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Chordate Diversity

Chordate Diversity - Phylum Chordata Four characteristics...

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Phylum Chordata Four characteristics: always found in embryo, may become altered or disappear in later stages o Notochord o Dorsal hollow nerve cord o Pharyngeal slits o Post-anal tail Other features o Enlarged sense organs o Closed circulatory system with a ventral heart o Cartilaginous endoskeleton o Segmented striated muscles Ancestral features from deuterostome ancestors o Three germ layers o Bilateral symmetry o Well developed coelom o Filter feeding o Complete digestive tract o Segmented body Subphylum Urochordata (Tunicates) Marine tank External “hardened shell”, also known as “sea squirts” Subphylum Cephalochordata (Lancelets) Blade-like shape Amphioxus Clade Craniata Lack true vertebra: cartilaginous axial endoskeleton lacks extensions that protect nerve cord Group Vertebrata Notochord replaced by vertebral column composed of cartilage or bone o Endoskeleton: vertebra, cranium, visceral arches, limb girdles, four jointed appendages (if present) Presence of a brain with special sense organs Heart Cranium with cartilaginous and/or ossified covering for the brain Lateral line system: sensory canals along sides of body that sense pressure changes in water, lost in  terrestrial
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Fishes Finns for motion, swim bladders for buoyancy Lateral line system Sensory abilities suited to aquatic habitat, good olfaction and vision Gills extract oxygen from water and regulate osmotic balance Osmoregulators: maintain body fluid composition within narrow range Suction feeding: draws water and prey into the mouth for ingestion and forces water through gill slits Supraclass Agnatha: jawless fish o Class Myxini: hagfishes Marine, bottom dwelling scavengers Osmoconformers o Class Cephalaspidomorphi: lampreys Parasitic, use mouth to attach to prey and tongue to rasp away tissue
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Chordate Diversity - Phylum Chordata Four characteristics...

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