Transcript Class Reptilia

Class Reptilia
(Reptum = creep)
CONQUEST OF LAND
Class Reptilia
• First reptiles known from 280 million
years ago, during the Permian period;
– greatest radiation of reptiles in Triassic
(after the Permian) 230 million years ago,
– Mesozoic era (230-70 million years ago) age
of dinosaurs;
– died out in Cretaceous, about 70-80 million
years ago
Class Reptilia
• Integument:
– epidermis- very thin layer;
• shed periodically
– dermis- thicker
• well developed,
• has chromatophores;
• contains scales- made of keratin same material as
our hair
Class Reptilia
Features that allowed them to conquer land
• Cornified
integument- dry
scales
– not homologous
to scales of
fishes- bony
dermal
– Keratin- same as
hair and nails
– protects against
dessication
Class Reptilia
• Metanephritic kidney
– have ureters that take urine directly to outside
– able to conserve water by producing
concentrated urine
– excrete uric acid instead of urea or ammonia
Class Reptilia
• Amniotic egg;
–
–
–
–
–
which store all food necessary for development
and prevents water loss;
are covered by leathery or calcareous shell;
laid in sheltered areas on land
Consists of 4 membranes
Class Reptilia
•
Amnion -("private pond")–
–
•
Chorion –
–
•
the outer most membrane
that surround the fetus;
in mammals it contributes to
the placenta
Allantois –
–
–
•
inner most membrane in egg
that forms a fluid filled sac
around the fetus
a membrane around the
fetus
that functions in respiration
and excretion;
also plays important role in
development of placenta in
mammals
Yolk Sac –
membrane around the yolk
(i.e., the food for the fetus)
Amnion
Class Reptilia
• Reptilian jaw
efficiently designed
for crushing
– jaws of fishes and
amphibians
designed for quick
closure,
– but jaws of reptiles
designed for
crushing prey
Class Reptilia
• Reptiles have some sort of copulatory organ
permitting internal fertilization;
– also associated with terrestrial existence
• Reptiles have more efficient circulatory system
and higher blood pressure;
– crocodilians have a four chambered heart (first seen in
vertebrates);
– all other reptiles with three chambered heart
– but it is more efficient in getting deoxygenated blood to
lungs;
– septum in ventricle separates blood that goes to lungs
and body
Class Reptilia
• Reptiles lungs are better developed than
those of amphibians– amphibians had skin and gill respiration;
– reptiles depend solely on lungs;
• All reptiles, except limbless members,
have better body support than
amphibians;
– more efficiently designed for travel on land
Class Reptilia
• Reptilian nervous
system more advanced
than amphibians;
– some parts of brain
(cerebrum) are enlarged;
– sense organs well
developed;
– hearing is poorly
developed;
– 12 pairs of cranial nerves
Class Reptilia
• Reptiles have direct development (I.e. no
larval stages)
– are oviparous
– Ovoviviparous
– some are viviparous
Class Reptilia
• Reptiles like amphibians are
poikilotherms,
– but some do have a degree of control of body
heat (i.e., lizard sunning self on rock)
Classification of Reptiles
Order Testudines
(=Chelonia)
turtles and tortoises
• 330 species
• body in case of
dermal plates;
• dorsal carapace and
ventral plastron;
• vertebrae and ribs
fused to shell
• jaws without teeth
Order Squamata
lizards and snakes
• Suborder
Sauria (lizards)
– 3000 species
– four limbs
– moveable
eyelids and eyes
with ear
openings
Order Squamata
lizards and snakes
cottonmouth
• Suborder Serpentes
(snakes)
– 2700 species
– limbs and ear
openings absent
– no eye lids; eyes can't
move
– Heat sensing pits in
Pit vipers
Black racer
Milking diamondback
Order Squamata
lizards and snakes
• Suborder
Amphisbaenia
(worm lizards)
– 130 species
– limb girdles
vestigial
– eyes hidden under
skin
Order Crocodilia
• crocodiles and alligators
– 25 species
– four chambered heart
– Oviparous; 20-50 eggs
Alligator; 4th tooth bottom jaw
not visible when mouth closed
Crocodile; 4th tooth bottom jaw
visible when mouth is closed,
jaw narrow
Order Sphenodonta
=Rhynchocephalia
• tuatara
– Two living species
– third eye (parietal) fairly
well developed
– no copulatory organs;
primitive
– Only found in New Zealand
– Long lived up to 70 yrs
– Live in burrows