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Reptiles
Ch. 31.1
What is a Reptile?
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Land vertebrate
Well developed skull
Backbone and tail
2 limb girdles
4 limbs
• 2 exceptions:
– Snakes (limbless)
– Turtles (hard shells that are fused to vertebrate)
• Reptiles: dry, scaly skin, lungs, and lay
terrestrial eggs with several membranes
• Live their entire lives out of water
• Skin is dry and has thick, protective scales
– Scales can be smooth or rough
• Dry, waterproof skin helps with living in
dry environments.
– Not always good though. The skin is
frequently shed
• Reptiles are found widely through the Earth.
• Very diverse lifestyle and look
• Can’t live in very cold climates
Evolution of Reptiles
• Fossils of 1st reptiles from ~350 mya
• Earth’s climate became cooler and less
humid
– Lakes and swamps dried up and reptiles
evolved to live in that dry area
Mammal-like Reptiles
• Displayed a mix of reptilian and
mammalian characteristics
• Dominated many land habitats
• Went extinct quickly (replaced by
DINOSAURS in the fossil record)
Enter the Dinosaurs
• Late Triassic and Jurassic time periods
– Very diverse and large number of reptiles
– 2 aquatic groups were in the seas
– Ancestors of turtles, crocodiles, lizards, and
snakes
– Dinosaurs were everywhere
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Dinosaurs varied in size
Quadriped or biped
Herbivore or carnivore
Lived as ‘families’
Laid eggs
Two main groups
– ORNITHISCHIA – bird hipped
– SAURISCHIA – lizard hipped
Exit the Dinosaurs
• Mass extinction
– Natural disasters: volcanic eruptions, lava
flows, dropping of sea level, asteroid in the
Yucatan Peninsula
• Major forest fires and dust clouds
Form and Function in Reptiles
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Well developed lungs
Double loop circulatory system
Water conserving excretory system
Strong limbs
Internal fertilization
Shelled, terrestrial eggs
Controllable body temperature
• Body Temperature Control: ectothermic –
rely on behavior to regulate temp.
• Feeding: wide range of food
• Respiration: spongy lungs provide more gas
exchange
• Circulation: efficient double loop
– Blood to and from the lungs; blood to and from
the rest of the body
• Heart has 2 atria and 1-2 ventricles
• Excretion: urine is produced in the kidneys,
urinary bladder stores urine and released in
the cloaca
• Response: complex eyes and can see color,
good sense of smell, mouth can ‘taste’
chemicals, can pick up vibrations/hear
• Movement: legged reptiles have stronger
limbs; rotated further under the body;
flippers for aquatic turtles
• Reproduction: internal fertilization;
oviparous (lay eggs that develop outside
mother’s body)
– Eggs have amnion, yolk sac, chorion, and
allantois
Groups of Reptiles
• Lizards and Snakes: SQUAMATA (scaly reptiles)
• Crocodilians: CROCODILIA (long and broad snout, squat
appearance)
• Turtles and Toroises: TESTUDINES (shell built into the
skeleton; carapce [dorsal], platron [ventral]
• TUATARAS: SPHENODONTA (resemble lizards
Ecology of Reptiles
• Habitats are endangered
• Hunting