Characteristics of Reptiles
 Class Reptilia includes snakes, lizards, crocodiles,
alligators and extinct dinosaurs.
 The majority of reptiles are terrestrial and are adapted
to a wide range of habitats.
Crocodile or alligator?
Gila monster
Heloderma suspectum
Characteristics of Reptiles
 Evolved from amphibians about 350 million years ago
and dominated the Earth between 245 million and 65
million years ago—the Age of Reptiles (Mesozoic era).
Characteristics of Reptiles
 Adaptations to terrestrial life include their dry, scaly
skin (resistant to water loss and wear and tear) and
their amniotic egg (consists of a hard shell and
multicellular membranes, which encase the embryo in
a secure, self0contained aquatic environment).
Characteristics of Reptiles
 Are ectothermic. Regulate their
body temperature by controlling
how much heat they absorb.
 Use lungs for respiration and have
a circulatory system composed of
two loops and a 3-chambered
heart, in which one chamber is
partially divided.
Characteristics of Reptiles
 More advanced nervous system
than amphibians. Most have a
highly-developed sense of
smell. Are equipped with a
specialized organ sensitive to
low concentrations of odors
called the Jacobsen’s organ,
located in the roof of the
mouth.
Characteristics of Reptiles
 Excrete nitrogenous wastes in the form of uric acid. In
the body, uric acid is much less toxic than ammonia or
urea. Thus, it requires little water for dilution, and
reptiles lose only small amounts of water in their
urine.
Characteristics of Reptiles
 More than 5,000 species of modern reptiles divided
into 4 orders:
1.
Order Testudines: turtles, tortoises, and terrapins.
Box Turtle:
Terrapene ornata
Geochelone nigra vicina
Galapagos tortoise
Diamondback Terrapin
Malaclemys terrapin
Orders of Reptiles
2.
Order Squamata: lizards and snakes.
Anole: Anolis carolinensis
Corn snake: Elaphe guttata
Orders of Reptiles
3.
Order Crocodilia: crocodiles and alligators.
American Alligator
Alligator mississippiensis
Siamese crocodile
Crocodylus siamensis
Orders of Reptiles
4. Order Rhyncocephalia: tuataras
Sphenodon punctatus
produced by embryo
Thin membrane enclosing the
fluid in which embryo floats
Surrounds all
membranes and
cushions developing
embryo
Encloses the yolk
A fat-rich food supp
Provides protection from damage
and evaporation of water from egg
Contains proteins and
water needed by embryo
Characteristics of Amphibians
Modern amphibians
share several key
characteristics:
Most species change
from an aquatic larval
stage to a land adult
form. This
transformation is
called metamorphosis.
Characteristics of Amphibians
 Most have moist, thin skin with no gills.
 Skin is equipped with numerous mucus glands that
supply a lubricant that keeps the skin moist in air.
African Reed Frog
Characteristics of Amphibians
 Larvae exchange oxygen and carbon dioxide through
their gills and skin. Most adults lose their fills and
respire through lungs and skin.
Characteristics of Amphibians
 All adult amphibians are carnivorous, with insects and
other arthropods as the most commonly consumed
prey. Most amphibian larvae are herbivores, feeding
on algae, bacteria, or tiny green plants.
Characteristics of Amphibians
 Are ectothermic (external-heat).
(Amphibians are ectothermic, which means their
blood temperature rises and falls with that of the
surrounding environment)
Characteristics of Amphibians
 Most have 4 pairs of limbs. Feet, if present, lack claws
and are often webbed.
Characteristics of Amphibians
 Are oviporous. Eggs lack multicellular membranes or
shells. They are usually laid in water or in moist
places and in most species are fertilized externally.
Characteristics of Amphibians
 Many show parental care, guarding their eggs and
keeping them moist.
Poison Arrow Frog
Characteristics of Amphibians
 Cloaca are the primary
excretory organs.
 A muscular cavity at the
end of the large
intestine through which
digestive wastes, urine
and eggs or sperm leave
the body.
Characteristics of Amphibians
 A 3-chambered heart. Does not mix oxygen and
deoxygenated blood very much. Little mixing
increases the amount of oxygen that is delivered to the
tissues.
Characteristics of Amphibians
 The amphibian circulatory system is divided into two
separate loops. One loop carries blood between the
heart and lungs. The other loop carries blood to the
organs and tissues in the body and returns it to the
heart. This “double loop” circulation delivers blood to
the body faster. Double-loop circulation occurs in
amphibians and is now used by them and all other
vertebrates.
Characteristics of Amphibians
 The senses of hearing, smell, and sight are well-
developed in most amphibians. Sound receptors are
located in the inner ear, which is embedded within
the head. Sounds are transmitted to the inner ear by
the tympanic membrane, or eardrum.
Characteristics of Amphibians
 The olfactory lobes, which are the center of the sense
of smell, are larger in amphibians than in fish. The
eyes can blink and are covered by a transparent,
movable membrane called a nictitating membrane.
Additionally, there is a continuous communication
among most areas of the body.