PHYLUM CHORDATASUBPHYLUM

VERTEBRATA CLASS REPTILIA

Biology 11

Class Reptilia Evolved from the amphibians and soon

displaced them Were much better adapted to land

Reptilia Objectives General characteristics Body systems: reproductive, respiratory,

circulatory, nervous and skeletal 4 orders and example animals

General Characteristics

1. Amniotic egg – shelled2. Internal fertilization3. Scales or plates4. If legs – 2 pair with claws, on ventral surface5. Well developed lungs6. Partial division of ventricle7. Exothermic

Class ReptiliaCharacteristics and Advances:1. Reproduction:A) The Amniotic Egg: reptiles solved the

problem of water cased development with the amniotic egg. It allowed them to take water with them onto land for the development of the young

B) Internal fertilization was now required

Amniotic egg Shell – porous, prevents rapid water loss Chorion – lines shell, gas exchange Amnion – encloses embryo Allantois – develops from embryo; carries on

embryonic respiration and excretion Yolk sac – contains food supply

Class Reptilia2. Respiratory System: Improved lungs no longer require skin

for getting O2 - skin can now dry out Now they can cover skin with scales,

shells or leathery layers

Class Reptilia3. Circulatory system Activity levels required more oxygenated

blood - the three and a half chambered heart

The ventricle was almost completely separated so that the right side of the heart pumps to the lungs and the left to the body

BUT still some mixing!

Class Reptilia4. Nervous system: Better senses developing along with a larger

brain, better land adaptation Cerebrum and cerebellum continue to increase

in size

Class Reptilia5. Behaviours Bigger brain and internal fertilization result

in specific behaviorsMate selection behaviorsTerritoriality

This tended to increase contribution of best fit males to gene pool

Class Reptilia

6. Skeletal

Appendages grow out from ventral side of reptiles raising their body off the ground - not belly draggers

Allows for better and faster movement on land

Class ReptiliaEvolution Reptiles reached their evolutionary climax

in the Mesozoic with the dinosaurs. They were the dominant vertebrate life for

over 200 million years!

Class Reptilia Evidence suggests that

the Mesozoic ended with a bang - as a large meteorite or comet struck the Earth

This first brought on intense heat, followed by at least a ten year global winter

95% of all life went extinct during this very short time frame including the trilobites

Class Reptilia However, the Earth was changing

anyway becoming cooler, drier, and more unstable

This favored adaptations that allowed survival in these conditions

Small isolated pockets of reptiles adapted and survived the end of the Mesozoic

Modern Day Reptiles

Order Rhynchoephalia: Tuatara (Sphenodon) Order Chelonia: Turtles Order Crocodilia: Crocs and gators Order Squamata: Snakes and lizards

Order Rhynchoephalia Tuatara (Sphenodon) – only living

example Found in New Zealand Resembles large lizard Parietal eye – third eye covered

by skin; senses sun’s radiation

Order Chelonia Turtle – sea turtles

230 speciesWebbed feetSoft-shelled

(streamlines)Omnivorous

Order Chelonia Terrapin – fresh water turtles

Claws and webbed feetSymmetrical plates called scutes covering bony

under layers Top shell – carapaceBottom shell - plastron

Order Chelonia Tortoise – land turtle

Long necks, short limbsAppendages completely drawn into shell, if

not – very aggressiveNo teethTympanic membrane (poor hearing) Good sense of smellGood color visionTemperature determines sex of eggs: low

temp = males

Order Crocodilia

Only reptile with a 4 chambered heart Carnivorous Raised nostrils and eyes (so rest of

body is underwater) Valve at back of mouth prevents

water from entering lungs when mouth is open

Order CrocodiliaAlligators Crocodiles

Less aggressive More aggressive

More terrestrial More aquatic

Rectangular head Triangular head

Teeth not visible when mouth is closed

Teeth visible when mouth is closed

Definite vocalizations No definite vocalizations

Can you tell the difference between an alligator and a crocodile?

E

B

C

D

A

FCroc

Croc

Gator

Gator

GatorGator

Order Crocodilian Both Alligators and Crocodiles…

Guard nest and care for youngAs with many turtles and some

lizards – temperature of nest determines sex of young○Low temperature = females

Order Squamata – Lizards/Snakes

Moveable eyelids See color (except geckos) External ear Vocalize Live in arid climates, conserve

water by excreting uric acid (white paste that is the pre-cursor to urine)

Lizards Iguanas – horned toad True chameleons – change color in

response to light, temperature and mood; arboreal (tree dwelling); tongue longer than body

Lizards Gila Monster (aka Beaded Lizard) – only

poisonous lizard known to the world Native to the desert southwest of the US and MexicoPoison is found in saliva… no fangs!The poison is a nerve toxin, that is produced in

glands located in the lower jaw. When a Gila Monster bites an animal, the poison flows into the wound via grooved teeth. This poison only rarely kills people.

Gila Monster

Beaded Lizard

Lizards Gecko (Geico?) – most primitive; pads

on toes to cling; makes noises, insectivores, eye has vertical pupil to see at night

Lizards Monitor – Komodo Dragon is largest = 10 feet

FYI: The Komodo Dragon is not venomous or poisonous; however, its saliva contains a number of toxic strains of bacteria which often infect the wounds inflicted on its prey, causing death.

Snakes Loss of limbs and external ears Evolved from lizards Most numerous reptile 2,800 species (300 poisonous)

Snake Feeding Carnivorous Kills via: Poison or constriction Swallow food whole

Jaw comes unhingedElastic ligamentsGlottis moves forward (so can breathe while

swallowing)Large esophagusNo sternumStrong stomach acid

SnakesNon-Poisonous: Garter snake Black snake King snake Boa constrictor

Poisonous: Vipers

Rattlesnakes, copperheads, adder

Elapsids (cause swelling of lymph nodes) Cobras, coral, kraits

RattlesnakeGarter

Non-Poisonous

Boa

Black

KingGarter

Poisonous Snakes

Copperhead

Puff Adder

Rattlesnake

Cobra

Coral Snake

Krait

Snake Venom

Snake Venom Neurotoxin – affect nervous system Hemotoxin or hemmoragin – affects red

blood cells All contain both types, the amounts of

each may differ Danger is in the amount and concentration

of injected venom and where its injected:In blood vessel… spread fastIn muscle or fat… spread slow

Top Ten Most Deadly Snakes1) Fierce Snake or Inland Taipan (Oxyuranus microlepidotus),

Australia. 2) Australian Brown Snake (Pseudonaja textilis), Australia. 3) Malayan Krait (Bungarus candidus), Southeast Asia and

Indonesia. 4) Taipan (Oxyuranus scutellatus), Australia. 5) Tiger Snake (Notechis scutatus), Australia.. 6) Beaked Sea Snake (Enhydrina schistosa), South Asian waters

Arabian Sea to Coral Sea.7) Saw Scaled Viper (Echis carinatus), Middle East Asia. 8) Coral Snake (Micrurus fulvius), North America. 9) Boomslang (Dispholidus typus), Africa. 10) Death Adder (Acanthophis antarcticus), Australia and New

Guinea.