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