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11-2 Fishes Fishes vertebrate that live water, use fins to move, most are ectotherms, obtain oxygen through gills, and have scales largest group of vertebrates (nearly 50%) gills remove oxygen from water (feathery) remove CO2 from blood stream fish open mouth water flows over gills and out slits below circulatory system closed heart with two chambers that pumps blood in a closed loop ...heart to gills...gills to rest of body and back to heart movement fins... thin membrane stretched across bony supports act like paddles large surface area allows for faster movement reproduction (external) most fishes have external reproduction eggs are laid...sperm is deposited reproduction (internal) sharks and guppies eggs are fertilized inside female ...young develop inside birthed when able to live on their own nervous system nervous system and sense organs help fishes find food and avoid predators most can see well in water.... good sense of touch...and smell ...some taste with whiskers... Three Main groups jawless, cartilaginous, and bony Jawless Fishes have no jaws or scales, skeletons are cartilage hagfish (large slimy worms) and lampreys (parasites to other fishes) mouth openings made for scraping, stabbing and sucking their food Cartilaginous Fishes Sharks, rays, and skates jaws, scales, and skeletons made of cartilage scales are pointed, tooth like...rougher than sandpaper. obtaining oxygen most cannot pump water over gills and rely on swimming or currents to move water to gills rays and skates .. lie around a lot.. take in water through small holes located behind eyes...water leaves through gills on underside .... obtaining food usually carnivores rays and skates hunt the ocean floor crush mollusks, crustaceans, and fishes with their teeth sharks will attack anything that smells like food they can smell and taste even a small amount (one drop of blood per 115 liters) rows sharp teeth that replace lost teeth ...flip up and move forward Bony Fishes have jaws, scales, a pocket on each of head that hold gills, a swim bladder, and a skeleton made of hard bone huge variety 95% of all fishes are bony fishes live in both salt and fresh water swim bladder gas-filled sac that helps the fish stay stable at different depths in the water the gas adjusted after the fish reaches the desired depth