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Class ReptiliaKingdom Animalia

Phylum Chordata

Subphylum Vertebrata

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What is a Reptile?

The Class Reptilia, or reptiles, means “to creep”, it traditionally included a

diverse group of animals: turtles, snakes, lizards and crocodiles,

alligators and caimans.

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General Characteristics

• Movement to Terrestrial Existence– First vertebrates to

have amniotic eggs– Amniotic egg maintains

aquatic environment • Leathery or Hard• Embryos of reptiles,

birds and mammals have four extraembryonic membranes

– Amnion– Yolk sac– Chorion– allantois

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6General Characteristics

• Amnion– Surrounds embryo– Amniotic fluid

• Yolk sac– Yolk a mixture of proteins and

lipoproteins• Chorion

– Involved in gas exchange– Membrane next to shell– Shell porous to gases– In mammals, chorion forms

placenta• Allantois

– Holds metabolic wastes as uric acid

– As embryo develops, also aids in gas exchange with chorion

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SALAMANDER EGGS

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General Characteristics

• Other adaptations for land• Impervious skin

• Keratin epidermal scales

• Horny tales• Water conserving kidneys• Enlarged lungs• Powerful jaw enclosure• Internal Fertilization• Respiration with lungs• Ectothermic, cold blooded• Have 3 or 4 chambered heart• 2 separate circulatory pathways

- pulmonary and systematic

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9SCALES

• Skin is especially adapted to prevent water loss• Epidermis (thick)

• Hydrophobic lipids reduces water loss• Scales (composed of β-keratin)

• Alligators keep scales their lifetime• Crocodilians and some lizards may have bony plates beneath scales

in dermis - osteoderms

• Dermis (thicker)• Chromatophores - a pigment-containing cell in many animals that,

when it expands or contracts, causes a change in the animal's skin coloring. Octopus, squid, and some frogs and lizards contain these cells.

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10GAS EXCHANGE

• All reptiles breathe by lungs

• Partitioned into sponge-like chambers

• Form a negative pressure mechanism for ventilation

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11Circulatory System

• Two separate circulatory paths:• Pulmonary• Systemic

• Heart• All retiles have 3 chambered hearts except for crocodilians, which have

4 chambered hearts• Low oxygenated blood from right atrium to ventricle • High oxygenated blood from lungs to ventricle to left atrium• Ventricle partly partitioned to prevent mixing• Crocodilians have two ventricles (4 chambered heart)

• Allows blood to flow even when oxygen not entering lungs during• Swimming underwater

• Higher blood pressure than amphibians• Ectothermic (cold-blooded animals) but with some behavioral

thermoregulation

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Support & Locomotion

• Strong endoskeleton• Limbs thrown outward• Abdomen closer to surface• Five toes• Limbs adapted for

• Climbing• Running• Paddling

• Some snakes & lizards are limbless

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13Excretion

• Kidneys have more nephrons or blood filtering units (Metanephric kidneys)• More blood flow• Higher pressure

• Excrete uric acid• Insoluble in water• Can be stored as a

paste

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14Osmoregulation

• Reabsorption of water• Internal respiratory surfaces• Relatively impermeable

exposed skin• Behavior

• Nocturnal• Avoidance of hot surfaces

• Storage of water in lymphatic spaces

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Nervous & Sensory System

• Cerebral hemisphere is larger than in Amphibians• Improved smell

• Jacobson’s Organ• Snakes can smell with their

tongue• Ears detect vibrations• Pythons, boas, and pit vipers find

prey using sensory pits in their heads that detect the body heat given off by prey. Using this extraordinary heat-seeking ability, pit vipers can even track down and kill prey animals in utter darkness.

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16What is Jacobson’s Organ?

• Reptiles taste and smell using an organ in the roof of the mouth called the Jacobson’s organ—a small cavity lined with sense detectors that recognize chemical changes in and around the mouth.

• This sense organ helps the animal locate prey, find mates, and generally obtain information about its surroundings.

• Monitor lizards and snakes continually flick their forked tongues, collecting small airborne particles that are carried back to the Jacobson's organ. The information they obtain in this way enables them to detect prey and follow scent trails.

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17Nervous & Sensory System

• Optic lobe and Cerebellum are enlarged• Increased vision• More refined motor

coordination• Independent eye movement• Different fields of vision• Dominant sense in most

reptiles• Colored vision

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Prepared by: DCMB