Reptilia
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Transcript of Reptilia
Reptilia
Damnjanović Ivana
Gambassa
Groups of ReptilesSauria (lizards) Serpentes (snakes) Testudines (turtles) Crocodylia (crocodiles) Rhynchocephalia (tuataras)
Reptile Characteristics• Ectothermic• Dry skin covered in scales• Most have 2 pairs of short legs & clawed feet• Oviparous reproduction (Internal fertilization – to
avoid desiccation of gametes)• Eggs have a leathery shell and yolk (amniotic)• Lungs to breathe• 3 or 4 chambered heart• No metamorphosis (young look like miniature parent)• Hibernate & aestivate
Ectothermy
– Body temperature regulated by ambient air temperature
Dry Scaly Skin
The body of reptiles is covered with horny epidermal scales to reduce water loss and provide protection.
Shedding
• Snakes turn old skin (scales, epidermis) inside out when shedding
• Turtles add new layers of keratin under old layers of the plate-like scutes (modified scales)
Reptile Legs• Short tetrapods for
walking• Positioning of the
legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.
Paired Limbs• The paired limbs usually have five toes and are
variously adapted for:• Swimming• Running• Climbing• (Absent altogether in the snakes)
Reptile Lungs• Respiration is no longer through the skin, but
only through internally protected and moistened lungs.
Reptile Hearts• Reptiles have a 3-chambered heart• Crocodiles have a 4-chambered heart
Nervous System
• Sense organs generally well-developed• Hearing generally poorly developed in most
Excretory Waste
• The excretory waste of the reptiles is uric acid unlike the dilute, water wasting ammonia in the urine of Amphibians.
Oviparous• Eggs have a leathery
shell to prevent desiccation
Amniotic Egg
Squamata
• “Characterized by scales”
• Lizards, snakes• Most recent products
of reptile evolution• Most successful - 95%
of known living species of reptiles
Squamata
• Lizards began diversifying at time when dinosaurs were near end of their dominance
• Were successful because of adaptability
• Adopt various body forms, occupy various habitats
Lizards
• Very diversified group • Terrestrial, burrowing,
aquatic, arboreal, aerial
• Many familiar groups
Lizards
• Geckos • Mostly small,
nocturnal, with adhesive toe pads (walk anywhere)
• Iguanas • Often bright-colored
New World lizards
Lizards
• Skinks • Elongate bodies
Lizards
• Chameleons• Tongue flicked to
greater distance than body length
Draco volans
Snakes
• 10 cm long up to 10 m long
• Highly specialized body form
Snakes• Rearranged internal
anatomy• Left lung reduced or
absent• Hearing - no obvious
external ear• Sensitive to vibrations
carried in ground
Snake Sense Organs
• Olfaction important, but not in nostrils
• Jacobson’s organs (vomeronasal organs)
• Tongue carries scent particles to organ
Snake Feeding
• Skull, jaws highly specialized for feeding
• Eat prey several times their own diameter
• Non-joined mandibles• Loose skull bones
Snake Feeding
• Venom - toxic concentrations in saliva
• Neurotoxic - blindness, paralysis
• Hemolytic - ruptures blood vessels, cells
Snake Feeding
• King cobra most dangerous, largest (5.5 m) - kill 9,000 people per year
Snake Locomotion
Crocodilia
• Unchanged for 160 million years
• Crocodiles larger, more dangerous than alligators
• Prey drowned, ripped into pieces by rapid rolling
• No natural enemies
Crocodilia
• Oviparous - lay eggs in mass of vegetation
• Guarded by mother• Incubation temperature
determines sex of alligator hatchlings
• Low - females• High - males• 5:1 (M:F) in some areas
Chelonia• Turtles • Very ancient group• Little change in
morphology since Triassic period
Turtle Shell Anatomy
Turtle Life Cycle
Sphenodonta
• Tuatara - single species in New Zealand
• Lizard-like, <66 cm• Lives in burrows• Slow-growing, long-
lived (77 years)