Chordates

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Chordates
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What is a Chordate?

• Chordates are animals that are characterized by a
  notochord, a dorsal hollow nerve chord, and
  pharyngeal (gill) slits at some stage of their
  development.

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Characteristics

• Notochord
• Flexible rod of specialized cells along its
  dorsal side
• Becomes the vertebral column (in vertebrates)
• Dorsal Nerve Chord
• Hollow tube just above the notochord
• Eventually becomes the brain and spinal cord
• Pharyngeal Slits
• Eventually becomes gills in aquatic organisms
• Becomes throat and ear structures in terrestrial
  organisms

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Contains 3 subphlya

• Urochordates (inverts)
• Cephalochordates (inverts)
• Vertebrates (verts)

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Invertebrate Chordates Urochordates

• 2,000 species
• Have gill slits as larvae and adults
• Have notochord and dorsal nerve cord as larvae
• Metamorphosis results in loss of notochord and
  tail, and the nerve chord shortens
• Examples tunicates (sea squirts)

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Invertebrate Chordates Cephalochordates

• 28 species
• Small fishlike creatures
• Have notochord, dorsal nerve cord, and gill slits
  as adults
• Lancelet is the closest living relative to early
  animals

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Vertebrate Chordates Vertebrates

• 41,ooo species 95 of chordates
• Bones or cartilage surround the dorsal nerve cord
• Contain skull and endoskeleton
• Have organs organized into systems

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How Vertebrates Regulate Body Temperature

• Endothermic warm-blooded
• An animal that generates its own body heat
• Examples birds and mammals
• Ectothermic cold-blooded
• Body temperature is determined by the environment
• Examples reptiles, fish, and amphibians

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Vertebrate Reproductive Development How long
the eggs remain within the female

• Oviparous egg birth
• Lay eggs and eggs hatch outside mothers body
• Examples Most fish, most reptiles, all birds,
  and 3 species of mammals
• Ovoviviparous egg-live birth
• Fertilized eggs remain inside of mother
• Nourished by egg yolk not the mom
• May lay the eggs and then hatch shortly
  thereafter OR eggs hatch inside of mother and
  young are born live
• Examples Some fish, some reptiles
• Viviparous live birth
• Young develop within the uterus
• Nourished by placenta
• Example Placental mammals (humans)

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Taxonomy of Vertebrates
Class Major Characteristics Examples
Agnatha Jawless fish Lamprey, hagfish
Chondrichthyes Cartilaginous fish Sharks, stingrays
Osteichthyes Bony fish Flounder, trout, etc.
Amphibians Part life in water, part life on land Frogs, toads, salamanders
Reptiles Amniote egg and scales Turtles, alligators, snakes
Aves Feathers, hollow bones Birds
Mammals Warm blooded, hair, produce milk Humans, primates, dogs, etc.
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Agnatha Jawless Fish

• AKA cyclostomes (round mouth)
• Most primitive living vertebrates
• Ostracoderms (extinct) lamprey (extant)
• Lack paired appendages
• cartilaginous skeleton
• rasping mouth to suck blood

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Chondrichthyes Cartilaginous Fish

• Sharks, skates, rays
• Skeleton made of cartilage
• Well developed jaws and paired fins continual
  water flow over gills (gas exchange) lateral
  line system (detects water pressure changes)
• Sexual reproduction with internal fertilization

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Osteichthyes Bony Fish

• Ossified (bony) endoskeleton scales operculum
  (gill covering) swim bladder (buoyancy) 2
  chambered heart with a single circulatory circuit
  through body
• Most numerous vertebrate
• Sexual Reproduction, most with external
  fertilization

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Amphibians Double Life

• 1st tetrapods on land
• Frogs, toads, salamanders
• 3 chambered heart with a double circulatory
  circuit (travels twice through body for complete
  trip)
• Double life metamorphosis- aquatic (larva)
  terrestrial (adult)
• Must have moist skin for gas exchange
• Must use WATER for reproduction

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Reptiles

• Lizards, snakes, turtles, crocs and gators
• Amniote (shelled) egg with extraembryonic
  membranes (gas exchange, waste storage, nutrient
  transfer)
• Waterproof scales of the protein keratin
• Well-developed lungs for gas exchange
• Most have 3 1/2 chambered heart crocodilians
  have 4
• No WATER needed for reproduction- first to truly
  adapt to life on land

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Aves Birds (Flighted Reptiles)

• Flight adaptations wings (honeycombed bone) and
  feathers (keratin)
• Toothless
• Airfoil wing
• Evolved from reptiles (amniote egg and leg
  scales)
• 4-chambered heart double circuit
• Internal fertilization
• Archaeopteryx (evolutionary link between reptiles
  birds)

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• Birds do not urinate.
• Kidneys extract nitrogenous wastes from the
  bloodstream.
• They excrete it in the form of uric acid.
• Uric acid very low solubility in water.
• Emerges as a white paste from the bird's cloaca.

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Mammals

• Mammary glands that produce milk
• Hair (keratin)
• 4-chambered heart
• Large brain
• Teeth differentiation
• Monotremes (egg-laying) duck-billed platypus
  and echidnas (spiny anteater),
• Marsupials (pouch) opossums, kangaroos, koalas
• Eutherian (placenta)all other mammals

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Mammalian Orders

• Order MONOTREME
• Egg laying mammals

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Mammalian Orders

• Order MARSUPIALIA
• Tiny, immature young nourished in pouch

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Mammalian Orders

• Order INSECTIVORA
• Insect-eaters

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Mammalian Orders

• Order CHIROPTERA
• Flying Mammals

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Mammalian Orders

• Order PRIMATE
• Highly developed brain
• Complex social behavior

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Mammalian Orders

• Order EDENTATA
• No teeth, usually feed on ants and termites

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Mammalian Orders

• Order LAGOMORPHA
• Chisel-teethed herbivores usually jumpers

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Mammalian Orders

• Order RODENTIA
• Herbivores (some omni) with sharp front teeth

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Mammalian Orders

• Order CETACEA
• Aquatic mammals

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Mammalian Orders

• Order CARNIVORA
• Carnivorous

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Mammalian Orders

• Order PROBOSCIDEA
• Herbivores with a flexible trunk

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Mammalian Orders

• Order SIRENIA
• Aquatic slow-moving herbivores

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Mammalian Orders

• Order PERISSODACTYLA
• Odd-toed hooved herbivores (ungulates)

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Mammalian Orders

• Order ARTIODACTYLA
• Even-toed hooved herbivores (ungulates)

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Vertebrate Chordates
Endo/Ecto-therm Circulation ( of chambers) Respiration Fertilization (where sperm unites w/egg)
Fish Ectotherms Single loop (2) Gills Internal or external
Amphibians Ectotherm Double loop (3) Larvae-gills Adult- lungs skin External
Reptiles Ectotherm Double loop (most 3 1/2 Crocodilians-4) Lungs Internal (some external)
Birds Endotherm Double loop (4) Lungs (more complex) Internal
Mammals Endotherm Double loop (4) Lungs (most complex) Internal