Phylum Chordata the chordates Chordata Characteristics Triploblastic Organ level of organization Bilateral symmetry Cephalization Eucoelomate Deuterostome Chordata Characteristics Complete digestive system Closed circulatory system Endoskeleton Chordata Characteristics All chordates possess these 4 unique characters at some point in their life even if they disappear later on notochord dorsal hollow nerve cord pharyngeal slits postanal tail mouth basic chordate body plan anus Chordata Characteristics Notochord a flexible rod like structure extends the length of the body an axis for muscle attachment in all jawed vertebrates it is replaced by a series of cartilaginous or bony vertebrae Chordata Characteristics Dorsal hollow nerve cord a single hollow tube like nerve cord dorsal to the alimentary canal and the notochord in vertebrates the anterior end becomes enlarged to form the brain brain Chordata Characteristics Pharyngeal slits perforated slit like openings that connect the pharyngeal opening and the outside formed by alternating pharyngeal grooves and pouches in aquatic chordates they become the gills in tetrapod 4 limbed vertebrates they become parts of the throat and ear cavity Chordata Characteristics Postanal tail located posterior to the anus associated with somatic musculature provides motility in the aquatic environment segmented myotomes anchored to notochord Phylum Chordata Subphylum Urochordata Subphylum Cephalochordata Subphylum Vertebrata Subphylum Urochordata tunicates ascidians sea squirts etc Subphylum Urochordata swimming tadpole larva possesses all 4 chordate characteristics sessile adults have lost all chordate characteristics except pharyngeal gill slits Subphylum Urochordata Larval Anatomy anus mouth Postanal tail gill slits notochord pharynx dorsal nerve cord Subphylum Urochordata Adult Anatomy incurrent siphon mouth excurrent siphon pharynx anus intestine gill slits used for filtering food Subphylum Cephalochordata the lancelets amphioxus Subphylum Cephalochordata have all 4 chordate characteristics throughout the lifecycle dorsal nerve cord notochord gill slits postanal tail Subphylum Vertebrata the vertebrates Subphylum Vertebrata have an endoskeleton consisting of a vertebral column and in most classes limb girdles and paired appendages axial skeleton consists of skull and vertebral column appendicular skeleton consists of paired limbs Subphylum Vertebrata outer epidermis skin that is modified into specialized structures e g hair scales feathers ventral heart with 2 4 chambers hemoglobin filled blood cells paired kidneys highly differentiated brain endocrine system with glands scattered throughout body Subphylum Vertebrata Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia Note that in your textbook this is a superclass Class Agnatha jawless fish Class Agnatha jawless with a sucker like oral disk containing well developed teeth fibrous and cartilaginous skeleton with no vertebrae no scales no paired appendages pore like gill openings two chambered heart no stomach only intestine Class Chondrichthyes the sharks and rays Class Chondrichthyes cartilaginous skeleton with bony jaws paired appendages two chambered heart heterocercal tail asymmetrical exposed gill slits no operculum no swim bladder internal fertilization gill slits Class Chondrichthyes skin is covered with dermal scales which are also modified to form teeth Class Chondrichthyes although many sharks are feared predators some are harmless filter feeders Class Osteichthyes the bony fish Class Osteichthyes mostly bony skeleton skin covered in dermal scales paired appendages two chambered heart gills supported by bony gill arches and covered by an operculum most have a homocercal tail asymmetrical have a swim bladder Class Osteichthyes some species of fish are sequential hermaphrodites they may change sex during their life Class Amphibia frogs toads and salamanders Class Amphibia mostly bony skeleton 4 limbs tetrapods smooth moist glandular skin three chambered heart gills lungs and or skin respiration ectothermic body temperature matches the temperature of the environment Class Amphibia metamorphosis usually occurs from a gill breathing larva to a lung breathing adult soft eggs tie amphibians to water Class Amphibia many amphibians have amazing parental behavior Subphylum Vertebrata Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia Amniotes The Amniotic Egg the 3 remaining classes reptiles birds and mammals have amniotic eggs amniotic eggs are shelled and contain a fluid filled sac the amnion that surrounds the embryo the evolution of the amniotic egg allowed the amniotes to reproduce away from water Class Reptilia lizards snakes turtles alligators and crocodiles Class Reptilia mostly bony skeleton 4 limbs tetrapods body covered by horny epidermal scales few glands three chambered heart except for crocodilians respiration exclusively by lungs amniotic egg ectothermic Class Reptilia many reptiles have temperature dependent sex determination The incubation temperature of the nest determines the sex of the offspring In crocodiles high temperatures produce males low temperatures produce females In turtles high temperatures produce females low temperatures produce males Class Reptilia some snakes retain their eggs internally and give live birth Class Aves birds Class Aves mostly bony skeleton with air cavities in the bones 4 limbs with forelimbs modified into wings four chambered heart amniotic egg in most species the female only has the left ovary scales on legs and feathers which are modified scales Class Aves endothermic body temperature is regulated metabolically flow through respiratory system air only goes through the lungs once Class Aves males often have exaggerated traits used to attract females Class Mammalia the mammals Class Mammalia mostly bony skeleton 4 limbs tetrapods body covered by hair can be modified into quills many glands e g mammary sweat scent four chambered heart respiration exclusively by lungs embryos develop in uterus or amniotic egg young are nourished with milk endothermic Class Mammalia 3 groups of mammals monotremes echidna and platypus lay eggs marsupials young are born altricial and complete much of their development in a pouch outside the uterus eutherians young complete development in the uterus Class Mammalia although we often only think of
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