Question

Earthworm belongs to the class of:
A. Archiannelida
B. Polychaeta
C. Oligochaeta
D. Nematoda

Answer 1

Hint: All the animals are kept into kingdom animalia and classified into many different phylum, class, order, family, genus and species based on the similarities and differences amongst themselves. Archiannelida, Polychaeta, Oligochaeta, Nematoda these are different classes.

Complete Answer:
Archiannelida: Members of this class are salt water animals with small bodies. Cephalisation absent. No distinct head, eyes, tentacle present and olfactory palps. Parapodia and setae are absent, clitellum is absent, animals are unisexual. Development is indirect. Larval stage is called Trochophore. Eg. Protodillus, Nerilla, Dinophilus.

Polychaeta: Most of the members are found in seawater. Cephalisation is more distinct. Head with well developed eyes, tentacles and olfactory palps. Setae numerous and are present in parapodia, parapodia helps in locomotion and also in respiration. Suckers are absent, clitellum absent, animals unisexual and gonads are formed only during breeding season. Development is indirect. Larval stage is called Trochophore.
E.g. Nereis - Sandworm, Aphrodite - Sea mouse
Arenicola - Lugworm, Seballa - Peacock worm, Glycera – Smooth blood worm

Oligochaeta: Most of the members are terrestrial, but some are aquatic. Cephalisation absent. No distinct head, eyes, tentacles and olfactory palps. Setae for locomotion. Number of setae is limited and situated in micro bags present in the body wall, a single setae is present in a bag. Parapodia & sucker are absent. Clitellum is present permanently for cocoon formation. Fertilization is external and is held in a cocoon. Bisexual or hermaphrodite cross fertilisation & external. Development is direct. No larva. E.g.Pheretima, Eutyphaeus, Lubricus - European earthworm, Megascolex - Largest earthworm

Nematoda: Symmetry - Bi lateral, Germ layer - Triploblastic, Level of organisation - Organ -system level and having tube within tube plan. Anterior end does not show a distinct head. No appendage.
Eg. Desmocolex, Trichinella,etc

Thus, the correct answer is option C.

Note: Classification and identification are very necessary in the world of biological diversity to enable researchers and even all the other people to live their life easily in accordance and cooperation with all the other species present in the ecosystem.