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Molluscs

Molluscs. Zoe Wong 6s 27. Classification:. Phylum: Mollusca The Phylum Mollusca contains the following subgroups:  Class: Aplacophora (solenogasters, deep-sea wormlike creatures)  Class: Bivalvia (clams, oysters, scallops, mussels)  Class: Cephalopoda (squid, nautilus, cuttlefish)

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Molluscs

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  1. Molluscs Zoe Wong 6s 27

  2. Classification: • Phylum: Mollusca • The Phylum Mollusca contains the following subgroups: Class: Aplacophora (solenogasters, deep-sea wormlike creatures) Class: Bivalvia (clams, oysters, scallops, mussels) Class: Cephalopoda (squid, nautilus, cuttlefish) Class: Gastropoda (snails, slugs, limpets, sea hares) Class: Monoplacophora (deep-sea limpet-like creatures) Class: Polyplacophora (chitons) Class: Scaphopoda (tusk shells)

  3. Diversity • vary from 50,000 to a maximum of 120,000 species • in 2001 estimated about 93,000 named species • Has been estimated that there are about 200,000 living species in total • 70,000 fossil species • 80% of all known mollusc species are gastropods

  4. Characteristics • Soft-bodied animals • Distributes in terrestrial and aquatic habitats • An anterior head • A ventral foot • A dorsal visceral mass • Surrounded by a thin fleshy mantle • Sheltered in calcareous shell • Exoskeleton • Carry out respiration by gills • Filter feeder

  5. Body Structure

  6. Reproduction • can be sexual • have both male and female reproductive organs • mating happens during some particular time and temperature • snail stabs the skin of the other snail • Female snail will then produce eggs internally and then fertilized by the sperm that has been exchanged • around 1 month for the snail to lay eggs • 14 days to hatch • 2 years fro the baby snails to become mature

  7. Evolution - Cephalopods Advantages of evolution : • the development of more efficient swimming • in response to increasing competition from predatory fish • better locomotion • moving the animal by jet propulsion • colour-changing cells in the skin

  8. Evolution - Gastropods Reasons for evolution : • mechanical stability • defense against predators • sexual selection • climatic selection Type of gastropods : • semi-slugs • slugs • in various other marine • non-marine gastropods

  9. Human interaction • pearls of bivalves and some gastropods • Sea silk • Tyrian purple dye • Food

  10. Sources • Wikipedia • Answer.com • Andrewgray • Yahoo! • Advanced-level Biology for HK

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