RePtiles

1. RePtiles

2. Common Characteristics • Fully adapted for life on land • All Amniotes – produce Amniotic Eggs • Dry, Scaly Skin • Ectothermic • More Efficient Circulatory and Respiratory Systems • Cloaca • Except for snakes, Reptiles have Paired limbs, most ending in 5 clawed toes

3. Amniotic Egg Amnion – extra membrane not found in amphibians which protects eggs from dessication (drying out) and other environmental problems

4. Reptile Reproduction • Internal Fertilization • Leathery-shelled eggs • Most Oviparous – eggs hatch outside the body – most do not give parental care • Sex determination of offspring by genotype or a function of temperature due to position in nest • Some lizards and snakes are Ovoviviparous – eggs hatch inside mother and appears to be giving live birth • Some Viviparous lizard species exist • Some rare cases of parthenogenesis – seen in some Komodo dragons and Burmese pythons

5. Reptile Eggs

6. reproductive and Excretory Organs • Excretion - Kidneys, Bladder, Ureters, Cloaca • At cloaca, water in urine reabsorbed to form uric acid – semisolid white crystalline excretion – like birds produce • Reproduction – Ovaries; Testes • Some sexually dimorphic – others very difficult to tell difference in sexes externally

7. Reptile Skin • All have or had (at some point in evolutionary history) horny epidermal scales composed of a protein called keratin • Relatively impermeable to water • May be thick or thin • Spikes and ridges are harder bits of skin, as are shell scutes on turtles and tortoises • Most have color produced by melanophores and/or chromatophores in skin

8. Reptile skin Shedding • All animals shed old skin cells in some way, but snakes and some lizards shed it all in one piece

9. Reptile Respiration • All reptiles use lungs • Greater surface area for gaseous exchange – crocodiles, lizards and turtles have chambers and sub-chambers in lungs • Contract and relax ribcage muscles to use lungs • Lack a diaphragm

10. Snake Respiration • Snakes and tuataras have simpler sac-like lungs • Snake hissing sound produced when air is forcibly expelled through glottis (open area just behind tongue leading to trachea) causing a piece of cartilage there to vibrate

11. Reptile Circulation • Ectothermic – “cold-blooded” – have behaviors to keep them warm • 3-chambered heart with 2 atria, 1 ventricle partially divided by incomplete septum • 4-chambered heart in crocodiles (and birds) • 2 aortic arches – left and right (birds have one); stronger pumping as reptiles larger than amphibians • More O2 = more energy for metabolism and complex movement

12. Reptile Feeding and Digestion • May be omnivorous, carnivorous, or herbivorous • Ex: Iguanas and tortoises herbivores • Ex: Strict carnivores: snakes and crocodiles • Turtles and tortoises lack teeth while other reptiles have sharp, well-developed teeth • Mouth  esophagus  stomach  liver and pancreas  small intestine colon  cloaca  anus

13. Snake Feeding • swallow prey whole as mandible and maxilla move independently • may constrict prey to suffocate it • may use poison venom on fangs to paralyze prey

14. Senses in Reptiles • Some reptiles rely on good vision for hunting – some have color vision • Most lack external ears but have an eardrum; snakes sense vibration through mandibles • Snakes’ hearing and vision not as developed as other reptiles but have other adaptations: • Jacobson’s organ in snakes – sac-like organs in roof of mouth – assists in sense of smell – finding prey and mates • Pit organs in some snakes act as heat sensors to detect prey

15. Reptile Brain • Forebrain – olfactory lobes – better sense of smell than amphibians; larger cerebral hemispheres • Midbrain – larger optic lobes than amphibians for better vision; cerebral peduncles • Hindbrain – larger cerebellum than amphibians allows more complex movements; medulla oblongata

16. Reptile Movement & Skeletal System • Reptile legs rotated further under body than amphibians, stronger and heavier bones allows them to bear more weight on land and get them up off ground. Some alligators can run short distances at speeds of 30 mph! Running Alligator • Bony plates within turtle’s shell are part of their skeleton; outside scutes on shell formed from skin • Snakes have 150 to over 400 vertebrae! Strong flexible joints in between. • Snake ribs not joined at belly allowing them to swallow large prey • Some snakes (boas, pythons) have vestigial hind limbs or pelvic bones • Some iguanas swim – Marine Iguanas

17. 4 Orders of Reptiles • Squamata – Snakes and Lizards • Crocodilia – Crocodiles and Alligators • Testudinata – Turtles and Tortoises • Sphenodonta - Tuataras

18. Squamata – Snakes and Lizards • Lizards – iguanas, chameleons, geckos, anoles • Lizards – usually have legs with clawed toes, movable eyelids, lower jaw with moveable hinge, tympanic membranes • Snakes – rattlesnakes, boas, pythons • Snakes – legless, transparent layer of skin over eyes, lack tympanic membranesbut sense vibrations through mandible, flexible jaw joint to allow ingestion of prey larger than head

19. Crocodilia – crocodiles, Alligators, Caimans • Crocodiles – long snout, sharp teeth (lower ones visible when jaw closed as top and bottom of snout same size), powerful jaws, muscular, 4-chambered heart – move quickly and aggressively to attack large prey in/out of water • Croc Babies Hatch and Hunt • Alligators – broader snout, with top of snout larger than bottom so most teeth covered when jaw closed • Caimans – most smaller (most 1-3 meters length, but some near 4 m or 15 ft ) crocodilian of Central and South America

20. Testudinata – Turtles and Tortoises • Unique protective shell – carapace and plastron • Many turtles can pull head and legs inside shell • Most have ribs fused inside carapace • Sharp beak but no teeth • Land or aquatic • Tortoises – turtles who live on land • Life span varies by species – box turtles average 50 years; about 80 in sea turtles, a Galapagos Tortoise in an Australian zoo lived at least 171 years!

21. Sphenodonta - tuataras • Look like large lizards • Only found in coasts off New Zealand; only 2 species • Spiny crest down back • Sunlight-sensing “Third Eye” on top of head covered in scales – may protect from overheating • Unique teeth: 2 rows upper jaw, 1 row lower jaw • Predators – eat small vertebrates • Life span – can live over 100 yrs

22. Reptile Evolution • Birds now classified as being reptiles • Their relationship: • The Origin of Birds

23. Birds Classified as Reptiles??? • “Both the fossil record and comparative analyses of living species (especially those based on molecular evidence) convincingly establish that, among living reptiles, birds and crocodiles are more closely related to each other than they are to lepidosaurs (snakes and lizards).” • “Because birds clearly arise from within the groups we traditionally consider to be reptiles, not separately from them, most systematists now formally consider birds (Aves) to be a subgroup within Reptilia.” from http://animaldiversity.org/accounts/Reptilia/

24. Reptile ecology • Part of food chains as predator and prey • Control rodent pests • Threatened by habitat loss and introduction of exotic species who eat them or compete for same resources in their habitat • Many gopher tortoises in South GA and Florida long leaf pine forests had habitats and burrows destroyed – some in “rattlesnake roundups” which also killed snakes and gopher frogs in the burrow