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Reptiles
SURVEY OF THE REPTILES
Reptiles have Following characteristics:
1. Their skull has one surface (condyle) for articulation with the first neck vertebra.
2
.
Respiration takes place by lungs.
3. They have metanephric (kidney Formed From the lower part of the middle part of ancestral kidney)
kidneys.
4. They have internal fertilization and amniotic eggs.
4.Reptiles have dry skin. It has keratinized epidermal scales. Keratin is a resistant protein. It is found in
epidermally derived structures of amniotes. It is chemically bonded to phospholipids. Therefore, it
prevents loss of water through body surfaces.
5. They are found on all continents except Antarctica. However, they are most abundant on tropical and
subtropical environments. There are 17 orders of reptiles.
ORDER TESTUDINES (CHELONIA) TURTLES (L. testudo, tortoise).
1. Teeth are absent in adults. They are replaced by a horny beak. They have keratinized beak.
2. They have short broad body.
3. Their shell consists or a dorsal carapace and ventral plastron.
4. Turtles have 225 species. They have a bony shell.
5. Their limbs articulate internally with the ribs.
Example: Turtles
Shell in turtles
Carapace: The dorsal portion of the shell is the carapace. Carapace is formed by the fusion of vertebrae,
ribs and bones in the dermis of skin. Keratin covers the bone of the carapace.
Plastron: The ventral portion or the shell is plastron. It is formed from bones of pectoral girdle and
dermal bone. Keratin also covers it. The shell of some turtle has flexible areas or hinges. These hinges
attach the anterior and posterior edges of the plastron. The hinges close the openings 0f the shell during
withdrawal of body into the shell.
Turtles have eight cervical vertebrae.These vertebrae can bearticulated to form an S-shaped structure.
It draws the head into the shell.
Reproduction and life span
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Turtles have long life spans. Most turtles reach at sexual maturity after seven or eight years. They can
live 14 or more years. The age of large tortoises of the Galapagos Islands may be above 100 years. All
turtles are oviparous. Females use their hind limbs to dig nests in the soil. There they lay eggs. Their
clutches contain 5 to 100 eggs.
They cover the eggs with and soil. Development takes from four weeks to one year. The parent does not
attend to the eggs during this time. The young are independent of the parent at hatching.
ORDER CROCODILIA (krokodeitos, lizard)
The order Crocodilia has 21 species. Dinosaurs and crocodilian, are derived from thearchosaurs. They
has e certain special skull characteristics:
1. They have openings in the skull in front of the eve.
2. They have triangular eye orbits.
3. They have laterally compressed teeth.
Examples: Lining crocodilians are alligators, crocodiles, gavials and caimans.
Adaptations in crocodiles:
Little changes take place in crocodilians over their 170-million year history.
(i) Snout:
Their snout is elongated. It is used to capture prey by a sideways movement of the head.
The nostrils are at the tips of the snout. Thus animal can breathe mostly submerged.
(ii) Air passage way:
Air passageways open into rear of the mouth and throat. There is a flap of Tissue near the
hack of the tongue. It forms a watertight seal. Therefore, breathing takes place without
inhaling water in the mouth. Secondary palate is a plate of hone. It separates the nasal and
mouth passageways.
(iii) Tail:
They have muscular elongate and lateral compressed tail. It is used or swimming. It is also
used for offense and defense.
(iv) Digestive System:
Teeth are used only for seizing prey. Food is swallowed as a whole. But crocodiles hold the
large prey. It rotates it and tears it into small pieces a he stomach is gizzard like. The
crocodilians swallow rocks and other objects. They use these rocks for breaking the ingested
Food.
iv) Reproduction:
Crocodilians are oviparous. They display parental care like birds. Nesting behavior and
parental care shows that both birds and crocodiles have common ancestor.
2. They are the most successful and diverse group or living reptiles.
Examples: Snakes, lizards, worm lizards
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The order Squamata is divided into three suborders. Ancestral member of these suborders originated in
the lepidosaur lineage about 150 million years ago.
a) Suborder Sauria: The Lizards
1. Suborder Sauria have about 3, 300 species of lizards.
2. The lizards have two pairs of legs.
3. Their upper and lower jaws arc united anteriorly.
4. Few lizards are legless. But they retain remanants of a pectoral girdle and
Sternum.
5. Lizards vary in length. Their length may be from a few centimeters to 3m.
6. Many lizards live on surface substrates. They move down under rocks or logs when necessary. Others
are burrowers or tree dwellers.
7. Most lizards are oviparous. Some are oviviparous or viviparous. They deposit eggs under rocks or
debris or in burrows.
GECKOS
Geckos are commonly found on the walls of houses in semitropical areas. Their body is short and stout.
They are nocturnal. They produce the sound of clicking. They have large eyes, their pupil contract and
narrow during the day. It widens at night. This is an adaptation for night vision. They has adhesive disks
on their digits. These disks help in clinging to trees and walls.
Iguanas
Iguanas have heavy bodies. They have short necks and distinct heads. This group includes the marine
iguanas of the Galapagos Islands and the flying dragons (Draco) of southeast Asia. Darco has lateral folds
of skin. It is supported by ribs. The ribs of Draco can expand to form gliding surface. It can glide 30 m or
more.
Chameleons
It is another group of iguanas. It is found in Africa and India. Chameleons are adapted for aboreal
lifestyles. They use a long sticky tongue to capture insects.
Venomous lizards
They are the gila monster (Heloderma suspectum) and the Mexican beaded lizard southwestern North
America(Heloderma horridum). These heavy bodied lizards live in southwestern America. The surface of
their teeth have groove. Venom is releascd into these grooves. The lizard chews the prey and introduces
venom into it. Lizard bites are not fatal to humans.
(b) Suborder Serpentes (serpere,
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There are about 2, 300 species in the suborder Serpentes. Majority of snakes are not dangerous to
humans. But three hundred species are venomous. 30, 000 to 40, 000 people the from snake bites each
year Worls widely. Most of these deaths are in Southeast Asia. In the United States about one hundred
people die each other from snake bites.
Body Structure
1. Snakes are elongated and lack limbs. Vestigial pelvic girdles and appendages are sometimes
present.
2. They contain more than two hundred vertebrae and pairs of ribs. Joints between vertebrae make
the body very flexible.
3. Snakes have adaptations in skull for swallowing large prey.Their upper jaws are moveable on the
skull. The upper and lower jaws are loosely joined. Therefore, each half of the jaw can move
independently.
4. They have different mechanism for focusing the eyes and the morphologyof the retina than lizards.
5. Their body is elongated and narrow. Therefore, left lung is reduced and gallbladder, right kidney and
gonads are displaced.
6. Most snakes are oviparous. A few species give to live young like the New World boas and garter
snakes.
Evolution of snakes
Zoologists debate the evolutionary origin of the snakes. The earliest fossils of snakes are 135-million-
year-old Cretaceous period. Some zoologists believe that the earliest snakes were borrowers. Loss of
appendages and changes in structure take place for borrowing habit. It is believed that early snakes
were aquatic or they lived in densely vegetated areas. Therefore, lost the legs.
(c)Suborder Amphisbaenia: Worm Lizards (amphi , douhle+boen, walk)
This order has about 13 species. They are specialized borrowers and live in soils. They are found in
Africa, South America, the Carribean West Indies and the Middle East. Most of them are legles. Their
skulls are wedge or shovel shaped.
EVOLUTIONARY PRESSURES IN REPTILES
The reptiles have striking adaptations for terrestrial life.
Adaptations in Chuckwalla (Sauromalus obesus)
It lives in the deserts of Southwestern United States. It has following adaptations:
(i) Adaptation in summer:
It can survive in late summer at temperate above 40 degree centigrade. Chukwallas browse
on plants. These plants wither. Therefore, chuckwallas aestivate to withstand these hot and
dry conditions. Chukwallas disappear below ground during aestivation.
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(ii) Adaptation for winter:
Temperature becomes model ate during the winter. But little rain falls. Thus lift in the desert is still not
possible. Therefore, summer sleep of chuckwalla enters into winter sleep. Rain fall started in March.
Therefore, greenery and appears in the desert. The chukwalla comes out from sleep. The chuckwalla
browses and drinks water. It stores large amount of water under its skin.
iii) Defense from predators:
Predators cannot prey chukwallas easily. If threatened, a chukwalla enters into rock crevice. It inflates
lungs with air. It increases its forms a wedge entrance or the rock walls. There is friction of its the rocks.
Therefore, chukwalla cannot be removed from rock.
EXTERNAL STRUCTURE AND LOCOMOTION
Skin
Skin of reptiles has no respiration functions. Reptilian skin is thick, dry or keratinized. Scales are
modified for various functions. For example, the snakes have large belly scales. The scales provide
contact with the substrate during locomotion. Reptilian skin is less glandular than that of amphibians.
Skin glands secrete phermones. These pheromones functions in sex recognition and defense.
The chromatophores of reptiles are dermal in origin. Cryptic coloration, mimicry and aposematic
coloration occur in reptiles. Colors also function in sex recongnition and thermoregulation.
Ecdysis:
The process in which reptiles periodically shed their outer epidermal layers of then is called ecdysis. All
reptiles undergo ecdysis. The blood supply to the skin does not move in the epidermis. The outer
epidermal cells lose contact with the blood supply and die. The lymph moves between moves the inner
and outer epidermal layers. It loosens the epidermis. Ecdysis begins in the head region. The epidermal
layers come off in one piece in many lizards and snakes . In other lizards, epidermal layers broken into
small pieces. The frequency of ecdysis is different in different species . It occurs more in young than in
adults.
Suppport and Movement
Skeleton
The reptailians are inherited skeleton from ancient amphibians. The skeletons of reptiles show many
notifications. The skeleton is highly ossified. Thus it provides greater support.
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1. Skull: Their skull is longer than that of amphibians. They have secondary palate. Secondary
palate partially separates the nasal passages from the mouth cavity. Palate was evolved in
archosaurs. It was an adaptation for breathing when the mouth is full of water or blood. It is also
present in other reptiles. They also have longer snouts. It increases the sense of olfaction.2.
2. Vertebrae: Reptiles have more cervical vertebrae than amphibians. The first two cervical
vertebrae are atlas and axis. They provide greater freedom of movement to head. An atlas
articulates with a single condyle on the skull. It helps in nodding. Axis is modified for rotational
movements. They have different number of cervical vertebrae. It provides additional neck
flexibility.3.
3. Ribs: The ribs of reptiles may be highly modified. The ribs of snakes have muscular connections
to large belly scales. It helps in locomotion. The cervical vertebrae of cobras are attached with
some special ribs. Cobra flares these ribs in aggressive displays.4.
4. Pelvic girdle: The pelvic girdle is attached to the vertebral column by two or more sacral
vertebrae.5.
5. Autotomy: If a lizard is grasped by the tail, caudal vertebrae are broken. Therefore a portion of
the tail is lost. The loss of tail is called autotomy. Autotomy is an adaptation that allows a lizard
to escape from a predator. Sometimes, the predator runs away from lizard after seeing its
broken moving tail. The lizard later regenerates the lost portion of the tail.
Locomotion
There are three types of locomotion in reptiles:
1. Locomotion in primitive reptiles is similar to salamanders. The body move low between paired
appendages. The appendages extend laterally and move in the horizontal plane.
2. The limbs of other reptiles are elongated and slender. They remain closer to the body. The knee and
elbow
.
joints rotate posteriorly. Thus, the body moves higher from the ground. Thus the legs support
the both vertically.
3. Many prehistoric reptiles were bipedal. The walking on the hind limbs is called bipedalism. They had a
narrow pelvis. Ihey have a heavy outstretched tail for balance. Bipedal locomotion treed the front
appendages. Thus these appendages are used capturing of prey or flight in some animals.
NUTRITION AND THE DIGESTIVE SYSTEM
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Tongue:
Most reptiles are carnivores. But turtles eat almost all the things. The tongues of the turtles and
crocodilians are nonprotrusible. It helps in swallowing. Some lizards and the tuatara late sticky tongues.
It is used or capturing the prey. The extended tongue of chameleons exceeds their body length.
Modification in snakes for swallowing
The skulls of snakes are greatly modified for feeding. The bones of the skull and jaws are attached
loosely. These bones move away from for ingestion of prey. In this way, snakes can ingest larger than a
snake’s normal head size. The bones of the upper jaw on the skull. The halves of both of the upper and
lower jaws are attached loosely by ligments at anterior side. Therefore, each half of the upper and lower
jaws can move independently. Opposite sides of the upper and lower jaws are moved forward and
retracted alternately alter the capturing of prey. Their teeth are posteriorly pointed. These teeth
prevent the prey from escaping. They also force the food into the esophagus.The glottis is much forward
in snake. Thus they can breathe during swallowing of prey.
Biting apparatus and biting mechanism
1. Vipers
Vipers possess hollow fangs. These fangs are present on the maxillary bone at the anterior margin of the
upper jaw. These fangs are connected to venom glands. The Maxillary Bone of the vipers is hinged. It can
moved backwards. Thus when the snake mouth is closed the fangs fold back and it lie along the upper
jaw. When the mouth opens, the maxillary bone rotates. It swings down the fangs. Thus the fangs
project outward from the mouth. Now vipers may strike at objects.
2. Rear fanged snakes
Rear-fanged snakes have groove in rear teeth. Venom is passed through grooves and injected into the
prey during swallowing.These snakes usually do not bite.Therefore, they are harmless to humans.
However, the African boomslang (Dispholidus typus) have killed men.
3. Coral snake, sea snake and cobra
The fangs of coral snakes, sea snakes. and cobras are attached to the upper jaw. It remains in an erect
position in opened mouth. The fangs lit into a pocket in the outer gum of the lower jaw when the mouth
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is closed. Fangs have a groove or it is hollow. The muscles of the venom glands contract and inject
venom into the fangs. Some cobras can spit venom at its prey. This venom may cause blindness.
Venom
Venom glands are modified salivary glands. The venoms of most snakes are mixtures of neurotoxins and
hemotoxins.
1. Neurotoxin:
Neurotoxin attacks on nerve centers. It causes respiratory paralysis. The venoms of coral
snakes, cobras, and sea snakes are neurotoxins.
2. Hemotoxins:
Hemotoxins break blood cells. It attacks blood vessel linings. The venoms of vipers are primarily
hemotoxins.
CIRCULATION
GAS EXCHANGE AND TEMPERATURE REGULATION
CIRCULATORY SYSTEM
Th circulatorysystem of reptiles is based on amphibians. The blood of reptiles must travel under high
pressures.
1. The reptiles possess two atria. These atria are completely separated in the adult. Veins from the body
and lungs open into them. The sinus venosus is absent in reptiles except in turtles. It has become a patch
of cells and act as a pacemaker.
2. The ventricle of most reptiles is incompletely divided. The ventricular septum is complete only in
crocodilians
.
3. The ventral aorta and the conus arteriosus divide during development. They form three major arteries
that leave the heart.
(a) A pulmonary artery: It leaves the ventral side of the ventricle. It takes blood to the
lungs.
(b) Two systemic arteries: One systemic artery arises from the ventral side of the heart. Second
systemic arterv arises from the dorsal side of the heart. It takes blood to the lower body and the head.
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Circulation of blood
The deoxygenated blood enters into the ventricle from the right atrium. It leaves the heart through the
pulmonary artery and moves to the lungs. Pulmonary veins bring oxygenated blood from lungs and
transfer it into left atrium. Blood then enters into the ventricle from. It leaves the heart through left and
right systemic arteries.
Mixing of blood: An adaptation
There is incomplete separation of the ventricle in most reptiles. The pulmonary artery contracts and
some blood moves from pulmonary circuit to the systemic circuit. All reptiles do not breathe constantly.
Therefore, the movement of blood from pulmonary circuit to systemic circuit has advantage for reptiles.
The breathing by lung stops when turtles withdraw into their shells. They also stop breathing during
diving. During periods of apnea (“no breathing
), blood flow to the lungs is limited. It conserves energy.
It allows more efficient use of the pulmonary oxygen supply .
GAS EXCHANGE
Reptiles exchange respiratory gases through internal respiratory surfaces. Thus they do not lose large
quantities of water. Larynx is present in them. However, vocal cords are absent in them. Cartilages
support the respiratory passages of reptiles. Their lungs are partitioned into sponge like interconnected
chambers. Lung chambers provide the large surface area or gas exchange.
Mechanism of respiration in most reptiles
Negative-pressure mechanism is responsible for lung ventilation. A posterior movement of the ribs and
the body wall expands the body cavity. It decreases pressure in the lungs. Thus lung draws air into the
lungs. Elastic recoil of the lungs and forward movements of the ribs and body wall compress the lungs.
Thus air is expelled out of it.
Mechanism of respiration in turtles
The ribs of turtles are a part of their shell. Thus movments of the body wall and ribs arc impossible.
Therefore, turtles exhale by contracting muscles. These contractions force the viscera (Internal organs)
upward and compress the lungs. They inhale by contracting muscles that increase the volume of the
visceral cavity. It creates negative pressure lung. This pressure draws air into the lungs.
TEMPERATURE REGULATION
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The terrestrial animals face high temperature (65 to 70°C). This temperature is not suitable for life. Thus
temperature regulation is important in terrestrial animals. Reptiles inn be:
1. Ectotherms:
The animals which use external heat sources for thermoregulation arc called ectotherms. Most
reptiles are ectotherms.
2. Endotherms:
The animals which generate internal heat during metabolism are called endotherms. Some
reptiles like monitor lizards and brooding Indian pythons arc endotherms. Female pythons coil
around their eggs. It raises its body temperature by 7.3oC above the air temperature. It uses
metabolic heat to raise this temperature.
Reptiles regulate their body temperature by following methods.
1. Heat regulation by hibernation and aestivation:
Some reptiles can survive in wide temperature fluctuations (2 to 41
o
C or some turtles).
However, body temperatures are regulated within a narrow range between 25 and 37
o
C. If they
are unable to maintain this range, they remain within the range in this retreat.
2. Behavioral methods of heat regulation:
Most thermoregulatory activities of reptiles are behavioral. A lizard orients itself at right angles
to the sun’s rays to warm itself. It presses its body tightly on a warm surface to absorb heat by
conduction. A lizard orients its body parallel to the sun’s rays to cool itsels. It seeks shade or
burrows. It take its body erect prostrate (legs extended and tail arched) to reduce conduction
from warm surfaces. Many reptiles are nocturnal in hot climates.
3. Physiological methods of heat regulation:
Various physiological mechanisms also regulate body temperature. Some reptiles use panting
for releasing neat. Panting releases heat through evaporative cooling. Marine iguanas absorb
heat by basking in the sun. It divert blood to the skin and arm up quickly. Marine iguanas reduce
heart rate and blood flow to the skin during ing into the ocean. It slows down heat loss.
Chromatophores also help in emperature regulation. Dispersed chromatophores increase the
rate of heat bsorption.
4. Heat regulation by torpor:
Many temperate reptiles withstand cold winter temperatures by entering into torpor. Torpor is
an inactive stage. The body temperatures and metabolic rates decrease during torpor. The body
temperatures of reptiles in torpor are not regulated. It is a difference from the true hibernators.
5. Heat regulation by hibernacula:
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The solitary reptiles migrate to a common site and spend winter there. These animals clumped
together. Heat loss from these groups is called hibernacula. Exposed surface area reduces
hibernacula. Sometimes, the animals can freeze and die in cooler winter. Death from freezing is
an important cause of mortality for temperate reptiles.
NERVOUS AND SENSORY FUNCTIONS
The brain of reptiles is similar to the brains of other vertebrates. The cerebral hemspheres are larger
than amphibians. This increase of size of brains has improved the smell. The optic lobes and the
cerebellum are also enlarged. It shows that reptiles much depend on vision. They have better
coordination of muscle functions.
Sense organs
The reptiles have complex sensory systems. It is evidenced by a chameleon’s method of feeding. It has
protruding eyes. Its eyes move independently. Each eye has different field of view. Initially, the brain
keeps both images separate. But when they an insect, both eyes converge on the prey. As a result
binocular vision is formed. It helps chameleon to determine whether the insect is within range of the
chameleon s tongue.
1. Eyes
(a) Focusing mechanism: Vision is the dominant sense in most reptiles. Their eves are similar to
amphibians. Snakes moves the lens forward for focusing the nearby objects. Iris contract and places
pressure on itrcous body. Vitreous both is gel-like in the posterior region of the eye. The displacement of
this gel pushes the lens forward. All other reptiles have different method to locus on nearby objects.
Their ciliary muscles press the ciliary body against the lens. It changes the shape of lens from elliptical to
more spherical. The spherical lens is used for focusing on nearby object. Reptiles have a greater number
of cones than amphibians. Thus they have well-developed color vision.
(b) Protection: The eyes of reptiles have upper and lower eyelids, a nictitating membrane and a blood
sinus. These structures protect and cleanse the surface of are eye. In snakes and some lizards, the upper
and lower eyelids fuse in the embryo. It forms a protective window of clear skin called the spectacle. The
blood sinus is present at the base of the nictitating membrane. It swells with blood and force debris to
the corner of the eye. It is rubbed out from this corner. Horned lizards rupture this sinus and blood
come out from it. It is a defensive act to confuse the predators.
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(c) Median eye: Some reptiles possess a median (parietal) eye. This eye is developed from outgrowths of
the roof of the forebrain. In the tuatara, this eye has a lens, nerve and a retina. The parietal eye is less
developed in other reptiles. Parietal eyes are covered by skin. Thus it cannot form images. However,
parietaleye can differentiate light and dark periods. Thus it is used to locate the position of the sun.
2. Ear
The structure of reptilian ears varies. The ears of snakes detect substrate vibrations.They lack a middle
ear cavity, an auditory tube and a tvmpanic membrane. A bone of the jaw articulates with the stapes.
The jaws and stapes receive substrate vibrations. Snakes can also detect airborne vibrations. In other
reptiles, a tympanic membrane is present on the surface. Or it may be in a small depression in the head.
The inner ear of reptiles is similar to amphibians.
3. Olfactory senses
Olfactory senses are better developed in reptiles than amphibians. They have partial secondary palate. It
provides more surfaces for olfactory epithelium. Many reptiles possess blind- ending pouches. This
pouch opens into the mouth cavity through the secondary palate. These pouches are called Jacobson’s
(vomeronasal) organs. These organs are present in diapsid reptiles. However, they are best developed in
the squamates. Jacobson’s organs develop in embnonie crocodilians. But it degenerate in adults.
Anapsids (turtles) lack these olfactory organs. The protrusible, forked tongues of snakes and lizards are
accessory olfactory organs. It detects chemicals present in air. A snake’s tongue come out and then
moves to the Jacobson’s organ. Jacobson detect odor molecules. Tuataras use Jacobson’s organs to
taste objects present in its mouth.
4. Pit organs
Rattlesnakes and other pit vipers have pit organs. Pit organs are present on each side of the face
between the eye and nostril. It is a heat-sensitive organ. Pit organs form depressions. These depressions
are lined with sensory epithellium. These are used to protect objects with temperatures different from
the snake’s surroundings. Pit vipers are nocturnal. Their pit organs help them to locate small, warm-
blooded prey.
EXCRETION AND OSMOREGULATION
Excretion
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Excretory organs: The kidneys of embryonic reptiles are similar fishes and amphibians. Terrestrial
animals have larger body size. They have higher metabolic rates. However, kidneys are capable of
processing wastes with little water loss. Their kidneys have in many nephrons
.
The functional unit
reptiles are called metanephric kidneys. Their function depends on a circulatory system. It delivers more
blood to kidney at greater pressures. Thus kidney filters large quantities of blood.
Mechanism of excretion: Most reptiles excrete uric acid. It is nontoxic and insoluble in w tier. It
precipitates in the excretory system. The urinary bladder or the cloacal absorb water. The uric acid is
stored in them in a paste like form. Nontoxic uric acid be stored in egg membranes. Thus it has made
possible the development of embryos in terrestrial environments.
Osmoregulation
There are many adaptations in reptiles to reduce water loss by evaporation. These are:
1. Their excretory system reabsorbs water.
2. They have internal respiratory surfaces.
3. They have impermeable exposed surfaces.
4. The behaviors that help regulate temperature also help conserve water.
5. Most reptiles are nocturnal. They do not come out hot day time. The burrowing at du% time reduces
water loss.
6. When water is available, many reptiles store large quantities of water in lymphatic spaces. Lymphatic
spaces are present under the skin or in the urinary bladder.
7. Many lizards possess salt glands below the eyes. These glands remove excess salt from the body.
REPRODUCTION AND DEVELOPMENT
Vertebrates have internal fertilization and the amniotic egg. It has adapted them completely on land.
The amniotic egg is not completely independent of water. Pores are present in the eggshell. They allow
the gas exchange. But it allows water to evaporate. Amniotic eggs require a large amount of energy
expenditures. This energy is provided by parents in the form of stored food. Parental care occurs in
present in some reptiles. They maintain high humidity around the eggs.
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Fertilization
Reptiles have internal fertilization. Fertilization occurs in the reproductive tract of the female. Then
protective egg membranes are formed around the eggs. All male reptiles possess an intermittent organ.
It transfers sperm into the female reproductive tract. Intermittent organs are absent in tuataras. Lizards
and snakes possess paired hemipenes at the base of the tail. Hemipenes are erected by turning inside
out, like a linger of a glove.
Gonads lie in the abdominal cavity. A pair of ducts transfers sperms into the cloaca in males. The female
may store sperms in seminal receptacle after copulation. Secretions of the seminal receptacle nourish
the sperm. Sperm may be stored for up to four years in some turtles, and up to six years in some snakes.
Sperm can be stored for winter in temperate latitudes. The individuals grouped in hibemacula in the fall
and copulation take place. Female stores sperms. Fertilization and development occur in thu spring.
Fertilization occurs in the upper regions of the oviduct. Oviduct opens into cloaca. Glandular regions of
the oviduct secrete albumen and the eggshell. The shell is tough and flexible. The egg shell is calcareous
and rigid in some crocodilians.
Parthenogenesis
Parthenogenesis occurs in six families of lizards and one species of snakes. In these species, no males are
present. Populations of parthenogenetic females have higher reproductive rate than bisexual
populations. A large population of reptiles died in the cold winter. The surviving reptiles can repopulate
rapidly in winter.
Reproductive behaviour
Reptiles have complex reproductive behaviour. Males actively seek females. Courtship behaviour helps
in sexual recognition. It is involved in physiological preparation for it production.
(a) Some males display head bobbing. These males have bright patches of color on the throat and
enlarged folds of skin.
(b) Courtship in snakes is based on tactile stimulation. The male displays tail-waving activity. It brings it
chin along the female. Then it entwines his body around her. Then male produces wavelike contractions
that pass from posterior to verior side of the body.
(c) Recent research indicates that lizards and snakes also use sex pheromones.
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(d) Voclizations are important only in crocodilians. During the breeding season, males bark or cough. It is
a territorial warning to other males. Roaring vocalizations also tract females and mating occurs in the
water.
Parental care
Most reptiles freely lay eggs. They do not care about them. Turtles bury their eggs on the ground or in
plant debris. Other reptiles lay their eggs under rocks, in debris, or in burrows. About one hundred
species of reptiles show parental care of eggs.
One example is the American alligator, Alligator mississippiensis. The female builds a nest or mud and
vegetation. It is about 1 m high and 2 m in diameter. She hollows out the cell of the mound. She partially
fills it with mud and debris. She deposits her eggs in the cavity and then covers the eggs. Temperature
within the nest influences the sex of the hatchlings. Temperature at or below 31.50 C produce females
offspring. Temperatures between 32.5 and 33° C produce male offspring. Temperatures around 32°C
result in both male and female offspring. Similar temperature effects on sex determination are found in
some lizards and many turtles. The female remains near the nest throughout the development and
protect the eggs from predation. She frees young from the egg shell. Then she picks them up in her
mouth, and transfers them into water. She forms shallow pools for the young and remain with them for
up to two years. The female feeds on small vertebrates and invertebrates and drops the food for young.
The young scraps this food.
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Reptiles SURVEY OF THE REPTILES Reptiles have Following characteristics: 1. Their skull has one surface (condyle) for articulation with the first neck vertebra. 2. Respiration takes place by lungs. 3. They have metanephric (kidney Formed From the lower part of the middle part of ancestral kidney) kidneys. 4. They have internal fertilization and amniotic eggs. 4.Reptiles have dry skin. It has keratinized epidermal scales. Keratin is a resistant protein. It is found in epidermally derived structures of amniotes. It is chemically bonded to phospholipids. Therefore, it prevents loss of water through body surfaces. 5. They are found on all continents except Antarctica. Howev