Lesson 22 Outline list Lesson 24
Fundamentals of Biology
Lesson 23
Reptiles
I. General Characteristics.
A. Scaly skin.
B. Lungs from birth.
C. Reproduce on land.
D. Eggs encased in shells.
E. Internal fertilization.
F. 3-chambered heart (most) with a partly divided ventricle.
G. Claws on toes.
H. Ectothermic.
II. Orders.
A. Squamata – snakes, lizards, and tuatara.
B. Testudinata – turtles and tortoises.
C. Crocodilia – alligators and crocodiles.
III. Skin.
A. Scales are part of the skin, not separate as in fish.
B. Skin is thick and dry to prevent heat and water loss.
1. Skin contains keratin (a protein)
and lipids which seal in moisture.
(2. Keratin is also a component of
feathers, horns, and hair.)
C. Scales are replaced in tortoises and crocodiles as they
wear away, but in snakes and lizards are shed several times a year in a molt.
IV. Eggs.
A. Fertilized internally.
B. Encased in a shell.
– Shell is porous, allowing gas
exchange but preventing water loss.
C. Four membranes
1. Amnion.
a. Encloses
the embryo.
b. Amniotic
fluid cushions and protects the embryo.
2. Yolk sac – contains the
yolk -- food for the embryo.
3. Allantois – stores embryonic
wastes.
4. Chorion.
a. Surrounds
all the other membranes.
b. Regulates
exchange of O2 and CO2.
V. The Tuatara.
A. Formerly classed as order Rhynchocephalia, now part of
order Squamata.
B. Only found on a few islands near New Zealand.
C. A non-functional eye on top of its head.
VI. Snakes
A. Methods of Locomotion.
1. Serpentine.
a. S-shaped
motion.
b. Used in
both crawling and swimming.
2. Concertina.
a. Drawing
into a tight S shape, then extending forward.
b. Used when
between two structures.
3. Rectilinear.
a. Wavelike
muscular action on ventral surface.
b. Scutes
(broad scales) grip the earth.
4. Sidewinding.
a. Continual
looping motion – only touches the ground at 2 or 3 points.
b. Used where
traction is poor; e.g. deserts.
B. Feeding.
1. Carnivorous: rodents, insects,
lizards, eggs, other snakes.
2. Locating the prey.
a. Eyes are
weak.
b. Nostrils
lead to nasal cavities.
c.
Jacobson’s organs enhance the sense of smell.
i. Tongue gathers traces of chemicals and deposits them on the Jacobson’s
organs.
ii. They detect very slight traces of odors.
d. Heat
sensing pits.
i. Present in pit vipers.
ii. Located between nostrils and eyes.
iii. Can sense warm-blooded animals even in total darkness.
e.
No ears, but can sense vibrations in the ground.
3. Killing the prey.
a. Swallow
alive.
b. Suffocate
by constriction.
c. Poison.
i. Supplied by glands in its head.
ii. Flows through the fangs.
4. Ingesting the prey.
a. Swallow
whole.
b. Quadrate
bone enables the jaws to spread far apart.
c. Lower jaw
bones connected in the front by an elastic ligament – they can move
independently to pull in prey.
d. Inward
pointing teeth make escape impossible.
e. Skin of
mouth and neck is extremely elastic – can stretch over very large animals.
f. Ribs may
even dislocate temporarily to accommodate prey.
C. Types of venom.
1. Neurotoxin.
a. Attacks
the nervous system.
b. Quickly
paralyzes prey.
2. Hemotoxin.
a. Slower
working, but more deadly for large animals.
b. Destroys
blood vessels and red blood cells.
D. Short, fixed-fang poisonous snakes.
1. Venom is usually neurotoxin.
2. Venom is delivered as the snake
“chews” its prey.
3. Cobras.
a. Native to
Asia.
b. King Cobra
is the largest poisonous snake – 18 feet.
4. Coral snakes.
a. Southern
U.S. and the tropics.
b. Brilliant
red, yellow, and black bands.
5. Sea snakes.
a. Large lung
enables them to remain submerged for hours.
b. Venom is 2
- 50 times more deadly than the King Cobra.
E. Long, retractable-fang poisonous snakes.
1. Venom is usually hemotoxin.
2. Vipers – not in U.S.
3. Pit vipers.
a. Water
moccasin – southern lakes and swamps.
b.
Copperhead. – eastern woodlands.
c.
Rattlesnake.
i. Most dangerous in the U.S.
ii. The rattle is a series of loose, horny segments.
VII. Lizards.
A. General Characteristics.
1. 2 pair of limbs.
2. Ears.
3. Closable eyelids.
4. Ventral scales are similar to the
rest of the body.
B. Types.
1. Chameleons.
a. Native to
Africa, Madagascar, India.
b. Tree
dwellers.
c. Toes and
tail can grasp branches.
d. Keen eyes
can act in unison or independently.
e. Grabs
insects with its long sticky tongue.
f. Change
color in response to light temperature, excitement.
2. Anole – American lizard capable
of color change.
3. Two poisonous lizards.
a. Gila
Monster of the SW U.S.
b. Mexican
beaded lizard.
c. Have venom
in lower jaws.
4. Monitor lizards.
a. Komodo
dragon is the largest – 10 feet.
b. Found on
the island of Komodo in the East Indies.
VIII. Turtles and Tortoises.
A. Tortoises – land dwellers; turtles – water dwellers.
B. Shell.
1. Dorsal carapace.
2. Ventral plastron.
C. Eyes.
1. Upper and lower eyelids.
2. Nictitating membrane.
3. Horny beaks, but no teeth.
D. Females bury eggs and then leave.
E. Giant tortoises of the Galapagos Islands can weigh 350
lbs.
F. Leatherback sea turtles may reach 1500 lbs.
IX. Alligators and Crocodiles.
A. Alligators.
1. Blunt, wide snout.
2. Teeth fit within the jaws.
B. Crocodiles.
1. Thinner, pointed snout.
2. Some teeth protrude.
C. Common Characteristics.
1. 4-chambered heart.
2. Stealthy carnivores.
a. Eyes and
nostrils on top of head.
b. Glide
silently under the surface of the water.
c. Kills its
prey by thrashing and tearing with its teeth.
d. Can close
its nostrils, ears, and windpipe.
3. Lay eggs in rotting vegetation to
keep warm.