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Chapter 26 Vertebrates A Summary AP Biology Spring 2011 Chordates Vertebrates include: Fish Amphibians Reptiles Birds Mammals Are coelomate, bilateral animals Chordates Many of 4 anatomical features that characterize chordates appear only during embryonic development Notochord: long, flexible rod that appears during embryonic development between the digestive tube and the dorsal nerve cord Dorsal, hollow nerve cord: formed from a plate of ectoderm that rolls into a hollow tube Pharyngeal clefts: grooves that separate a series of pouches along the sides of the pharynx; in most chordates the clefts develop into slits that allow water to enter and exit he mouth without going through the digestive tract A muscular tail posterior to the anus Vertebrates Have an internal skeleton and big brain Internal skeleton: enlcoses and protects internal organs and works with muscles to produce movement Have several advantages of external skeletons: Cells are living so skeleton foes not have to be molted Allows for greater flexibility Is lightweight Vertebrates Notochord develops into vertebral column which encloses and protects spinal cord Have large brains with paired eyes and ears With the exception of lampreys, have jaws Vertebrates Circulatory and respiratory system Paired gills evolved in early vertebrates and allowed for faster, more efficient gas exchange Before transition to land, several species of fish developed small outpouchings in the side of the gut that evolved into lungs Have a closed circulatory system which makes circulation faster Gradually, there was less reliance on gills and more on lungs and circulatory system (heart, blood vessels), which work in connection Vertebrates Other organ systems Have paired kidneys to deal with internal fluid composition Reproduce sexually Have well developed immune system Gnathostomes Vertebrates that have jaws Jaws of vertebrates evolved from modification of skeletal parts that had once supported the pharyngeal (gill) slits Gnathostomes Class Chondrichthyes: sharks and rays Have flexible endoskeletons composed of cartilage, possess streamlined bodies, are denser than water, will sink if stop swimming Gnathostomes Class Osteichthyes: bony fish Most numerous of vertebrate groups Two main classes of bony fish are ray finned and lobed fins Have an ossified endoskeleton, covered in scales, posses a swim bladder Pisces Fish Are cold blooded vertebrates that have: Gills Scales Two chambered heart Gnathostomes Tetrapods that have four limbs and feet Class amphibia Not all have legs Frogs Amphibia Cold-blooded Initially breath through gills Then develop lungs Can also exchange gas through their moist skin Have a three chambered heart Close ties with water Their eggs lack a shell Fertilization is external Can exhibit complex social behaviour Amniotes Tetrapods that have a terrestrially adapted egg Consist of mammals and reptiles and birds Amniotic egg Important evolutionary development for life on land Have shell that retains water and can be laid in a dry environment Have extraembryonic membranes that function in gas exchange, waste storage and transport of nutrients to embryo Reptilia Cold-blooded Have eggs with a chitinous covering Lay eggs on land Undergo internal fertilization Have a four chambered heart First vertebrates to have internal fertilization Have scales containing keratin Adaptation for terrestrial living Obtain oxygen through their lungs, not skin Reptilia Extinct reptiles: Dinosaurs (lived on land) Pterosaurs (flying reptiles) Plesiosaurs (marine reptiles) Modern reptiles: Turtles, tuataras, lizards, snakes, alligators, crocodiles Most are ectothermic Regulate body temperature through behavioral adaptations rather than by metabolism Aves Birds Warm-blooded Have eggs with shells Lay amniotic eggs Wings, feathers, hollow bones Four-chambered heart High rate of metabolism Have keratin containing scales on their legs Scales and eggs are reptilian characteristics Aves Most birds bodies are constructed for flight: Light, hollow bones Relatively few organs Wings Feathers Endotherms: maintain warm, consistent body temperature Feathers and in some cases a layer of fat insulate birds and help maintain internal temperature Have larger brains than amphibians and nonbird reptiles do Mammalia Warm-blooded (endotherms) Active metabolism Most are born rather than hatched Use internal fertilization Large brains Four-chambered heart Have hair and produce milk to feed their young All have teeth of differing size and shape Mammalia Some have a placenta (eutherians) Structure that nourishes fetus Embryo develops internally in a uterus connected to mother by placenta, where nutrients diffuse from mother to embryo Mammalia Marsupials do not have a placenta Developing embryo receives little nourishment from mother in the uterus About eight days after fertilization, fetus must continue its maturation in mother’s pouch (nurses) Mammalia Monotremes: egg laying mammals Duck billed platypus and spiny anteater Derive nutrients from shelled egg Mammalia: Primates Humans are primates Primates descended from insectivores, probably from small, tree dwelling mammals Have dexterous hands and opposable thumbs Make it possible to do fine motor tasks Nails have replaced claws Hands and fingers contain many nerve endings and are sensitive Mammalia: Primates Eyes are front facing and set close together Front facing eyes fosters face-to-face communication Close set eyes are responsible for overlapping fields of vision, which enhances depth perception and hand-eye cordination Mammalia: Primates Devote much energy to parenting of young Engage in most intense parenting of any mammal Usually have single births and nurture young for long time period Mammalia: Primates Include: Humans Gorillas Chimpanzees Orangutans Gibbons Old world and new world monkeys
