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AP Biology Chapter 34 Lecture Notes I. Invertebrate Chordates and ...
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Short Description: AP Biology. Chapter 34 Lecture Notes. Vertebrate Evolution and Diversity. 13 separated from the other toes so they can grasp ...
Content Inside: AP Biology Chapter 34 Lecture Notes Vertebrate Evolution and Diversity I. Invertebrate Chordates and the Origin of Vertebrates A. Vertebrates are deuterostomes but not all deuterostomes are vertebrates, e.g., deuterostomes include echinoderms and invertebrate chordates such as tunicates and lancelets. B. Four anatomical features characterize the phylum Chordata 1. The following four features appear sometime during the life of a chordate, often during embryonic development: a) Notochord is longitudinal flexible rod located between the digestive tube (gut) and nerve cord. It is made of large cells encased in stiff fibrous tissue to provide support along the length of the animal. It can be found as the disks between the vertebrae of vertebrates or as a complete notochord in some adult invertebrates, e.g. lancelets or tadpole tunicates (fig 34.2, 34.3, 34.4). b) Dorsal hollow nerve cord develops from a plate of ectoderm that forms into a tube dorsal to the notochord. It will develop into the central nervous system, e.g., brain and spinal cord. c) Pharyngeal Slits are openings from the pharynx to the outside of the animal’s body. They function to let water that enters the mouth to exit the digestive tract without passing through its entire length. Many invertebrate chordates use them to filter food from water. In vertebrates, these slits have evolved into gills, jaws, hearing bones, etc. d) Muscular, Postanal Tail extends past the anus in most chordates. This tail contains part of the skeleton and muscles and helps aquatic species to swim. C. Invertebrate chordates provide clues to the origin of vertebrates 1
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