Chapter 33 Part 2
- 1. Chapter 34: Vertebrates (sea squirts through birds)
- 5. Subphylum Urochordata The urochordates include the tunicates, a.k.a., sea squirts The tunicates are mostly sessile, filter feeding animals that look almost nothing like a chordate However, their larval form possesses all of the basic characteristics of a chordate
- 7. Tunicate Larva The notochord serves as a primitive internal support structure
- 8. Subphylum Cephalochordata Cephalochordates, the lancelets, retain a chordate body plan throughout life In addition to the four defining chordate characteristics, lancelets, as well as tunicate larvae, have somites Somites are blocks of musculature arranged in segments along the bodies of lancelets and fishes (as well as derivations of this segmentation found in tetrapods)
- 10. Class Myxini Class Myxini are represented in modern times by the hagfish Technically hagfish are not fish; they are more like “sophisticated” lancelets
- 12. Notochord, Nerve Cord, Etc.
- 13. In more modern forms, the notochord exists during development but is modified with development, e.g., into the gelatinous material of the intra-vertebral disks
- 14. Class Cephalaspidomorphi Class cephalaspidomorphi is represented in extant lineages by lampreys Jawless fish were the vertebrate forerunners of the jawed fish Lampreys in addition lack paired fins
- 15. Lamprey: Jawless Vertebrate Lamprey have vertebrae (backbones) but no jaw As vertebrates, lampreys are (just barely) members of subphylum Vertebrata
- 16. Lamprey Larvae are like Lancelets Lamprey larvae are suspension feeders that resemble lancelets, even burying themselves in sediment as to lancelets
- 17. Early (and armored) Jawless Fish
- 18. Superclass Gnathsomata Jawed fish are referred to as gnathostomes (superclass gnathsomata) for their defining feature: jaws Jawed fish also have skulls, vertebrae, and paired appendages (fins)
- 19. Early Gnathostomes Many vertebrate characteristics are adaptations to vigorous swimming Jaws, of course, aid in eating Especially carnivorous eating…
- 20. Class Chondrichthyes Class Chondrichthyes includes the sharks and rays Members of this class are named for their cartilaginous skeletons, i.e., unmineralized (or less mineralized/ossified) skeletons
- 23. The Osteichthyans These are bony fish, both ray-finned and lobe-finned fish
- 24. Osteichthyans are Bony Fish The bony fish are all of the fish you are familiar with except the sharks, rays, and chimaeras The skeleton of bony fish displays ossification, i.e., calcium phosphate in addition to the cartilaginous base Bony fish additionally possess flattened scales Bony fish also secrete mucus onto their skin to aid in reducing their coefficient of drag Bony fish additionally possess a gas-filled swim bladder that allows them to adjust their buoyancy to match that of the water Sharks and rays lack a swim bladder and consequently sink when not moving
- 25. Class Actinopterygii Members of class Actinopterygii are the ray-finned The lobe-finned fish are members of Sarcopterygii
- 26. Anatomy of a Ray-Finned Fish
- 27. Class Actinistia
- 28. A Coelacanth Lobe fins are supported by musculature and a bony skeleton; they may be employed for “walking” upon the bottom and other substrate found within bodies of water
- 29. Class Dipnoi Members of class Dipnoi are the lung fish The lungfish are named for the lungs they retain and use for gulping air, especially when air is less readily available within the freshwaters in which they reside
- 31. Class Amphibia Amphibians are the lineage descended from the earliest tetrapods: the terrestrial vertebrates
- 32. Various Extant Amphibians The amphibians were the dominant terrestrial vertebrates during the Carboniferous period, i.e., the same time the seed-less, vascular plants dominated the land Most amphibians are dependent on the water, minimally for reproduction; this is because their eggs are not desiccation resistant In addition, many amphibians employ their skin for gas exchange, thus requiring that their skin remain moist Thus, amphibians tend to be not as well-adapted to long term, especially multi-generational excursions away from moist habitats
- 33. Tetrapods The tetrapods are the terrestrial descendants of some lobe-finned fish, starting approximately with the amphibians
- 34. Reconstruction of an Extinct Tetrapod
- 35. Class Reptilia Note how the reptiles are indicated as sister group to the mammals In fact, the reptiles and mammals together form a clade known as the amniotes The defining features of the amniotes are keratinized (waterproof) skin and the amniotic (shelled) egg
- 37. Class Reptilia is Paraphyletic Class Reptilia, if it excludes the birds, is paraphyletic
- 38. The Amniotes The amniotes were the first fully terrestrial vertebrates, achieving true freedom from water except, of course, for the need to drink
- 39. Amniotic Egg The amniotic egg is shelled, an adaptation to desiccation prevention The amniotic egg employs extraembryonic membranes to transfer stored nutrients and water, exchange gasses, and remove wastes
- 41. Giant Aquatic Reptiles Non-Archosaur Giant Reptiles (i.e., these are lizards!)
- 42. Class Aves – Birds Members of class Aves (birds) have… Feathers Forelimbs modified as wings Horny bills made of keratin (feathers and hair are also made of keratin) No teeth (reduces weight) Grind their food in a gizzard (since no teeth) Reduced or absent organs (reduces weight) Hollow bones (reduces weight) Acute vision (e.g., high-speed tree-branch avoidance) Some of these adaptations were present in the dinosaur ancestors of birds (e.g., possessing gizzard, bipedalism, feathers, etc.)
- 43. Feathers and Light-Weight Bones
- 44. Archaeopteryx More primitive extinct birds were more saurischian dinosaur like