Presentation on theme: "Vertebrate Evolution and Diversity Chapter 34. Vertebrates belong to phylum Chordata. Includes 3 subphyla, vertebrates and 2 phyla of invertebrates, urochordates."— Presentation transcript:
Notochord, present in all chordate embryos - flexible rod between digestive tube and nerve cord. Dorsal, hollow nerve cord develops in vertebrate embryo from plate of ectoderm that rolls into tube dorsal to notochord - can develop into spinal cord.
Vertebrates Neural crest, pronounced cephalization, vertebral column, closed circulatory system - subphylum Vertebrata. Neural crests start of formation of cranium; cephalization - collection of nervous tissue that forms brain.
Jawless vertebrate 2 classes of jawless vertebrates still living: Class Myxini (hagfish) and Class Cephalaspidomorphi (lampreys). Hagfish - skeletons made of cartilage making them flexible, but no backbone.
Chondrichthyes - skeleton made of cartilage. Cartilaginous skeleton usually replaced by bone; chondrichthyes - process prevented. Fertilize internally; some lay eggs (oviparous), few give birth to live young (viviparous)
Osteichthyes - bony fish - endoskeleton made of bone. Bony fish have swim bladder not found in cartilaginous fish - helps control buoyancy of fish. Bony fish actually broken down into 3 groups: ray-finned fishes, lobe- finned fishes, lungfishes.
Class Amphibia - amphibians - salamanders, frogs, caecilians (legless animals that burrow) Fertilization external - lay eggs. Most amphibians rely heavily on moist skin to carry out gas exchange with environment - still tied to water. Some adult frogs have lungs.
Amniotes Mammals, birds, reptiles, including turtles, lizards, snakes, crocodiles. Transition to land - adaptations were needed: amniotic egg, waterproof skin, increasing use of rib cage to ventilate lungs.
Amniotic eggs of most amniotes have shell that retains water - can be laid in dry place. Inside shell of amniotic egg - several extraembryonic membranes that function in gas exchange, waste storage, and transfer of stored nutrients to embryo.
Reptiles Class Reptilia divided into 4 orders. Reptiles - several adaptations for terrestrial life not found in amphibians - leathery skin to prevent dehydration, lungs. Fertilization internal, eggs laid (amniotic eggs)
Snakes - limbless reptiles - still have pelvic bones - evidence that they evolved from reptiles with legs. Crocodiles and alligators - largest living reptiles. Breathe through their nostrils that are pointed upward out of water.
Birds Birds - class Aves - broken down into 28 orders (few flightless birds) Birds evolved to have hollow bones to allow for flight and feathers. Modern birds - toothless - grind food in muscular gizzard near stomach.
Mammals Mammals - class Mammalia - identified by mammary glands. Most mammals give birth to live young after internal fertilization. Nutrition done via placenta. Most mammals capable of learning due to larger brains.
Monotremes - duck-billed platypus and echindas - lay eggs that have yolks to support embryo. Marsupials - born early in development crawl into pouch in mother to complete development. Eutherians - placental mammals.