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Chapter 34 - CR - Chapter 34 Vertebrates 1 of 38 Half a...

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1 of 38 of 38 Chapter 34 Chapter 34 Vertebrates
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2 of 38 of 38 Half a Billion Years of Backbones Half a Billion Years of Backbones By the end of the Cambrian period (540 mya), an astonishing variety of animals inhabited Earth’s oceans One of these types of animals gave rise to vertebrates, one of the most successful groups of animals These animals get their name from vertebrae , the series of bones that make up the backbone There are approximately 52,000 species of vertebrates and they include the largest organisms ever to live on the Earth Figure 34.1
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3 of 38 of 38 34.1: Chordates have a notochord 34.1: Chordates have a notochord and a dorsal, hollow nerve cord and a dorsal, hollow nerve cord Vertebrates are a subphylum of the phylum Chordata Chordates are bilaterian animals Deuterostomia Two groups of invertebrate deuterostomes, the urochordates and cephalochordates They’re more closely related to vertebrates than to invertebrates Derived characteristics that separate chordates from each other include presence of: Notochord, brain, head, vertebral column, jaws/mineralized skeleton, Lungs, lobed fins, legs, amniotic eggs, and milk production
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4 of 38 of 38 Derived Characters of Chordates Derived Characters of Chordates All chordates share a set of derived characters Some species possess some of these traits only during embryonic development Muscle segments Brain Mouth Anus Dorsal, hollow nerve cord Notochord Muscular, post-anal tail Pharyngeal slits or clefts Figure 34.3
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5 of 38 of 38 The notochord A longitudinal, flexible rod located between the digestive tube and the nerve cord Provides skeletal support throughout most of the length of a chordate In most vertebrates, a more complex, jointed skeleton develops and the adult retains only remnants of the embryonic notochord Dorsal, Hollow Nerve Cord Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord Develops into the central nervous system : the brain and the spinal cord
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6 of 38 of 38 Pharyngeal Slits or Clefts Grooves in the pharynx called pharyngeal clefts develop into slits that open to outside of the body They function as suspension-feeding structures in many invertebrate chordates They’re modified for gas exchange in aquatic vertebrates They develop into parts of the ear, head, and neck in terrestrial vertebrates Muscular, Post-Anal Tail A tail extending posterior to the anus In many species it is lost during embryonic development The chordate tail contains skeletal elements and muscles which provides much of the propelling force in many aquatic species
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7 of 38 of 38 Tunicates, subphylum Urochordata Belong to the deepest-branching lineage of chordates Marine suspension feeders known as sea squirts Most resemble chordates during their larval stage Which may be as brief as a few minutes As an adult, a tunicate draws in water through an incurrent siphon, filtering food particles
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