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Animal Evolution – The Chordates

Animal Evolution – The Chordates. Chapter 26 Part 1. Impacts, Issues Transitions Written in Stone. Fossils such as Archaeopteryx , an ancient winged dinosaur with feathers, are evolutionary evidence of transitions between species. 26.1 The Chordate Heritage. Chordates

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Animal Evolution – The Chordates

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  1. Animal Evolution – The Chordates Chapter 26 Part 1

  2. Impacts, IssuesTransitions Written in Stone • Fossils such as Archaeopteryx, an ancient winged dinosaur with feathers, are evolutionary evidence of transitions between species

  3. 26.1 The Chordate Heritage • Chordates • 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

  4. Modern Chordate Groups

  5. Embryonic Chordate Characteristics • Four characteristics of chordate embryos may not persist in adults • Notochord of 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

  6. Invertebrate Chordates • Lancelets are the only group of chordates that retains all chordate characteristics as adults

  7. Fig. 26-2b, p. 434

  8. a Dorsal, hollow nerve cord b Notochord c Pharynx with gill slits d Tail extends beyond anus eyespot aorta gonad pore of atrial cavity segmented muscles (myomeres) tentacle-like structures around mouth epidermis midgut hindgut anus Fig. 26-2b, p. 434

  9. Animation: Lancelet body plan

  10. Invertebrate Chordates • Tunicates have typical chordate larvae, but adults retain only the pharynx with gill slits

  11. Fig. 26-3a, p. 435

  12. nerve cord notochord gut pharynx with gill slits Fig. 26-3a, p. 435

  13. Fig. 26-3b, p. 435

  14. Fig. 26-3c, p. 435

  15. pharynx with gill slits Fig. 26-3c, p. 435

  16. 1 cm Fig. 26-3d, p. 435

  17. Craniates • Craniates have a braincase of cartilage or bone (cranium) that encases the brain, paired eyes, and other sensory structures on the head • Craniates includes fishes, amphibians, reptiles, birds, and mammals • Hagfishes are the only modern craniates that are not vertebrates

  18. Hagfishes • Soft bodied, boneless fishes

  19. Fig. 26-4a, p. 435

  20. tentacles gill slits (twelve pairs) mucous glands Fig. 26-4a, p. 435

  21. Fig. 26-4b, p. 435

  22. Fig. 26-4c, p. 435

  23. 26.1 Key ConceptsCharacteristics of Chordates • Four traits characterizes the chordates: • A supporting rod (notochord) • A hollow, dorsal nerve cord • A pharynx with gill slits in the wall • A tail extending past an anus • Certain invertebrates and all vertebrates belong to this group

  24. 26.2 Vertebrate Traits and Trends • Vertebrates are chordates with an internal skeleton (endoskeleton) of cartilage or bone with a supportive backbone (vertebral column) made up of individual vertebrae • Modern vertebrates (except lampreys) have jaws derived from gill-supporting structures

  25. Gill-Supporting Structures

  26. supporting structure for gill slits gill slits A In early jawless fishes, supporting elements reinforced a series of gill slits on both sides of the body. Fig. 26-6a, p. 437

  27. jaw, derived from support structure B In early jawed fishes (e.g., placoderms), the first elements were modified and served as jaws. Cartilage reinforced the mouth’s rim. Fig. 26-6b, p. 437

  28. location of spiracle (modified gill slit) jaw support jaw C Sharks and other modern jawed fishes have strong jaw supports. Fig. 26-6c, p. 437

  29. Animation: Evolution of jaws

  30. Evolution of Internal Skeleton • Fishes evolved appendages (fins) for swimming • Pelvic and pectoral fins gave rise to paired limbs in amphibians, which began the move to land

  31. Evolution of Other Systems • Living in water (fish) • Blood moves in a single circuit from heart to gills (respiratory organs that function in water) • Moving to land • Modification of the respiratory system (lungs) and circulatory system (two circuits) • Efficient kidneys to conserve water, and a system of internal fertilization

  32. Chordate Family Tree

  33. ray-finned fishes “reptiles” lungfishes tunicates lampreys lobe-finned fishes cartilaginous fishes mammals amphibians birds lancelets hagfishes amniotes tetrapods swim bladder or lungs jawed vertebrates vertebrates craniates ancestral chordates Origin of the first jawless fishes. Jawed fishes, including the placo-derms and sharks, evolve. Diversification of fishes and amphibians. Armored fishes go extinct. Reptiles arise and start to diversify. Early amphibians in decline. Dinosaurs and marine reptiles evolve. Birds, mammals, and modern amphibians arise. Dinosaurs dominate. Dinosaur diversity peaks, then extinction by period’s end. Adaptive radiation of mammals. Adaptive radiation of fishes, and the first amphibians move onto land. Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Tertiary 488 443 416 359 299 251 200 146 66 Fig. 26-5, p. 436

  34. Animation: Vertebrate evolution

  35. 26.2 Key Concepts Trends Among Vertebrates • In vertebrate lineages, a backbone replaced the notochord • Jaws and fins evolved in water • Fleshy fins with skeletal supports evolved into limbs that allowed vertebrates to walk onto land • On land, lungs replaced gills and circulation changed in concert

  36. 26.3 The Jawless Lampreys • Lampreys have no jaws or paired fins; they undergo metamorphosis, and many are parasites of other fishes

  37. 26.4 The Jawed Fishes • Jawed fishes typically have paired fins and a body covered with scales • 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

  38. Ray-Finned Bony Fishes

  39. Fig. 26-9a, p. 439

  40. swim bladder kidney ovary nerve cord brain gills cloaca intestine stomach liver heart Fig. 26-9a, p. 439

  41. Fig. 26-9b, p. 439

  42. Fig. 26-9c, p. 439

  43. Fig. 26-9d, p. 439

  44. Lungfish • Lungfishes have gills and lunglike sacs for breathing air

  45. Coelacanth • The only modern lobe-finned fish; closely related to amphibians

  46. 26.5 Amphibians—First Tetrapods on Land • Tetrapods (four-legged walkers) • Branched from lobe-finned fishes in Devonian • Amphibians • Land-dwelling vertebrates that return to water to breed, undergo metamorphosis, and have a three-chambered heart

  47. Adapting to Life on Land

  48. Fig. 26-12a, p. 440

  49. Fig. 26-12b, p. 440

  50. Fig. 26-12c, p. 440

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