Higher Chordates

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Higher Chordates

• Amphibia, Reptilia, Aves

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Subphyla Vertebrata
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Evolution of tetrapods

• One of the most significant events in vertebrate
  history was when the fins of some lobe-finned
  organism evolved into the limbs and feet of
  tetrapods

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LE 34-20
Millions of years ago
265
340
325
295
420
415
400
385
370
280
355
310
Devonian
Carboniferous
Silurian
Permian
To present
Paleozoic
Ray-finned fishes
Coelacanths
Lungfishes
Eusthenopteron
Panderichthys
Elginerpeton
Metaxygnathus
Acanthostega
Ichthyostega
Hynerpeton
Greerpeton
Amphibians
Amniotes
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Clade Tetrapoda

• Four limbs with feet and digits
• Land-dwellers
• Ears for detecting airborne sounds (parts derived
  from pharyngeal clefts)
• Head separated from body by neck

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Class Amphibians

• 4,800 species
• Two lives
• aquatic larva develops into a terrestrial adult
• Gas exchange
• Lungs and moist skin
• All amphibians must lay eggs in water
• Ectothermic
• absorbing external heat as main source of body
  heat (in turn doesnt need as much food)

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Order Urodela

• Salamanders
• tailed ones

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Order Anura

• Frogs and toads
• tail-less ones
• Powerful hind legs
• Hove long, sticky tongue to capture prey
• Some have coloration for warning or camouflage

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Order Apoda

• Caecilians
• Legless ones
• Wormlike
• Burrowing
• Nearly blind

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Frog Metamorphosis

• Larval stage of frog is a tadpole (aquatic
  herbivore)
• Has gills, lateral line system, finned tail
• Tail regresses (cells die off and parts
  reabsorbed for other uses in the adult)
• Adult develops legs, lungs, external eardrums,
  is a carnivore
• salamander caecilian larvae look much like
  the adults

http//www.youtube.com/watch?v8OKQM9D1xQQ
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Clade Amniotes

• Reptiles (including birds), and Mammals
• Amniotic egg
• contains membranes that protect the embryo
• Rib cage to ventilate the lungs (more efficient
  gas exchange (no longer need air to diffuse
  through skin)
• Impermeable skin (conserves water)

Improvements in gas exchange relative to the
amphibians Thoracic rib cage keeps weight of
body from collapsing organs Improved lung
ventilation functions aspiration breathing
Increased lung surface area to support increased
metabolism
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LE 34-24
Yolk sac contains yolk, a stockpile of nutrients.
Blood vessels in the yolk sac membrane transport
nutrients from yolk to embyo.
Chorion and membrane of the allantois exchange
gases btw. Embryo and air. Oxygen CO2 diffuse
freely across the shell.
Allantois (trash dump) is a disposal sac for
certain metabolic wastes of embryo.
Extraembryonic membranes
Amnion
Chorion
Allantois
Yolk sac
Embryo
Amniotic cavity with amniotic fluid
Amnion (air bag) protects embryo in a fluid
filled cavity that provides cushion against shock.
Yolk (nutrients)
egg white other nutrients stored here
Shell
Albumen
Shell slows dehydration in the air allowing
expansion into new habitats LAND!
Most mammals lost the shell over evolutionary
time and avoid dessication by developing inside
mom
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LE 34-23
Saurischian dinosaurs other than birds
Ornithischian dinosaurs
Ichthyosaurs
Crocodilians
Mammals
Squamates
Parareptiles
Birds
Plesiosaurs
Tuatara
Turtles
Pterosaurs
Saurischians
Dinosaurs
Lepidosaurs
Archosaurs
Diapsids
Synapsids
Reptiles
Ancestral amniote
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Class Reptilia

• Lizards Snakes, Turtles, Crocodiles
• Ectothermic
• absorbing external heat as main source of body
  heat (in turn doesnt need as much food)
• Scales
• waterproof barrier (contain keratinhuman nails)
• Shelled eggs
• Internal fertilization

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Reptile Evolution

• 300 million years ago
• Diapsids vertebrates with a pair of temporal
  holes on both sides of the skull behind the eye
  socket
• Lepidosaurs give rise to tautaras, lizards, and
  snakes
• Archosaurs give rise to crocodiles, pterosaurs,
  and dinosaurs

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Order Testudines

• Turtles and tortoises
• Shields (shell) fused to backbones
• Classification is uncertain b/c they are anapsids
• No temporal
  skull holes

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Order Sphenodontia

• Tuatara
• Lizard-like
• Only in New Zealand

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Order Squamates

• lizards and snakes
• Legs or no legs
• Some have temperature sensing
  organs, poisonous, loose jaw
  bones, use tongue to help smell

http//www.youtube.com/watch?vLLk4rsCNFFU
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Crocodilia

• Alligators and crocodiles

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Order Birds?

• Birds are reptiles???

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Birds evolved from reptiles!

• Almost every feature of their reptilian anatomy
  has undergone modification in their adaptation to
  flight!

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Aves Evolution

• 150 million years ago
• Archaeopteryx, had teeth, clawed wings feathers

http//dinosaurs.about.com/od/thedinobirdconnectio
n/a/dinobirds.htm
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Class Aves

• 8,600 species
• Fly
• Lightweight (reduction in skull, teeth (none),
  organs (no urinary bladder, reduced gonads)
• Wings Feathers
• Keratin (scales of reptiles)
• Large pectoral muscles, hollow bones,
  aerodynamic wings
• Why fly?
• Food resources, migration

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Aves Characteristics

• Endothermic
• Maintain stable internal environment using
  metabolic heat
• Efficient respiratory system
• Air sacs for lungs
• Four chambered heart
• High metabolism
• Acute vision

The air sacs permit a unidirectional flow of air
through the lungs. Unidirectional flow means that
air moving through bird lungs is largely 'fresh'
air has a higher oxygen content. In contrast,
air flow is 'bidirectional' in mammals, moving
back and forth into and out of the lungs. As a
result, air coming into a mammal's lungs is
mixed with 'old' air (air that has been in the
lungs for a while) this 'mixed air' has less
oxygen. So, in bird lungs, more oxygen is
available to diffuse into the blood.
http//people.eku.edu/ritchisong/birdrespiration.h
tml
Fish have 2 chambers, one atrium and one
ventricle. Amphibians and reptiles have 3
chambers 2 atria and a ventricle. Crocodiles are
the one reptilian exception, as they have 4
chambers (2 atria, 2 ventricles). Birds and
mammals have 4 chambers (2 atria and 2
ventricles).
http//www.peteducation.com/article.cfm?c151829
aid2721
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Aves Diversity

• Wings
• Fly, run, swim
• Feet
• Wade, grasp, perch
• Beaks
• Rip, crack, poke, scoop, spear
• Complex mating rituals