1. Relate reptile evolution to the geologic
intervals in which they evolved, became dominant and declined, and state
the factors which may have contributed to their success and decline.
2. Diagram a phylogenetic tree of reptile evolution,
including the ancestral types, groups which became extinct, groups which
have survived relatively unchanged, and new classes which evolved from the
reptiles.
3. Describe the amniote egg, including the
functions of the amnion, chorion, allantois and yolk sac; list the classes
of vertebrates which are amniotes.
4. State the usual pattern of reptile reproduction.
5. Describe how reptilian skin is designed
to land-adapt reptiles better than amphibia.
6. List and detail nine characteristics of
reptiles that allowed a complete break from dependence upon water.
7. Describe the way in which the heart of alligators
and crocodiles is different from other reptiles.
8. State the type of kidney which reptiles
have, and name the other classes of vertebrates which have this kidney.
9. Describe how the reptilian kidney assists
in water conservation, and state what the liquid waste excreted by reptiles
consists of.
10. Describe the reproduction and life cycle
of a crocodilian such as the American alligator.
11. Describe the unique arrangement of the
pectoral and pelvic girdles in the turtles.
12. List the types of habitats that different
species of turtles may live in and describe any unique modifications for
certain habitats.
13. List the suborders of the Order Squamata
and give some representatives of each suborder.
14. Name the most specialized and also the
most successful group of modern day reptiles.
15. Compare the eyelids, external ear openings,
lower jaw arrangement and limbs of snakes and lizards.
16. Name the family to which such beneficial
snakes as the bull snake, king snake, garter snake and racers belong.
17. List the poisonous snakes which are native
to western Nebraska and the western portions of the United States.
Resources: Text: Animal Diversity, Chapter
18
Internet Resources:
http://www.xmission.com/~gastown/herpmed/
http://www.mhhe.com/hickmanad4e
CLASS REPTILIA ~ 7000 SPECIES
-best remembered for their ancestral forms,
the dinosaurs, although these are far removed
-made final break from water
-4 remaining groups from original 17 orders
CLASS REPTILIA
-skull w/one surface for articulation
-respire w/ lungs
-metanephric kidney; uric acid main nitrogenous
waste
-internal fertilization (male penis)
-***AMNIOTIC EGG covered w/ shell
(leathery or calcium)
-dry skin w/ keratinized epidermal scales
Keratin- protein, protective when
chemically bound to phospholipids, prevents water loss
-paired limbs
-well ossified skeleton
-3chambered heart (crocs w/4)
-Ectothermic
-dioecious
ORDER TESTUDINES- turtles ~330
species
-teeth absent in adults, replaced by
horny beak; body short, broad; shell w/ dorsal
carapace, ventral plastron
(in some plastron flexible allowing shell to close when
turtle drawn in)
-clutches of 5-100 eggs layed in
nest and covered w/soil, development 4 weeks to
1 year; no parental care
-long life span due in part to very
low metabolism, some in excess of 100 years
-conservation measures; maternal genetics
ORDER SQUAMATA- snakes, lizards
(~3300 lizards; 2300 snakes) 95% of all reptiles
-most successful and diverse group of
living reptiles
-recognize by specific characteristics
of skull and jaw
Lizards- movable eyelids; external
ear opening; usually 2 pr legs; mobile jaw
apparatus; few venomous
Snakes- extreme elongation of
body; jaw apparatus allowing snake to swallow
prey larger than snakes own diameter.
Heat pits (pit vipers); no ear; transparent
non mobile eyelid; capable of focusing
eye.
300 venomous species world
wide; 30,000 to 40,000 deaths/year,
mainly in S.E. Asia
ORDER CROCODILIA ~25 species
Crocodiles, Alligators
-4 chambered heart
-elongated, muscular, laterally compressed
Crocodiles- long, slender snout:
Alligators- short, broad snout
-stomach gizzard-like
-prey usually swallowed whole; if
too large, crocs tear apart by grasping limb and
rotating bodies wildly until dismembered
ORDER RHYNCHOCEPHALIA- one
species; living fossil, Sphenodon punctatus
in N.Z.
ADVANCES ALLOWING COMPLETE BREAK FROM WATER:
1. TOUGH, DRY, SCALY SKIN (NO RESPIRATORY
FUNCTION)
-reduces water loss, physical injury
-less glandular than amphibs; secretions
include pheromones for sex recognition
and defense
-scales modified for various functions
-epidermis shed periodically in snakes
and lizards (molt) blood does not extend to
epidermis, therefore, cells lose contact
w/blood supply and die; molt usually
initiated in head region
-chromatophores present in dermis, function
much like amphibs; cryptic coloration,
mimicry; color and color changes function
in sex recognition and thermoregulation
2. SHELLED EGG THAT CONTAINS FOOD AND PROTECTIVE
OUTER COVERING
**single most significant change allowing success
of reptiles. Self contained aquatic
environment complete w/ nourishment (yolk
and protective covering)
-only vulnerability; placed neatly in
nest, makes nice meal for others many bury or hide
eggs
-amniotic egg- Amnion fluid filled
bag encloses embryo, free floating embryo protected
from shocks and adhesions
Allantois- collects wastes
of metabolism
Chorion- outer most membrane
3. JAW DESIGNED FOR CRUSHING OR GRIPPING
-jaw muscles, large, long
-most remarkable adaptation ---> snake
jaw
*bones of skull and jaw loosely joined
and may spread apart to allow prey larger than
head size to be eaten
*each half of upper and lower jaws
move independently of each other, loosely joined
by anterior ligaments
*after prey captured, opposite sides
of upper and lower jaws alternately thrust forward
and retract
*teeth point posteriorly ---> prevent escape, help force food back
-glottis, respiratory opening,
located far forward so snakes can breath while swallowing prey
-fangs in upper jaw
*in vipers maxillary bone hinged
so fangs fold back along jaw. Mouth opens, fangs
swing down and out, therefore,
may strike objects of any size
-cobras have fixed fangs, when mouth
closed fit in pocket
-fangs hollow or grooved, venom injected
by muscle contraction (venom glands, in some,
modified salivary glands)
-venom: Neurotoxic, hemotoxic (hemolytic),
usually combo of both
4. COPULATORY ORTANS PRESENT, PERMITTING
INTERNAL FERTILIZATION
-fert. occurs in female repro. tract before
protective egg membranes are built
-lizards, snakes posses paired hemipenis at base of tail, erected by turning inside out.
-sperm can be stored in seminal receptical
of female
*secretions or receptical nourish and
arrest activity of sperm
*sperm may be sored up to 4 years in
turtles, 6yrs in some snakes
-complex reproductive behavior
5. REPTILES HAVE MORE EFFICIENT CIRCULATORY
SYSTEM AND HIGHER
BLOOD PRESSURE
-on average reptiles larger than amphibs.,
blood must travel at higher pressure to
reach distant body parts. (giraffe,
2X that of human)
-two atria completely separated
-ventricle of most incompletely divided
(except crocs.)
-right atrium receives deoxygenated blood
left atrium receives oxygenated blood ventricle
pumps to appropriate systems
-crocs 1st vertebrate group w/ four chambered
heart
6. REPTILE LUNG BETTER DEVELOPED
-exchange of respiratory gases across internal
surfaces to prevent large amts. of water loss
-lung ventilation by negative pressure
mechanism
*expand body cavity decreases pressure
in lung ---> draws air in
-contraction of body wall compresses lung
---> forces air out
-pharyngeal respiration retained
by some turtles
-no cutaneous respiration
7. KIDNEYS ADVANCED METANEPHROS TYPE W/
URETERS
-increased body size, higher metabolism
require kidneys capable of producing wastes
w/ little water loss
-function dependent upon circ. system delivering
more blood at greater pressures to filter
large quantities of blood.
-uric acid principal product
-water reabsorbed by bladder or cloacal
walls.
8. ALL REPTILES, EXCEPT LIMBLESS MEMBERS,
HAVE BETTER BODY SUPPORT,
MORE EFFICIENT DESIGN FOR LAND TRAVEL
-more vertebrae
-limbs more elongate, slender
-limbs held closer to body
-knee joint rotated anteriorly
-elbow joint rotated posteriorly, therefore,
body higher off ground and weight supported
vertically
-in snakes, loss of limbs accompanied by
greater use of body wall
9. REPTILIAN NERVOUS SYSTEM MORE ADVANCED
-increased size of cerebrum ---> improved
sense of smell
-enlarged optic lobes and cerebellum
---> increased reliance on vision and better
coordination of muscle function
-vision dominant sense, eyes similar to
amphibians
Chameleon- eyes swivel independently
(diff fields of view)
Binocular vision provides depth perception,
helps determine range
-snakes focus by moving lens forward
by contraction of iris
-in all others focusing a function of changing
shape of lens
-reptiles have great # of cones in retina (well developed color vision)
Auditory
-snakes lack middle ear cavity and tympanic
membrane, detect vibrations through
jaw
-in other reptiles tympanic membrane
on surface or in small depression on head
Olfaction
-Jacobson's organs- blind-ending pouches
that open into mouth cavity, lined w/
olfactory epithelium and richly
innervated
-forked tongue accessory olfactory
organ, samples airborne chemicals.
Tongue flicked out and then
moved to Jacobson's organ
-pit organs- heat sensitive pits
on each side of head between nostril and eye
Sensory epithelium w/ dense
packing of free nerve endings from 5th cranial
nerve
Sensitive to infrared energy, can sense temp. differences smaller than .003 oC
Track warm blooded prey, as effective in dark as in light
Thermoregulation
Ectothermic- most thermoregulatory
activities behavioral (basking)
Physiological: panting
(evaporative cooling)
reduce blood flow to avoid heat loss
chromatophores
Hibernacula- group of
hibernating reptiles, reduce individual heat loss by
reducing total surface
area.
*unlike true hibernators,
body temp of reptile in Torpor, not regulated;
winter too cold
or retreat too shallow, animal can freeze and die
*cold death important source of mortality for temperate reptiles