What characteristics distinguish phylum Mollusca?
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 adaptations do Mollusca have?
The subclass Coleoidea, which includes squid, cuttlefish and octopus, have a number of other unique adaptations among the molluscs. They have highly developed eyes, a complex nervous system, ink glands and skin cells with the ability to change color (known as chromatophores).
Do mollusks have tentacles?
Many molluscs have tentacles of one form or another. The most familiar are those of the pulmonate land snails, which usually have two sets of tentacles on the head: when extended the upper pair have eyes at their tips; the lower pair are chemoreceptors.
Does phylum Mollusca have segmentation?
The phylum Mollusca is the second most diverse phylum after Arthropoda with over 110,000 described species. Mollusks may be primitively segmented, but all but the monoplacophorans characteristically lack segmentation and have bodies that are to some degree spirally twisted (e.g. torsion).
What are 2 differences in phylum Mollusca and phylum echinodermata?
The key difference between Mollusca and Echinodermata is the habitat they live in. Molluscs live in both terrestrial and aquatic environments. In contrast, echinoderms only live in marine environments. Clams, oyster and squid, are some molluscs while sea cucumber, starfish and sea urchin are some echinoderms.
How are molluscs adapted to life in the ocean?
Molluscs on the rocky shore are mostly univalved (one shell). They cannot burrow into sand like the bivalves for safety so they have very strong shells with an operculum (trapdoor attached to the foot muscle). Limpets are a good example of this. They are particularly well adapted for life on rocky surfaces.
What are some adaptations of the early members of the phylum Mollusca?
Molluscs are generally regarded members of the Lophotrochozoa, a group defined by having trochophore larvae and, in the case of living Lophophorata, a feeding structure called a lophophore. The other members of the Lophotrochozoa are the annelid worms and seven marine phyla.
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.
Do all mollusks have a shell?
Mollusks usually have a shell (although some do not). Mollusks also have an extension of the body wall called the mantle. The mantle encloses the mantle cavity which contains the Ctenidia (gills), anus and excretory pores.
Does Mollusca have Metameric segmentation?
Metameric segmentation is absent in platyhelminthes, Echinodermata, Mollusca etc. Metameric segmentation is the characteristic of Annelida (e.g., earthworm) and Arthropoda (e.g. Cockroach).
What segmentation does Mollusca have?
Mollusks also share features of their organ systems with segmented worms. Unlike segmented worms, however, mollusks do not have body segmentation. The basic mollusk body shape is usually quite different as well.
How many sucker lined arms does a cephalopod have?
With eight sucker lined arms and in some cases a pair of tentacles, a cephalopod can maintain a pretty tight grip. But how a cephalopod maintains that grip differs between squid and octopus. Squid use their suckers primarily for grabbing food.
What kind of beak does a cephalopod have?
A cephalopod is also characterized by a horny beak secreted by the walls of the buccal cavity, and a radula within the buccal cavity. All cephalopods are carnivorous. The strong beak is at the entrance to the buccal cavity , on the floor of which lies the radula.
Where are the ctenidia located in a cephalopod?
All cephalopods have one pair of unciliated ctenidia within the mantle cavity, with the exception of Nautilus, which has two pairs of ctenidia. The movement of water over the ctenidia is controlled by muscular contractions of the funnel or mantle wall.
How does a cephalopod close its mantle completely?
Locomotion in cephalopods is accomplished mainly by jet propulsion. To close its mantle completely, a squid fits two cartilaginous ridges on the mantle wall into two cartilaginous grooves on the opposite funnel wall; contraction of circular muscles around the mantle cavity then forces water out the funnel.
