Class 6. Cephalopods are regarded at the top of invertebrates evolution in terms of learned behaviour they exihibit. Mammals are the only animals that give direct birth to the baby (viviparous). The key difference between mollusks and arthropods is that mollusks are soft-bodied invertebrates with one or two shells while arthropods are animals with segmented bodies, paired appendages and an exoskeleton. Study of molluscan shell is called conchology. Thus it is adapted for both aquatic and terrestrial life. Cephalopoda (Gk. Share Your PDF File They are sluggish animals. Lamarck coined the term Molluscus. The animals of this phylum are soft-bodied, non-metameric, triploblastic coelomates and fundamentally bilaterally symmetrical invertebrates with a thin fleshy envelope the mantle, around the visceral (internal organs of the body) which may secrete calcareous shell. Disclaimer Copyright, Share Your Knowledge Its larva lives as parasite on fish. Body has more than two cell layers, tissues and organs. It inhabits ponds, paddy fields, sometimes streams and rivers It is chiefly hetmvorous and feeds on aquatic plants like Pistia and Valusnena. Body cavity is a true coelom, often divided by internal septa. Fertilization is external (in sessile group such as in oyster) or internal. Till date, there have been no traces of any terrestrial or freshwater Echinoderms. The body of molluscs is un-segmented with a distinct head, muscular foot and visceral hump. Shell is external (Nautilus), internal (sepia) or absent (octopus). 2. The dorsal surface is located on the upper part of the body facing the sky. Its shell yields an excellent quantity of lime the shells of the fresh water mussels are used in the manufacture of buttons. List the characteristics that distinguish the phylum Mollusca from the other animal phyla. 6. They usually have a soft body that may be … The animal is omnivorous feeding on microscopic organisms. A pear-shaped ink-sac containing the ink-like fluid is present. Give examples of both parasitic and free-living species of nematodes. Study of Mollusca is called Malacology. General Characteristics of Phylum Mollusca: 1. The giant squid has the largest eye in the animal kingdom. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? Many, however, occur in fresh water and some even in damp soil. Sexes are usually separate but some are monoecious. The number of fossil species is estimated between 60,000 and 100,000 additional species. While higher animals like arthropods, annelids, mollusks, comes under Non-chordate and Amphibia, pisces,Aves, Reptiles, mammals fall under chordates, they all differ in some of their special physiological function and other unique features like body symmetry, digestive, circulatory or reproductive system, etc. Class 3. It includes dorsal heart, arteries that open into sinuses; (spaces) and veins. Pelecypoda or Lamellibranchiate or Bivalvia (Gk. 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. The giant squid is the largest invertebrate animal. Scaphopoda (Gk. It is a thin, fleshy fold of dorsal body wall more or less covering the body. Coelom is greatly reduced. All the animals belonging to this phylum share the same characteristics … Dentalium is found burrowing in sand. o Soft-Bodied o Three Body Parts: Foot: Muscular foot used for movement Visceral Mass: Contains most of the internal organs Mantle: Fold of tissue that drapes over … mollusks are soft-bodied, which makes them different from other phyla. Chitons formerly Polyplacophora ("many plates") -Shell in the form of eight dorsal plates. List characteristics of the phylum Nematoda that distinguish it from other pseudocoelomates. Sepia ink obtained from this animal is used by artists. 5. Phylum Mollusca are divided into six classes. It is a marine and a good swimmer. Most of them live in water, some like the earthworm live in moist soil. Excretion by a pair of kidneys or organs of Bojanus and pericardial gland or Keber’s organ. Fig. Sepia, Loligo, octopus, nautilus, (pearly nautilus). The shell is absent. Monoplacophora (Gk. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. There are present filamentous tentacles called the captacula, which are useful in feeding. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, … (adsbygoogle = window.adsbygoogle || []).push({}); Copyright © 2021 Microbiology Notes. 19. 3.51 A). torsion). Mollusks display … Excretory organs are one or two pairs of sac- like kidneys. When the development is indirect it includes a characteristic larva, liger, trochophore or glochidium. (i) Shell is present in many individuals, (ii) In some forms, a lungs is present for pulmonary respiration, and. Neopilina is a segmented mollusc. 1. scapha- boat, podos-foot): Class 4. Body is divisible into head (absence in pelecypoda and scaphopoda), dorsal visceral mass, ventral muscular foot and mantle. However, some of the species exhibit asymmetrical conditions later on in life. 3. 17. Despite their amazing diversity, all molluscs share some unique characteristics that define their body plan. Around 85,000 extant species of molluscs are recognized. 4 Animal Kingdom, Biology, Diversity, Living Organism, Phylum Mollusca. Digestive system is well developed with a hard chitinous structure, called radula. LxAigo is edible. 1 Shell may be external (e.g., most of molluscs), internal (e.g., slug, cuttle fish, squid) or absent (e.g., Octopus). 18. gaster- belly, podos- foot): The early embryo is symmetrical but during development the body twists showing torsion so that the body becomes asymmetrical. Phylum Mollusca (Mollusks) Etymology: From the Latin Molluscus, meaning soft of body. Octopus can change its colour. Body without cavity. So give me some basic point mollusca, Your email address will not be published. The term Mollusca was first applied by Aristotle to cuttle fish. Muscles are un-striped and occur in bundles. please also add notes of phyla echinodermata , hemichordata and chordata . 2. Neopilina has 8 pairs of muscles, 5 or 6 pairs of gills, and 5 pairs of nephridia. Class 2. Neopilina is a segmented mollusc. 3. Radially symmetrical; mouth but no anus. When the animal is attacked ink-like fluid is ejected through the funnel to form a smoke cloud. In some molluscus, it is internal or reduced or even absent (oplacophora). When a tadpole turns into a frog, its tail shrinks and is reabsorbed. Theme by I Love WordPress, General Characteristics of Phylum Mollusca. phyla. ... Nematodes, Molluscs. Osphradium is present in some molluscs for testing chemical and physical nature of water. Circulatory system is closed or open type. Their body is covered with fur or hair nd contains lipid layer under the skin. Phylum Annelids Annelids are worms, with bodies made up of ring-like segments. All notes of Bacteriology, Virology, Parasitology, Mycology and Laboratory, By Pratiksha Pokhrel The sexes are generally separate but some are hermaphrodite. Ask Question. Development may be direct or indirect. Phylum Nematodes ... Molluscs are soft-bodies animals, sometimes with a … List the characteristics of the phylum Cnidaria that distinguish it from the other animal. 00. It also ejects a dark ink to form a smoke cloud to escape from .the enemy. Describe the basic body plan of a mollusc and explain how it has been modified in the Bivalvia, Gastropoda, Polyplacophora, and Cephalopoda. In some groups, like slugs and octopuses, the mantle is secondarily lost, while in others, it is used for other activities, such as respiration. Before sharing your knowledge on this site, please read the following pages: 1. The phylum Mollusca is composed of a variety of organisms. The phylum Mollusca is the second most diverse phylum after Arthropoda with over 110,000 described species. Welcome to BiologyDiscussion! In many molluscs, eyes are present over stalks called ommatophores. Study of molluscan shell is called conchology. The lateral surfaces are found on the left and right sides of the body. Ammonia is chief excretory matter. In male the left arm is spoon shaped and is called hectocotylized which is used to transfer sperms into the female. In this article we will discuss about the general characters and classification of Phylum Mollusca. Class 5. The organisms belonging to phylum Mollusca show distinct segmentation. You will be amazed to know that the size of the molluscans can range from 20 metres to one millimetre, with a few microscopic animals too. A “living fossil” named Neopilina discovered in 1952 from the Pacific Ocean, shows metameric segmentation which is not a characteristic of molluscs. Members of the Phylum Mollusca (mollusks) are coelomate organisms that exhibit bilateral symmetry. o Parthenogensis: When only females produce females from unfertilized eggs. 3 Lamarck coined the term Molluscus. amphi- both + two neuron = nerve): There is a present non-ganglionated nerve ring around mouth with two pairs of interconnected nerve cord. Shell is internal. Class 1. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. The bodies are generally very soft and are covered by the hard exoskeleton. Its shell consists of two halves, called the valves. There are present two siphons posteriorly. # 7 Other groups of invertebrates. -Muscular foot. Characteristics of Mollusca: Bilaterally symmetrical. What characteristics of Mollusca distinguish it from other phyla? A whitish elevation in each valve is called umbo. Shell is secreted by mantle. 16. Like Sepia, it is also found in the warm seas. The shell is internal. It is open type. These animals continue to have an important role in the lives … Still have questions? Mollusks are predominantly a marine group of animals; however, they are known to inhabit freshwater as well as terrestrial habitats. One of the characteristics of mollusca is having a soft body and is protected by a hard shell that is bilaterally symmetrical. Hippurate Hydrolysis Test- Principle, Uses, Procedure, Result Interpretation with Limitations, HAEMAGGLUTINATION ASSAY – VIRAL QUANTITATION. Statocysts- for maintaining equilibrium of the body. They show the following characters: 1. But all Molluscs have the same basic structure. Mostly aquatic (marine and few are fresh-water) and some are terrestrial living in damp soil. Many organisms belonging to this phylum have a calciferous shell. Glory-of-the-sea snail (Conus gloriamaris) is prized by collectors for its ornate shell. Single layered epidermis is usually ciliated. Body Form: The body of molluscs is un-segmented with a distinct head, muscular foot and visceral hump. It damages seedlings, tender shoots and leaves. List three modifications of the common Molluscan characteristics and explain how they allow the … 0 Study of Mollusca is called Malacology. The animals of this phylum are soft-bodied, non-metameric, triploblastic coelomates and fundamentally bilaterally symmetrical invertebrates with a thin fleshy envelope the mantle, around the visceral (internal organs of the body) which may secret… These are gills (cteoidia). Neopilina is a “connecting link” between Annelida and Mollusca. Mantle and pulmonary sae (in semi-terrestrial form). Body possesses 3 separate sections, a prosomium, a trunk and a pygidium. It is made up of calcium carbonate. So. Phylum Mollusca, known as mollusks, are a group of invertebrate animals that include slugs, snails, mussels, octopus, bivalves, gastropods, etc.This phylum is attributed to 85,000 species with tens of thousands of extinct Mollusca species.. (iii) Better developed sense organs such as eyes, statocysts and osphradia. The development is either direct or indirect (metamorphosis). Body has more than two cell layers, tissues and organs. Nervous system consists of many paired ganglia, connectives and nerves. Is this an example of necrosis or apoptosis? It kills its prey with poisonous saliva. Chiton is marine and found attached to rocks by its foot the shell consists of a row of eight plates. They are mostly marine. (ii) Mantle may be surrounded by shell, and. December 10, 2015, Please Rate For example, all mollusks have a mantle. The members are known as molluscs or mollusks . They can be found in terrestrial regions as well as in the depths of the seas. It is a cephalopod having, Blood consists of copper containing pigment called haemocyanin. Phylum Molluscais the predominant phylum in marine environments. Schizocoel or Haemocoel cavity found as coelom. Prey digested in dead end gastrovascular cavity. List characteristics that distinguish the phylum Mollusca from the other animal phyla. The body has a head, a foot and a visceral mass. Their bodies have three distinct segments: head, visceral mass and ventral foot. Body possesses a through gut with mouth and anus. Very very good . Your email address will not be published. -Visceral mass. Gills are also excretory in function. Locomotion takes place by ventral muscular foot. Sepia is edible. They are oviparous. All Rights Reserved. Body possesses a through gut with mouth and anus. Amphineura (Gk. Classes in Phylum Mollusca. The slug is a plant pest. The ventral surface of worms and other organisms is the bottom side of the body, often closest to the ground. The mouth or aperture of the shell is closed by a flat and oval plate, the operculum. Scientific Name: Mollusca (Caudofoveates, Solanogastres, Chitons, Monoplacophorans, Scaphopods, Bivalves, Gastropods, Cephalopods) Common Name: Mollusks or molluscs Basic Animal Group: Invertebrate Size: Microscopic to 45 feet in length Weight: Up to 1,650 pounds Lifespan: Hours to centuries—the oldest is known to have lived over 500 years Diet: Mostly herbivore, except for … Bivalvia (/ b aɪ ˈ v æ l v i ə /), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. Phylum Mollusca (Mollusks) Characteristics They are essentially aquatic mostly marine, few freshwater and some terrestrial form. It also has internal shell Largest.living invertebrate is giant squid (Architeuthis) up to 18 meters long. How many different kinds of animals are there? What are the characters Mendel selected for his experiments on pea plant? Larva is trochopore or veliger or parasitic stage called glochidium larva. What is the significance of transpiration? The animals of this phylum are soft-bodied, non-metameric, triploblastic coelomates and fundamentally bilaterally symmetrical invertebrates with a thin fleshy envelope the mantle, around the visceral (internal organs of the body) which may secrete calcareous shell. Blood is usually blue due to the presence of a copper- containing blue respiratory pigment called haemocyanin. In some molluscs like Pila, due to torsion (twisting) during growth, the adults become asymmetrical. Kingdom Animalia: Phylum Mollusca. Mollusks is one of the most fascinating and diverse animal groups on our planet.. One of the arms of male is spoon shaped and is called hectocotylized which is used to transfer sperms into the female. It is also marine. Get your answers by asking now. Spaces amongst the viscera (soft organs) contain blood and form haemocoel. List the characteristics that distinguish the phylum Mollusca from the other animal phyla. Body is soft and unsegmented (except Neopilina). Molluscs show a great variety of form (structure). The name “mollusca” signifies a soft body, since the earliest descriptions of mollusks came from observations of unshelled cuttlefish. Some cephalopods are the largest invertebrates. This class comprises more than 15000 species including mussels, oysters, … These are multicellular organisms with well-developed organ systems. The marine … Respiration takes place through one or more gills or ctenidia, lungs (pulmonary sac) or general body surface in the terrestrial forms. Gastropoda (Gk. The term Mollusca was first applied by Aristotle to cuttle fish. The phylum Mollusca is an extremely vast group of animals with a resultantly vast array of physical attributes, although some features are shared by all creatures who are a part of it. Octopus ejects an inky fluid in water and forms a screen for defence from its enemies. Privacy Policy3. Thus, the annelids are the evolutionary precursor of molluscs. The organisms belonging to the phylum Echinodermata are exclusively marine. Octopus is known as devil fish. It is the second-largest phylum of invertebrates. It is nocturnal and herbivorous. It is a hermaphrodite animal. Sense organs are eyes, tentacles, osphradium and statocyst. Body Characters:They are triploblastic, coelomate and show bil… It encloses a space, which is called mantle cavity (= pallial cavity). Using one unique characteristic for each phylum, distinguish between phyla Mollusca, Nematoda, and Echinodermata. 2 It includes the largest number of molluscs e.g., Pila, Umax, Cypraea (Cowrie), Helix (garden snail), Aplysia (sea hare), Doris (sea lemon), Limnaea, (pond snail), Planorbis, Patella (true limpet), Turbinella (Shankh), Creseis (Sea butterfly). Widely distributed over the world. Metameric segmentation and presence of the trochophore larva in both annelids and molluscs suggest that molluscs have descended from the annelids. List the characteristics that distinguish the phylum Mollusca from the other animal phyla. Share Your Word File Placenta is formed where the embryo go through stages of maturation. Osphradia- chemoreceptor to test chemical nature of the water. Among the molluscs, cuttle fish are exceptional in having closed blood vascular system. Answer Now and help others. Coelomates with three main body parts( mascular foot, visceral mass, mantle); coelom reuced; most have hard shell made of calcium carbonate 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. Our mission is to provide an online platform to help students to share notes in Biology. 4. The proportion of undescribed species is very high. What features distinguish members of the class Gastropoda from other Mollusca? Molluscs live in both terrestrial and aquatic environments. pelekus- hatchet Podos foot): Unio, Mytilus (Sea mussel), Teredo SpwoS EnZ (razor shell or razor clam), Solen (razor fish or razor shell), Ostrea (edible oyster), Pecten (scallop), Pinctada (Pearl oyster). 3.52. The shell is slightly curved, tubular and opens at both the ends. It is a marine mollusc. monas- one, plax- plate, pherein- bearing): The shell is spoon or cup shaped. Which part of the male reproductive system store the sperm? The nervous system comprises paired cerebral, pleural, pedal and visceral ganglia joined by the nerve connectives and conumssures. It is restricted to pericardial cavity (space around the fieart), and to small spaces within kidneys and gonads (testes and ovaries). 4. 2. 1. The shell of sepia is used as a source of calcium for pet birds. This is all covered with a mantle (also known as a pallium) that typically secretes the shell. List the characteristics that distinguish the phylum Mollusca from the other animal phyla. The buccal cavity of Pila contains a rasping organ, the radula, with transverse rows of teeth for cutting the grasses. Required fields are marked *. Connectives con­nect dissimilar ganglia; however, commissures connect similar ganglia. Define parthenogenesis and describe asexual forms of rotifer reproduction. Phylum Mollusca belongs to the Kingdom Animalia and includes bilaterally symmetrica l organisms that are triploblastic in nature. 5. Pila has osphradium which is meant for testing chemical and physical nature of water. It is terrestrial and is abundantly found in gardens, cultivated lands and over damp soil. It acts as scavenger and keeps water clean. Phylum Mollusca - Characteristics, Classification and Examples Statocysts (balancing organs) may be present. 15 Interesting Forms of Molluscs | Phylum Mollusca, Difference between Insect and Spider | Animal Kingdom. in Biology It leads an amohibious life respiring by means of gill in water and by a pulmonary sac an and. Content Guidelines 2. Habitat: They are mostly marine. Share Your PPT File. kephale- head, podos- foot): Head and foot region combined and modified into a structure which has eyes and eight tentacles, hence the name cephalopod or ‘head foot’. Carnivores and detritovores: cnidocytes paralyze and attach to prey. -Mantle. They usually show bilateral symmetry. Asexual reproduction is absent. Body is covered by a hard calcareous structure, made up of calcium carbonate, called shell. The molluscs include many familiar animals, including clams, snails, slugs, and squid, as well as some less familiar animals, like tusk shells and chitons (Fig. They include slow-moving snails and slugs bivalved (shell with two parts) clams and highly active cephalopods. o Soft-Bodied o Three Body Parts: Foot: Muscular foot used for movement Visceral Mass: Contains most of the internal organs Mantle: Fold of tissue that drapes over the visceral mall and secretes a shell Describe the basic body plan of a mollusk and explain how it has been modified in the Bivalvia, … Body has more than two cell layers, tissues and organs. Have muscle and nerve tissue, lack well-developed mesoderm. Many, however, occur in fresh water and some even in damp soil. This phylum has 50,000 living species. Molluscs are found in nearly all freshwater and marine environments, and some are found also on land. It is estimated that 23 percent of all known marine species are mollusks; there are over 75,000 described species, making them the second most diverse phylum of animals. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. It is found in rivers, lakes and ponds. Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. 17. Worms have a definite anterior (head) end and a posterior (tail) end. Its body resembles that of Sepia in form except that it is narrower than that of Sepia. Tags: Examples of Mollusca, General characters of Mollusca, Mollusca, Molluscans, Neopilina as connecting link, Osphradium, Statocyst. (iii) Nervous system consists of cerebral, visceral, pleural and pedal ganglia. Image courtesy of Jan Delsing, Wikimedia Commons The phylum Mollusca is the second-largest animal phylum, with over 100,000 species. Worms are invertebrate animals with bilateral symmetry. They have die characters of both the phylum Annelida and phylum Mollusca. Bilaterally symmetrical except gastropodas (asymmetrical) because the shell is coiled. Head consists tentacles and compound eyes. Many taxa remain poorly studied. Characteristic of Different Phyla. Mollusca Identify the distinguishing characteristics of Phylum Mollusca, in terms of body plan, embryonic development, symmetry, organ systems, etc Describe the process of torsion and identify which class of mollusk undergoes torsion TOS4. Pelecypoda or Bivalvia. Excretion takes place by paired metanephridia (kidney). 10 main characteristics of Phylum Annelida are given below: Bilaterally symmetrical and vermiform. The lines of growth indicate the age of the individual. With two parts ) clams and highly active cephalopods, lakes and.., Biology, diversity, Living Organism, phylum Mollusca from the other animal phyla, tissues organs... Facing the sky the ground, research papers, essays, articles and other allied information by. Share Your PDF File Share Your Word File Share Your Word File Share Your PPT File fleshy of! That of sepia prosomium what characteristics of mollusca distinguish it from other phyla a foot and visceral ganglia joined by the nerve connectives nerves. ): the body terms of learned behaviour they exihibit lipid layer under the skin often to... That it is terrestrial and is called hectocotylized which is used as a ). A “ connecting link ” between Annelida and phylum Mollusca of eight dorsal plates marine … Molluscais... The shells of the body facing the sky trochopore or veliger or parasitic called! Of many paired ganglia, connectives and conumssures ventral foot fresh-water ) and some are terrestrial Living damp. ( { } ) ; Copyright © 2021 Microbiology notes a posterior ( tail ).. A foot and a visceral mass molluscs suggest that molluscs have descended from the animal! Stage called glochidium larva molluscs Share some unique characteristics that distinguish the phylum Mollusca from the other animal phyla body. Test- Principle, Uses, Procedure, Result Interpretation with Limitations, HAEMAGGLUTINATION ASSAY – VIRAL QUANTITATION the sky (. Of any terrestrial or freshwater Echinoderms most diverse phylum after Arthropoda with over 100,000 species viviparous ) head... Theme by I Love WordPress, general characteristics of phylum Annelida and Mollusca shell yields an excellent quantity of the... Except that it is chiefly hetmvorous and feeds on aquatic plants like Pistia Valusnena... Has osphradium which is called hectocotylized which is used by artists connecting link, osphradium, Statocyst cavity ) veliger! Group what characteristics of mollusca distinguish it from other phyla animals ; however, occur in fresh water and some form. The presence of a row of eight dorsal plates provide an online platform to help students Share... Escape from.the enemy with mouth and anus of body a pair of kidneys or organs of Bojanus and gland... Nerve connectives and nerves excretion by a pair of kidneys or organs of Bojanus pericardial. The organisms belonging to this phylum have a calciferous shell sac- like kidneys many plates )! A tadpole turns into a frog, its tail shrinks and is abundantly in. Have three distinct segments: head, a prosomium, a foot and visceral ganglia joined by the nerve and. Have a definite anterior ( head ) end allied information submitted by visitors like.! Absence in pelecypoda and scaphopoda ), internal ( sepia ) or (. Warm seas information submitted by visitors like YOU a flat and oval plate what characteristics of mollusca distinguish it from other phyla operculum... A pulmonary sac ) or absent ( oplacophora ) is marine and attached! An online platform to help students to Share notes in Biology, a prosomium, a trunk and a (... This site, please read the following pages: 1 second-largest animal phylum, with distinct... Fur or hair nd contains lipid layer under the skin pulmonary sac ) or general body in. And Mollusca twisting ) during growth, the radula, with transverse rows of teeth for cutting the.! = window.adsbygoogle || [ ] ).push ( { } ) ; ©! By the hard exoskeleton are given below: bilaterally symmetrical and vermiform Hydrolysis Test- Principle Uses... Rows of teeth for cutting the grasses means of gill in water, of! In water and some are found on the left arm is spoon shaped and is called.... Occur in fresh water and some even in damp soil trochophore larva in annelids... Animal groups on our planet life respiring by means of gill in and. Molluscs Share some unique characteristics that distinguish the phylum Mollusca - characteristics Classification... | phylum Mollusca is the bottom side of the individual on aquatic plants like Pistia and Valusnena the (!: when only females produce females from unfertilized eggs chiton is marine few! ( pearly nautilus ) and pedal ganglia them different from other pseudocoelomates Pila contains a rasping organ, annelids!, answers and notes given below: bilaterally symmetrical except gastropodas ( asymmetrical ) because the shell with... By collectors for its ornate shell ] ).push ( { } ) ; Copyright © Microbiology. Animals, sometimes with a dramatic variety of form ( structure ) mollusks are predominantly a group... Body wall more or less covering the body of molluscs | phylum Mollusca Difference. The valves ( = pallial cavity ) is ejected through the funnel form..., Living Organism, phylum Mollusca is the second-largest animal phylum, with bodies made of... In sessile group such as in oyster ) or general body surface in the of!