Question

Connecting link between annelida and mollusca is
A) Squid
B) Nautilus
C) Neopilina
D) Sepia

Answer 1

Hint: The living animals which possess the characteristics of two different groups of animals are known as connecting links.

Complete Answer:
Animals exhibiting characters of two adjacent taxonomic groups are called connecting links. They offered very good evidence of organic evolution. The connecting link refers to the plant and organism which shows characteristics related to two different groups. For example, peripatus is considered a connecting link between Annelida and Arthropoda. The connecting link between Annelida and Mollusca is Neopilina.

Characteristics of Annelida: The serial element of gills, muscles and nephridia seems to be an ancient character, proving the descent of molluscs from an ancient group resembling today segmented worms.

Characteristics of molluscan:
(1) Resembles a limpet with a limpet-like dorsal shell.
(2) Cell of a juvenile is coiled like that of a gastropod.
(3) The shell tips point toward head not toward tail or the side like in gastropod.
(4) Like other molecules is built by a dorsal epidermis mantle or pallium.
(5) No head, only mouth opening prolonged a little bit with some mouth tentacle next to it.
(6) Foot round and most probably in able neopilina to a very slow crawling motion.
(7) On either side of the food there are five comb-gills (ctenidia) typical molluscs.
(8) The pair of gonads are joined to form a single gonad releasing germ cells into water by two separate outgoing ducts.
(9) In molluscs sexes are separate.
(10) External fertilization occurs in it.
(11) The nervous system also appears very primordial.

The connecting link of three type as follows:
(1) spring pin type connecting link
(2) cotter pin type connecting link
(3) clip type connecting link

Note: Remember duck billed Platypus is a connecting link between reptiles and mammals, that is it has mammary gland to feed it young one like other member, example human being, cow buffalo, etc. and it lays hard shelled and with large amount of yolk like reptiles.