Amphibians and Reptiles

Ron ChakrabartyMark Juhn

Daniel MontgomeryAndrew Tung

AmphibiansFamily Amphibia

Amphibians – General/Unique CharacteristicsMoist, glandular skin with no scales

Feet lack claws and are often webbed

Possession of gills at some point in its lifeLack of amnion in the egg

Embryonic membrane and surrounds and protects the embryo

Amphibians - EvolutionFirst vertebrates to begin exploring

terrestrial landEarliest fossil found about 400 million years Most likely evolved from fishAir bladder mutated/adapted to lungsFins evolved into limbs?

To give stronger support

Amphibians – Classification into Orders There are three different orders for an

amphibian Anura – 4200 species of frogs and toads Urodela – 430 species of newts and

salamanders Gymniophiona – 165 known species of

caecilians

Amphibians - AnuraConsists of frogs and toadsHave tails as tadpoles, but lack tails as adultsLong hind legs for jumping and swimmingLive mostly in freshwater, but some live in drier

habitatsCommon Anurans – bullfrog, spring peeper, American

toad, spade-foot toadThe difference between a frog and a toad is that toads

have shorter legs, drier skin, and more warts than frogs.

Length – 1 to 12 inchesEat mainly insects and small invertebrates

Amphibians – Urodeles – also called CaudataConsist of newts and salamandersHave long tails and small, underdeveloped

feet.Includes the largest amphibian in the world –

the Giant Salamander lives in Japan and can be up to 5 feet long.

Live near water or in moist soilEat insects and some smaller invertebratesIncludes one genus that is shaped like an eel

– no legs or pelvis and has gills and lungs

Amphibians - GymniophionaConsists of caecilians

Small, worm-shaped amphibiansBlindLegless

Only 165 species known because some are so small

Largest caecilian is 4.5 feet long

Amphibians - SymmetryAmphibians have bilateral symmetry

They can be divided into identical halves across exactly one plane

CephalizedConcentration of brain cells near the anterior

end of the amphibian

Amphibians – Body cavityAll amphibians are coelomates

All have a true coelom A coelom is a hollow, fluid-filled body cavity that is

lined both internally and externally by mesoderm. Provides support for the chest

Amphibians – Structural SupportSkeleton - General

Vertebrae – form a backboneLimbs – support while walking or standing

Pectoral girdle – shoulder and supporting bones from front limbs

Pelvic girdle – “hips” from back limbsCervical vertebra – neck movement

Amphibians – SkeletonFrogs – specialized bones in skeleton,

different from other amphibiansRadio-ulna – “forearm”Tibiofibula – “calf”Phalanges – fingers adapted for jumping – on

all four limbsBones are generally thicker (for impact when

landing)

Amphibians – SkinServes as method of respiration and as a

method of protectionMakes them more affected by pollution –

chemicals can diffuse into the bodyHealth of amphibians in one habitat represents

the condition of their environment

Amphibians - RespirationLarvae have gills

Allow oxygen into the organism when it is underwater

Larvae undergoes metamorphosis Gills disappear and lungs are made

Amphibians - RespirationAdult amphibians can breathe through their

skin and lungs.Pulmonary respiration (breathing through

lungs) – takes in air through nostrils and mouth Adult frogs have to voluntarily force air down

their throats (buccal pumping) because they lack a diaphragm, and this is why they mainly use cutaneous respiration.

Amphibians - RespirationCutaneous respiration (breathing through skin) –

many amphibians use this type of respiration as their main type of breathing and use their lungs as backupSkin is moist and permeable

Allows diffusion of oxygen, water, and carbon dioxideHowever, this makes amphibians vulnerable to

dehydration

Amphibians – Transportation and CirculationAmphibians have a three-chambered heartCirculatory system has two loops

Pulmonary circulation Carries deoxygenated blood to lungs from heart

Moves through contraction of atriumSystemic circulation

Oxygenated blood from heart to rest of body

Amphibians – Transportation and CirculationBlood in heart

Deoxygenated blood enters right atriumPulmonary veins carry oxygenated blood from

lungs to left atriumOxygenated and deoxygenated blood mix in

ventricleVentricle pumps blood to lungs

All known as the “double-loop” system

Amphibians – Digestive SystemAll adults are carnivorous

Many larva are herbivorous Frogs

Other larva are carnivorous Salamander

Amphibians - Digestive SystemPharynx – opens into the esophagusEsophagus – elastic tube that brings food down from

the pharynx to the stomachAllows amphibian to swallow large amounts of food

Stomach – has tiny glands that secrete gastric juicesDigests/breaks down food

Small intestine – Digestion is completedDuodenum – upper portionIleum – coiled middle portion of small intestine

Mesentery – holds small intestine in place

Large Intestine – Holds waste

Amphibians – ExcretionSmall intestine empties into the large

intestineIndigestible waste is collected

Processed by kidneysPushed into cloaca

Waste from kidneys, urinary bladder, eggs and sperm pass through cloaca

Waste exits through vent

Amphibians – Water BalanceAmphibians skin is permeable

Water and nutrients can come in through the skin

However, this also makes it more vulnerable to dehydration because water can diffuse out of their skin in dry environments Therefore, amphibians must live in wet

environments Many are active only at night when water loss is

minimized

Amphibians – Water BalanceUrine

Flows from kidneys to cloaca through urinary ductsGoes to urinary bladder

Water-storing organ

Amphibian larva excrete nitrogen compounds as ammoniaVery toxic, so must be excreted quickly or diluted

with waterTo conserve water, adults instead transform

ammonia into urea Less toxic Excreted with less water although uses energy

Amphibians – ReproductionFrogs come out of hibernation in the first

days of springMigrate to ponds and streams, where males

attract females by using vocal sacs Females only respond to frogs of the same species

When females come, males climb onto their backs and “hug” them – called amplexus – until eggs are laid through the vent .Into the water for most amphibiansWhen eggs are laid, males discharge sperm

onto the eggs – direct external fertilization

Amphibians – Reproductive SystemMales

Sperm cells develop in the testesGoes to urinary tract during mating season

FemaleEggs develop in the ovariesEggs enlarge, mature, and move to the body

cavity during breeding season Leave female through oviducts and are coated with

a protective slime

Amphibians - DevelopmentTadpoles hatch within a few days and develop

gillsEventually, a mouth opensGoes through metamorphosis – Changes from an

aquatic larva to an adult Legs Lungs Teeth Tail disappears

Metamorphosis happens because of thyroxine Produced in thyroid, circulates through blood,

stimulates metamorphosis

Amphibians – DevelopmentAlternative reproductive patterns

Some amphibians lay eggs in a warmer environment Under a rock, in a log, in a tree Some frogs build a nest

Made out of mucus, whipped into a frothy material by kicking it rapidly

Some do not go through metamorphosis Salamanders that remain in the larval stage for

their whole life No thyroxine produced

Some do not go through the larval stage Hatch from eggs as small version of adult

Amphibians – Nervous SystemTympanic Membrane – eardrumColumella – bone that transmits sounds from

the eardrum to the inner earOlfactory Lobes – sense of smellOptic Lobes - sight

Amphibians – Nervous SystemBrain

Same size as fishCerebrum – responsible for learningCerebellum – muscle coordination

Nerves extend directly from brain to body, protected by spinal cord

Lateral line – detect vibrations in waterLost during metamorphosis

ReptilesFamily Reptilia

Evolved from amphibians Oldest known reptiles date back to early

carboniferous period (359- 299 m.y.a)Small, four-leggedAte insectsLived in dry climates

History

Evolved from thecodonts. Success

Legs placed under bodyAdapted to dry climatesMass extinction

Dinosaurs

ExtinctionAsteroid Impact Hypothesis

Huge asteroid hit Yucatán PeninsulaDust cloudSupported by high amount of iridium in

sedimentsMultiple Impact Hypothesis

Bad environmental conditionsMany asteroid impacts

Dinosaurs

Reptiles – Structural Support/ Body Cavity/SymmetrySymmetry- Bilateral Body Cavity- ColoemStructural Support- Endoskeleton

Have breast bone to guard lungs and heart

Reptiles - RespirationHave large lungs for gas exchangeLunges divided into chambersAlveoli- small sacs that are created by the

folding of the lungs. (more oxygen)Snakes

Only right lung functions, as big as half the length of body

Left is nonfunctional or gone

Reptiles - RespirationLungs are filled by expanding rib cageRibs contract to normal and air is released

from lungsSimilar to human respiration

Reptiles - Water Balance/ExcretionRespiratory and excretion systems help

reptiles conserve waterAll tissues for respiration are internal to keep

moistureLand reptiles give of nitrogenous waste in the

form of uric acidReptiles lose little water in urine

Reptiles – Water Balance/ExcretionRespiratory and excretion systems help

reptiles conserve waterAll tissues for respiration are internal to keep

moistureLand reptiles give of nitrogenous waste in the

form of uric acidReptiles lose little a water in urine

Reptiles - ClassificationClassified into four orders

Chelonia – Turtles and tortoisesCrocodilia – Alligators and crocodilesSquamata – Lizards and snakesRhynchocephalia - tuataras

Reptiles - Chelonia 250 species of turtles and tortoisesTortoise- TerrestrialTurtle- AquaticAncient chelonians- like modern turtles and tortoises Turtle design

Body enveloped in a shell Carapace- Dorsal of the shellPlastrons- Underside of shellRibs attached to inner carapacePelvic and pectoral girdles- inside ribs Sharp beak

Tortoise designDomed carapace

defense from predators limbs covered in thick scales

Order Chelonia

Chelonia mydas(green sea turtle)

Reptiles - CheloniaHabitats

Some always terrestrial or aquatic, some live in both Shells and limbs- adapted to different habitats

Aquatic turtles- streamlined, disk-shaped shell for turning and webbed feet

Limbs are flippers for swimming

ReproductionOffspring born through eggsFemale finds a location, makes a hole, puts eggs in

it, covers nestLeaves young alone to hatch

CrocodilesClosest related to dinosaurs Heavy-bodied and aquaticHave a valve at the back of the throat

Prevents water from entering the air passage

Crocodilia

Crocodylus rhombifer(Cuban Crocodile)

Reptiles - SquamataLizards

Eat insectsSome plants

Predator Protection Agility, speed, and camouflage Autotomy

Reptiles - SquamataSnakes

No legs Ancestors lived in thick vegetation, legs slowed

themBackbone of 100 to 400 vertebrae

Ribs attached Framework for muscles

Muscles affect skin, scales enlarge and contract which moves snake

Kill by constriction or injecting venom

Notechis scutatus(Tiger Snake)

(Elapid)

Bitis gabonica(Gaboon Viper Snake)

Dispholidus typus(Boomslang Snake)

(grooved teeth in the back of the mouth)

Boa constrictor

Reptiles - RhynchocephaliaAncient, only Tuataras from genus

SphenodonTuatara means spiny crestLive only on New ZealandBurrow during the day and eat small insects,

worms, and animals during the night.

Sphenodon Punctatus(Tuataras)

Reptiles – Transportation and CirculationTwo circulatory loops

Pulmonary loop Carries deoxygenated blood from the heart to the

lungsSystematic loop

Carries oxygenated blood from the heart to the tissues

Carries deoxygenated blood back to the heart

Two atria, two ventricles or one divided by the septum

Reptiles – Transportation and CirculationHigh flexibility in a reptilian heartPulmonary arteries can restrict

Skips lungs. Deoxygenated bloodbodySome take blood from lungs for energy

conservationReptiles stop breathing when inactive

When active, blood goes to lungs, and more oxygen goes to the muscles

Reptiles – Nutrition and DigestionMouth, tongue, teeth, esophagus, stomach,

and rectum Simple digestive tract

Moderately sized gut Don’t chew food like mammalsSome herbivorous reptiles swallow rocks

called gastrolithes to help digestionReptiles- Most acidic digestion system of any

animal

Reptiles – Water Balance/ExcretionTwo kidneysReptiles use the colon to reabsorb waterLand reptiles remove nitrogenous waste in

uric acidLittle water lost

Some reptiles can get rid of salt with salt glands and nasal areas

Reptiles – Nervous SystemBrain size= an amphibian

Cerebrum is largerGood vision

Large optic lobesHearing

Sound waves hit tympanic membrane (eardrum)

Columella moves and takes sound to the inner ear

Recognized in inner ear by receptors

Jacobson’s organOn roof of mouthSenses odorsPit vipers

Detect warm-blooded prey body heat Heat-sensitive pit under eyes

Detects position of the prey

Nervous System Cont.

Reptiles – Reproductive SystemThree patterns

OviparityOvoviviparityViviparity

Differ in length of time eggs are in the female and the nutrition given

Reptiles – Reproductive SystemOviparity

Female reproductive tract puts shell on egg Egg placed in an optimal place

Ovoviparity Eggs stay in female body Right before hatching-eggs are laid

Or hatch in the female

Reptiles – Reproductive SystemViviparity

No shellStays in female body until bornPlacenta give nutrients and oxygen

motherembryo Placenta formed from egg membranes

Reptiles – Reproductive SystemMany mothers don’t care for eggs or

offspringSome lizards and snakes protect and keep eggs

warm until hatchingMost care- Crocodiles and alligators

Female crocodile builds a nestCarries offspring in mouth to water

The End(Works Cited on next page)

Amphibians and ReptilesWorks Cited

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http://www.mcwdn.org/Animals/Reptile.html Lerner, Lee. "Amphibians." The Gale Encyclopedia of Science 2008: 189-191.

Gale Virtual Reference Library. Gale. Vernon Hills High School. 23 Mar 2009 <http://go.galegroup.com/>.

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W. Ben Cash, Richard G. Zweifel, T. R. Smithson, "Amphibia", in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.029600