Reptiles

Reptiles

Overview of Reptiles

• Lizards, snakes, turtles, crocodilians and birds

Traits

• Scales contain keratin
• Protects from desiccation and damage
• Ectothermic: Do not use metabolism to regulate body temperature
• Most reptiles
• Behavioral thermoregulation: Move between sun and shade to maintain optimal temp
• Requires far less energy to support ectotherm (10%)
• Endothermic: Do use metabolism to regulate body temperature
• Most birds

Evolution of Reptiles

• Earliest reptiles 310 MYA
• Were Diapsid: Skulls with a pair of holes on each side of the skull
• Muscles pass through holes to attach to jaw
• Diapsids form two lineages
• Lepidosaurs: Tuataras, Lizards and Snakes
• Archosaurs: Turtles, Crocodilians, Pterosaurs and Dinosaurs

Diversity of Reptiles

Lepidosaurs

Tuataras

• Two species of "ancient" lepidosaur
• Lizard-like
• In New Zealand

Squamates

• Lizards and snakes
• ~7,900 species
• Range from large to small Examples: Pygmy chameleon vs Komodo Dragon
• Snakes
• Lack legs
• some retain vestigial pelvic bones
• Efficient movement on land
• Waves of lateral bends
• Can grip the ground with ventral scales
• Adaptations to being predators
• Acute chemical sensors
• Sense ground vibrations
• Pit vipers can sense heat
• Enables hunting at night

Archosaurs

Turtles

• Have lost the two holes in skull
• But still diapsids
• Box like shell
• Upper and lower shields fused to vertebrae, clavicle and ribs
• Fossil evidence shows the shell developed in stages
• Early turtles could not retract head into shell
• 2 methods evolved: sideways and straight in
• Adaptations to Deserts (tortoise) and Sea (Sea turtles)

Crocodilians

• Alligators and Crocodiles
• Old lineage dates back to the triassic
• Adapted to aquatic habitats
• Nostrils turned up to breath while mostly submerged

Birds

• ~ 10,000 species
• Extensive adaptation to flight
• Reduced weight
• Hollow bones
• No urinary bladder
• One ovary
• Toothless
• Wings and feathers
• Feathers: made of B-keratin
• Wings: form airfoils like airplane wings
• Large pectoral muscles power wings
• Increased respiratory and circulatory systems
• Excellent vision
• Endothermic
• Flight enables
• New food sources Example: Flying insects
• Long distance migration
• Display complex behaviors Example: Breeding season courtship and display
• Fertilization is internal (due to shell)
• Evolution of birds
• Evolved from theropods Example: Archaeopteryx
• Some birds have lost flight Example: Ratites: Ostrich, kiwis, emu
• Penguins "fly" in the water
• Beaks and feet show a great deal of variation