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Chapter 25 Animal Evolution – The Chordates Sections 1-5

Chapter 25 Animal Evolution – The Chordates Sections 1-5. 25.1 Transitions Written in Stone. Transitional fossils provide evidence of the evolution of birds from dinosaur ancestors Archaeopteryx , an ancient winged dinosaur with feathers Confuciusornis , a bird with claws on its wings

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Chapter 25 Animal Evolution – The Chordates Sections 1-5

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  1. Chapter 25Animal Evolution –The ChordatesSections 1-5

  2. 25.1 Transitions Written in Stone • Transitional fossils provide evidence of the evolution of birds from dinosaur ancestors • Archaeopteryx, an ancient winged dinosaur with feathers • Confuciusornis,a bird with claws on its wings • Sinosauropteryx, a dinosaur with feathers • The structure, biochemistry, and genetic traits of living organisms also provide information about the evolution of modern animal groups

  3. Archaeopteryx

  4. Confuciusornis

  5. Sinosauropteryx

  6. 25.2 Chordate Traits and Trends • Chordates (phylum Chordata) • Most diverse lineage of deuterostomes • Some are invertebrates; most are vertebrates • Bilateral and coelomate • Cephalized and segmented • Complete digestive system • Closed circulatory system • Classified by embryonic characteristics

  7. Chordate Characteristics • Four characteristics of chordate embryos may not persist in adults • Notochordof stiff connective tissue that extends the length of the body and supports it • Dorsal, hollow nerve cord parallels the notochord • Gill slits across the wall of the pharynx • Tail that extends beyond the anus

  8. Invertebrate Chordates • Lancelets (subphylum Cephalochordata) are the only group of chordates that retains all chordate characteristics as adults • Tunicates(subphylum Urochordata) have typical chordate larvae, but adults retain only the pharynx with gill slits

  9. eyespot notochord dorsal nerve cord pharynx with gill slits tail extends past anus anus Figure 25-2a p420

  10. A Lancelet

  11. ANIMATED FIGURE: Lancelet body plan To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  12. Free-swimming tunicate larva dorsal nerve cord notochord postanal tail pharynx with gill slits

  13. water flows in water flows out pharynx with gill slits secreted “tunic” Figure 25-3b1 p420

  14. Overview of Chordate Evolution • Tunicates are the invertebrate lineage most closely related to the vertebrates • Vertebrates are chordates with an internal skeleton (endoskeleton) of cartilage or bone • Modern vertebrates (except lampreys) havejawsderived from gill-supporting structures

  15. Overview of Chordate Evolution (cont.) • Fins with bony supports evolved in a subgroup of jawed fishes • Bony fins later evolve into limbs of the first four-legged walkers (tetrapods) • The development of eggs allowed that enclosed embryos within waterproof membranes allowed amniotes to disperse widely on land

  16. Evolutionary Tree for Chordates Chordates Vertebrates Tetrapods Amniotes Jawless fishes Cartilaginous fishes Ray-finned fishes Lobe-finned fishes Reptiles (with birds) Amphibians Lancelets Tunicates Mammals Amniote eggs Four limbs Bony appendages Swim bladder or lung(s) Jaws Backbone ancestral chordate

  17. ANIMATED FIGURE: Vertebrate evolution To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  18. Take-Home Message: What traits define the major subgroups of chordates? • All chordate embryos have a notochord, a dorsal tubular nerve cord, a pharynx with gill slits in its wall, and a tail that extends past the anus • There are two groups of invertebrate chordates: lancelets and tunicates • Most chordates also have a backbone and so are vertebrates; limbs evolved in one lineage that later colonized the land • Amniotes, a tetrapod subgroup with specialized eggs, are the predominant vertebrates on land

  19. 25.3 Jawless Fishes • Fishes are aquatic, nontetrapod vertebrates that typically have gills throughout their lifetime • They are ectotherms, animals whose body temperature varies with that of their environment • The first fishes were jawless; the skeleton consisted of cartilage, and the brain was enclosed in a cranium

  20. Two Groups of Jawless Fishes • Two groups of jawless fishes survived to the present: lampreys and hagfishes • Both groups have a skeleton composed of cartilage, and lack the scales and paired fins typical of jawed fishes • Their gill slits are uncovered and visible at the body surface

  21. Lampreys • Modern lamprey live their whole life in fresh water or live in the sea as larvae, then return to fresh water to breed • Unlike most fish, lampreys undergo metamorphosis; their larvae resemble larval tunicates or adult lancelets • Many adult lampreys are parasites that attach to other fish with an oral disk with toothlike structures made of keratin

  22. Lamprey

  23. Hagfishes • Hagfishes are marine bottom-feeders with poor eyesight; they use sensory tentacles to locate worms and carcasses • Their mouth has dental plates covered with sharp barbs of keratin • The most recent genetic comparisons indicate that hagfishes and lampreys constitute a monophyletic group

  24. Hagfish

  25. Take-Home Message:What are jawless fishes? • Jawless fishes are gilled, aquatic vertebrates with a cartilage skeleton; they do not have jaws or scales • Lampreys and hagfishes have hard mouthparts made of keratin • Lampreys undergo metamorphosis and some parasitize other fish as adults • Hagfishes are marine scavengers

  26. 25.4 Evolution of Jawed Fishes • Jaws evolved from gill arches, skeletal elements that support a fish’s gills • Jawed fishes typically have a body covered with scales and two pairs of fins: pectoral fins and pelvic fins • Armored placoderms were the most numerous vertebrates in the seas during the Devonian period – the “Age of Fishes” • Another group of early jawed fish lineages is the acanthodians (spiny fins)

  27. location of spiracle (modified gill slit) supporting structure for gill slits jaw, derived from support structure jaw support gill slits jaw Evolution of Jaws Stepped Art

  28. ANIMATED FIGURE: Evolution of jaws To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  29. Dunkleosteus, a Placoderm

  30. Placoderm with Paired Fins pelvic fins pectoral fins

  31. Take-Home Message: What traits characterized jawed fishes? • Jaws evolved during the Silurian period by the modification of the first pair of gill arches in a jawless ancestor • Jawed fishes were the first vertebrates with paired fins • Placoderms were an early group of jawed fishes that had bony plates on their head and neck; some grew to great size • Acanthodian lineages were smaller and lacked bony armor

  32. 25.5 Modern Jawed Fishes • Cartilaginous fishes(Chondrichthyes) have a cartilage skeleton, gill slits, and teeth that shed • Sharks and rays • Bony fishes(Osteichthyes) have a bony skeleton, gill covers, and a swim bladder • Ray-finned fishes, lungfishes, coelacanth

  33. Relationships among Jawed Vertebrates tetrapods lobe-finned fishes “bony fishes” ray-finned fishes acanthodians (extinct) cartilaginous fishes placoderms (extinct)

  34. Cartilaginous Fishes: Predatory Shark

  35. Cartilaginous Fishes:Plankton-Feeding Shark

  36. Cartilaginous Fishes: Manta Ray

  37. Bony Fishes • In bony fishes, bone replaces cartilage in the skeleton and gill slits are hidden beneath a gill cover • Most bony fishes have a swim bladder that allows it to adjust its buoyancy • Modern bony fishes include two lineages: ray-finned fishes and fleshy-finned fishes

  38. Ray-Finned Fishes • Ray-finned fishes have thin, membranous fins with flexible fin supports derived from skin • Sturgeons are members of one ancient ray-finned lineage; gars are members of another early ray-finned lineage • Most ray-finned fishes (including salmon, perch, and sardines) belong to the most recently evolved lineage, the teleosts –some have a highly modified body plan

  39. Ray-Finned Fishes: Perch swim bladder kidney ovary nerve cord brain anus intestine stomach liver heart gills

  40. Ray-Finned Fishes: Gar

  41. Highly Modified Ray-Finned Fishes

  42. ANIMATED FIGURE: Bony fish body plan To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

  43. Lobe-Finned Fishes • Lobe-finned fishes, the fish most closely related to tetrapods, have fleshy fins supported by bones • There are two lineages, the marine coelacanths and the freshwater lungfishes • Lungfishes have both gills and air sacs, modified outpouchings of the gut wall that function in respiration

  44. Coelacanth

  45. Lungfish

  46. Take-Home Message: What are the characteristics of jawed fishes? • Jawed fishes are cartilaginous fishes and bony fishes. Both groups typically have scales • The ray-finned lineage of bony fishes is the most diverse group of vertebrates • Lobe-finned fishes are the fish closest to the tetrapods

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