bristles known as chaetae.
- Radula is unique to the molluscs, and is found in every class of mollusc except the bivalves. Bivalves use cilia to bring minute organisms closer to their mouth.