Comparing Vertebrates

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Comparing Vertebrates
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The Chordates

• A chordate is an animal that has, for at least
  some stage of its life, a dorsal, hollow nerve
  cord a notochord pharyngeal pouches and a tail
  that extends beyond the anus
• Dorsal hollow nerve cord runs along the back
  part of the body with nerves that branch and
  connect to organs
• Notochord long supporting rod that runs through
  the body just below the nerve cord
• Pharyngeal pouches found in the pharynx region
  may develop into gills
• Post anal tail contains bone and muscle and is
  used in swimming by aquatic species

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Chordate Characteristics
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Most Chordates are Vertebrates
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Nonvertebrate Chordates

• The two groups of nonvertebrate chordates are
  tunicates and lancelets
• Both are soft-bodied marine organisms

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Tunicates

• Tunicates are filter feeders that exhibit all of
  the chordate characteristics as larva but not as
  adults

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Lancelets

• Lancelets are small, fishlike creatures that
  thrive on the sandy ocean floor
• An adult lancelet has a head region that contains
  a mouth

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Evolution of Vertebrates
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Chordate Origins

• Many studies suggest that the most ancient
  chordates were closely related to echinoderms

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The Chordate Family Tree
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Evolutionary Trends in Vertebrates

• Adaptive Radiation
• Over the course of evolution, the appearance of
  new adaptations such as jaws and paired
  appendages has launched adaptive radiations in
  chordate groups
• Convergent evolution occurred many times during
  chordate evolution when unrelated species
  encountered similar ecological conditions and
  evolved similar adaptations

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Chordate Diversity
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Temperature Control in Chordates
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The Digestive System of Chordates
WELL ADAPTED FOR A VARIETY OF FEEDING HABITS
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Chordate Respiration

• Aquatic chordates gills
• Land vertebrates - lungs

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Chordate Circulation

• Those that use gills for respiration have a
  single-loop circulatory system
• Blood travels from the heart to the gills, then
  to the rest of the body, and back to the heart in
  one circuit
• Those that use lungs for respiration have a
  double-loop circulatory system
• 1st loop carries blood between the heart and
  lungs, oxygen poor blood from the heart is pumped
  to the lungs, while oxygen rich blood from the
  lungs returns to the heart
• 2nd loop carries blood between the heart and the
  body oxygen rich blood from the heart is pumped
  to the body, while oxygen poor blood from the
  body returns to the heart

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Chordate Hearts

• During the course of chordate evolution, the
  heart developed chambers and partitions that help
  separate oxygenated and deoxygenated blood
  traveling in the circulatory system
• Gilled vertebrates 2 chambered hearts
• Amphibians 3 chambered hearts
• Reptiles 3 chambered hearts with partitions
• Birds, mammals, crocodiles 4 chambered hearts
  that are completely partitioned

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Chordate Excretion

• Fishes and aquatic amphibians
• Excrete ammonia directly from gills via diffusion
• Mammals, land amphibians, and cartilaginous
  fishes
• Ammonia is changed into urea before excreted
  using kidneys
• Reptiles and birds
• Ammonia is changed into uric acid before excretion

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Chordate Response

• Nonvertebrate chordates have a relatively simple
  nervous system with a mass of nerve cells that
  form a brain
• Vertebrates have a more complex brain with
  distinct regions, each with a different function

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Chordate Movement

• Nonvertebrate chordates lack bones but have
  muscles for movement
• The skeletal and muscular systems support a
  vertebrates body and make it possible to control
  movement

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Chordate Reproduction

• Oviparous (eggs develop outside mothers body)
• Most fishes and amphibians
• Ovoviviparous (eggs develop within the mothers
  body)
• Sharks
• Viviparous (born alive)
• Most mammals