1 / 12

Phylum Mollusca (Chapter 27.4)

Phylum Mollusca (Chapter 27.4). Please set up your notebook for Cornell Notes. Mollusks Characteristics Soft-bodied w/ external or internal shell Have a free swimming larval stage called trochophore Also appear in annelids. Form and function Body plan Bilaterally symmetrical Four parts

tamika
Download Presentation

Phylum Mollusca (Chapter 27.4)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Phylum Mollusca (Chapter 27.4) Please set up your notebook for Cornell Notes

  2. Mollusks • Characteristics • Soft-bodied w/ external or internal shell • Have a free swimming larval stage called trochophore • Also appear in annelids

  3. Form and function • Body plan • Bilaterally symmetrical • Four parts • Foot  flat structure for crawling, shovel-shaped for burrowing or tentacles for capturing prey • Mantle  thin layer of tissue that covers the body • Shell  made by glands in the mantle that secrete calcium carbonate • Reduced or lost in some groups • Visceral mass  internal organs

  4. Feeding • Herbivores, carnivores, filter feeders, detritivores or parasites • Snails and slugs have a raspy, tongue shaped structure known as a radula • Can scrape algae off rocks, drill thru shells and tear tissues • Octopi and some sea slugs use sharp jaws to eat • Some octopi use poison to subdue prey • Clams, oysters and scallops are filter feeders • Siphon  a tube-like structure that brings water in and out of the body

  5. Respiration • Aquatic mollusks use gills inside the mantle cavity • Terrestrial mollusks use a large mantle cavity lined with blood vessels • Lining must be moist • Circulation • Some mollusks have an open circulatory system (ie. Snails and clams) • Other mollusks have a closed circulatory system (ie. Octopi and squid)

  6. Excretion • Nephridia remove ammonia from the blood and release it outside of the body • Response • Simple nervous system  small ganglia, few nerve cords and eyespots • Clams, oysters • Complex nervous system  well developed brains and can remember things for long periods • Octopi, squid, cuttlefish

  7. Movement • Snails secrete mucus along base of foot then use rippling motion • Octopi use jet propulsion by drawing water into mantle and expelling from siphon • Reproduction • Sexual • External fertilization  release large number of eggs and sperm into water • Snails and two shelled mollusks • Internal fertilization • Tentacled mollusks and some snails • Some mollusks are hermaphrodites but fertilize other organisms eggs

  8. Classes of mollusks • Class Gastropoda shell-less or single shelled, move by using foot on ventral surface • Snails, slugs, nudibranches (sea slugs) • Nudibranches recycle nematocysts from cnidarians to use for protection • Snails withdraw into shell for protection

  9. Class Bivalvia two shelled mollusks • Clams, oysters, mussels, scallops • Tend to stay in one place • Filter feeders

  10. Class Cephalopoda soft-bodied, head attached to a foot that is divided into tentacles • Octopi, cuttlefish, squid, nautilus • Small internal shell or no shell • The only cephalopod with shell is a nautilus • Large eyes

More Related