Reptiles: The First Amniotes

Amniotic egg

• Have embryonic membranes that protect the embryo from desiccation, cushion the embryo, promote gas transfer and store waste materials

• Have leathery or hard shells that protect the embryo, albumen that cushions and provides moisture and nutrients fro the embryo, has a yolk that supplies food to the embryo

• Distinguishes the reptiles, birds and mammals from other vertebrates

Amniotic egg• Amnion: encloses the embryo in a fluid filled sac and

protects against shock and desiccation• Chorion: aids in gas exchange• Allantois: stores N-waste• Yolk: embryo develops at the surface

7 examples of reptiles

Subclass #1: Anapsida

• Turtles represent this lineage• Form of their skull and shell is recognizable

in 200-million year old fossils and as far back as 245 million year old rocks in South Africa

Galapagos Tortoise• Vulnerable• Can be up to 880 lbs and 6

ft long• Can live up to 100 yrs in

the wild and 170 yrs in captivity

• #s are decreasing due to hunting, habitat destruction and the introduction of non-native species

Subclass #2: Diapsida• Include modern snakes, lizards and tuataras

(Lepidosauromorpha)• Archosauromorpha (a subgroup) includes dinosaurs and

most are extinct• Archosaurs: Include crocodilians and birds (dinosaurs

closest living relatives)

Subclass #3: Synapsida

• No members of this group survive today• Important because therapsids (a group of

synapsids) gave rise to the mammals

Characteristics of reptiles

• Dry skin with keratinized epidermal scales• Keratin is a resisitant protein used for

protectiveness and prevents water loss• Live on all continents except Antartica

Order Testudines

• Turtles• 300 species of turtles• Have long life spans• Large tortoises may live in excess of 100

years• Tortoises are entirely terrestial

Order Testudines• All turtles are oviparous (lay eggs that develop outside of

the body)• Females use their hindlimbs to excavate nests in the soil• They lay and cover with soil clutches of 5 to 100 eggs• Development takes 4 weeks to a year and the parent does

not attend to the eggs during the time

Snapping turtle• One of the largest freshwater

turtles• Makes a hissing sound when in

danger or feels threatened• Has a powerful jaw and a

highly mobile head• Live up to 47 yrs in captivity

and up to 30 years in the wild• Omnivores• Live in shallow ponds, lakes

and streams• A popular ingredient in turtle

soup

Alligator snapping turtle• Vulnerable• Largest freshwater turtle

in North America• Can be up to 249 lbs • Average is 175 lbs and 26

in in length• http://dsc.discovery.com/v

ideos/dirty-jobs-snappy-snapping-turtles.html

Sea Turtles• Endangered• Marine reptiles• Found everywhere

except in the Artic• Almost always

submerged so they have an anaerobic system for breathing

• Hawksbill sea turtle

Sea Turtle continued• Have large lungs so they

can have rapid gas exchange

• Emerge from the water to breed

• The female will lay eggs under the sand

• The temp of the sand determines the gender of the offspring

• Green sea turtle

More sea turtles

• The lighter the sand, the increase of temperature, the lower the incubation time females

• Immune to the sting of the box jellyfish

• Flatback sea turtle

Lights, Camera, Sea Turtles• http://video.nationalgeogr

aphic.com/video/player/news/animals-news/leatherback-sea-turtle-buoyancy-vin.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/turtles-and-tortoises/crittercam-leatherback-turtle.html

More Sea Turtle videos• http://video.nationalgeogr

aphic.com/video/player/animals/reptiles-animals/turtles-and-tortoises/loggerhead-turtle-predation.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/turtles-and-tortoises/crittercam-black-turtle.html

More sea turtles• http://video.nationalgeogr

aphic.com/video/player/animals/reptiles-animals/turtles-and-tortoises/turtles-baby-predation.html

• http://video.nationalgeographic.com/video/player/news/animals-news/us-oil-spill-turtle-relocation-vin.html

American Boxing turtles

• Usually kept as pets• Can live up to 50

years• Omnivores• Dig holes to winter in• Eat invertebrates and

vegetation

Turtles vs. Tortoises

• Webbed feet with long claws• Found in Africa & America• Flat shells• Dwells in water• 20-40 years• Kept as pets

• Short and sturdy feet with bent legs• Found in asia and africa• Large dome shells• Dwells on land• 80-150 years• Not kept as pets

Turtles vs. tortoises

Carapace, plastron

Carapace: the dorsal portion of the shell, keratin cover the bones of the carapace

Plastron: the ventral portion of the shell, keratin cover the bones of the plastron

Alligator facts• Transparent third eyelid gives underwater protection. • 80 teeth; 40 top, 40 bottom • Teeth are conical; used for grabbing and holding, not for cutting. • Young alligators can replace teeth every year or so. • Mother 'gators will care for their young for up to two years. • Use feet to swim slow and to keep balance in water; use tail to swim

fast • 4-chambered heart • Integumentary sense organs on jaws, nose, around eyes and on upper

palate • Egg tooth; a toughened bit of epidermis on the tip of a hatchling’s

nose, which allows it to break out of its egg; it is absorbed a few weeks after hatching

Alligator vs. Crocodile

• Hibernate• Males up to 14 ft• More docile• Rounded snout• Show fewer teeth when the mouth is closed• Fresh water• Grayish black

• Don’t hibernate• Males 19+ ft• More aggressive• Pointed snout• Show more teeth when the mouth is closed• Brackish water• Light tan to brown

Alligators vs. Crocodiles

Order Sphenodonitda• Tuaturas• Superficially unchanged from their extinct relatives that

were present at the beginning of the Mesozoic era• Present only on remote offshore islands and are protected

by New Zealand law• Feed on insects or occasionally small invertebrates at dusk

and dawn

Order Squamata• Ovipoarous: organism lays eggs that develop outside the

body of the female• Ovoviviparous: organisms lay eggs that develop within the

female reproductive tract and that are nourished by food stored in the egg

• Viviparous: organisms with eggs that develop within the female reproductive tract and are nourished by the female

Order SquamataSuborder Sauria: The lizards

• Usually have 2 pairs of legs• Vary from a few cm to 3 m• Geckos: short and stout/ nocturnal/ adapted

for night vision/ have adhesive disks to aid in clinging to trees and walls

Order SquamataSuborder Sauria-iguanias

• Robust bodies, short necks, and distinct heads

• Marine iguanas in the Galapagos and the flying dragons of Southeast Asia

Flying Dragon

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/lizards/flying_reptiles.html

Chameleons• Live mainly in Africa and India• Adapted to aboreal lifestyles• Use a long, sticky tongues to capture insects• Can change color in response to illumination, temperature

or their behavioral state

Gila monsters

• Gila monsters and the Mexican beaded lizard are the only venomous lizards

• Venom is released into grooves on the surface of teeth and introduced into prey as the lizard chews

Suborder Serpentes—The snakes

• About 2900 species• About 300 species are venomous• Most are oviparous• Upper and lower jaws are loosely joined so

that each half can move independently of each other

King Cobras

• World’s longest venomous snakes

• Can be up to 18.5 feet and 13 pounds

• Skin: olive green, tan or black

• Cream belly and smooth scales

King cobras

• Can live up to 20 years

• Use their forked tongue to pick up the scent of prey then finds its location by flicked its tongue and using its eye sight

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/cobra-vs-mongoose-predation.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/cobra_eatsratsnake.html

More king cobras• Cobra swallows its prey

whole• Venom can kill a healthy

human in 30-45 minutes• Reproduction: female

builds a nest to incubate its eggs (20-40) when they are about to hatch the female leaves and gets prey so that it is not tempted to eat the young

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/cobra_reproduction.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/lizards/cobra_repelsmonitorlizard.html

King Cobras

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/cobra_babyhunt.html

Garter Snake• Most widely distributed snake

in North America• Meat eaters• Follow pheremone scented

trails to find other snakes• Reproduction: stop eating for 2

weeks before mating, the female attracts male with pheremones, the female can store the males sperm for years, the young incubate in the lower abdomen and snakes give birth to live young, 3-80 are born at a time

Sidewinder rattlesnake

• Venomous• Move in a J-shape• Nocturnal in the hot

months• Diurnal all the rest of

the year• Homeothermy when

first born

Sidewinder

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/snake_rattle_mating.html

Boas

• Example: anaconda– Large nonvenomous

snakes– Aquatichttp://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/mouse_escapingfromboa.html

Anacondas

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/anaconda_stalkscapybara.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/anaconda_bitesman.html

pythons

• Nonvenomous snakes• Ambush predators• Constrictors• Lay eggs

Vipers

• Venomous snakes• Long hinged fangs

which are used to inject venom into their prey

• Nocturnal• Ambush• Give birth to young

Snake videos

• http://video.nationalgeographic.com/video/player/animals/mammals-animals/otters-and-meerkats/meerkat_challengingadder.html

• http://video.nationalgeographic.com/video/player/animals/mammals-animals/otters-and-meerkats/meerkat_challengingadder.html

• http://video.nationalgeographic.com/video/player/animals/reptiles-animals/snakes/cobra_reproduction.html

Suborder Amphisbaenia—Worm Lizards

• About 135 species• Specialized burrowers that live in soils in Africa, South

America, the Caribbean and the Mideast• Legless and their skulls are shovel shaped• Feed on worms and small insects and are oviparous

Tyrannosaurus Rex• Found in western north

America• 67 to 65.5 million years

ago• Bipedal carnivore• 42 ft in length and 68

metric tons• Skulls up to 5 ft in length• Endothermic• Could eat 500 pounds of

meat in one bite

Maiasaurs• Live in herds• Bipedal or quadpedal• Herbivores• 3-4 tons• Eats 200 lbs of food per

day• 25-30 feet• Duck billed • Lived 74 million years

ago• Found in what is now

Montana

Eoraptor

• Small meat eater• 231 million years ago• 22 pounds and 3 feet

long• omnivore

Seismosaurus

• 110 feet long• 154-144 million years

ago• Walked on 4 legs• Found in New Mexica• “earth shaking lizard”

Triceratops

• 65 million years ago• Herbivore• 3 horns

Veloceraptors

• Bipedal carnivore• 75-71 million years

ago

Troodon

• 75 – 65 million years ago

• “Wondering tooth”• 6.5 feet in length• 130 pounds• Found in Wyoming,

Texas, New Mexico

Ankylosaurus

• 13,000 pounds• Armoured• 30 feet• 66-65 million years

ago

Microraptor

• 2.2 pounds• 40 cm long• 4 winged

Reptile skinNo respiratory functionsThick, dry and keratinized

EcdysisThe shedding of the reptilian skinGenerally begins in the head region and is shed in one pieceFrequency of ecdysis varies from one species to another

ChromatophoresFunction in sex recognition and thermoregulation

Support and Movement

Secondary palate• Partially separates the nasal

passage from the mouth cavity.

• An adaptation for breathing when the mouth is full of food or water

• Longer snouts allow for a greater sense of smell

Secondary palate

Support and Movement

Reptile Vertebrae• First two cervical vertebrae

provide greater movement for the head and facilitates nodding

• A variable number of other cervical vertebrae provide additional neck flexibility

Reptile Vertebrae

Support and movement

Ribs• Highly modified• Ribs of snakes have

muscular connections to the large belly scales to aid locomotion

Ribs

Support and Movement

• Tail loss• When lizards are grasped by the tail, caudal

vertebrae can be broken and a portion of the tail is lost

• The lizard can later regenerate the lost portion of the tail

• Autonomy

Locomotion in reptiles

• In primitive reptiles, the body is slung low between paired, stocky appendages

• The limbs of other reptiles are more elongate and slender and are held closer to the body

• Many prehistoric reptiles were bipedal• http://www.arkive.org/smooth-snake/

coronella-austriaca/video-06.html

locomotion

• http://arkive.org/galapagos-giant-tortoise/geochelone-spp/video-00.html

Digestion and nutrition

• http://www.arkive.org/parsons-chameleon/calumma-parsonii/video-08b.html

Digestion and nutrition

• Most reptiles are carnivores• The tongues of turtles aid in swallowing• Some lizards and the tuatara have sticky tongues

for capturing prey• The tongue extension of chameleons exceeds their

body length• The bones of the upper jaw are movable in the

skull of the snake and ligaments loosely join the halves of the jaw so they can move independently of each other

Feeding vipers

Possess hollow fangs in the upper jawThe fangs connect to venom glands that inject venom when the viper bitesMay strike organisms of any size

Rear-fanged snakes

Possess grooved rear teethVenom is channeled into the grooves and worked into the prey to silence them during swallowingUsually do not strike

Venom GlandsModified salivary glandsMixtures of neurotoxins and hemotoxinsNeurotoxins: Attack nerve centers and cause respiratory paralysisHemotoxins: break up blood cells and attack blood vessel linings

Snake venoms and treatment for it

• The best treatment for a venomous snake bite is the get to the emergency room immediately

Circulatory system in reptiles

• Based on the same as the amphibians• The blood must move under higher

pressures to reach distant body parts since they are larger then amphibians

Gas Exchange

• Reptiles exchange gases across internal respiratory surfaces to avoid losing large quantities of water

• A larynx is present but no vocal cords• Lung chambers provide a large surface area

for gas exchange

Lung ventilation

• Ribs move and the body wall expands the body cavity decreasing the pressure in the lungs drawing air into the lungs

• Air is expelled by elastic recoil of the lungs and forward movement of the ribs and the body wall which compress the lungs

• Turtles exhale and inhale by contracting their lungs

Temperature regulation

• Most use external sources to regulate their body temps so they are ectotherm

• Lizards: to warm themselves it orients themselves at a right angle to the sun’s rays, burrows, etc. to reduce the conduction from warm surfaces…in hot climate they are nocturnal

• Chromatophores can regulate body temp• Enter into torpor to decrease metabolic rates

Temperature regualtion

Hibernacula

• A common site of hibernation for organisms that are usually solitary but hibernate in the winter together

• Body temp is not regulated• If winter is too cold, the reptile can freeze

and die

Nervous system

• Larger then amphibians due to an improved sense of smell

• Optics lobes and cerebellum are enlarged due to a reliance on vision and coordinated muscle functions

Chameleons and binocular vision

• Eyes swivel independently of each other

• Initially images are kept separate but when the prey is seen then they see is as one image

Reptilian eyes

• Reptiles rely heavily on their sense of sight

• The have many cones in their eyes so they probably have well-developed colored vision

• Median eye can be used for differentiation of light and dark and used for orientation to the sun

Reptile ears

• Ears of snakes detect vibrations

• Snakes can detect airborne vibrations

Excretion and Osmoregulation

• Require kidneys capable of processing wastes with little water loss

• Excrete uric acid• Urinary bladder reabsorb water• Can store large quantities of water in

lymphatic spaces under the skin or in the urinary bladder

• Possess salt glands below the eyes for ridding the body of excess salt

Reproduction

• Internal fertilization• Sperm may be stored for up to 4 yrs in

some turtles and up to 6 yrs in some snakes• Parthogenesis: no males have been found, a

form of asexual reproduction• Courtship: head bobbing reveals bright

colors on the throat, tail-waving displays

courtships

• Vocalization is only important in crocodiles• American alligators: if nest occurs at or

below 31.5 degrees then the result is a female and if the temps are between 32.5 and 33 then a male is the result