Biology~Advanced StudiesDOL 54-55

*Reptiles

IV. Class Reptilia

A. General Characteristics1. ex: turtles, lizards, snakes, crocodiles2. dry, scaly skin

a. prevents water lossb. must shed skin as animal grows

3. breathe through lungs entire life4. sexual repro, internal fertilization

a. lay amniotic eggs w/leathery shells on land5. most orders have 4 legs

a. snakes lack legs6. bilateral symmetry

7. ectothermic

8. habitat = land &/or water, worldwide9. Oldest reptile fossils = 350 million years old

a. share common ancestor w/ dinosaurs, birdsb. Mesozoic Era = “age of dinosaurs”

1) died out in mass extinction at end of Cretaceous Period 65 million years ago

B. Reptile Anatomy and Physiology

1. Feedinga. incl. herbivores, carnivores, insectivoresb. digestive system adapted for food type

1) Snakes – may unhinge jaws to eat large prey2) Chameleon tongues are nearly as long as

their body

3) Alligators/crocs have powerful jaws & teeth

2. Respiration

a. spongy lungs w/more surface area than amphibiansb. rib muscles cause chest to expand & contract during breathing so lungs can take in airc. several croc species breathe through nostrils while

mouths are open

3. Circulation

a. closed, double-loop systemb. most have a 3-chambered heart

1) 2 atria, & a partially divided ventricle2) crocs/alligators have 4 separate chambers

*Comparison of vertebrate heart anatomy

4. Excretion

a. kidneys produce urine1) some reptiles send urine directly to cloaca2) some have a urinary bladder before the cloaca

b. aquatic forms excrete NH3

c. terrestrial forms convert NH3 to less toxic uric acid1) cloaca absorbs excess water, leaving a mostly

solid waste

a) conserves water in animal’s body

5. Response

a. brain incl. well developed cerebrum & cerebellumb. diurnal reptiles have complex eyes, see colorc. snakes may have good sense of smell

1) nostrils & Jacobson’s organ on roof of mouth detect chemicals/odors

a) flicking tongue helps draw air ind. simple ears, w/ external eardrum & inner ear

1) snakes can sense vibrations through skull bones e. some snakes can sense body heat of prey w/ pit

organs

6. Movementa. walk, swim, run, burrow, climb, slither/slide

1) those w/ legs have larger, stronger bones & muscles, support body weight better than amphibiansa) most have 5 clawed toes per foot that help

grasp & climbb. aquatic turtles may have flipper-like feetc. legless reptiles use muscular waves to propel bodies

7. Sexual reproductiona. internal fertilization, oviparous development

1) sperm deposited into female’s cloacab. fertilized amniotic eggs are laid externally

1) covered by 4 membranes & a leathery shella) amnion, yolk sac, chorion & allantoisb) also seen in birds

c. some snakes & lizards are ovoviviparous w/young born alive

d. most do not care for young1) crocodilians are an exception

C. Reptile Orders

1. Order Squamata = lizards & snakesa. over 8000 speciesb. lizards

1) legs, clawed toes, external ears, movable eyelids, scales relatively same size

2) ex: iguana, chameleon, gecko, skink3) some are venomous

a) ex: Gila monster, Mexican beaded lizard

c. snakes1) lack legs, lack external ears, immovable eyelids,

may have fangs, larger belly scales (scutes)2) ex: garter snake, king snake, python, milk snake

a) over 2000 species, over 600 are venomousb) 4 venomous types, 20 species in USc) rattlesnake, copperhead, water moccasin (cotton mouth) & coral snake

d) native to all states but Maine, Hawaii & Alaska

Venomous Snakes of KS

2. Order Crocodiliaa. part of Subclass Archosauria

1) incl. birds and extinct dinosaurs & pterosaursb. incl. largest living reptile speciesc. carnivorousd. mothers protect eggs & younge. key differences

1) Alligators – fresh water, in N./S. America, Chinaa) wide U-shaped snout; stronger jawsb) wider upper jaw, lower teeth hidden when

mouth is closedc) darker grayish-black coloringd) more docilee) avg. 14 ft. longf) lay eggs on mounds of vegetation

2) Crocodiles – brackish water, tropics worldwide

a) Narrow, V-shaped snout; less powerb) 4th bottom tooth visible when mouth is closedc) lighter olive brown coloringd) more aggressivee) avg. 19 ft. longf) lay eggs in mudg) glands on tongue to excrete salt

3) Caimans – closely related to alligators

a) native to Central & South Americab) avg. 5-7 ft. longc) narrower body w/ U-shaped snoutd) very aggressivee) strong swimmers

Broad Snouted Caiman

From top to bottom:

•American crocodile

•Spectacled caiman

•American alligator

4) Gavials – a.k.a. gharials

a) very narrow snout, smooth dorsal skin, weak legs, light & fragile skull

b) native to rivers mainly in India & Nepalc) avg. 7-10 ft. long d) fish eaterse) critically endangered

3. Order Testudinesa. turtles (water), tortoises (land) & terrapins

(land & brackish, marshy water)b. shell built into skeleton

1) dorsal = carapace, fused to vertebrae2) ventral = plastron, usually flatter3) most can pull head & legs into shell for

protection

c. very strong jaws that lack teeth w/ beak-like tipsd. many species have extremely long life spans

Turtles Tortoises Terrapins

Habitat Water;fresh or marine

Land; may be far from

water source

Land & marshy, water; may be

limited to eastern or southern US

Shell Flattened Rounded, domed Flattened

FeetFlat, webbed, flipper-like for

swimming

Blunt, stumpy for walking; front adapted to dig

Flat, webbed for swimming

Diet Plants, insects, small animals

Plants Not well studied

Examples Green Sea Turtle, Pig-nosed Turtle

Ornate Box Turtle, Galapagos Tortoise

Red-eared Slider, Diamondback

Terrapin

Pictures

4. Order Sphenodontaa. tuataras

1) only surviving members of orderb. found on islands near New Zealandc. similar shape to lizards w/ differences

1) lack external ears, have primitive scales, have 3rd “parietal eye”

a) part of brain structure sensitive to lightb) best seen until about 6 months old