Ans: Phylum Mollusca is considered the second largest phylum in the animal kingdom. Typically, at least in the more primitive members of each group, there are one or more pairs of gills called ctenidia which lie in a posterior cavity the pallial cavity or in a posterolateral groove surrounding the foot. Most bivalves are either suspension or deposit feeders that indiscriminately take in particles, but then elaborately sort them based on size and weight, typically assimilating bacteria, protists, and diatoms.
The trochophore stage is often succeeded by a stage in which the , the "equatorial" band of cilia nearest the apical tuft, develops into the velum "veil" , a pair of cilia-bearing lobes with which the larva swims.
These are soft-bodied animals with an outer covering of calcium shells.Next
The foot carries a pair of , which act as balance sensors.
A phylogenetic study suggests the Polyplacophora form a clade with a monophyletic Aplacophora.Next
The largest class of Phylum Mollusca are the Gastropods.
It contains the body organs.Next
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The shell is secreted by a mantle covering the upper surface. Most bivalves burrow into soft sediment using a well-developed foot, but there are forms that lie either attached or free-living on the bottom of seas and lakes; still others live attached or cemented to rocks and other hard surfaces e.Next
Mollusks have osphradia that are used to test the chemical nature of water.
The blood of these molluscs contains the as an -carrier.Next
The particles are sorted by yet another group of cilia, which send the smaller particles, mainly minerals, to the prostyle so eventually they are excreted, while the larger ones, mainly food, are sent to the stomach's a pouch with no other exit to be digested.
In some groups, however, the shell is absent or greatly reduced, and many shell-less forms are commonly referred to as slugs the shell-less marine nudibranchs are commonly known as sea-slugs. Molluscs have, for centuries, also been the source of important luxury goods, notably , , dye, and. Scroll down to continue reading! In fact, some groups traditionally classified as molluscs may have to be redefined as distinct but related.Next
Some may not have a shell.
They also provide habitat, protection, and food to a wide array of other taxa. These creatures have been important to humans throughout history as a source of food, jewelry, tools, and even pets.Next
The coelomic cavity is reduced.