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• Vertebrates belong to phylum Chordata.
• Includes 3 subphyla, vertebrates and 2 phyla of invertebrates, urochordates and cephalochordates.
• 4 characteristics: notochord; dorsal, hollow nerve cord; pharyngeal slits; and muscular, postanal tail.
• 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.
• Pharyngeal gill slits connect pharynx, just posterior to mouth, to outside of animal.
• Most chordates have muscular tail extending posterior to anus.
Tunicates
• Sessile marine animals that adhere to rocks, docks, and boats.
• Invertebrates - urochordates.• Chordate characteristics are
present as larva.• Suspension-feeders.
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.
• Have appendicular skeleton, supporting 2 pairs of appendages (fins, legs, or arms).
• Can be made of either bone, cartilage, or both.
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.
Jawed fish
• Jawed fish broken into 2 classes (extant).
• Chondrichthyes (cartilaginous fishes: sharks, rays), Osteichthyes (bony fishes: ray-finned fishes, lobe-finned fishes, lungfishes).
• 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.
http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/AnimalsIII/coelacanth.jpg
Lungfish
Tetrapods
• Tetrapods -land animals - walk on all fours - transition from water animals to land animals - amphibians.
• 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)
• Reptiles - ectotherms - cannot maintain own internal temperature (cold-blooded).
• Turtles return to water to lay eggs; have not evolved since 1st appearance.
• Lizards - most numerous reptiles.
• 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.
• Large brains of birds (proportionately larger than reptiles or amphibians) support very complex behavior.
• Birds - endotherms - metabolism allows them to regulate internal temperature.
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.
• Primates - most advanced of eutherians.
• Opposable thumb characteristic of most advanced primates.
• Divided into 2 groups: prosimians (lemurs), anthropoids (apes, humans).
• Hominoid - great apes and humans collectively.
• Hominid - group closely related to humans.
• Human evolution included many adaptations - larger brains, ability to stand upright.