reptiles. general characteristics 1. amniotic egg – shelled 2. internal fertilization 3. scales or...
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Reptiles
General Characteristics
1. Amniotic egg – shelled2. Internal fertilization3. Scales or plates4. If legs – 2 pair with claws5. Well developed lungs6. Ectothermic – don’t generate their
own body heat
Importance of the AmnionAmphibians had to lay their eggs in water
to prevent them from drying out and killing the embryo inside.
With the advance of the reptilian egg with its leathery outer shell and amniotic sac, now the animal could live its life fully on land without fear that its eggs would dry out as the embryo developed inside.
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Taxonomic BreakdownKingdom –
AnimaliaPhylum –
ChordataClass –
Reptilia
Order Testudines
Order Chelonia or TestudinesTurtle – sea turtles
230 speciesWebbed feetSoft-shelled (streamlines)Omnivorous – eat both plants and animals
Order Chelonia or testudinesTerrapin – fresh water turtles
Claws and webbed feetSymmetrical plates called scutes covering bony under
layers Top shell – carapaceBottom shell – plastron or parapace
Order Chelonia or testudines Tortoise – land turtle
Long necks, short limbsAppendages completely drawn into shell, if not – very aggressiveNo teethTympanic membrane (poor hearing) Nicitating membrane (3rd eyelid)Good sense of smell, good color visionTemperature determines sex of eggs: low temp = males
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Order Squamata
Order Squamata – Lizards/Snakes Iguanas – horned toad, anoles (chameleons) change color
in response to light, temperature, and mood True chamelons – arboreal (tree dwelling); tongue longer
than body
Skinks – shiny cylindrical body, weak legs, tails fall off when grabbed
Gila Monster (aka Beaded Lizard) – only poisonous lizard known to the world Native to the desert southwest of the US and MexicPoison is found in saliva… no fangsThe poison is a nerve toxin, that is produced in glands located in
the lower jaw. When a Gila Monster bites an animal, the poison flows into the wound via grooved teeth. This poison only rarely kills people.
Gila MonsterBeaded Lizard
Gecko (Geico?) – most primitive; pads on toes to cling; makes noises, insectivores, eye has vertical pupil to see at night
Monitor – Komodo dragon is largest = 10 feetFYI: The Komodo dragon is not venomous or
poisonous; however, its saliva contains a number of toxic strains of bacteria which often infect the wounds inflicted on its prey, causing death.
Snakes
Loss of limbs and external earsEvolved from lizardsMost numerous reptile2,800 species (300 poisonous)
Snake Anatomy
Long, thin – head, trunk, tail Scales and scutes
Protect skinPrevent water lossMolting or ecdysis
SkeletonFlexible spine of 150 vertebrae1 pair ribs attached to each
vertebrae
Snake Systems• Respiratory – 1 well developed right lung; left missing• Circulatory – 3 chambered heart; partially divided ventricle• All organs long and thin and lie alternating, not side by side
Snake Movementhttp://www.ucs.louisiana.edu/~brm2286/locomotn.htm
Lateral undulation – crawling quickly or swimming, s-shaped motion, most common
Rectilinear locomotion– straight movement, no lateral movement, used by large snakes
Sidewinding – twists into loops and touches ground at 2-3 points; used by desert dwelling snakes or on slippery surfaces
Concertina locomotion– pulling up the body into bends and then straightening out the body forward, used in crawling through tunnels or narrow passages
Snake Sense Organs
Internal ear – low frequency; sensitive to vibrations Acute sense of smell
Jacobson’s organ – roof of mouthTongue picks up scent particles and inserts into Jacobson’s organTongue is forked shaped to sense the direction of the smells
Snake Sense OrgansSightCornea – permanently protected with spectacleMost have poor vision with exception of the
arboreal (tree dwelling) snakes
Snake FeedingCarnivorousKills via: Poison or constrictionSwallow food whole
Jaw comes unhingedElastic ligamentsGlottis moves forward (so can breathe while
swallowing)Large esophagusNo sternumStrong stomach acid
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Swallow Prey
Non poisonous snakesGarter snakeBlack snakeKing snakeBoa constrictor
Poisonous SnakesVipers
Rattlesnakes, copperheads, adderHeat sensitive pits on head (pit vipers)Long thin fangs – fold up when mouth is closed
Rattlesnake
Copperhead
Puff Adder
Elapsids (cause swelling of lymph nodes)Cobras, coral, kraitsPermanently erect fangs (short) Hydrophiidae (family) – sea snakes
Highly poisonous – nonaggressiveColubridae (family, both non and poisonous) – African
boomslang and twig snakes rear fanged
Cobra Coral SnakeKrait
Top Ten Most Deadly Snakes1) Fierce Snake or Inland Taipan (Oxyuranus microlepidotus ), Australia. The most toxic
venom of any snake. Maximum yield recorded (for one bite) is 110mg. That would probably be enough to kill over 100 people or 250,000 mice. These rare snakes are virtually unknown in collections outside of Australia.
2) Australian Brown Snake (Pseudonaja textilis ), Australia. One 1/14,000 of an ounce of this venom is enough to kill a person.
3) Malayan Krait (Bungarus candidus ), Southeast Asia and Indonesia. 50% of the bites from this snake are fatal even with the use of antivenin treatment.
4) Taipan (Oxyuranus scutellatus ), Australia. The venom delivered in a single Taipan bite is enough to kill up to 12,000 guinea pigs.
5) Tiger Snake (Notechis scutatus ), Australia. The Tiger snake is a very aggressive snake that kills more people in Australia that any other snake on that continent.
6) Beaked Sea Snake (Enhydrina schistosa ), South Asian waters Arabian Sea to Coral Sea..7) Saw Scaled Viper (Echis carinatus ), Middle East Asia. Saw Scaled Vipers kill more people in
Africa that all the other venomous African snakes combined. Its venom is 5 times more toxic than that of the cobra and 16 more toxic than the Russell's Viper.
8) Coral Snake (Micrurus fulvius ), North America. Coral Snakes have a very potent venom but many are too small to deliver enough venom to kill a human. This is the only elapid (relative of the cobras and mambas) in the US.
9) Boomslang (Dispholidus typus ), Africa. The Boomslang is the most seriously venomous rear-fanged snake in the world. They have very long fangs and can open their mouths a full 180 degrees to bite. Famous herpetologist Karl P. Schmidt died 28 hours after a Boomslang bite. The day after the bite, he called in to say he felt well and would be in to work...2 hours before he literally dropped dead from the bite.
10) Death Adder (Acanthophis antarcticus ), Australia and New Guinea. The Death Adder looks like a viper but is more closely related to the cobras. A dosage of 10mg of Death Adder venom is enough to kill a human. A good sized Death Adder can deliver up to 180mg in a single bite.
Snake Venom
Snake VenomNeurotoxin – affect nervous systemHemotoxin or hemmoragin – affects red blood cellsAll contain both types, the amounts of each may
differDanger is in the amount and concentration of
injected venomWhere:
In blood vessel… spread fastIn muscle or fat… spread slow
Snake ReproductionOviparous – lay eggsOviviparous – retain
eggs in body, born aliveViviparous – primitive
placenta forms; receives nourishment from mother (rare)
Order Crocodilia
Order CrocodilianCarnivorous 4 chambered heartRaised nostrils and eyes (so rest of body is
underwater) Valve at back of mouth prevents water
from entering lungs when mouth is openTeeth in sockets (thecodont)
Eyesight in ReptilesMost reptiles are sight hunters, and can see
in color both during the day and at night. Most reptiles have both an upper and lower eyelid along with a nictitating membrane.
Some reptiles even have a third eye in the middle of their forehead called a median eye or a parietal eye. The tuatara’s parietal eye can actually see, but in most lizards it is barely noticeable and can only detect light and dark.
Order CrocodilianDifferences Between Alligators and Crocodiles
Alligators Crocodiles
Less aggressive More aggressive
More terrestrial More aquatic
Rectangular head Triangular head
Teeth not visible when mouth is closed
Teeth visible when mouth is closed
Definite vocalizations No definite vocalizations
Order CrocodilianBoth Alligators and Crocodiles are…
Oviparous (egg-laying)Guard nest and care for youngAs with many turtles and some lizards – temperature
of nest determines sex of youngLow temperature = females
Hearing & SmellingAll reptiles can hear, but some hear better
than others; for example, snakes hear mainly vibrations and are not good at picking up actual sound
All reptiles can smell, but some smell better than others; for example, snakes and lizards have extra olfactory organs called Jacobson’s organs specifically for smelling.
Certain snakes (rattlesnakes and pit vipers) can detect temperature differences in their surroundings through pit organs on the sides of their head, almost like infrared vision.
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The End