ReptilesJessica Brown

Miila Hall

Cold-blooded Tetrapods, four appendages Considered as the first animals on land with the

ability to live and multiply on land (amniotic egg) Amniotic egg- a shelled, water-like sac that enables

reptiles to complete their life cycles on dry land. Dry skin with scales 3-chambered hearts No metamorphosis Binocular vision Well-developed brain and a central nervous system Strong skeletal system with a rib cage

Characteristics

Originated around 320-310 million years ago

During the Carboniferous period Were called reptile-like amphibians because

they could survive efficiently on land Jacques Gauthier discovered a cladistic

definition of the crown group known as turtles, lizards, and snakes and crocidiles share common ancestors.

Evolution and Relationships

Approx. 300 species of turtles Bony shell, limbs internal to the ribs, and a keratinized

beak. Keratin is a resistant protein found in epidermally

derived structures of amniotes Dorsal side of the shell is the carapace, which forms

the fusion of vertebrate, expanded ribs, and bones in the skin.

Long life spans- 14 or more years Turtles vulnerable to extinction due to predation,

hunting, and threatened at time of birth. Types of turtles- sea turtles, green sea turtles,

freshwater turtles

Order Testudines

21 species Openings in the skull, triangular eye orbits, laterally

compressed teeth Snout is elongated to capture food by sweeping their

head. A flap of tissue near the back of the tongue forms a

watertight seal so it can breathe without inhaling water into the mouth.

A secondary palate separates the nasal and mouth passageways.

Tail used for swimming, defense, and attacking Oviparous and display parental care of hatchlings. Include- alligators, crocodiles, gavials, and caimans

Order Crocodylia

Tuataras Lizardlike reptiles from Mesozoic era Two rows of teeth on the upper jaw and a

single row in the lower jaw that can decapitate a small bird.

Only present in offshore islands Oviparous Feed on insects

Order Sphenodontida

Divided into three suborders:

Suborder Sauria- Lizards 4,500 species Two pairs of legs Upper and lower jaw Oviparous yet some are ovoviviparousor viviparous Geckos, iguanas, chameleons Geckos are nocturnal and haveClicking vocalizations Adhesive disks allow them to cling totrees and walls Iguania are robust with short necksand distinct heads Flying dragons Chameleons have the ability to changecolor in response to illumination, temperature,or their behavioral state

Order Squamata

2,900 species Around 300 are venomous Elongate and lack limbs, joints that make snake flexible, two

hundred vertebrate Skull adaptations that allow the snake to swallow large amounts of

prey Oviparous Reduction or loss of left lung an displacement of gall bladder, the

right kidney, and often, the gonads. Vipers, cobras, and boas

Suborder Serpentes

Worm lizards 135 species Specialized burrowers Legless and skulls are wedge or shovel

shaped Skin has ringlike folds called annuli and

loosely attaches to body wall Feed on worms and small insects Oviparous

Suborder Amphisbaenia

Skin has no respiratory functions Periodically shed the outer, epidermal layers of the skin

called ecdysis Movement of lymph between the inner and outer epidermal

layers loosens the outer epidermis. Chromatophores are primarily dermal in origin and function

like those of amphibians. Cyptic coloration, mimicry, and aposematic coloration occur. Have a cervical vertebrate Tail loss, or autotomy, is an adaptation that allows a lizard

to escape from predators The lizard regenerates the lost portion of the tail Laterally move in a horizontal plane Bipedal, meaning to walk on hindlimbs

External Structure & Locomotion

Most are carnivorous, although turtles can be herbivores Some have sticky tongues to catch prey Tongue extension in chameleons Snakes have a loose jaw that spreads apart to ingest prey

much larger than their normal head size. After prey is captured, alternately the jaw thrusts forward

and retracts The glottis is far forward so the snake can breathe during

swallowing

Nutrition & Digestive System

Blood must travel under higher pressures to reach body parts.

Two atria, turtles have a patch of cells that act as a pacemaker

Ventral aorta divide during development and become three major arteries

All reptiles breathe intermittently. Exchange respiratory gases across the surface to avoid

losing large quantities of water Larynx is present; vocal cords are absent To warm itself, a lizard may stand at an angle to the

suns rays or press itself to warm surfaces. To cool itself, seeks shade or burrows itself.

Circulation, Gas Exchange, and Temperature

Cerebral hemispheres are somewhat larger causing an improved sense of smell

Eyes swivel independently with binocular vision Nictitating membrane and a blood sinus to protect and

cleanse the eye Possess a median, or parietal, eye can differentiate light

and dark periods for the sun Olfactory senses are better developed Jacobson’s organs are pouches that open through the

secondary palate into the mouth cavity. Rattlesnakes and other vipers have pit organs that are

used to detect objects with temperatures different from their surroundings.

Nervous and Sensory

Require kidneys to process wastes and little water loss.

Excrete uric acid The behaviors to regulate temperature also

help conserve water Produce salt glands to rid the body of

excess salt Blood-filtering units are called nephrons

Excretion & Osmoregulation

Internal fertilization and the amniotic egg Tract of female before protective egg membranes are laid down around an

egg Male reptiles, except tuataras, possess an intromittent organ for

introducing sperm into the female tract Parthenogenesis can be present in some types of lizards Courtship functions in sexual recognitions Head-bobbing in males and revealing brightly colored patches of skin on

the throat Entwines his body around the female and runs his chin along the female After egg is laid it is usually abandoned

Reproduction & Development

Shell- sturdy and leathery for protection Albumen- the “white” of the egg, contains protein Chorion- outermost membrane surrounding the

embryo of the reptile Allantois- fetal membrane formed as an outgrowth

of the embryo’s gut Yolk Sac- membranous sac containing yolk

attached to the embryo Yolk- rich in protein and fat and nourishes the

developing embryo Amnion- the innermost membrane that encloses

the embryo

Amniotic Egg