26.2 reptiles - mr. mack's virtual...
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26.2 Reptiles
KEY CONCEPT Reptiles were the first amniotes.
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26.2 Reptiles
Reptiles are a diverse group of amniotes.
• Reptiles share several characteristics.– ectotherms– covered with dry scales– reproduce by laying or retaining amniotic eggs– three-chambered heart– cloaca
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26.2 Reptiles
• Reptiles have two reproductive strategies.– Oviparous reptiles deposit eggs into an external nest.– Viviparous reptiles retain eggs and give birth to live
offspring.
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26.2 Reptiles
Reptiles have been evolving for millions of years.
• Over time, amniotes evolved into three different groups. – synapsids– anapsids– diapsids
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26.2 Reptiles
• The diversity of ancient reptiles led to the evolution of modern reptiles, birds, and mammals.
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26.2 Reptiles
There are four modern groups of reptiles.
• Turtles, tortoises, and terrapins are the remaining anapsids.– bony shell encases body– 200 species
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26.2 Reptiles
• Sphenodonts are closely related to lizards.– diapsids– primitive characteristics– two species
Sphenodon punctatus
Tuatara
Sphenodon guntheri
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26.2 Reptiles
• Snakes and lizards are very closely related and share a number of features.– diapsids– shed skin at regular intervals– flexible skull– Jacobson’s organ
brain
tongue
Jacobson’sorgan
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26.2 Reptiles• Both alligators and crocodiles are members of the reptilian
order Crocodylia: Family Alligatoridae and Family Crocodylidae
• Crocodylians are more closely related to birds than other diapsids.
– diapsids– semi-aquatic predators– 23 species
Crocodile Alligator
All alligators are crocodiles, but not all crocodiles are alligators.