Lecture 6new - To describe the origins and evolutionary...

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To describe the origins and evolutionary trends  of vertebrates. To know the differences of invertebrate and  vertebrate chordates. To study the emergence of first vertebrates that  gave rise to the existing vertebrates. To describe the evolution of early humans to  modern humans.
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A division comprising vertebrates. Coelomate, bilateral animals. Most are vertebrates; only a few are  invertebrates .
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A notochord Tubular, dorsal nerve cord Gill slits punctuates the wall of pharynx Post-anal tail
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A notochord: a long rod of stiffened tissue (not  bone/cartilage); as a support. Tubular, dorsal nerve cord: anterior end develops into brain. Gill slits punctuates the wall of  pharynx: a muscular tube that function sin feedings,  respiration or both. Tail extending past an anus.
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Tunicates Lancelets Hagfishes 
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Simplest  and invertebrate chordates.
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Baglike animals one several cm long. Have gelatinous/leathery tunic secreted by the adults  around them. Live in seas as individuals/ in colonies. Their larvae are bilateral swimmers. Undergo metamorphosis. Filter feeders ; water flows in through siphon and flows  out through another siphon; filtration through pharynx Pharynx -also acts a respiratory organ.
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Live in near-shore marine sediments Three to 7 cm long Have all the characteristics of chordates Use  notochord  and muscles for swimming  motions just like tunicates. Have simple brain and head. Have  closed circulatory system   unlike  tunicates. Mode of respiration by diffusion of gases via thin 
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Filter feeders : cilia beats water into mouth cavity food gets trap in mucus of  pharynx trapped food delivered to the rest of the gut. Have large food-trapping area relative to the overall  body length 
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Hagfishes represent the next  level in chordate  complexity….why?
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The only animal with cranium but back- boneless Sensory tentacles surround their fleshy  mouth Tongue rasps on their prey’s soft tissues. Draws small invertebrate prey and tissues of  a dead or dying fish into its mouth. Non-active animals; low metabolic rates Release sticky mucus once disturbed,  fending off possible predators
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Bones (vertebrae) Have fins Gills Jaws 
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Craniates are animals with cranium E.g. fishes, amphibians, reptiles, birds and mammals.
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Lecture 6new - To describe the origins and evolutionary...

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