PHYLUM CHORDATA • Dorsal Notochord-long rod that supports the bodybecomes the vertebrae in most. • Dorsal Nerve cord-becomes the central nervous system. • Pharyngeal gill slits-openings in the throat for feeding & breathing-becomes the Pharynx in humans. • Tail-forms in embryos and extends past the anus. Evolution of Fishes Primitive fishes lacked jaws and paired fins Ancestral jawless fish ruled the seas during Devonian Period: Age of Fishes Evolution of Fishes CLASS PISCES: FISHES CLASS PISCES BECAUSE THERE ARE 20,000 SPECIES THERE ARE 3 SUBCLASSES SUBCLASS AGNATHA (JAWLESS FISH) SUBCLASS CHONDRICHTHYES (CARTILAGE) SUBCLASS OSTEICHTHYES (BONY FISH) Jawless Fishes = Agnathans No true teeth/jaw Skeleton made of fibers/cartilage Cartilage-strong supporting tissue (softer/more flexible than bone) Lack true vertebrae (keep notochord as adults) ONLY VERTEBRATE PARASITES! 2 groups: Lampreys and Hagfishes Lampreys Parasites Sucker-like oral disks with teeth to grasp and suck tissues/flesh Hagfishes Detritivores No eyes Toothed tongue Secrete slime 6 hearts Tie into knot Hagfish Cartilaginous Fishes = Chondrichthyes Sharks, Rays, Skates Cartilage skeleton (no bone) Sharks have thousands of teeth in rows Skates and Rays glide with wing-like pectoral fins (bottom-dwelling) CARTILAGINOUS FISH 850 Species of Sharks, Rays, & Skates Skeleton is made of cartilage. S-shaped swimming/rigid fins. External Gill slits. Store oils & constant motion to stay afloat. Scales are small bony plates (at one time used as sandpaper). RAYS & SKATES Flattened body for a bottomdwelling niche Spiracles & eyes on the dorsal side. Mouth, nostrils & gill slits on ventral side. Stingrays have a hollow barb. Manta ray grows to 18’. SHARKS Close to 300 species. Largest fish in the worldWhale Shark. Can smell 1drop/blood In 1 million parts/water. Lateral line detect vibrations in the water Ampullae of Lorenzini Sense changes in electrical field. WHALE SHARK Bony Fishes = Osteichthyes Bone skeleton (hard, calcified tissue) Ray-Finned Fishes-fins formed from bony spines covered by thin layers of skin (largest group) Lobe-Finned Fishes-fleshy fins with bones (some jointed like arms/legs)…ex. Lungfish & Coelacanth Fish: •Aquatic Vertebrates •Paired Fins Caudal fin Dorsal fin •Scales •Gills Lateral line Scales Eye Mouth Anal fin Pelvic fin Pectoral fin Operculum (gill cover) Feeding Herbivores, carnivores, parasites, filter feeders, and detritivores Digestive tract: mouthesophagusstomachpyloric cecaintestineanus (solid waste) Enzymes added by liver and pancreas Digestive System Intestine Esophagus Stomach Liver Pyloric cecum Mouth Anus Pancreas Respiration Gills on sides of pharynx to exchange gases Gill Filaments-feathery structures with capillaries for gas exchange Gill Rakers-prevents prey from escaping through gills Gill Arches-support and protect gills Operculum-protective bony cover over gill openings Gills Lungfish Adaptation to oxygenpoor water Tube brings oxygen from air into fish’s mouth to “LUNG” Circulation Closed system 2 chambered heart Single loop: heartgillsbody (back to heart) Fish Heart Sinus Venosus-sac that collects oxygen poor blood from veins; sends blood toAtriumlarge muscular chamber; sends it toVentriclelarge muscular chamber that pumps blood; sends it toBulbus Arteriosus-muscular tube that connects toAorta-large blood vessel that sends blood to gills Fish Heart Sinus Venosus Ventricle Atrium Bulbus arteriosus Circulation in a Fish Gills Body muscle circulation Digestive system circulation Heart Brain and head circulation Excretion Eliminate nitrogenous waste as ammonia (urine) Kidneys filter waste from blood Kidney Diffusion through gills Response/Nervous System •Well-developed nervous system with brain •Eyes with color vision •Taste/Smell •Lateral Line System- detect currents/vibrations in water (sense nearby fishes) Brain Olfactory Bulbs-smell (olfaction) Cerebrum-smell (and voluntary activities) Optic Lobe-process info from eyes Cerebellum-coordinates body movements Medulla Oblongata-controls internal organs Olfactory bulb Cerebrum Optic lobe Cerebellum Medulla oblongata Movement • Swim Bladder-internal gas filled organ to adjust buoyancy in bony fish only Movement continued… Contract paired sets of muscles Fins propel Dorsal/Ventral fins for stability (Dorsal/Anal) Paired fins for fine movements/turning (Pectoral/Pelvic) Caudal fin for speed Reproduction External/Internal fertilization Oviparous-eggs (embryo) develop and hatch outside mom’s body; obtain food from egg yolk Ovoviviparous-eggs stay in mom’s body; obtain food from egg yolk; young are “born alive” Viviparous-embryos stay in mom’s body; obtain food from mom; young are born alive •Anadromous-live in ocean but migrate to fresh water to breed; Ex. Salmon Migrations • Catadromous- Breed in the oceans but live in freshwater • Eels migrate to the Sargasso Sea, they spawn at depths of 300 meters and die when done