26.2 Reptiles

Reptiles are a diverse group.

• Reptiles share several characteristics.– ectotherms– covered with dry scales– reproduce by laying or retaining amniotic eggs– three-chambered heart (most)– cloaca

Evolutionarily, what problem did reptiles have to overcome?

26.2 Reptiles

KEY CONCEPT Reptiles were the first amniotes.

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.

26.2 Reptiles

Reptiles have been evolving for millions of years.

• Over time, amniotes evolved into three different groups. – synapsids– anapsids – diapsids

26.2 Reptiles

• The diversity of ancient reptiles led to the evolution of modern reptiles, birds, and mammals.

26.2 Reptiles

There are four modern groups of reptiles.

• Turtles and tortoises• Lizards, worm lizards and snakes• Crocodilians• tuatara

26.2 Reptiles

There are four modern groups of reptiles.

• Turtles, tortoises, and terrapins are the remaining anapsids.– Unique characteristic: bony shell encases body– 200 species

26.2 Reptiles

The Turtle Shell

• Carapace: top• Plastron: bottom• 59-61 fused bones

connected by bony bridges on the sides and fused to the vertebrate and ribs on the inside

• So successful an adaptation that everything else evolved around it– No running or jumping or

flying turtles!– Opportunistic eaters

• Lures, ambush

26.2 Reptiles

The type of limbs tells a lot about the habitat of a turtle

26.2 Reptiles

• Snakes and lizards are very closelyrelated and share a number of features.– diapsids– shed skin at regular intervals– flexible skull– Jacobson’s organ

brain

tongue

Jacobson’sorgan

26.2 Reptiles

Survival Adaptations

• Freezing• Losing tail• Changing color• Threat displays

Lizards can run but snakes….

26.2 Reptiles

video

26.2 Reptiles

• Instantly recognizable by outer appearance• Large toothy snout• Compressed tail

• Important characteristics are internal!• Heart & brain more

advanced• Crocodilians are more

closely related to birds..

– diapsids– semi-aquatic predators– 23 species

26.2 Reptiles

Adaptations as an aquatic predator?

• Eyes, nostrils and ears high on head in same plane• 3rd eyelid (nictitating membrane)• Nostrils and ears can close when dive• Valve at the back of the mouth closes (glottis) for

catching prey w/o drowning• Muscular compressed tail• Webbed feet• Four chambered heart

26.2 Reptiles

Crocodilian locomotion

• Belly crawl• High walk• Gallop• Swimming• Jumping

26.2 Reptiles

Alligators versus crocodiles?

Alligator

• Rounded snout (u shaped)

• Upper teeth overlap and hide bottom teeth

• Lack modified salivary glands into functional salt glands

• Pressure sensory organs only around jaws

Crocodile

• Pointy V shaped snout• Teeth interlock• Salt glands for living in

brackish and salty water• Pressure sensory organs

on virtually every scale

26.2 Reptiles

Threats to Reptiles (Conservation)

• H• I• P• P• O

Habitat LossIntroduced SpeciesPollutionPopulation (people)Overconsumption of resources

Dilemma

Don’t buy wild caught reptiles for petsDon’t buy products from reptiles – turtle soup, items made from turtle shells, reptile skin boots/beltsAppreciating reptiles