Chapter 34: Vertebrates

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Chapter 34 Vertebrates

• By Amelia Abuzuhri and
• Katherine Duffy

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Section 1

• Name is derived from the series of bones that
  make up vertebral column or backbone.
• Vertebrates are members of Chordates, which is a
  group made up of vertebrates and some closely
  related invertebrates.
• Chordates are bilaterian animals and belong to
  clade known as Deuterostomia.
• Chordates are named for a skeletal structure, the
  notochord.

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Section 1 Characters of Chordates

• Notochord is longitudinal, flexible rod located
  between digestive tube and nerve cord. Present in
  all chordate embryos and some adult.
• Composed of large fluid filled cells enclosed in
  fibrous tissue. Provides skeletal support
  throughout length of chordate.
• Notochord provides firm but flexible support
  against which the muscles work during swimming.
• In humans the notochord is made up of gelatinous
  disks between vertebrae.

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Characters Notochord cont.
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CharactersDorsal, Hollow Nerve Cord

• Nerve Cord develops from plate of ectoderm,
  during the embryo stage, it rolls into tube
  located located dorsal to notochord.
• Dorsal is a hollow nerve cord which is unique to
  chordates other animal phyla have solid nerve
  cords and are located ventrally.
• This nerve cord of the embryo later develops into
  the central nervous system--gt brain and spinal
  cord.

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Characters Pharyngeal Slits or Clefts

• During embryonic stage in chordates there are a
  series of pouches separated by grooves along the
  pharynx, Pharyngeal clefts.
• These grooves later develop into Pharyngeal
  Slits which allow water to enter the mouth
  without passing through the digestive system.
• In most vertebrates these slits are modified for
  gas exchange and are known as gill slits.
• However in tetra pods, clefts dont develop into
  slits but into other structural parts.

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Lancelets

• Bladelike shape and lack a backbone, but do have
  notochord, dorsal, hollow nerve cord, pharyngeal
  slits, and post-anal tail.
• Adults can reach up to 5cm, closely resemble
  idealized chordate, and are members of subphylum
  Cephalochordata.
• Burrow in sand of seafloor and leave cilia
  exposed to obtain nutrients. Use contractions of
  muscles to swim.

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Tunicates

• Subphylum?Urochordata are more closely related
  to chordates than Lancelets. Chordates
  characteristics more apparent in larvae stage.
• Finds substrate in water and attaches and looses
  all chordate characteristics.

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Section 2

• Craniates? chordates with a head.
• Have 2 Hox gene clusters (lancelets/tunicates
  have 1) and have a neutral crest.
• Neutral crest? collection of cells near dorsal
  margins in embryo. Gives rise to various
  structures in body.
• More active, higher metabolic rate, and more
  extensive muscular system.
• Hagfish?least developed craniate. Have skull but
  lack jaw and vertebrae are snakelike.
• Secrete a slime to drive away predators which
  sticks to gills of predator then suffocating it.

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Craniates

• Haikouella craniate discovered in 1999 in
  southern China.
• Hagfish is in the class of Myxini.

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Section 3

• Vertebrates branched off from other craniates,
  and transcribed new gene factors? Dlx family
  resulted in more genetic complexity (extensive
  skull/backbone).
• Lampreys (oldest living lineage of vertebrates)
  are a parasite in marine/freshwater environments
  with clamping mouths that tend to feed on fish
  blood.
• Have relatively short life span, after they
  reproduce they die within a few days.
• Lamprey cartilage is unlike most vertebrae in
  that it contains no collagen, it is a stiff
  protein matrix.

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Conodonts/Orgins of Bone and Teeth

• Conodonts were a slender, soft-bodied vertebrate
  with prominent eyes and teeth.
• Teeth were barbed like books made of dental
  tissue that were mineralized. Gave way to
  discovering vertebrates without jaws, but with
  teeth.
• Mineralization was only discovered after lampreys
  were, this gave way to divergence of
  unmineralized skeleton to mineralized.