The document discusses the class Reptilia, or reptiles. It describes reptiles as the first vertebrates to lay amniotic eggs, which allow for terrestrial reproduction by maintaining an aquatic environment for the embryo. Reptiles have skin adapted for prevention of water loss, lungs for breathing air, and three-chambered hearts with two circulatory pathways. Their adaptations have allowed reptiles to thrive on land despite being ectothermic.

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2. Class Reptilia
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
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4. The Class Reptilia, or reptiles, means
“to creep”, it traditionally included a
diverse group of animals: turtles,
snakes, lizards and crocodiles,
alligators and caimans.
What is a Reptile?
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5. • 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
General Characteristics
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6. • 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
General Characteristics
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7. SALAMANDER
EGGS
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8. • 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
General Characteristics
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9. • 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
SCALES
• 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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10. • All reptiles breathe by
lungs
• Partitioned into
sponge-like chambers
• Form a negative
pressure mechanism for
ventilation
GAS EXCHANGE
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11. • Two separate circulatory paths:
• Pulmonary
• Systemic
Circulatory System
• 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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12. • Strong endoskeleton
• Limbs thrown outward
• Abdomen closer to surface
• Five toes
• Limbs adapted for
• Climbing
• Running
• Paddling
• Some snakes & lizards are limbless
Support & Locomotion
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13. • 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
Excretion
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14. • Reabsorption of water
• Internal respiratory surfaces
• Relatively impermeable
exposed skin
• Behavior
• Nocturnal
• Avoidance of hot surfaces
• Storage of water in lymphatic
spaces
Osmoregulation
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15. • 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.
Nervous & Sensory System
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16. • 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.
What is Jacobson’s Organ?
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17. • 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
Nervous & Sensory System
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18. Prepared by: DCMB
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