RePtiles Common Characteristics - PowerPoint Presentation

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RePtilesSlide2

Common Characteristics

Fully adapted for life on landAll Amniotes – produce Amniotic Eggs

Dry, Scaly SkinEctothermic More Efficient Circulatory and Respiratory SystemsCloaca Except for snakes, Reptiles have Paired limbs, most ending in 5 clawed toes Slide3

Amniotic Egg

Amnion – extra membrane not found in amphibians which protects eggs from

dessication

(drying out) and other environmental problemsSlide4

Reptile Reproduction

Internal FertilizationLeathery-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 nestSome lizards and snakes are Ovoviviparous – eggs hatch inside mother and appears to be giving live birth

Some Viviparous lizard species existSome rare cases of parthenogenesis – seen in some Komodo dragons and Burmese pythonsSlide5

Reptile EggsSlide6

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 produceReproduction – Ovaries; Testes

Some sexually dimorphic – others very difficult to tell difference in sexes externallySlide7

Reptile Skin

All have or had (at some point in evolutionary history) horny epidermal scales composed of a protein called keratin

Relatively impermeable to waterMay be thick or thinSpikes 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 skinSlide8

Reptile skin Shedding

All animals shed old skin cells in some way, but snakes and some lizards shed it all in one pieceSlide9

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 lungsLack a diaphragm Slide10

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 vibrateSlide11

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 amphibiansMore O

2 = more energy for metabolism and complex movementSlide12

Reptile Feeding and Digestion

May be omnivorous, carnivorous, or herbivorous

Ex: Iguanas and tortoises herbivoresEx: Strict carnivores: snakes and crocodilesTurtles and tortoises lack teeth while other reptiles have sharp, well-developed teethMouth

 esophagus  stomach  liver and pancreas  small intestine colon  cloaca  anusSlide13

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 preySlide14

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 mandiblesSnakes’ 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 matesPit organs in some snakes act as heat sensors to detect preySlide15

Reptile Brain

Forebrain – olfactory lobes – better sense of smell than amphibians; larger cerebral hemispheres

Midbrain – larger optic lobes than amphibians for better vision; cerebral pedunclesHindbrain – larger cerebellum than amphibians allows more complex

movements; medulla oblongata Slide16

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 skinSnakes 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 Slide17

4 Orders of Reptiles

Squamata – Snakes and LizardsCrocodilia

– Crocodiles and AlligatorsTestudinata – Turtles and TortoisesSphenodonta - Tuataras

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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, pythonsSnakes – legless, movable eyelids, tympanic membranes, flexible jaw joint to allow ingestion of prey larger than headSlide19

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 closedCaimans – most smaller (most 1-3 meters length, but some near 4 m or 15 ft ) crocodilian of Central and South AmericaSlide20

Testudinata

– Turtles and TortoisesUnique protective shell – carapace and plastron

Many turtles can pull head and legs inside shellMost have ribs fused inside carapaceSharp beak but no teethLand or aquatic

Tortoises – turtles who live on landLife 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!Slide21

Sphenodonta - tuataras

Look like large lizards

Only found in coasts off New Zealand; only 2 speciesSpiny crest down back Sunlight-sensing “Third Eye” on top of head covered in scales – may protect from overheatingUnique teeth: 2 rows upper jaw, 1 row lower jawPredators – eat small vertebrates

Life span – can live over 100 yrsSlide22

Reptile Evolution

Birds now classified as being

reptiles

Their relationship: The Origin of Birds Slide23

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/Slide24

Reptile ecology

Part of food chains as predator and preyControl rodent pests

Threatened by habitat loss and introduction of exotic species who eat them or compete for same resources in their habitatMany 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