Exploring the Evolution of Reptiles and Their Modern Diversity

1. 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?

2. KEY CONCEPT Reptiles were the first amniotes.

3. Reptiles have two reproductive strategies. • Oviparous reptiles deposit eggs into an external nest. • Viviparous reptiles retain eggs and give birth to live offspring.

4. Reptiles have been evolving for millions of years. • Over time, amniotes evolved into three different groups. • synapsids • anapsids • diapsids

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

6. There are four modern groups of reptiles. • Turtles and tortoises • Lizards, worm lizards and snakes • Crocodilians • tuatara

7. There are four modern groups of reptiles. • Turtles, tortoises, and terrapins are the remaining anapsids. • Unique characteristic: bony shell encases body • 200 species

8. 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

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

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

11. Survival Adaptations • Freezing • Losing tail • Changing color • Threat displays Lizards can run but snakes….

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13. 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

14. 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

15. Crocodilian locomotion • Belly crawl • High walk • Gallop • Swimming • Jumping

16. Alligators versus crocodiles? Alligator Crocodile Pointy V shaped snout Teeth interlock Salt glands for living in brackish and salty water Pressure sensory organs on virtually every scale • 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

17. Threats to Reptiles (Conservation) • H • I • P • P • O Habitat Loss Introduced Species Pollution Population (people) Overconsumption of resources Dilemma Don’t buy wild caught reptiles for pets Don’t buy products from reptiles – turtle soup, items made from turtle shells, reptile skin boots/belts Appreciating reptiles