Mollusca is comprised of approximately 200,000 described living species, making it one of the largest animal phyla, and consists of eight living classes that are predominantly marine, with gastropods and bivalves the only ones to have spread to freshwater. The proportion of undescribed species is very high. Species representing each of these classes are included in this guide. Cephalopoda (Gk. 52 0 obj <>/Filter/FlateDecode/ID[<872E2FCD5300F8449209B98516DCCF31>]/Index[44 21]/Info 43 0 R/Length 60/Prev 25964/Root 45 0 R/Size 65/Type/XRef/W[1 2 1]>>stream PDF | On Jan 1, 2016, Richard C. Brusca and others published Phylum Mollusca | Find, read and cite all the research you need on ResearchGate �``hʄ�� _� ��}z5ױI�F�:����%����TR�CѧN(�C����bk3c��1��W3��� _��g�U�[,����G.�t�ѻJX�qz�;�:7��J67:]=���H;UO The phylum Mollusca has about 100,000 described species and potentially 100,000 species yet to be described (Strong et al., 2008). The buccal cavity of Pila contains a rasping organ, the radula, with transverse rows of teeth for cutting the grasses. scapha- boat, podos-foot): Class 4. It is terrestrial and is abundantly found in gardens, cultivated lands and over damp soil. • There are 8 known living classes of molluscs and new species are constantly being discovered. Connectives con­nect dissimilar ganglia; however, commissures connect similar ganglia. Class 11 Biology Animal Kingdom: Phylum Mollusca: Phylum Mollusca. (iii) Nervous system consists of cerebral, visceral, pleural and pedal ganglia. The mouth or aperture of the shell is closed by a flat and oval plate, the operculum. It is divided among seven classes (Ruppert et al., 2004) and is present on nearly every con-tinent. 6. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Among the molluscs, cuttle fish are exceptional in having closed blood vascular system. Neopilina is a “connecting link” between Annelida and Mollusca. Shell is internal. TOS4. The development is either direct or indirect (metamorphosis). Monoplacophora (Gk. It also has internal shell Largest.living invertebrate is giant squid (Architeuthis) up to 18 meters long. monas- one, plax- plate, pherein- bearing): The shell is spoon or cup shaped. The head comprises of tentacles and compound eyes. Molluscs can be divided into ive principal classes, namely Gastropoda, Bivalvia, Scaphopoda, Polyplacophora and Cephalopoda. hޤ�mo�0���}l51�$q�TU�2Z����NB|H���B�W+�~wv�[���}�v_� �� ����"B����}T�!���J�� E��H/ 7. Class Gastropoda Subclass Vetigastropoda They have die characters of both the phylum Annelida and phylum Mollusca. Sepia is edible. Sepia, Loligo, octopus, nautilus, (pearly nautilus). Osphradium is present in some molluscs for testing chemical and physical nature of water. Classification of Phylum Mollusca. One of the arms of male is spoon shaped and is called hectocotylized which is used to transfer sperms into the female. Amphineura: It is a small class of marine molluscs dating back from the Cambrian period. Only the gastropods have entered the terrestrial habitat, and some families of snails and mussels are commensalistic. Privacy Policy3. The nervous system comprises paired cerebral, pleural, pedal and visceral ganglia joined by the nerve connectives and conumssures. amphi- both + two neuron = nerve): There is a present non-ganglionated nerve ring around mouth with two pairs of interconnected nerve cord. They exhibit organ system level of organization. The body of molluscs is un-segmented with a distinct head, muscular foot and visceral hump. In many molluscs, eyes are present over stalks called ommatophores. Its shell yields an excellent quantity of lime the shells of the fresh water mussels are used in the manufacture of buttons. However, local taxonomic knowledge of this phylum is largely incomplete. Mollusks – Block 1 Nabinger Purpose This lesson is intended to introduce the phylum Mollusca and to go over its general physical characteristics. (ii) Mantle may be surrounded by shell, and. When the animal is attacked ink-like fluid is ejected through the funnel to form a smoke cloud. Gills are also excretory in function. Disclaimer Copyright, Share Your Knowledge When the development is indirect it includes a characteristic larva, liger, trochophore or glochidium. D notochord extends upto cephalic region . Phylum MOLLUSCA, class Polyplacophora: (poly - plax - pherein) CHITONS, 500 spp., (all similar in ecology & morphology) mm's - >35cm, common at low levels on rocky shores, can crawl when immersed in water, clamp to a substrate when emmersed. The organisms belonging to phylum Mollusca exhibit the following characteristics: 1. Asexual reproduction is absent. They are bilaterally symmetrical, triploblastic and coelomate animal. 44 0 obj <> endobj Phylum Mollusca. Thus, the annelids are the evolutionary precursor of molluscs. Scaphopoda (Gk. Deuterostomes (like the echinoderms) 2. Mollusks can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda. What are the three important components of biodiversity? There are around 100,000 recognized extant species of molluscs. South Africa has recorded 347 sponge species, comprising around 4% of sponge diversity worldwide. Neopilina is a segmented mollusc. ��Y����m��a�:�*���C\;��έv���l{6M׺�;��u��[�]���jPa���۩UŦ�f���r�dv��U�c1�d�b��2 ��F��CT��L��2ݘ�d?

phylum mollusca classes pdf

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