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T HREE M AIN C LASSES 1. Class Gastropoda (snails, slugs, limpets) 2. Class Bivalvia (muscles, clams, oysters) 3. Class Cephalopoda (octopus, squid, nautilus,

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Presentation on theme: "T HREE M AIN C LASSES 1. Class Gastropoda (snails, slugs, limpets) 2. Class Bivalvia (muscles, clams, oysters) 3. Class Cephalopoda (octopus, squid, nautilus,"— Presentation transcript:

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2 T HREE M AIN C LASSES 1. Class Gastropoda (snails, slugs, limpets) 2. Class Bivalvia (muscles, clams, oysters) 3. Class Cephalopoda (octopus, squid, nautilus, cuttlefish) Limpets

3  Bilateral Symmetry  Invertebrate - no backbone  Hydrostatic Skeleton (fluid under pressure)  Triploblastic  Coelomate › 1 st animals to posses a coelom  Yes, even before annelids… › Small cavity; surrounds heart, nephridia, gonads  Protostomate › Blastopore become mouth – ‘primitive’

4  Provides room for organ development  Surface diffusion of › Gases › Nutrients › Wastes  Storage  Elimination of reproductive products  Hydrostatic support

5  Size: <1cm – 18m › Garden slug – Giant squid  3 Body Regions › Mantle – tissue that covers the body  May secret a shell  Fxn : excretion, gas exchange, elimination of wastes, reproductive products › Visceral mass – contains organs › Head foot – elongate foot w/ anterior head

6  Open circulatory system in all except cephalopods  Radula – rasping/scraping structure › Covers tonguelike structure

7  Snails, limpets, slugs  Over 35,000 species  Habitat: Marine, freshwater, terrestrial  Operculum ‘lid’ › Dorsal posterior end › Used for protection from predators & desiccation

8  Undergo Torsion during larval stage- › 180° Twist of visceral mass & mantle  Allows head to enter shell first for protection  Allows for clean water in front of the snail to enter mantle cavity  Makes snail more sensitive to stimuli coming from the direction in which it moves

9  Locomotion › Flattened foot  Sometimes ciliated  Muscular contractions › Cilia over mucous trail

10  Nervous Communication › Ospharidia  Chemoreceptors  Detect sediment & chemicals in inhalant H 2 0  Helps detect prey › Ganglia linked by nerves › base or end of tentacles  Photo receptors  Lens & Cornea › Statocysts in the foot (balance)

11  Cardiovascular: › Open Circulatory System  Blood “hemolymph” leaves blood vessels  Blood bathes tissue directly in hemocoel ‘sinus’ › Function of blood: transport nutrients, wastes, & gasses  Respiration › Gills › Diffusion of O 2 across mantle

12  Digestion › Food trapped in mucus strings  Gets incorporated into protostyle › Protostyle – rotating ‘mucoid mass’ in gut of gastropod › Radula › Ciliated digestive tract

13  Excretory Waste Removal › Wastes excreted through coelom from blood › Aquatic – produce ammonia › Terrestrial – produce uric acid (less toxic) – conserves water › Nepheridium – excretory organ

14  Reproduction › Marine snails – external fertilization  Dioecious  Gametes discharged into sea › Freshwater & Terrestrial snails – internal fertilization  Monecious  Copulation - Exchange sperm – or -  One snail may act as the male, the other as the female

15  Mussels, clams, oysters, scallops  Habitat: Marine, freshwater  Help remove bacteria from polluted water  2 convex halves- valves  Proteinaceous hinge

16  Tongue & grooves in shell to prevent twisting  Umbo – swollen area – looks like a notch › Oldest part of shell  Sheet like mantle

17 Muscular movement:  Adductor muscles to close shell › Defense against predation  Sea stars can break this muscle  Steaming bivalves…  Sessile (immobile)

18 Nervous Communication  3 pairs of interconnected ganglia  Margin of the mantle is main sense organ › has sensory cells › Tentacles › Photo receptors or Lens & Cornea  Statocysts – balance/gravity  Osphraidium – chemoreceptors in mantle

19  Cardiovascular System › Open circulatory system › Blood flow: › heart  tissue sinuses  nepheridia  gills  heart  Respiration › Gills covered in cillia › diffusion

20 Digestive System  Filter feeders  Gills trap food particles  Move down food grooves (ciliated tracts)  Labial palps sort food particles

21  Excretory System › 2 Nepheridia › Duct system › Nephridiopores in anterior region for excretion of wastes

22 Reproduction  Most dioecious – male/female  Few monoecous – hermaphroditic  Most external fertilization › Spew out gametes and fertilize in sea  Some internal fertilization (fresh water only) › Female sucks in sperm from inhalent water › Young clams shed from gills

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24  Most complex mollusc  All except nautilus have a reduced shell › Cuttlefish & squid have internal shell › Nautilus has a coiled shell for support  Modified foot for food capture, attachment, locomotion, & reproduction  Visceral mass located in head segment

25 Muscular movement  Jet propulsion Jet propulsion  Foot modified into tentacles

26 Nervous Communication  Highly developed nervous system  Brains are large  Fusion of ganglia  Statocysts (gravity)  Eyes

27 Cardiovascular  1 st to have Closed circulatory system  Heart consists of 2 auricles and 1 ventricle  Have contractile arteries and branchial hearts Respiration  Gills & diffusion

28 Digestive System  Jaws & Radula  Tentacles w/ adhesive cups or foot to capture prey  Feed on small invertebrates  Efficient predators


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