Reptiles, Birds and Mammals

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Reptiles, Birds and Mammals

• Biology I Honors

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Remember What a Vertebrate IS

• Vertebrates belong to a larger group called
  Phylum Chordata
• Members of this group have
• Notochord
• Pharyngeal gill slits
• Post anal tail
• Dorsal hollow nerve cord
• Vertebrates are all chordates, but have the added
  improvement of a backbone

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Background on Vertebrates

• The first vertebrates were Jawless fish
• The first true Jawed Vertebrates were the fish
• Cartilaginous fish
• Bony fish
• The bony fish are the most successful vertebrate
  group
• HOWEVERlimited to living in water only
• A long time ago, some bony fish group had
• particularly thick fins
• These allowed it to creep onto land for short
  periods of time
• This led to the rise of the TETRAPODS

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Recently Discovered - Tiktaalik roseae an
intermediate fossil between fish and amphibians
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The Tetrapods

• These animals are vertebrates that can get around
  on land 4 legs
• One tetrapod group, The Amphibians, is not
  totally adapted to land
• Still rely on skin for breathing
• Skin must be thin and moist
• water loss through skin is a big problem
• Still must return to water to reproduce
• External fertilization
• Eggs are unprotected
• Larvae swim (TADPOLES)

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The TRUE Land Dwellers

• The first group of vertebrates to be totally
  successful on land and independent of water
  (except for drinking) was The Reptiles
• The reptiles then gave rise to two other
  important groups
• Birds
• mammals
• Together, reptiles, birds and mammals are called
  AMNIOTES because of certain reproductive
  structures they share in common

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The Amniotes

• All amniotes are able to have babies on land
  without returning to water
• This is due to the advantages of the amniotic egg
  that FIRST arose in REPTILES

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The Amniotic Egg
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Wait How can mammals be amniotes? They dont
lay eggs!

• Amniotes may not all lay shelled eggs
• Reptiles and birds do
• Mammals dont
• They DO all share the same EXTRAEMBRYONIC
  MEMBRANES in common
• Mammals just retain all these structures AND the
  baby inside the mothers body
• AND many of the membrane structures go into the
  formation of the placenta in mammals
• Placenta the organ that attaches the mother and
  fetal blood supply and provides
• Oxygen, nutrients, etc. to baby

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The REPTILES the first vertebrates TRULY
adpated to land

• Adaptations of Reptiles to Land
• Legs (of course amphibians had these, too)
• Lungs better than amphibian lungs
• Dry thick skin
• NOT used as a respiratory organ
• NO danger of water loss
• Amniotic eggs

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Major Groups of Reptiles

• Lizards
• Snakes
• Crocodiles and Alligators
• And dont forget the dinosaurs

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The Birds

• All the adaptations of reptiles for land PLUS
• Flight!
• Feathers are the unique feature of birds
• Also
• Endothermic
• Excellent heart and lungs
• Leads to lots of energy production - FLIGHT

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The Mammals

• All the adaptations of reptiles
• Unique features
• Hair
• Mammary glands
• Provide milk to young

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Three main groups of mammals

• Placental mammals
• Embryo/fetus connected directly to mothers
  bloodstream by the placenta
• Organ attaches to wall of uterus
• Umbilical cord attaches baby to placenta
• Provides oxygen and nutrients to baby
• Removes wastes

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Three Main Groups of Mammals

• Marsupials
• Young born in embryonic state
• Must crawl to pouch
• Latch on to mammary gland in mothers pouch for
  the rest of development

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Three Main Groups of Mammals

• Monotremes
• Egg layers
• Link to reptiles
• Only two
• Spiny echidna
• Duck-billed platypus

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Other Mammal Features

• Endothermic
• 4 chambered heart and good lungs
• energetic