Biology, asked by rajasswetha, 1 year ago

Expalin the salient features of phylum mollusca

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Answered by Alia15
9
Molluscs are categorised under invertebrata. 

*Molluscs are bilaterally symmetrical, triploblastic gastropods with reduced coelom. *Mollusca is derived from a Latin word, which means “thin-shelled and soft”.
*Locomotion in molluscs is by means of a muscular foot.  
*Water molluscs breathe through their gills, while land molluscs have lungs.
*Circulatory system in molluscs is open. 
*Snail is a small molluscan  Snail is protected by its external skeleton called as shell. Snails are found in wet places. Entire body except the foot lies inside the shell. When disturbed, snail even retracts the foot in to the shell. Snail moves with the help of single muscular foot. The under surface of the muscular foot is lubricated with mucus. The muscular foot glides over the surface. The rhythmic contractions and relaxations of this muscular foot brings about pulling action in the body. The secreted mucus also reduces the risk of injury from sharp objects. 
Answered by Anonymous
5
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➧ Some Phylum in Animal Kingdoms are:-
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❶❭ Porifera:-━━━━━━━━━━━━━━━☟

❱ Body is cylindrical & asymmetrical.

❱ Canal system is present.

❱ Cellular level of organisation.

❱ It is diploblastic.

❱ They reproduce by budding in Asexual Reproduction.

❱ Special cells are choanocytes.

❱ Skeleton is in the form of spicules.

▶Ex:- Sycon & Sponges

❷❭ Coelenterata:-━━━━━━━━━━━━━━━☟

❱ Body is Radially symmetrical.

❱ Canal system is absent.

❱ Tissue grade level of organisation.

❱ Body wall is diploblastic.

❱ Opening served by mouth & anus.

❱ Special Cell or Cnidoblasts.

❱ It occurs in the form of polyp & Medusa.

❱ It have gastrovascular cavity.

❱ It poses tentacles called Nematoblasts.

▶Ex:-  Hydra & Jellyfish

❸❭ Platyhelminthes:-━━━━━━━━━━━━━━━☟

❱ Body is bilaterally symmetrical, flattened & Ribbon shaped.

❱ Digestive system is absent or incomplete.

❱ Body cavity is absent.

❱ Body is triploblastic.

❱ It is bisexual or Hermaphrodite.

❱ Respiration is an aerobic.

❱ They possess sućker.

❱ Circulatory or respiratory system is absent.

▶Ex:-  Planaria & Tape worm

❹❭ Nematoda:-━━━━━━━━━━━━━━━☟

❱ Body is bilaterally symmetrical or cylindrical.

❱ Body has tissue level of organisation.

❱ It is mostly parasites organism.

❱ Body is triploblastic.

❱ Respiratory or circulatory system is absent.

❱ Sex are separate.

❱ They have tissue but no real organ.

▶Ex:-  Ascaris & Hook worm

❺❭ Annelida:-━━━━━━━━━━━━━━━☟

❱ Body is cylindrical, bilaterally symmetrical & metamerically.

❱ Body structure ring-like segment.

❱ Respiration by gills or moist skin.

❱ Body is triploblastic.

❱ Excretory organs are nephridia.

❱ Digestive & circulatory system are well developed.

❱ Locomotory organs are parapodia.

❱ They have true body cavity.

▶Ex:-  Earthworm & Leech

❻❭ Arthropoda:-━━━━━━━━━━━━━━━☟

❱ Body is bilaterally symmetrical & segmented.

❱ Exoskeleton shed periodically during growth.

❱ Body is covered with non living exoskeleton.

❱ Body wall is triploblastic.

❱ Body divided into head, Thorax & abdomen.

❱ It have jointed appendages.

❱ It possess compound eyes & antennae.

❱ Respiration by gills, trachea & book lungs.

▶Ex:-  Cockroach & Spider

❼❭ Mollusca:-━━━━━━━━━━━━━━━☟

❱ Body is bilaterally symmetrical.

❱ Shell formed of calcium carbonate.

❱ Body covered with mantal & hard shell.

❱ Body is triploblastic & Coelomate.

❱ Body divided into head, foot & visceral mass.

❱ Foot is ventral & muscular.

❱ Respiration by gills or ctenida.

❱ Blood may be Black - blue.

▶Ex:-  Octopus & Unio

❽❭ Echinodermata:-━━━━━━━━━━━━━━━☟

❱ Body is radially symmetrical.

❱ Body size is spherical or cylindrical.

❱ Body surface covered with spines.

❱ Body is triploblastic & have coelomic cavity.

❱ It possess power of regeneration.

❱ No head tail right & left side.

❱ Body differentiated into oral & aboral surface.

❱ It have water vascular system.

▶Ex:-  Starfish & Antedon

❾❭ Chordata:-━━━━━━━━━━━━━━━☟

❱ Nerve cord hollow tubular & dorsal.

❱ Notochord is present.

❱ Heart is ventral.

❱ Circulatory system is always closed.

❱ RBCs are present.

❱ Endoskeleton is present.

❱ A series of pharyngeal gill-silts present in the pharyngeal wall.

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