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Chapter 34 Phylum Hemichordata- Acorn Worms

Chapter 34 Phylum Hemichordata- Acorn Worms. Have three body regions: proboscis, collar, and trunk Have both a ventral and dorsal nerve cord anterior portion of dorsal is hollow Have pharyngeal gill slits Have ciliated larvae identical to echinoderms Have a hydrostatic skeleton

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Chapter 34 Phylum Hemichordata- Acorn Worms

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  1. Chapter 34Phylum Hemichordata- Acorn Worms • Have three body regions: proboscis, collar, and trunk • Have both a ventral and dorsal nerve cord anterior portion of dorsal is hollow • Have pharyngeal gill slits • Have ciliated larvae identical to echinoderms • Have a hydrostatic skeleton • Filter-feeders using their pharyngeal slits

  2. Hemichordata

  3. Hemichordata

  4. Hemichordata

  5. Hemichordata

  6. Hemichordata

  7. Chapter 34 Vertebrate Evolution and Diversity Characteristics of Chordata 1. Notochord 2. Dorsal hollow nerve cord 3. Pharyngeal Slits 4. Muscular Postanal Tail

  8. Notochord: This is a longitudinal, flexible rod of cartilage that is located between the gut and the dorsal nerve cord. The notochord can last into adulthood, but in most cases it is replaced by the vertebral column. The spongy material in between the vertebral bones is all that is left of the notochord.

  9. Notochord

  10. Dorsal, Hollow Nerve Cord: This is a tube that is formed from a plate of ectoderm that is rolled up into a tube. It is located dorsal to the notochord, it lies above the gut and beneath a single, hollow nerve cord. Due to its hollow structure the dorsal nerve cord is considered very unique. It will develop into the chordate's central nervous system.

  11. Pharyngeal Gill Slits: These structures are openings of the upper digestive tube. During the embryonic stage these slits connect the outside to the pharynx. Early chordates used them to filter feeding. Over time the slits became modified to function in gas exchange.

  12. Muscular Post anal Tail: Most chordates have a tail extending beyond the anus. In many aquatic species the tail is equipped with skeletal and muscular tissue for movement. Anus Tail

  13. Subphylum Urochordata

  14. Subphylum Urochordata-sea squirtstunicates; cellulose in outer covering

  15. Subphylum Urochordata

  16. Subphylum Urochordata

  17. Subphylum Urochordata

  18. Subphylum Cephalochordata lancelets

  19. Subphylum Cephalochordata lancelets • Most like early chordates (but chordates did not descend from them) • Marine filter feeders • Feeble swimmers • Muscles segments develop from blocks of mesoderm called somites that are arranged around each side of the notochord.

  20. Subphylum Cephalochordata lancelets

  21. Subphylum Cephalochordata lancelets

  22. Subphylum Cephalochordata lancelets

  23. Fossils of early vertebrates

  24. Subphylum Vertebrata • Notochord develops into a cartilaginous or boney vertebral column that surrounds and protects the spinal cord • Have a cranium or skull that surrounds and protects the brain • Have a advanced closed circulatory system • Cephalization increases dramatically

  25. Embryonic formation of the neural crest

  26. Class Myxini-Jawless fish-Hagfish-All marine No limbs or appendages; Cartilaginous skeleton; no vertebrae

  27. Class Myxini-Jawless fish-Hagfish

  28. Class Myxini-Jawless fish-Hagfish

  29. Class Myxini-Jawless fish-Hagfish

  30. Class Myxini-Jawless fish-Hagfish

  31. Class Cephalaspidomorphi-lamprey-Jawless fish; Cartilaginous skeleton; No limbs or appendages; notochord has dorsal extensions that partially enclose the nerve cord “vertebrae”

  32. Class Cephalaspidomorphi-lamprey

  33. Class Cephalaspidomorphi-lamprey

  34. Class Cephalaspidomorphi-lamprey

  35. Class Cephalaspidomorphi-lamprey

  36. Class Cephalaspidomorphi-lamprey

  37. Evolution of the Vertebrate Jaw

  38. Ostracoderms- armored but no jaws; some were active and had paired fins

  39. Ostracoderms

  40. Placoderms-first jaws • Skeletal rods called gill arches of the most anterior pharyngeal gill slits became the jaw

  41. Placoderms Placoderms

  42. Chondricthyes sharks and rays • Completely cartilaginous skeleton; • Strong powerful swimmers • Must swim constantly to produce water flow over gills due to no operculum • Lateral line system that detects sound waves • Oviparous • Ovoviviparous • Viviparous • Cloaca

  43. Chondricthyes sharks and rays

  44. Chondricthyes sharks and rays

  45. Chondricthyes sharks and rays

  46. Osteichthyes-bony fish • Operculum-bony covering over gill arches pulls water into mouth and over the gills • Swim bladder- gives buoyancy regulates level in water; evolved from crude lungs • Bony fish evolved in freshwater first and developed crude lungs to supplement gills for gas exchange; then when they returned to salt water, the opening to the lungs closed and they evolved into swim bladders • Two chambered heart

  47. Ray-finned fishes

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