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Exploring the Evolution of Chordates: From Lancelets to Mammals

Delve into the evolutionary journey of chordates, from lancelets to mammals, including key characteristics and transitional species. Discover the intricate development of vertebrates, from the Echinodermata to Amniotes, and their diverse adaptations. Uncover the fascinating origins of major vertebrate groups, such as sharks, amphibians, and reptiles, as well as the significance of chordate traits in human evolution.

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Exploring the Evolution of Chordates: From Lancelets to Mammals

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  1. The Chordata Chapter 34

  2. We’ve done some of this before …

  3. Fig. 34-2 Echinodermata (sister group to chordates) Cephalochordata (lancelets) ANCESTRAL DEUTERO- STOME Chordates Urochordata (tunicates) Notochord Myxini (hagfishes) Common ancestor of chordates Craniates Petromyzontida (lampreys) Head Vertebrates Chondrichthyes (sharks, rays, chimaeras) Vertebral column Actinopterygii (ray-finned fishes) Gnathostomes Jaws, mineralized skeleton Actinistia (coelacanths) Osteichthyans Lungs or lung derivatives Lobe-fins Dipnoi (lungfishes) Lobed fins Amphibia (frogs, salamanders) Tetrapods Reptilia (turtles, snakes, crocodiles, birds) Legs Amniotes Amniotic egg Mammalia (mammals) Milk

  4. Fig. 34-2 Echinodermata (sister group to chordates) Cephalochordata (lancelets) ANCESTRAL DEUTERO- STOME Chordates Urochordata (tunicates) Notochord Myxini (hagfishes) Common ancestor of chordates Craniates Petromyzontida (lampreys) Head Vertebrates Chondrichthyes (sharks, rays, chimaeras) Vertebral column Actinopterygii (ray-finned fishes) Gnathostomes Jaws, mineralized skeleton Actinistia (coelacanths) Osteichthyans Lungs or lung derivatives Lobe-fins Dipnoi (lungfishes) Lobed fins Amphibia (frogs, salamanders) Tetrapods Reptilia (turtles, snakes, crocodiles, birds) Legs Amniotes Amniotic egg Mammalia (mammals) Milk

  5. Figure 34.2 Chordate characteristics

  6. Figure 34.4b Subphylum Cephalochordata: the lancelet Branchiostoma

  7. The lancelet, Subphylum Cephalochordata, has all four chordate synapomorphies Figure 34.4a Subphylum Cephalochordata: lancelet anatomy

  8. , Class Myxini A skull of cartilage, but no jaw and no vertebrae Figure 34.9 A hagfish

  9. Figure 34.7 Phylogeny of the major groups of extant vertebrates

  10. Lampreys, Class Pteromyzontida The first vertebrates lack jaws Figure 34.9 A sea lamprey

  11. Cartilaginous fishes, (class Chondricthyes): jaws, paired appendages, mineralized skeletons Figure 34.11 Cartilaginous fishes (class Chondrichthyes): Great white shark (top left), silky shark (top right), southern stingray (bottom left), blue spotted stingray (bottom right)

  12. Note: The BCOR 12 tutoring room (Sunday night from 7:30-9pm) has been changed to L/L A101 (not A161).  Darlene will NOT be available this Sunday. HW is due this Sunday night at 11:59 p.m., as usual.

  13. Clicker Question Why are humans considered members of the chordates when we have no notochord, pharyngeal slits, or muscular tail? • Our mammalian ancestors show some of these traits. • Other similar traits appear in humans. • Our nerve cord has replaced the notochord. • Embryonic humans have these traits. • More than one of the above.

  14. Fig. 34-2 Echinodermata (sister group to chordates) Cephalochordata (lancelets) ANCESTRAL DEUTERO- STOME Chordates Urochordata (tunicates) Notochord Myxini (hagfishes) Common ancestor of chordates Craniates Petromyzontida (lampreys) Head Vertebrates Chondrichthyes (sharks, rays, chimaeras) Vertebral column Actinopterygii (ray-finned fishes) Gnathostomes Jaws, mineralized skeleton Actinistia (coelacanths) Osteichthyans Lungs or lung derivatives Lobe-fins Dipnoi (lungfishes) Lobed fins Amphibia (frogs, salamanders) Tetrapods Reptilia (turtles, snakes, crocodiles, birds) Legs Amniotes Amniotic egg Mammalia (mammals) Milk

  15. Ray-finned fishes (class Actinopterygii): lungs or lung derivatives Figure 34.12a Ray-finned fishes (class Actinopterygii): yellow perch Clade = Ostichtyes, the “bony fishes”

  16. Figure 34.13 Anatomy of a trout, a representative ray-finned fish

  17. Fig. 34-2 Echinodermata (sister group to chordates) Cephalochordata (lancelets) ANCESTRAL DEUTERO- STOME Chordates Urochordata (tunicates) Notochord Myxini (hagfishes) Common ancestor of chordates Craniates Petromyzontida (lampreys) Head Vertebrates Chondrichthyes (sharks, rays, chimaeras) a q u a t i c o s t i c h t h s Vertebral column Actinopterygii (ray-finned fishes) Gnathostomes Jaws, mineralized skeleton Actinistia (coelacanths) Osteichthyans Lungs or lung derivatives Lobe-fins Dipnoi (lungfishes) Lobed fins Amphibia (frogs, salamanders) Tetrapods Reptilia (turtles, snakes, crocodiles, birds) Legs Amniotes Amniotic egg Mammalia (mammals) Milk

  18. The coelocanth (class Actinistia) first appeared in the fossil record in the Devonian Figure 34.18 A coelocanth (Latimeria), the only extant lobe-finned genus

  19. Transitional tetrapods -- feet in place but gills and tail with fin Figure 34.16 Skeleton of Acanthostega, a Devonian tetrapod fish

  20. Class Amphibia Figure 34.17 Amphibian orders: Newt (left), frog (right) Clade = Tetrapods Synapomorphy: four walking legs

  21. Figure 34.18 “Dual life” of a frog (Rana temporaria)

  22. Note: The Tri-Beta honors society will be having its regular intro bio tutoring sessions Monday and Tuesday after break, 6 - 8pm in Rowell 244. This is in addition to the regular Sunday sessions in Living and Learning.

  23. Class Reptilia Figure 34.22 A hatching reptile Clade: Amniotes Synapomorphy: the amniotic egg

  24. Amnion: cushioning chamber for embryo Chorion: gas exchange to exterior Allantois: disposal sac Yolk sac: surrounds yolk Figure 34.24 Amniotic egg

  25. Figure 34.23 A hypothetical phylogeny of amniotes

  26. Figure 34.24 Extant reptiles: Desert tortoise (top left), lizard (top right), king snake (bottom left), alligators (bottom right)

  27. Figure 34.23 A hypothetical phylogeny of amniotes

  28. Archaeopteryx (150 mybp): feathered wings and powered flight, but retained ancestral characteristics such as teeth, clawed wings, and a long tail.

  29. Modern birds: endotherms with feathers of keratin, circa 10,000 species Figure 34.29 A small sample of birds: Blue-footed boobies (top left), male peacock (top right), penguins (bottom left), perching bird (bottom right)

  30. Figure 34.23 A hypothetical phylogeny of amniotes

  31. Synapsid reptiles evolved into large carnivores and herbivores during the Permian period. Diversity was much reduced in the Permian -Triassic extinction.

  32. Class Mammalia: amniotes that have hair and produce milk

  33. Figure 34.36 Hypothetical cladogram of mammals

  34. Fig. 34-33a (a) A young brushtail possum

  35. Eutherians, the placental mammals: internal gestation

  36. Figure 34.35 A phylogenetic tree of primates

  37. Figure 34.34 Prosimians:Lemurs

  38. Figure 34.39 Upright posture predates an enlarged brain in human evolution

  39. Fig. 34-2 Echinodermata (sister group to chordates) Cephalochordata (lancelets) ANCESTRAL DEUTERO- STOME Chordates Urochordata (tunicates) Notochord Myxini (hagfishes) Common ancestor of chordates Craniates Petromyzontida (lampreys) Head Vertebrates Chondrichthyes (sharks, rays, chimaeras) Vertebral column Actinopterygii (ray-finned fishes) Gnathostomes Jaws, mineralized skeleton Actinistia (coelacanths) Osteichthyans Lungs or lung derivatives Lobe-fins Dipnoi (lungfishes) Lobed fins Amphibia (frogs, salamanders) Tetrapods Reptilia (turtles, snakes, crocodiles, birds) Legs Amniotes Amniotic egg Mammalia (mammals) Milk

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