Phylum: gas exchange between water and blood vessels-currents

Phylum: MolluscaGeneral Characteristics-soft bodied, most secrete a hard protective shell made of calcium carbonate-coelomates-three main body parts: a muscular foot, (movement), a visceral mass (containing most internal organs) and a mantle (fold of tissue that drapes over the visceral mass and secretes a shell if present)- most mollusc’s mantle extends beyond the visceral mass, producing a water-filled chamber (mantle cavity)-many use a radula (straplike organ) to scrape up food-most are separate sexes, gonads located in the visceral mass-3 major classes: Gastropoda (snails and slugs), Bivalvia (clams, oysters, scallops, mussels), and Cephalopoda (squids and octopuses)EnvironmentGASTROPODA:-mostly marine, some freshwater and land ranging from deserts to rainforestsBIVALVIA:-all aquatic, includes shallow to deep, and freshwater to oceanicCEPHALOPODS:-marine, mostly oceanic-habitats range from caves to self-dug dens in sand-shell substratesFeedingGASTROPODA:-contains carnivores, herbivores and detritus feeders-uses radula to graze on algae, plants, buds, roots, or flowers on land-radula used to drill hole in other shells and then extend it into the shell to tear and swallow the soft tissuesBIVALVIA:-gills are used for feeding in most species-most are filter-feeders, trap small food particles in mucus that coats their gills, cilia convey those particles to their mouth-large particles flushed with water out by the closing of the valvesCEPHALOPODA:-predators with great senses-grab on prey with suckers, engulf with tentacles and draw the food to them-some bite their food into smaller bite-size pieces before digesting, often with a paralyzing saliva-bottom-dwelling tend to eat: molluscs, crustaceans and polychaete worms-open-ocean tend to eat: fish, prawns and cephalopods-others will dangle their long arms down on a school of fish and catch the food that goes through the armsRespirationGASTROPODA:-aquatic species have gills inside their mantle cavities-terrestrial species breathe through a special mantle cavity that is lined with moist blood vessels so oxygen can enter the cellsBIVALVIA:-single pair of large gills-lamellae or fold with cilia increase the surface area for gas exchange between water and blood vessels-currents over the gills move water through the incurrent opening into the mantle cavity-water moved through the siphon to the gills before the exchange, exits through suprabranchial chamber and excurrent openingCEPHALOPODA:-two gill hearts move blood through the capillaries of the gills-only molluscs with a closed circulatory system, blood remains separate from fluid in the body cavityInternal TransportGASTROPODA:-open circulatory system, blood pumped by a heart-some blood will travel through the body tissues in spaces called sinuses leading to gill and back to the heart-nutrients obtained by digestion will be carried throughout the body by bloodBIVALVIA:-open circulatory system, not all blood contained in blood vessels-blood is pumped by a heart, oxygen and nutrients carried by blood-coelom is like a bag that surrounds their hearts-2 gill hearts move blood through the gill’s capillaries whereas the systematic heart provides the body with oxygenated bloodExcretionGASTROPODA:-feces eliminated through anus-nitrogen-containing waste (ammonia) removed through the tube-like nephridiaBIVALVIA:-feces excreted through anus-metabolic waste removed by nephridia (invertebrate organs similar to kidneys)CEPHALOPODA:-wastes excreted through nephridia in the form of urine and fecesResponseGASTROPODA:-snails have a definite head with 2 or 4 sensory tentacles and a one piece shell called a protoconch-when threatened, they will curl up into their shells for protection-slugs hide under logs/rocks in broad daylight to avoid predators-others swim quickly away, or squirt ink or have bright colouring to warn predators of their poisonBIVALVIA:-2 shells hinged together at the back, held together by 1-2 powerful muscles, secretes a layer called “Mother of Pearl”-sessile, move around rapidly by flapping their shells if threatened-some will close their bivalves and dig into mud while mussels will secrete sticky threads to attach themselves to rocksCEPHALOPODA:-chromatophores allow organisms to change colour and patterns to match a new environment, helps to camouflage and communicate when danger or emotion is detected-others defend themselves by releasing ink-have photophores as organs that produce light to startle predatorscan also tell the difference between brightness, size, shape, and horizontal or vertical orientation of things, helps them match to their backgroundMovementGASTROPODA:-move with their stomach foot located on their ventral side-can be attached firmly to the surface but very slowBIVALVIA:-“foot” muscle fibres run in all directions, used for digging/anchoring-helps anchor the organism to a surface but hard to move quicklyCEPHALOPODA:-jet propulsion; draw in oxygenated water into their mantle cavity to the gills, circular muscles contract around the mantle cavity and expels water out of the tube-aim their siphon in different directions and forces a jet of water that can propel them-some crawling along the ocean with their arms-others can move a short distance by moving a flap of muscles around the mantle cavityReproductionGASTROPODA:-most have separate sexes, reproduce sexually-external fertilization for marine and a few have internal-some are hermaphrodites and others are protandric hermaphrodites (male at birth, become female later)BIVALVIA:-separate sexes, eggs and sperm are shed into sea at the same time-larvae is developed after a sperm and egg fertilizeCEPHALOPODA:-separate sexes, spermatophore is passed to the female’s genital pore using specialized arms which is the male’s gonoduct-this arm (hectocoylus arm) may tip off into the female’s mantle cavity in some species-some species don’t have this arm, male’s reproductive organ is long and strong enough to transfer their spermatophores directly into the female-fertilized eggs are released into open water, then most die (semelparous)


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