BIOL 152 1st Edition Lecture 15 Outline of Last Lecture Invertebrates Outline of Current Lecture Vertebrates Current Lecture Vertebrates Shared Characteristics of Chordates 1 Notochord 2 Dorsal hollow nerve cord 3 Pharyngeal slits 4 Muscular post anal tail Urochordates Marine suspension feeders Cephalochordate Free swimming larva and adult Retain chordate characters as adult Segmented muscle somites Chordate Evolution Garstang s hypothesis paedomorphorosis species born in aquatic environment and became sexually aquatic in water FALSE Chordate Evolution Appearance of the brain Lancelets have an enlarged nerve cord tip Similar gene expression of Hox genes in the lancelet nerve cord and the vertebrate brain These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Craniates Skull brain eyes other sensory organs No jaws no vertebrae Contain duplicated pairs of Hox genes Neural crest cells Pharyngeal cleft become gill slits Higher metabolism and more extensive muscular tissue Two chambered heart and hemoglobin Vertebrates More complex nervous system and skeleton Another Hox gene duplication Vertebrae Appendages fins in aquatic species Basal vertebrates Lampreys Suspension feeders as larvae and parasites as adults Cartilaginous skeleton Origins of bone and teeth Unmineralized cartilage lampreys and before Transition to scavenging and predation conodont teeth Mineralization began in mouth and then skull Gnathostomes Hinged jaws Four clusters of Hox genes Paired appendages Enlarged forebrain Lateral line system Mineralized axial skeleton Origin of jaws Mutations and natural selection changed the size and orientation of gill arches Supporting evidence 1 Both consists of flattened bars of bony tissue that hinge and bend forward 2 Both derived from neural crests 3 Muscels that move both are derived from same embryonic cells Chondrichthyes Cartilage fish Carnivores with sharp vision olfaction and hearing Can detect electric fields Can adapt for buoyancy Chondrichthyes conservation Over 300 000 are severely threatened today from overfishing Factor in coral reef decline indirect effect Internal fertilization with secondary distinctions Oviparous lay eggs that hatch outside mothers body Viviparous young develop within uterus Ovoviviparous fertilized eggs that remain within mothers body Young born after hatching
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