The Chordates

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The Chordates

• Chapters 30-32
• Biology Miller Levine

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Chordates

• Phylum Chordata
• Includes two invertebrate subphyla lancelets and
  tunicates
• Subphylum Vertebrata

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Chordate Characteristics

• Dorsal, hollow nerve cord the brain and spinal
  cord
• Notochord flexible, longitudinal rod located
  between the digestive tract and the nerve cord
• Pharyngeal pouches gill structures in the
  pharynx
• Post-anal tail tail to the rear of the anus

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Chordate Characteristics

• The characteristics are not always visible in the
  adult form, but are always present in the embryo

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Vertebrates

• Subphylum that includes mammals, birds, reptiles,
  amphibians and the various classes of fishes
• Unique features include cranium and backbone

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Fishes
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Agnathans

• Jawless fish
• Class Myxini (hagfishes)
• Class Cephalaspidomorphi (lampreys)

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Class Chondrichthyes

• Cartilaginous fishes
• Include sharks and rays
• Have a flexible skeleton made of cartilage
• Lateral line system row of sensory organs
  running along each side of the body, detects
  minor vibrations

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Class Chondrichthyes
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Class Osteichthyes

• Bony fishes (trout and goldfish)
• Also have a lateral line system
• Operculum protective flap that covers the gills
  
• Swim bladder gas-filled sac that keeps them
  buoyant

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Class Osteichthyes

• Most are ray-finned fishes fins supported by
  thin, flexible rays
• Lobe-finned fishes fins are supported by stout
  bones
• Lungfishes must surface to gulp air into their
  lungs

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Lungfishes
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Amphibians
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Class Amphibia

• Frogs and salamanders
• Exhibit a mixture of aquatic terrestrial
  adaptations
• Need water to reproduce
• Depend on their moist skin to supplement lung
  function in exchanging gases

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Class Amphibia

• First vertebrates to colonize land
• Tetrapods (four legs) terrestrial vertebrates
  (amphibians, reptiles, birds mammals)

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Reptiles
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Class Reptilia

• Snakes, lizards, turtles, crocodiles, and
  alligators
• Have many additional adaptations for living on
  land
• Water-proofed scales to prevent dehydration
• Amniotic egg water-containing egg enclosed in a
  shell

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Class Reptilia

• Ectotherms warms itself by absorbing external
  heat
• Can survive on less than 10 of the calories
  required by mammals
• Mesozoic era age of reptiles the time of
  the dinosaurs

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Birds
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Class Aves

• Birds
• Reptilian features scales on legs, amniotic egg
  
• Almost all species are able to fly

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Class Aves

• Adaptations for flight
• Light, hollow bone
• Absence of some internal organs
• Are toothless
• Endotherms maintain temperature using metabolic
  heat
• Wings strong muscles, feathers

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Mammals
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Class Mammalia

• Probably evolved from reptiles
• Most are terrestrial, some are aquatic (dolphins,
  whales), some can fly (bats)
• Two unique features hair and mammary glands
• Are endotherms
• Have a fluid filled amniotic sac

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Three Major Groups

• Monotremes egg-laying mammals (platypus)
• Marsupials pouched mammals (kangaroo)
• Eutherians placental mammals
• Make up almost 95 of mammals
• Marsupials and Eutherians both have a placenta
  which joins the embryo to the mother and provides
  nutrients to the embryo

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Class Mammalia
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Primates

• Order that includes monkeys, apes humans
• Early primates were small, arboreal
  (tree-dwelling) mammals
• Limber shoulder joints, dexterous hands, eyes
  close together on face, excellent hand-eye
  coordination

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Primates

• Divided into two main groups
• Prosimians (lemurs)
• Anthropoids (monkeys, apes humans)
• Humans are most closely related to apes