How are annelids and mollusks related?

How are annelids and mollusks related?

Molluscs include such familiar creatures as clams, oysters, snails, and octopi. They share a distant common ancestor with the annelid worms, an evolutionary heritage suggested by their larval form, called a trochophore larva, found in all molluscs and in certain marine annelids called polychaete worms.

What common features do mollusks and annelids share?

Like mollusks, however, they have a coelom. In fact, the annelid coelom is even larger, allowing greater development of internal organs. Annelids have other similarities with mollusks, including: A closed circulatory system (like cephalopods).

What evidence shows that mollusks and segmented worms are related how are they different?

Evolution of Mollusks Scientists believe these two groups are related because, when they are in the early stage of development, they look very similar. Mollusks also share features of their organ systems with segmented worms. Unlike segmented worms, however, mollusks do not have body segmentation.

How the members of phylum Mollusca are different from the members of phylum Annelida?

Mollusks have a coelom and several organ systems. Most also have a shell, head, foot, and radula, which is a feeding organ. Mollusks are either free-living heterotrophs or parasites. Annelids are segmented invertebrates in Phylum Annelida.

What are characteristics of Mollusca?

Molluscs (also know as mollusks) are soft-bodied, bilaterally symmetrical, segmented, coelomate animals; usually shelled having a mantle, ventral foot, anterior head, and a dorsal visceral mass.

How do you characterize the mollusks?

The main distinguishing feature is a hard outer shell. It covers the top of the body and encloses the internal organs. Most mollusks have a distinct head region. The head may have tentacles for sensing the environment and grasping food.

What is the difference between Mollusca and Arthropoda?

Mollusks are the soft-bodied invertebrates with one or two shells, whereas arthropods are the invertebrates with segmented bodies, jointed legs and appendages. Furthermore, mollusks have mantles that secrete calcareous outer or inner shell while arthropods have an exoskeleton made up chitin.

How are echinoderms and mollusks similar different?

Mollusks have soft bodies, and most secrete a shell to protect it. Echinoderms don’t have shells, but they have other means of protection. Their name comes from the Greek words for “spiny skin,” and many echinoderms such as sea urchins have long spines growing from their bodies.

What are characteristics of Mollusca that distinguish it from other phyla?

Mollusks all have a mantle, a shell secreted by the mantle, a visceral hump, a foot, and a radula. Mollusks are different from other phyla because they have these things, most of which are unique to the phylum Mollusca. Describe the valve of a clam. The valve of a clam is also known as each half of the clam’s shell.

What do annelids have in common with mollusks?

Like mollusks, annelids exhibit protostomic development. Annelids are bilaterally symmetrical and have a worm-like appearance. Their particular segmented body plan results in repetition of internal and external features in each body segment.

What are the body forms of molluscs?

Although mollusk body forms vary, they share key characteristics, such as a ventral, muscular foot that is typically used for locomotion; the visceral mass, which contains most of the internal organs of the animal; and a dorsal mantle, which is a flap of tissue over the visceral mass that creates a space called the mantle cavity.

What is the function of the muscular foot in molluscs?

The muscular foot varies in shape and function, depending on the type of mollusk (described below in the section on mollusk diversity). It is a retractable as well as extendable organ, used for locomotion and anchorage. Mollusks are eucoelomates, but the coelomic cavity is restricted to a cavity around the heart in adult animals.

How many species are in the phylum Mollusca?

Mollusca is the predominant phylum in marine environments, where it is estimated that 23 percent of all known marine species belong to this phylum. It is the second most diverse phylum of animals with over 75,000 described species.