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Phylum Chordata Vertebrates Phylum Chordata Reproduction Amniote – vertebrates that have an amnion Anamniote - vertebrates that lack an amnion, or extraembryonic membrane that surrounds the embryo and encases it in amniotic fluid All members of the phylum (the most advanced of the animal phylum) have a stiffening notochord. Notochords are stiff rods of connective tissue. The also have a tubular dorsal nervous system and gill slits behind the oral opening at sometime during their development. The notochord serves as a rigid support and a foundation for muscles and bone. 5% of 45,000 species of chordates lose their notochord as they develop. These are invertebrate chordates. 95% retain the notochord or the vertebral column that forms around it. These are called Vertebrate Chordates. Classification of Groups Within the Phylum Chordata Phylum Chordata Subphylum Vertebrata: Class Agnatha (jawless fish) – Hagfish; lamprey Class Chondrichthyes (cartilage skeleton) – Sharks; Rays; Skates Class Osteichthyes (bony skeleton) – tuna; seahorse; puffers Class Amphibia – frogs; salamanders Class Reptilia – crocodiles; turtles; snakes Class Aves – gulls; penguins; terns Class Mammalia – Whales; seals Fish Vertebrates Live in water Possess gills Have fins There are more species of fish and more individuals than species and individuals of all other vertebrates combined. Range in size form 10 millimeters to over 20 meters (.4 inches to 60 feet) Weigh from 0.1 gram to 41,000 kilograms. (.004 ounces to 45 tons) Ectotherms – cold blooded (can not maintain a steady internal temperature) 40% of species live all or part of their life in freshwater. 60% live exclusively in salt water. Class Agnatha (a = lacking; gnathos = jaw) Examples – Hagfish and Lampreys 75 species Characteristics Lack jaws No paired appendages/fins Have gill slits Have openings to slime glands Have round sucking mouths surrounded by organs sensitive to touch Tails are flattened Eye are covered by thick skin Ectothermic anamniote Hagfish: Pink Live in colonies Feed on the inner tissues and internal organs of its prey Lamprey; Have a toothed, funnel-shaped mouth Rasps through scales and skin to get nutrients from blood Class Chondrichthyes (chondros = cartilage; ichthys = fish) True bones do not exists. jaws with teeth Anamniote 800 species paired fins Examples-Sharks and Rays Tend to be larger than either Agnathans or bony fish. Only a small fraction of all fish species are members of this group. Nearly all are marine; a few species will inhabit estuaries and very few are found in fresh water. Skates have flattened bodies with spreading pectoral fins – They move by flapping of these fins. Rays: Some have a defensive barb on their tail Some grow to 7 meters across (giant Manta) Some have the ability to shock their prey. smooth skin Do not have gas bladders, so slightly negatively buoyant; they sink if they stop swimming. flattened bodies with spreading pectoral fins move by flapping of fins Sharks: 80% are less than 2 meters long Not very intelligent Hunt prey by vibrations in the water and also by smell. Do not have gas bladders, so slightly negatively buoyant; they sink if they stop swimming. Covered with a tooth-like placoid scale. Largest – Whale shark; 18 meters (60 feet), 41,000 kilograms (90,000 pounds); feed on plankton Carcharodon (Karcharos = sharp; odontos = tooth) Great White Shark; 7 meters, 1,400 kilograms Other “dangerous” species: Mako; Tiger; Hammer head Class Osteichthyes (osteum = bone; ichthys = fish) 27,000 + species Anamniote Paired fins Success due to light, hard, strong skeleton that supports them. Most numbers and successful of all vertebrates. Representatives of this class are found in every marine habitat. 90% of all fish belong to the Class Osteichthyes and the Order Teleostei (teleos = perfedt; osteon = bone) perch, tuna, flounder,etc. a gas filled swim bladder to help maintain neutral buoyancy. independently movable fins for well controlled swimming. capable of great speed for pursuit or avoidance of predators. effective camouflage. social organization orderly pattern of migration. ability to cluster together in defensive schools. Over 77 million tons of bony fish are taken annually form the ocean for consumption. Movement, Shape & Propulsion A fish’s resistance to movement (drag) is determined by the frontal area, body contour and surface drag. Drag increases geometrically with increasing speed. Faster swimming fish must be highly modified to minimize drag. The most effective antidrag shape is a tapering torpedo-like body plan. This shape produces minimum drag when they are: circular in cross-section greatest width is ¼ the length the point of max width occurs about 2/5 the distance from the leading tip Thrust come from a combines effort of the body and fins. Muscles in slender flexible fish (eels) create S-shaped waves along the body. The body pushes against the water. This movement is not efficient; body length to width ratio must be too high (this increases the surface area that creates drag) More efficient forms have shorter less flexible bodies that undulate more rapidly and a hinged tail to transfer muscular energy to the water. How Efficient? In the fastest fish 60-80% of muscle force delivered to the tail results in forward movement. Marlin & swordfish can travel 33 meters/second (75 mph) Maintenance of Level The density of a fish’s tissue is greater than surrounding water. This difference is offset by propulsive forces and by buoyant gas or fat-filled bladders (swim bladder) The quantity of gas is controlled by: secretion and absorption of gas from the blood muscular contraction of the bladder. Fast predators lack a swim bladder. The volume would have to change too rapidly and the chance of rupture is great. Class Reptilia 6200 species amniote Each of the 3 main groups within the Class Reptilia have marine representatives: turtles sea snakes marine lizards Each of these groups: are ectothermic breathe air using lungs are covered with scales and an impermeable skin have salt glands that concentrate and excrete salt Marine Turtles Most successful living marine reptile 8 Species More streamlined Shell lacks enough internal space for head and limbs Forelimbs are modified as flippers Hind limbs act as rudders Most abundant and wide spread are the 2 species of green sea turtles The largest of the turtles is the Atlantic Leatherback Have a skin covering the shell Reach 2 meters in length Weigh more than 6oo kilograms (1300 pounds) All marine turtles are in danger of extinction: breeding beaches are being developed Their eggs and shells are in demand They drown in fishing nets Feeding areas are polluted Floating plastic bags are mistaken for food and eaten Marine Crocodiles One living species Lives in mangrove swamps and isolated mainland shores in the tropical western Pacific Very aggressive and hunts in packs 7 meters long Weighs over 2.000 pounds Marine Lizards One surviving species – Galapagos Marine Iguana. Live among the intertidal rocks and beaches of the Galapagos Islands Grow to more than 1 meter in length Weigh 9 kilograms (20 pounds) Swim by undulating body and tail Live in colonies and feed on off-shore seaweeds. Sea Snakes 50 species of sea snakes Most are native to the Indian Ocean and the western Pacific areas There are none in the Atlantic They hunt among the coral heads Sea snakes must return to the surface to breathe The young are born alive in the water Venom is among the most powerful animal poison known. Prey is held in the mouth until saliva which contains the neurotoxin enters wounds and takes effect. Class Aves Marine birds: are endotherms – they generate and regulate metabolic heat have thin hollow bones without fatty insulation have light weight beak replacing jaws and teeth 4 chambered heart to circulate blood under high pressure have a respiratory system that can accept large quantities of oxygen all birds lay eggs on land 8800 species amniotes Only 3% of known birds are classified as sea birds. Sea birds have salt secreting glands in their head like marine reptiles. Groups of sea birds: Tubenoses 100 species – world’s most oceanic birds; examples – albatrosses, petrels and shear waters Albatross Wingspan of 12 feet Weighs 22 pounds Wings are aerodynamic; can soar at high speeds using very little energy Pelicans This group includes pelicans, cormorants, frigate birds, and Boobies All have throat patches All have webbed feet They do not spend much time over open ocean The frigate can not walk or swim; its skeleton weighs less than its feathers Penguins Have lost the ability to fly Excellent swimmers Have fatty insulation making feathers greasy Neutrally buoyant; can dive to depths of 875 feet and stay submerged for 10 minutes Class Mammalia 4500 species amniote 3 Living groups Cetacea – Porpoises, dolphins, and whales Carnivora – seals, sea lions, walruses and sea otters Sirenia – manatees and dugongs All exhibit mammalian characteristics: endothermic breathe air give birth to living young young suckle milk produced in mammary glands have hair at some time during life All marine mammals have 4 common features: Streamlined body shape with limbs adapted for swimming (drag is reduced by a slippery skin or hair covering) They generate internal body heat through high metabolic rate and conserve the heat by layers of insulation (fat or fur) A respiratory system modified to collect and retain large amounts of oxygen. Many osmotic adaptations allow marine mammals to do away with the need for fresh water. Order Cetacea (whales) 90+ species Range in size from 6 feet to 110 feet Can weigh up to 110 tons Suborder Odontoceti (toothed whales) Have teeth and are active predators Have a high brain weight to body weight ratio Use echolocation (biological answer to sonar) to find prey Suborder Mysticeti Baleen whales – have no teeth; filter feeders (blue whales, humpback, and grey whales) Order Carnivora Suborder Pinnipedia (seals, sea lions, and walruses) True seals – smooth head, no external ears Elephant seals have diving record of 5,120 feet. Order Sirenia Bulky, small brained manatees and dugongs Herbivores 15 feet; 1500 pounds