CHAPTER 26
Nonavian Reptiles
26-1
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Hatching Komodo Lizard
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Diversity
Diversity
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The Age of Reptiles lasted over 165 million
years and included the dinosaurs
A mass extinction occurred at the end of the
Mesozoic (meteor)
Modern reptiles represent surviving lineages
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Tuatara is the sole survivor of a group that
otherwise disappeared 100 million years ago
Lizards, turtles, and snakes
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Origin and Early Evolution of Amniotes
History
 Amniotes (animals that have an amnion - reptiles,
birds, mammals) arose from amphibian-like tetrapods
 Skulls of amniotes could be separated into groups
based on three patterns of openings in the temporal
region
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Anapsids
 Have a skull with no temporal opening behind the orbits
 Modern turtles (arose from diapsid)
Diapsids
 Gave rise to all other traditional “reptiles” (except turtles) and
to birds
 Skull has two temporal openings (Below and above cheek)
Synapsids
 Mammal-like reptiles with a single pair of temporal openings
low on the cheeks
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Synapsids One opening
Mammals
Diapsids 2 openings
Birds & Reptiles
Anapsids No Opening
Turtles
26-5
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26-6
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Origin and Early Evolution of Amniotes
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These openings are associated with
large muscles that elevate the lower jaw
Changes in jaw musculature
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26-7
Might reflect a shift from suction feeding in
aquatic vertebrates to terrestrial feeding
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Origin and Early Evolution of Amniotes
Characteristics of Amniotes
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Amniotic Egg
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Amnion, allantois, chorion, and yolk sac
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Amnion = surrounds embryo, cushion
Allantois = stores metabolic waste
Chorion = respiratory surface
Surrounding the organism is a porous, parchment-like or
leathery shell
Rib Ventilation of the Lungs - Aspiration (draw air
into lungs) by muscles lowering liver - diaphragm
Thicker and more Waterproof skin - contains keratin,
that makes scales, hair, feathers, and claws
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26-9
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Origin and Early Evolution of Amniotes
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All amniotes
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Lack gilled larvae and have internal fertilization
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Eliminated the need for aquatic environments
Penis is the most common copulatory organ
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Derived from cloacal wall, appears to be an amniote
innovation
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Characteristics of Nonavian Reptiles
REPTILES:
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Jaws of nonavian reptile
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Efficiently designed for applying crushing or
gripping force to prey
Larger jaw muscles have mechanical advantage
over the jaws of fishes which are designed for
suction feeding or for quick closure
Tongue is muscular and mobile
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Functions to move food in mouth for mastication
and swallowing
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Characteristics of Nonavian Reptiles
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Retiles Circulatory System: efficient
and versatile circulatory system
Right atrium receives deoxygenated blood
and is partitioned from the left atrium
which receives oxygenated blood
 Blood doesn’t mix like amphibians
 Heart has 2 atria, and 1 divided ventricle
(crocodiles have 2 atria, and 2 ventricles)
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26-12
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To
body
Right
atrium
From
lungs
To
lungs
Left atrium
From
body
Incomplete division
Ventricle
26-13
Reptile’s Heart
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Characteristics of Nonavian Reptiles
Excretion
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Urine is produced in the kidneys.
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In some reptiles, urine flows in tubes directly into a
cloaca.
In others, a bladder stores urine before it is expelled.
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Water and most salts resorbed in the bladder
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Salt is removed by salt glands near the nose,
eyes, or tongue
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Characteristics of Nonavian Reptiles
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The nervous system of reptiles is more
complex than that of amphibians
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Brain of reptiles is small, however, cerebrum is
relatively enlarged
Enlargement of cerebrum correlated with increase
of sensory information and muscle control during
locomotion
Reptiles have good vision
Snakes and many lizards use a highly sensitive
sense of smell to find prey and mates
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Olfaction assisted by a Jacobson’s organ, a specialized
olfactory chamber in the roof of the mouth
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Characteristics and Natural History of Reptilian Orders
Order Testudines (Turtles)
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Fossils appear 200 million years ago
Shells consist of a dorsal carapace and a
ventral plastron
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Outer horny layer of keratin and an inner layer of
bone
Bony layer is a fusion of ribs and vertebrae
Lack teeth and use tough, horny plates for gripping
food
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26-18
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Snapping Turtle
26-19
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Characteristics and Natural History of Reptilian Orders
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Breathing
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Consequence of having a rigid shell
 Turtle cannot expand chest to breathe
Solve problem by using abdominal and pectoral
muscles as a “diaphragm”
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Form and Function
in Turtles
Liver
Kidney
Cloaca
Bladder
Digestive
tract
Lung
Heart
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Characteristics and Natural History of Reptilian Orders
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Nervous System and Senses in Turtles
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Brain is small, less than 1% percent of body weight
 Some turtles can learn a path through a maze
Have a middle and an inner ear but sound
perception is poor
 Make few sounds aside from those made during
mating
Good sense of smell, acute vision, and color
perception about equal to humans
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Characteristics and Natural History of Reptilian Orders
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Reproduction and Development Turtles
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Oviparous
Fertilization is internal
Bury their eggs in the ground
Female lays her eggs in a nest and deserts them
In some turtle families nest temperature
determines sex of hatchlings
 Low temperatures produce males
 High temperatures produce females
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Pond Turtle: Sex determined by temperature
26-24
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Galapagos Tortoise Mating
26-25
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Green Sea Turtle - herbivore, tropical oceans, only go on land to lay eggs
26-26
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Alligator Snapping Turtle: Has pink lure in mouth to attract fish
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Characteristics and Natural History of Reptilian Orders
Order Squamata: Lizards and Snakes
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Account for up 95% of living reptiles
Divided into Suborders (Sauria, Serpentes)
Oviparous and Viviparious
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Associated with cold climates - mother can regulate
temperature of young
Increasing the length of time eggs are kept in
oviduct
Young obtain nutrition from yolk sacs, via the
mother, or a combination of both
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Tokay Gecko
26-29
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Suborder Sauria
Suborder Sauria: Lizards
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Geckos
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Iguanids
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Small, agile, nocturnal forms
Adhesive toe pads allow them to walk on ceilings
Include many New World lizards as well as the
marine iguana of the Galápagos
Chameleons
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Arboreal lizards of Africa and Madagascar
Many have an extendible tongue
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Large male marine Iguana -feeding underwater on algae.
Can stay underwater for 30 minutes. Only marine lizard.
26-31
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A chameleon snares a dragonfly
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Suborder Sauria - Lizards
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Some have degenerate limbs
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Glass lizards are nearly limbless (legless
lizard)
Movable eyelids = lizard. Snakes have a
transparent covering
Have an external ear that snakes lack
26-33
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26-34
The glass lizard - legless. Different from snakes:
-Deep flexible groove running along body
-Moveable eyelids
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Characteristics of Reptilian Orders
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Conserve water by producing semisolid urine
Some can store fat in tails to provide energy
and metabolic water during drought
Gila monster and beaded lizard are the only
lizards capable of a venomous bite
Lizards keep body temperature relatively
constant by ectothermy
26-35
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Gila Monster - venomous
- Feeds on birds, nests, mammals
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Characteristics of Reptilian Orders: Snakes
Suborder Serpentes: Snakes
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Limbless and have lost pectoral and
pelvic girdles (except in pythons)
Feeding apparatus allows them to eat
prey several times their own diameter
Two halves of lower jaw are loosely joined,
allowing them to spread apart
 Skull bones also loosely articulated so
mouth can accommodate large prey
 To allow breathing during the slow process
of swallowing, the tracheal opening is
extended
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26-37
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26-38
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Characteristics of Reptilian Orders : Snakes
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Eyeballs have reduced mobility, non movable
eyelid
Most have poor vision
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Arboreal snakes in tropical forests have highly
developed vision
Lack external ears
Can feel vibrations at low frequencies,
especially vibrations carried in the ground
Chemical senses rather than vision or
hearing are main senses used to hunt prey
26-39
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Parrot Snake -tree snake of Central America
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Characteristics of Reptilian Orders : Snakes
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Jacobson’s organs
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Pair of pits in the roof of the mouth
Lined with olfactory epithelium
Forked tongue picks up scent particles and
conveys them to this organ
Skin is infolded between scales
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When stretched by a large meal, the skin is
unfolded
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Blacktail Rattlesnake - flicks tongue to smell surroundings.
Scent particles are transferred to Jacobson’s organs on roof of mouth.
26-42
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ConcertinaUses force
Against trees
Lateral Uses ground
irregularities
SidewinderThrows body
forward in loops
RectilinearUse muscles on
ribs to contract
and relax
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Snake Locomotion
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Characteristics of Reptilian Orders : Snakes
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Pit vipers, such as rattlesnakes
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Have “pits” with nerve endings sensitive to heat
emitted by warm-bodied birds and mammals
Viper fangs are hollow and hinged to inject venom
when snake strikes
Of an average of 8,000 snake bites each year in
the U.S., only about 12 result in death
Nonvenomous snakes
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Kill prey by constriction or by biting and
swallowing
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Pit Organ:
Can sense temperature
changes of 0.003º C.
26-45
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Nonvenomous African House Snake- constricting a mouse
26-46
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Spectacled Cobra Flattened neck shows
a threatening display.
26-47
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Characteristics of Reptilian Orders
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Snakebite and Toxicity
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Most snake venoms are a complex combination of
venom types
Neurotoxins act on the nervous system, causing
blindness or inhibit respiration
Hemorrhagin type venoms break down blood
vessels
 Blood leaks into tissue spaces
Sea snakes and the Australian tiger snake have
the most deadly venom per unit volume
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The Venom Gland is a modified salivary gland, connected by a duct to a hollow fang.
26-49
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Characteristics of Reptilian Orders : Snakes
World total for deaths from snakebite is
about 50,000 to 60,000 each year
 Less than 20% of all snakes are
venomous, although venomous species
outnumber nonvenomous species by 4 to
1 in Australia
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Characteristics of Reptilian Orders : Snakes
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Reproduction
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Most are oviparous and lay shelled eggs
Others, including pit vipers, are ovoviviparous
A few snakes are viviparous
Female snakes can store sperm and lay several
clutches of fertile eggs long after a single mating
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Characteristics of Reptilian Orders: Tuatara
Order Sphenodonta: The Tuatara
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Only 2 living species in New Zealand
Once widespread across New Zealand,
the 2 species are now restricted to
small islands
Loss of the tuatara populations caused
by human introduction of nonnative
species which preyed upon the tuatara
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Tuatara are vulnerable because they have
slow growth and reproductive rates
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Tuatara - living reptile fossil
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Characteristics of Reptilian Orders: Tuatara
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Lizard-like and live in burrows
Slow growing and may live to 77 years
of age
Well-developed 3rd median eye on
head, buried beneath skin
26-54
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Characteristics of Reptilian Orders: Crocodiles
Order Crocodilia: Crocodiles and Alligators
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Relatives gave rise to the of dinosaurs and to
birds
There are 3 families of modern crocodilians
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Alligators and caimans are found primarily in the
New World and have a broader snout
Crocodiles are widely distributed, narrow snout
One species of Gharial (gavial) occurs in India
and Burma and has a very narrow snout
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Nile Crocodile: 4th Tooth of
Lower Jaw is visible,
Longer, pointed snout
American Alligator:
Wider shorter snout
Darker colloration
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
26-56
Gharial:
Growth on snout
in males only.
Makes noise to
attract females.
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Characteristics and Natural History of Reptilian Orders
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All have long, well-reinforced skull and jaw
musculature for a powerful bite
Thecodont dentition
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Teeth are set in sockets
Four-chambered heart
Alligators and crocodiles are oviparous
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Usually 20–50 eggs are laid in mass of vegetation
Unguarded nests are easily discovered and raided
by predators
High nest temperatures produce males
Low temperatures produce females
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Opposite of turtles
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QUIZ
1. Most reptiles reproduce with
a. external fertilization and external
development.
b.internal fertilization and internal
development.
c. internal fertilization and external
development in water.
d.internal fertilization and external
development in shelled eggs.
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QUIZ
1. Most reptiles reproduce with
a. external fertilization and external
development.
b.internal fertilization and internal
development.
c. internal fertilization and external
development in water.
d.internal fertilization and external
development in shelled eggs.
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QUIZ
2. The amnion sac of a reptile egg functions
as a
a. membrane that exchanges oxygen and
carbon dioxide for the embryo.
b.membrane that stores wastes produced
by the embryo.
c. source of nutrient-rich food for the
developing embryo.
d.shock-absorbing fluid-filled sac
protecting the embryo.
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QUIZ
2. The amnion sac of a reptile egg functions
as a
a. membrane that exchanges oxygen and
carbon dioxide for the embryo.
b.membrane that stores wastes produced
by the embryo.
c. source of nutrient-rich food for the
developing embryo.
d.shock-absorbing fluid-filled sac
protecting the embryo.
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QUIZ
3. Reptiles with the most well-developed
hearts include
a. turtles and alligators.
b.crocodiles and turtles.
c. crocodiles and alligators.
d.alligators and lizards.
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QUIZ
3. Reptiles with the most well-developed
hearts include
a. turtles and alligators.
b.crocodiles and turtles.
c. crocodiles and alligators.
d.alligators and lizards.
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QUIZ
4. The two parts of a turtle or tortoise's shell are
a. terrapin and plastron.
b.carapace and plastron.
c. carapace and terrapin.
d.terrapin and carapace.
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QUIZ
4. The two parts of a turtle or tortoise's shell are
a. terrapin and plastron.
b.carapace and plastron.
c. carapace and terrapin.
d.terrapin and carapace.