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Reptiles. Key features of Reptiles. Strong, bony skeletons and toes with claws Two pairs of limbs, except snakes Legs positioned vertically for support of body and movement on land. External Structural Adaptations for Land.

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Reptiles

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Reptiles l.jpg

Reptiles


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Key features of Reptiles

  • Strong, bony skeletons and toes with claws

  • Two pairs of limbs, except snakes

  • Legs positioned vertically for support of body and movement on land


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External Structural Adaptations for Land

  • Claws-aid in climbing, digging and movement in various terrains

  • Toes modified into suctions cups aid in climbing

  • Absence of limbs

    • Snakes use scaly skin and highly developed skeletal and muscular systems to move


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Ectothermic Metabolism

  • Regulate their temperature by basking in the sun or seeking shade

  • Become sluggish in very cold temperatures

  • Intolerance to cold limits their geographic range


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Temperature Regulation

Regulate their temp by behavior

  • Bask in sun to speed up metabolism

  • Hide in shade to prevent overheating


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Reptiles Continued

  • Dry, scaly skin, almost watertight

  • Amniotic eggs, almost watertight

  • Contains a water and food supply

  • Respiration through well developed lungs

  • Grape shaped chamber called alveoli

  • Alveoli increase the respiratory surface area for gas exchange

  • Strong muscles in rib cage help to move air in and out


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Respiration

  • Well developed lungs

    • Tissues involved in gas exchange are located inside body

    • Kept moist in even in the driest environments


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Heart

  • Ventricle of heart partly divided by a septum

  • Still incomplete separation of oxygen-rich and oxygen-poor blood

  • Crocodiles and alligators

    have a ventricle that is totally separated into two pumping chambers


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Circulation

Double loop circulation


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Reproduction

  • Internal fertilization

  • Many reptiles are oviparous-young hatch from eggs

  • Some lizards and snakes are ovoviviparous-female retains eggs in her body until shortly

    before hatching or hatching

    may occur inside her body


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Excretion

  • Conserve water by excreting nitrogenous wastes in dry or pasty form as crystals of uric acid


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1st Orders of ReptilesSquamata

  • Snakes and lizards

  • lower jaw is loosely connected to skull allowing mouth to open wide to accommodate large prey

  • Lizards can regenerate tail, but will not have vertebrae

  • Molting occurs in both


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Squamata

  • Order consists of 5,640 species of lizards and snakes

  • Loosely jointed upper jaw and paired reproductive organs in males

  • Lizards-presence of limbs

  • Common lizards- iguanas, chameleons, skinks and geckos

  • Live everywhere except Antarctic

  • Special adaptations- agility and camouflage

  • 2 species are venomous- Gila monster (SW U.S.) and beaded lizard (western Mexico)


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Squamata Continued

  • Blend with background chameleons- remain inconspicuous

  • Horned lizards- spiked armor,when disturbed they inflate,hiss and squirt blood from eyes

  • Skinks and geckos- lose their tails and regenerate-escape from predators

  • Most lizards are small- .3m in length; iguanas- 1m in length

  • Largest lizards- monitors- Komodo Dragon (Indonesia) 3m (9.8 ft) in length, 140 kg (308.6 lbs)


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Adaptations of Snakes


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Movement

  • A snake has a backbone of 100 to 400 vertebrae, with a pair of ribs attached

  • Provides the framework for thousands of muscles

  • Interaction of bones, muscles, and skin enables a snake to move various ways:

    Example:

    side winding


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Feeding

  • Snakes eat animals, but lack

    structural adaptations common to other carnivores

  • Snakes do not see or hear well, have no limbs, and teeth and small mouth cannot rip and grind flesh


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Locating Prey

  • Snakes evolved a sense of smell which they use to locate their prey

  • Flicks its forked tongue to gather chemicals from the environment

  • Transfers chemicals to two pits in the roof of the mouth-Jacobsons organ where nerves are highly sensitive to the chemicals

  • Some snakes inject toxic venom by biting with fangs and injecting

  • Hemotoxins-attack the circulator system-disrupt the clotting of blood.

  • Neurotoxins-disrupting the nerve pathways-dangerous to respiratory and heart functions.


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Reproduction

  • Most male snakes rely on the scent of female snakes of heir own species

  • Before mating, a male and female snake may glide alongside by side, with the male stroking the female with his chin and flicking his tongue over her body

  • Fertilization is internal


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Reproduction Continued

  • Most snakes are oviparous

  • Female lays eggs that hatch outside her body

  • To break out a hatchling uses a special tooth which is lost soon after

  • Other snakes are ovoviviparous

  • Female carries the eggs in her body throughout development

  • Young are born live

  • All newborns must fend for themselves, relying on their many specialized adaptations for survival on land


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Defense

  • Natural selection resulted in modifications for defense.

  • Camouflage is beneficial for both seeking prey and hiding from predators.

  • Many snakes are green and blend with foliage

  • Others are brown and hide against the bark of trees


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Swallowing and Digesting Prey

  • A snakes upper and lower jaws are hinged and move independently.

  • when unhinged, the jaws stretch to allow the mouth to open extremely wide.

  • While swallowing it whole the snake thrusts its windpipe into the throat, allowing the snake to breathe

  • The process of can take several hours


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Defense Continued

  • Some ward off danger by rapidly changing body shape

  • Extending a hood like cobras

  • Some hiss

  • Others make mechanical noises

  • Such as the rattle of the rattlesnake.


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2nd Order of ReptilesChelonia

  • Turtles and tortoises

  • Hard bony shell-dorsal

    is carapace and

    ventral is plastron

  • Lack teeth, but have beaks

  • Many herbivores but some are carnivores


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Chelonia

  • Order consists of about 265 species of turtles and tortoises

  • Tortoise are terrestrial

  • Turtles live in water

  • Body covered by a shell made of hard plates- 2 parts- a carapace and plastron

  • Retractable head

  • Forelimbs of a marine turtle have evolved into flippers and freshwater turtles have webbed toes

  • Migratory behavior of sea and river turtles

  • Returns to land to lay eggs


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3rd Order of Reptiles Crocodilia

  • Crocodiles and alligators

  • Most closely related

    to dinosaurs

  • Aggressive carnivores

  • Care for their young after hatching


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Order composed of 20 species of large lizard-shaped reptiles- crocodiles, alligators, caimans and gavials 

Crocodilians live in or near water in tropical/ subtropical regions of the world

Crocodiles-nocturnal animals; Africa, Asia and Americas

Alligators-China and southern U.S.

Caimans-Central America, some in Florida

Crocodilian


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  • Carnivorous

  • Eyes on head, nostrils on top of snout

  • See and breathe while in water

  • Parental care- both parents care for young by carrying in jaws until development


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4th Order of ReptilesRhynchocephalia

  • Tuataras

  • Two species native to New Zealand

  • Most active at low temperatures


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Rhynochocephalia

  • Only living species-New Zealand

  • Resembles a large lizard about 60 cm long

  • Parietal eye-functions as a thermostat-protects from overheating

  • Active at low temperatures, feed at night on insects, worms and small animals


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Limited competition for the insects and plants that could be used as food on the land

An increase in competition for food and space among all the life-forms in aquatic environments

310 million years ago… reptiles were the first vertebrates to make the complete transition to life on land


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Adaptations to Land


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Adaptations to Land

  • Amniotic Egg

  • Legs

  • Lungs

  • Scales or plates


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Allantois stores the nitrogenous wastes produced by the embryo until the egg hatches

An egg with a protective membrane and a porous shell enclosing the developing embryo

Egg forms a “nursery” to protect the embryo

Egg derives its name from the amnion, the thin membrane enclosing the salty fluid in which the embryo floats

Yolk sac encloses the yolk, a protein rich food supply for the developing embryo

Amniotic Egg


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  • The chorion regulates the exchange of oxygen and carbon dioxide between the egg and the outside environment

  • Amniote egg is surrounded by a leathery shell that may be hard in some species (Birds) because of the presence of calcium carbonate

  • The male places the sperm inside the female before the shell is formed. This is called internal fertilization, makes water transport of sperm unnecessary


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Origin and Evolution

  • From the studies of fossils and comparative anatomy, biologists infer that reptiles arose from a group of ancestral reptiles called cotylosaurs, which lived about 310 million years ago.


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The End


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