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  1. Biology I: Chapter 31-1 Reptiles and Birds

  2. REPTILES

  3. Reptile Characteristics • Subphylum: Vertebrata • Dry, scaly skin, and lungs • Dry, scaly terrestrial eggs with several membranes

  4. Reptile Characteristics • Backbone • Tail • Two limb girdles • Four limbs • Example: iguana

  5. Exceptions • Snakes are limbless! • Turtles have hard shells fused to their vertebrae!

  6. Reptiles • Dry body prevents water loss in a dry environment • Disadvantage: the skin must be shed as it grows • Can live across the globe, except in extremely cold environments

  7. Evolution of Reptiles • Reptiles were the first animals to adapt their eggs to dry habitats • First reptiles are from 350 mya • Did not become common until about 40-50 million years later when the conditions of Earth were drier

  8. Mammal-Like Reptiles • At the end of the Permian Period ~245 mya, a great variety of reptiles roamed the Earth

  9. Mammal-Like Reptiles • Displayed a mixture of mammalian and reptilian characteristics • Dominated many land habitats • Became extinct in just a few million years • Replaced by another group of reptiles…

  10. Enter the Dinosaurs • Late Triassic and Jurassic periods • Two groups of large aquatic reptiles swam in the seas • Ancestors of modern turtles, crocodiles, lizards, and snakes populated many land habitats

  11. Enter the Dinosaurs • Dinosaurs were everywhere! • Saurischia: lizard-hipped dinosaurs • Ornithischia: bird-hipped dinosaurs • Dinosaurs are the ancestors of modern birds

  12. Exit the Dinosaurs • Mass Extinction 65 mya: the end of the Cretaceous Period • Caused by a dramatic series of natural disasters • Volcanic eruptions, dropping in sea level, huge asteroid or comet smashing into the now Yucatan Peninsula in Mexico, etc. • Opened up niches on land and in the sea, providing opportunities for other kinds of organisms to evolve

  13. Form and Function in Reptiles • Adaptations that have contributed to the success of reptiles on land: • Well developed lungs • Double-loop circulatory system • Water-conserving excretory system

  14. Form and Function in Reptiles • Adaptations that have contributed to the success of reptiles on land (continued): • Strong limbs • Internal fertilization • Shelled, terrestrial eggs • Control of body temperature by changing environments

  15. Body Temperature Control • The ability to control body temperature is an enormous asset for active animals • Ectotherm: animal that relies on interactions with the environment to help it control body temperature • Turtles, snakes and other modern reptiles

  16. Body Temperature Control • To keep warm: bask in the sun during the day or stay under water at night • To cool down: move into the shade, go for a swim, or take shelter in underground burrows

  17. Body Temperature Control

  18. Feeding • Eat a wide variety of foods • Iguanas are herbivores and have long digestive systems to break down plant material • Snakes, crocodiles and alligators are carnivores • Chameleons have sticky tongues as long as their bodies to catch insects

  19. Respiration • Lungs are spongy, providing more gas-exchange area than those of amphibians • Many have muscles around their ribs that expand the chest cavity to inhale and collapse the cavity to force air out • To exchange gases with the environment, reptiles have two efficient lungs, or like some snakes, one lung

  20. Circulation • Efficient double-loop circulatory system • Blood to/from: lungs • Blood to/from: body • 2 atria and 1 or 2 ventricles • Most have 1 ventricle with a partial septum, or wall, separating the oxygen-rich and oxygen-poor blood

  21. Circulation • Crocodiles and alligators have the most developed hearts of living reptiles • 2 atria and 2 ventricles • Arrangement also found in birds and mammals

  22. Circulation

  23. Excretion • Urine is produced in the kidneys • Urine contains either ammonia or uric acid • Ammonia: those reptiles that drink a lot of water; i.e. crocodiles and alligators • Uric acid: those reptiles that need to conserve water, that live entirely on land; eliminated into a pasty white solid

  24. Response • Pattern of brain is similar to that of an amphibian • The cerebrum and cerebellum are large compared to rest of the brain • Active during the day

  25. Response • Tend to have complex eyes and can see color well • Pair of nostrils: snakes have a good sense of smell • Pair of sensory organs in the roof of the mouth: detect chemicals • Simple ears with an external eardrum

  26. Movement • Reptiles with legs: • Run, walk, burrow, swim or climb • Reptiles without legs: • Squirm and twist • Backbones of reptiles help accomplish much of their movement

  27. Reproduction • All reproduce by internal fertilization • Most males have a penis that allows them to deliver sperm into the female’s cloaca • The fertilized egg is covered with a leathery shell

  28. Reproduction • Most are oviparous and lay the eggs in nests • Amniotic egg: egg composed of shell and membranes that create a protected environment in which the embryo can develop out of the water • An important adaptation to land

  29. Groups of Reptiles • The four surviving groups of reptiles: • Lizards and snakes • Crocodilians • Turtles and tortoises • Tuatara

  30. Lizards and Snakes • Order Squamata: scaly reptiles Most lizards: • Legs • Clawed toes • External ears • Movable eyelids

  31. Lizards and Snakes • Order Squamata: scaly reptiles Most snakes: • Lost both pairs of legs during their evolution • Highly efficient predators • Some can produce venom

  32. Crocodilians • Order Crocodilia • Alligators, crocodiles, caimans, and gavials • Long, broad snout and squat appearance • Fierce carnivores

  33. Crocodilians • Maternal care of young • Live only in the tropics and subtropics • Alligators: live only in fresh water, exclusively in North and South America • Crocodiles: live in either fresh or salt water and are native to Africa, India and Southeast Asia

  34. Turtles and Tortoises • Order Testudines • Shell built into the skeleton • Carapace: the dorsal part of the shell • Plastron: ventral part of the shell • Lacking teeth, these reptiles have horny ridges that cover the upper and lower jaws

  35. Turtles and Tortoises • Turtle: live in the water • Tortoises: live on land • Terrapin: turtle that is found in water that is somewhat salty

  36. Tuataras • Order Sphenodonta • Only member of its order • Found in a few small islands off the coast of New Zealand • Resemble lizards • Lack external ears and retain primitive scales • “Third eye”: part of a complex organ located on top of the brain…function still unknown

  37. Ecology of Reptiles • Many are in danger because of loss of habitat • Humans also hunt them for food, to sell as pets, for their skins, etc. • Some are now protected