Chapter 20-Reptiles

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Class Reptilia

• Snakes, lizards, skinks, turtles, and crocodilians• Strong, bony skeleton and toes w/claws• Ectothermic metabolismEctothermic metabolism• Dry, scaly skin• Amniotic eggsAmniotic eggs• Respiration through well-developed lungs• Ventricle of heart partly divided by a septum• Internal fertilization

Ectothermic MetabolismEctothermic Metabolism

• Metabolism too slow to generate own body heat

• Intolerance to cold-become sluggish and unable to function

• Absorb heat from environment– BaskingBasking in sun to heat up– Shade to cool down– Maintain relatively constant by alternating

Sun Basking

Water Retention

• Do not lose water through skin or require water to reproduce like amphibians

• Skin -light and flexible scales

• Overlapping minimizes water loss

• Enables reptiles to live in dry environments

Overlapping Scales

Watertight Eggs

• Fertilized eggs need moisture to develop

• Internal fertilization allows for moisture to surround eggs

• Amniotic eggAmniotic egg- Tough-shelled egg containing a water and food supply– Most reptiles– All birds– Some mammals

Amniotic Eggs

Respiration

• Lungs w/many folds increase gas exchanging surface

• Strong muscles attach to rib sage aid expansion and contraction of lungs

• Incomplete septum separates ventricle of heart– Crocodilians have completely

divided ventricle

• Complete septum separates atrium of heart

• More separation of oxygen-rich and oxygen-poor blood

• Oxygen delivered to body cells more efficiently

Reptilian Heart Structure

Reproduction• Internal fertilizationInternal fertilization- Male introduces semen

directly into females body– Protects gametes from drying out

• Oviparous (most)- Young hatch from eggs– Most cases parents do not protect

• Ovoviviparous (some)- Female retains eggs in body until just before hatching; sometimes hatching occurs in mother– Eggs less vulnerable to predation

• Nourishment of eggs from yolk

Order Squamata

• Includes lizards and snakes

• Lower jaw loosely connected to skull

• Mostly carnivores; some herbivores

• Mouth opens wide to accommodate prey

• Extremely successful predators

http://video.search.yahoo.com/video/play?p=komodo+dragons&ei=UTF-8&vm=r&fr=yfp-t-501&tnr=21&vid=000164848944

Order Squamata/Suborder Sauria- Lizards

• Mostly small (<30 cm)• Largest: Kimodo dragons (<3 m)• Tail may break off to avoid

predation (regenerates w/no vertebrae)

• Molt skin periodically• Include:

– Iguanas– Chameleons– Geckos– Anoles– Horned lizards– Monitors– Skinks

http://video.search.yahoo.com/video/play?p=jesus+lizard&n=21&ei=utf-8&js=1&vm=r&fr=yfp-t-501&tnr=20&vid=000163111524

Order Squamata/Suborder Sauria- Lizards

Green Iguana Veiled chameleon Leopard Gecko

Anole Texas horned lizard Nile monitor

Order Squamata/Suborder Serpentes- Snakes

• Legless w/no eyelids nor external ears– No pectoral girdle– Five-point movement in

jaw– Elastic ligament allows

lower jaw to spread– No chewing or cutting

teeth– Ovoviviparous– 2/3 in family Colubridae

and non-venomous

Gaboon viper

Green tree python

Order Squamata/Suborder Serpentes- Snakes

• Several hundred vertebrae

• Jacobson’s Organs- Depressions in roof of mouth detect smell

• Feeding: All snakes subdue prey and swallow whole– Constrictors squeeze prey

until suffocation• Anacondas, boas, pythons,

and king snakes

Ball python

http://video.search.yahoo.com/video/play?p=constrictor&n=21&ei=utf-8&js=1&vm=r&fr=yfp-t-501&tnr=20&vid=000164319803

Order Squamata/Suborder Serpentes/Family Boidae- Constrictor Snakes

Anaconda Emerald tree boa

Banded king snake Scarlet king snake

Order Squamata/Suborder Serpentes- Snakes

• Venomous snakes

– Modified salivary glands produce venom to inject into prey with grooved or hollow teeth

– Families:

• Elapidae- Cobras, kraits, mambas, taipans, and coral snakes

• Hydrophiidae- Sea snakes

• Viperidae- Rattlesnakes, moccasins, adders, vipers and copperheads

http://vimeo.com/3263747

Order Squamata/Suborder Serpentes- Venomous Snakes

Coral snake King cobra Krait

Sea snake Puff adder Eyelash viper

Order Squamata/Suborder Serpentes- Venomous Snakes

                                        

Water mocassin (a.k.a. Cottonmouth) Copperhead

Order Squamata/Suborder Serpentes- Rattlesnakes

• Rattle- 5 to 7 rings of keratin and protein• New ring each molt• Pit organ- Openings between eye and nostril detect infrared• Venom- Hemotoxin affects red blood cells causing

hemorrhaging

Timber rattlesnake Diamondback rattlesnake

Order Squamata/Suborder Amphisbaenia- Worm Lizards

• ~ 135 species

• Amphis – double; baen – to walk

– Move easily backwards and forwards

• Burrowers

• Unique single median tooth on upper jaw

• Annuli – ring-like folds in skin

• Oviparous – Feed on worms and small insects

Order Chelonia (Testudines)- Turtles and Tortoises

• 250 species• Body encased in shell

– Bony plates covered w/leathery skin

– Vertebrae fused to dorsal– Provides support for muscles– Some for protection– Carapace- dorsal part of the

shell– Plastron- Ventral

• No teeth;powerful beak• Many herbivores; some

carnivores

Gopher tortoise

Giant tortoise

Order Chelonia (Testudines)- Turtles and Tortoises

• Turtles- Stream-lined, disk-shaped shell for water movement

• Tortoises- Dome- shaped shell

Alligator snapping turtle

Box turtle Sea turtle

Order Crocodilia- Alligators, Crocodiles, Caimans, and

Gavials• Large aggressive carnivores• Capture prey by stealth,

drowns, and eats• Eyes and nostrils on top of

head to allow for seeing and breathing while under water

• Strong neck w/large mouth (100s of sharp teeth)

• Throat valve prevents water entering into lungs

• Uniquely care for young after hatching

Caiman

Gavial

Order Crocodilia- Alligators, Crocodiles, Caimans, and

GavialsAmerican alligator Nile crocodile

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Order Rhynchocephalia- Tuataras

• Native to New Zealand

• Lizard-like• Uniquely active at low

temp./night• Unchanged for 150

million yrs.• 2 species

– Genus Sphenodon