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Chapter 23

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  1. Chapter 23 Phylum Chordata Sub-phyla: Cephalochordata & Vertebrata Superclasses: Agnatha & Gnathostomata

  2. Five Chordate Hallmarks • A. Notochord • B. Dorsal Tubular Nerve Cord • C. Pharyngeal Slits • D. Endostyle or Thyroid • E. Post Anal Tail

  3. Five Chordate Hallmarks • Notochord • Longitudinal flexible rod extending the length of the body • It is present throughout the life of jawless vertebrates • In most adult vertebrates, it is replaced by cartilage or bone vertebrae although it may remain between or within the vertebrae

  4. Lamprey

  5. Five Chordate Hallmarks • Dorsal Tubular Nerve Cord • Nerve cord lies dorsal to the alimentary canal • The anterior end becomes enlarged to form the brain and the remainder becomes the spinal cord

  6. Five Chordate Hallmarks • Pharyngeal Slits or Pouches • Opening that lead from the pharyngeal cavity to the outside • In tetrapods, the pharyngeal pouches give rise to a variety of structures including the Eustachian tubes, parathyroid glands, tonsils and middle ear cavity • In fish, the structures become fully functioning gills used in respiration and filter feeding in some

  7. Pharyngeal Slits in Sharks & Lamprey

  8. Five Chordate Hallmarks • Endostyle or Thyroid Gland • The endostyle or thyroid gland is a recent addition as a chordate characteristic • In primitive chordates, the endostyle functions to secrete mucous and aids the pharynx in filter feeding • In higher vertebrates, the thyroid secretes iodinated hormones that regulate metabolism • Typically located in the pharyngeal area of the body

  9. Five Chordate Hallmarks • Post Anal Tail • Skeletal & muscular elements that extend past the anus • In most vertebrates, it remains as a waggable tail which is useful in balance, propulsion, mobility, etc • In humans and some apes, it has become reduced to a few bones at the bottom of the sacrum called the coccyx

  10. Phylum Chordata • Sub-PhylumUrochordata (means “tail cord”) • About 3000 species commonly called sea squirts • Adults are sessile and produce a tough outer layer called a tunic • Only sea squirt tadpole larva are motile and exhibit all the chordate hallmarks

  11. Phylum Chordata • Sub-Phylum Cephalochordata (means “head-cord”) • Lancets are slender, flattened, translucent animals about 5-7 cm long • About 25 species are found on sandy bottoms of coastal waters around the world • Commonly called amphioxus, it shows all the hallmark characteristics in simple form • They are considered a sister form and not an ancestor of the vertebrates

  12. Lancet

  13. Phylum Chordata • Sub-Phylum Vertebrata (means “back bone”) divided into two Superclasses • SuperclassAgnatha (means “without jaws”) • SuperclassGnathostomata (means “jawed mouth”)

  14. Phylum Chordata • Superclass/Sub-PhylumAgnatha – 2 classes • Class Myxini (means “slime”) • There are 65 species of hagfish • They are scavengers &/or predators that feed on annelids, mollusks, crustaceans, and dead or dying fish • They have sensory tentacles called barbels used to locate food • Sense organs of touch, taste, and smell, but no eyes so they are virtually blind • Two keratinized plates rasp away flesh from its prey • Can secrete enormous amounts of slime when disturbed thus making them impossible to hold

  15. Phylum Chordata • Class Myxini – 65 species of hagfish

  16. Phylum Chordata • Superclass/Sub-phylumAgnatha – 2 classes • Class Cephalaspidomorphi (means “head shield / body”) • There are 22 species of lampreys • Their larval form are called ammocoetes and resembles amphioxus Amphioxus

  17. Phylum Chordata • Superclass/Sub-phylumAgnatha – 2 classes • Class Cephalaspidomorphi (means “head shield / body”) (con’t) • They remain in freshwater, filter-feeding stage for 3-7 years • Adults can be 15 cm to 60 cm in length • They may be parasitic or non-parasitic depending upon the individual species • They have 7 pairs of gills that are non-ventilated with water from the mouth • Sense organs for touch, taste, smell and well developed eyes • Parasitic adults attach to prey with sucker-like mouth and bore a hole in the flesh with their sharp keratinized teeth • Non-parasitic adults do not feed as adults, thus they spawn and die within a few months.

  18. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Chondrichthyes (means “cartilage fish”) • Example Sharks

  19. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Actinopterygii (means “modern bony fish”) • Example - Tuna

  20. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Sarcopterygii (means “lungfish”) • Example Coelacanth

  21. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Amphibia -(means “double life”) • Example - Frogs

  22. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Reptilia means (“to creep”) • Example – Snakes, Turtles, Lizards

  23. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Aves means (“to fly”) • Example - Birds

  24. Phylum Chordata • SuperclassGnathostomata – seven classes • Class Mammalia means “(breast animal”) • Example – humans, horses, dogs, dolphin

  25. Phylum Chordata • Class Vertebrata • General Characteristics: • Highly specialized tripartite brain which is encases in a protective skull with 12 pairs of cranial nerves • Backbone which is encloses a nerve cord The vertebrae are grouped into five regions • Cervical (neck) • Thoracic (chest) • Lumbar (back) • Sacral (pelvic) • Caudal (tail)

  26. Phylum Chordata • Class Vertebrata • General Characteristics: (con’t) • Endoskeleton composed of bone or cartilage or a combination of both • Axial skeleton includes the bones of the skull, ribs and backbone • Appendicular skeleton includes the bones of the arms and legs • Pectoral Girdle located anteriorly and attached to the forelimbs • Pelvic Girdle located posteriorly and attached to the hind limbs

  27. Axial Skeleton

  28. Appendicular Skeleton

  29. Pectoral Girdle

  30. Phylum Chordata • Class Vertebrata • General Characteristics: (con’t) • Paired sense organs specialized for sensing vibrations in water called a “lateral line” • Well developed and complex nervous system • CNS – Central Nervous System – made up of the brain & spinal cord • PNS – Peripheral Nervous System – made up of the nerves that connect to the organs, muscles, and epidermis

  31. Phylum Chordata • Class Vertebrata • General Characteristics: (con’t) • 4-legged = tetrapod • 5-digits = pentadactyl