Is phylum Mollusca Monoecious or dioecious?

Molluscs are either dioecious, with separate sexes, or hermaphroditic, one individual bearing both male and female sex organs. The eggs of aquatic species of bivalves and some species of gastropods develop into trochophores, which in turn usually develop into veliger larvae.

Are molluscs and annelids dioecious?

Mollusks are mostly dioecious and are divided into seven classes. The phylum Annelida includes worm-like, segmented animals. Segmentation is both external and internal, which is called metamerism. Annelids are protostomes.

What are the 3 major classes of phylum Mollusca?

The three major groups of mollusks are gastropods, bivalves, and cephalopods (SEF ul o pods). The largest group is the gastropods. These are mollusks like snails and slugs that have just one shell or no shell at all.

Is Mollusca Oviparous or viviparous?

Birds, reptiles, amphibians, most fish, insects, mollusks, arachnids, and monotremes are oviparous animals. Most mammals are viviparous animals.

Does a Mollusca have a shell?

mollusk, also spelled mollusc, any soft-bodied invertebrate of the phylum Mollusca, usually wholly or partly enclosed in a calcium carbonate shell secreted by a soft mantle covering the body.

What characteristics distinguish phylum Mollusca?

Characteristic Features of Phylum Mollusca

They are bilaterally symmetrical.
They are triploblastic, which three layers.
They show organ system grade of organisation.
The body is soft and unsegmented.
Body is divisible into three regions – head, a visceral mass, and ventral foot.
Body is covered by a mantle and shell.

What do platyhelminthes and molluscs have in common?

Both flatworms and molluscs are triploblastic, bilaterally symmetric, and cephalized. But molluscs have developed a true coelom, an internal body cavity enclosed by mesodermal membranes.

Are all molluscs cephalized?

Mollusks represent another group in which cephalization has been lost and regained. For example, bivalves are not particularly cephalized (although some scientists have argued that they are “all head”). However, as with the echinoderms, certain mollusks regained cephalization.

What are the 5 Mollusca classes?

The Phylum Mollusca consist of 8 classes: 1) the Monoplacophora discovered in 1977; 2) the worm-like Aplacophora or solenogasters of the deep sea; 3) the also worm-like Caudofoveata; 4) the Polyplacophora, or chitons; 5) the Pelecypoda or bivalves; 6) the Gastropoda or snails; 7) the Scaphopoda, or tusk shells; and 8) …

What is the only group of terrestrial mollusks?

All terrestrial molluscs belong to the class Gastropoda.

Are Mollusca viviparous?

Mollusca : Normally oviparous and development through a trochophore or veliger larva.

Are molluscs viviparous?

Introduction to Mollusca and the Class Gastropoda Molluscs have extreme variation in reproductive characteristics. Gastropods can be oviparous, ovoviviparous, or viviparous. Larval forms are present in some taxa.

Is phylum Mollusca Monoecious or dioecious?