AmphibiansAmphibians

Amphibian Evolution:Amphibian Evolution: Arose from lobe-fined ancestor called Arose from lobe-fined ancestor called

CrossopterygiansCrossopterygians Land plants & insects provided Land plants & insects provided new food new food

sourcesource Had primitive lungs & short, limb like fins Had primitive lungs & short, limb like fins

for short periods on land for short periods on land Appeared during late Devonian Appeared during late Devonian Icthyostega Icthyostega early amphibian with 4 limbs, early amphibian with 4 limbs,

lungs, & a tail for swimminglungs, & a tail for swimming

IcthyostegaIcthyostega

Well developed limbs (*showed Well developed limbs (*showed adaptations for life on land but probably adaptations for life on land but probably spent most of their time in water)spent most of their time in water)

Large tail finLarge tail fin Lateral line canals on headLateral line canals on head Large sharp teeth, indicating a diet of fishLarge sharp teeth, indicating a diet of fish

IcthyostegaIcthyostega

Adaptations:Adaptations: MetamorphosisMetamorphosis Moist, thin skin with no scales (the structure of Moist, thin skin with no scales (the structure of

amphibian skin indicates the habitats in which they can amphibian skin indicates the habitats in which they can survive)survive)

Most use gills, lungs, and skin in respiration Most use gills, lungs, and skin in respiration Feet, if present, lack claws and are often webbedFeet, if present, lack claws and are often webbed Both Both internal & external naresinternal & external nares (nostrils) (nostrils) Three chambered heart Three chambered heart (two atria & one ventricle) (two atria & one ventricle) Double loop blood circulation to lungs & rest of body Double loop blood circulation to lungs & rest of body

cellscells Eggs lack multicellular membranes or shells. Eggs lack multicellular membranes or shells. They are usually laid in water or in moist places and are They are usually laid in water or in moist places and are

usually fertilized externallyusually fertilized externally

Double loop blood Double loop blood circulationcirculation

Adaptations: cont…Adaptations: cont… Skin with Skin with keratinkeratin (protein) to prevent water loss (protein) to prevent water loss NecksNecks to more easily see & feed to more easily see & feed Most with Most with smooth, moist skin smooth, moist skin to take in dissolved to take in dissolved

oxygen oxygen Some with Some with oral glandsoral glands to moisten food they eat to moisten food they eat Webbed toesWebbed toes without claws without claws Ectothermic Ectothermic - body temperature changes with - body temperature changes with

environment environment Show dormancy or Show dormancy or torportorpor (state of inactivity during (state of inactivity during

unfavorable environmental conditions) unfavorable environmental conditions) HibernateHibernate in winter and in winter and aestivateaestivate in summer in summer Aquatic larva called Aquatic larva called tadpoletadpole goes through goes through

metamorphosismetamorphosis to adult Metamorphosis controlled by to adult Metamorphosis controlled by hormone called hormone called thyroxinethyroxine

Adaptations: cont…Adaptations: cont… External fertilization with External fertilization with amplexusamplexus (male clasps (male clasps

back of female as sperm & eggs deposited into back of female as sperm & eggs deposited into water) water)

Eggs coated with sticky, jelly like materialEggs coated with sticky, jelly like material so so they attach to objects in water & do not float they attach to objects in water & do not float away away

Eggs hatch into tadpoles in about 12 days. Eggs hatch into tadpoles in about 12 days. Males with vocal sacs to croak Males with vocal sacs to croak Digested system adapted to swallow prey Digested system adapted to swallow prey

whole whole Well developed muscular systemWell developed muscular system

Classification:Classification:

Anura Anura - frogs & toads - frogs & toads UrodelaUrodela - salamanders & newts - salamanders & newts ApodaApoda - caecilians - caecilians Trachystoma Trachystoma - sirens or mud eels - sirens or mud eels

Anuran Characteristics:Anuran Characteristics: Both Both terrestrial & freshwaterterrestrial & freshwater species species TadpoleTadpole with tail, gills, & two-chambered with tail, gills, & two-chambered

heart heart Adults without a tailAdults without a tail, four limbs, & lungs , four limbs, & lungs Frog skin smooth & moist for Frog skin smooth & moist for

cutaneous respirationcutaneous respiration, while , while toads is toads is rough & wartyrough & warty (poison glands) (poison glands)

Long hind limbsLong hind limbs for jumping for jumping Long, Long, forked tongue hinged at front of forked tongue hinged at front of

mouthmouth

Anuran Characteristics:Anuran Characteristics:

Urodela Characteristics:Urodela Characteristics:

Includes Includes salamanders & newtssalamanders & newts Have Have elongated bodies with a tail & elongated bodies with a tail &

four limbs four limbs  Smooth, moist skinSmooth, moist skin for cutaneous for cutaneous

respiration respiration Less able to stay on dry landLess able to stay on dry land than than

anurans anurans

Urodela Characteristics:Urodela Characteristics: Size from a Size from a few centimeters long to 1.5 few centimeters long to 1.5

metersmeters Nocturnal when live in drier areasNocturnal when live in drier areas NewtsNewts are aquatic species are aquatic species Lay Lay eggs in water or damp soileggs in water or damp soil Some bear live young Some bear live young May or may not go through tadpole May or may not go through tadpole

stagestage (some hatch & look like small adult) (some hatch & look like small adult)

Urodela Characteristics:Urodela Characteristics:

Apodan Characteristics:Apodan Characteristics:

Includes Includes caecilianscaecilians Tropical, burrowing,Tropical, burrowing, worm likeworm like amphibians amphibians Legless Legless Small eyes & often blindSmall eyes & often blind Eat worms & other invertebrates Eat worms & other invertebrates Average length 30 centimetersAverage length 30 centimeters, but can grow , but can grow

up to 1.3 meters up to 1.3 meters internal fertilization internal fertilization Female bear live young Female bear live young

Apodan Characteristics:Apodan Characteristics:

Trachystoma Characteristics:Trachystoma Characteristics:

Includes Includes mud eels or sirensmud eels or sirens Known as Known as "rough mouth""rough mouth" amphibians amphibians Found in Found in eastern U.S. & southern eastern U.S. & southern

EuropeEurope Have Have minute forelimbs & no hindlimbsminute forelimbs & no hindlimbs

Trachystoma Characteristics:Trachystoma Characteristics:

External Frog Anatomy:External Frog Anatomy:

Live Live double lifedouble life on land & water on land & water Powerful hind legsPowerful hind legs for jumping & swimming for jumping & swimming

fold under bodyfold under body when at rest when at rest Bulging eyes Bulging eyes to stay submerged but still see to stay submerged but still see

predators predators Blinking eyelidsBlinking eyelids protect eyes from dust & protect eyes from dust &

dehydration dehydration Nictitating membranesNictitating membranes clear to moisten eye & clear to moisten eye &

see underwater see underwater Internal nostrils or naresInternal nostrils or nares allow frog to allow frog to

breathe underwater breathe underwater

External Frog Anatomy:External Frog Anatomy: Tympanic membranes or eardrums behind Tympanic membranes or eardrums behind

each eye transmit sound through bone called each eye transmit sound through bone called columella to inner ear columella to inner ear

Eustachian tubes connect mouth & middle Eustachian tubes connect mouth & middle ear to equalize pressureear to equalize pressure

Males Males croakcroak or make sound to or make sound to attract females attract females & ward off other males& ward off other males

Have protective coloration from cells called Have protective coloration from cells called chromatophoreschromatophores

Granular glands Granular glands secrete foul tasting or secrete foul tasting or poisonous substance poisonous substance

Mucus glands Mucus glands lubricate skin for oxygen to be lubricate skin for oxygen to be dissolved & absorbed dissolved & absorbed

External Frog Anatomy:External Frog Anatomy:

Internal Frog Anatomy:Internal Frog Anatomy: Skeletal System Skeletal System (adaptation for life on land)(adaptation for life on land) Rigid spine Rigid spine to bear weight of bodyto bear weight of body Nine spinal vertebraeNine spinal vertebrae (1 cervical in neck, 7 (1 cervical in neck, 7

trunk, & 1 sacral supporting hind legs) trunk, & 1 sacral supporting hind legs) UrostyleUrostyle long, slim bone connecting sacral long, slim bone connecting sacral

vertebrae & trunk vertebrae & trunk No rib cageNo rib cage, but , but pectoral girdlepectoral girdle forms forms

shoulders & connects front legs shoulders & connects front legs Pelvic girdle connects to hind legs Pelvic girdle connects to hind legs A fused lower forelimb (radio-ulna) and a hind A fused lower forelimb (radio-ulna) and a hind

limb (tibiofibula)limb (tibiofibula)

Internal Frog Anatomy:Internal Frog Anatomy: Digestive SystemDigestive System Tongue Tongue sticky, forked, & hinged at frontsticky, forked, & hinged at front of of

mouth so can be extended out to catch insects mouth so can be extended out to catch insects Can pull eyes inward to help swallow food Can pull eyes inward to help swallow food Two, sharp, backward-pointing  Two, sharp, backward-pointing  vomerine teethvomerine teeth

in roof of mouth help prevent prey from escaping in roof of mouth help prevent prey from escaping Maxillary teethMaxillary teeth line the edge of the upper jaw line the edge of the upper jaw Alimentary canalAlimentary canal (mouth, pharynx, esophagus, (mouth, pharynx, esophagus,

stomach, small & large intestines, and cloaca) is stomach, small & large intestines, and cloaca) is where food is digested, absorbed & wastes where food is digested, absorbed & wastes eliminated eliminated

Stomach makes Stomach makes gastric juicesgastric juices to break down to break down food food

Internal Frog Anatomy:Internal Frog Anatomy: Pyloric sphincter musclePyloric sphincter muscle controls movement controls movement

of food from stomach into first part of small of food from stomach into first part of small intestine called intestine called duodenumduodenum

Liver Liver makesmakes bile to digest fats; stored bile to digest fats; stored in in gall gall bladderbladder

PancreasPancreas makes makes pancreatic juicepancreatic juice to digest to digest food in small intestine food in small intestine

IleumIleum is coiled mid portion of small intestine is coiled mid portion of small intestine MesenteryMesentery is a fanlike membrane holding the is a fanlike membrane holding the

intestine in place intestine in place WastesWastes collect in large intestine & then move collect in large intestine & then move

into into cloacacloaca along with along with eggs, sperm, & urineeggs, sperm, & urine until they leave body through the until they leave body through the anusanus or vent or vent

Internal Frog Anatomy:Internal Frog Anatomy: Circulatory SystemCirculatory System Need more oxygenNeed more oxygen to burn increased amount to burn increased amount

of food needed to live on land of food needed to live on land 3 chambered heart3 chambered heart ( (right atriumright atrium receives receives

deoxygenated blood from body, deoxygenated blood from body, left atriumleft atrium receives oxygenated blood from lungs, & receives oxygenated blood from lungs, & ventricleventricle pumps blood to lungs & rest of the pumps blood to lungs & rest of the body) body)

Double loop blood circulationDouble loop blood circulation ( (pulmonarypulmonary from heart to lungs & from heart to lungs & systemicsystemic from heart to from heart to rest of body) rest of body)

Conus arteriosusConus arteriosus carries blood from ventricle to carries blood from ventricle to body cells body cells

Internal Frog Anatomy:Internal Frog Anatomy: Circulatory System cont…Circulatory System cont…1.1. Sinus venosus – deoxygenated blood enters firstSinus venosus – deoxygenated blood enters first2.2. Right atrium – deoxygenated blood from the sinus Right atrium – deoxygenated blood from the sinus

venosus entersvenosus enters3.3. Ventricle – deoxygenated and oxygenated blood Ventricle – deoxygenated and oxygenated blood

enters the ventricleenters the ventricle4.4. Conus Arteriosus – both kinds of bood is expelled into Conus Arteriosus – both kinds of bood is expelled into

this chamberthis chamber5.5. Lungs – deoxygenated blood leaves the conus Lungs – deoxygenated blood leaves the conus

arteriosus and travels to the lungsarteriosus and travels to the lungs6.6. Left atrium – oxygenated blood from the lungs enters Left atrium – oxygenated blood from the lungs enters

the left atrium the left atrium 7.7. Ventricle - oxygenated and deoxygenated blood is Ventricle - oxygenated and deoxygenated blood is

forced into the ventricle, then to the conus arteriosus forced into the ventricle, then to the conus arteriosus where it is sent separate wayswhere it is sent separate ways

8.8. Body – oxygenated blood leaves the conus arteriosus Body – oxygenated blood leaves the conus arteriosus and travels to the bodyand travels to the body

Circulatory SystemCirculatory System

Internal Frog Anatomy:Internal Frog Anatomy:

Respiratory SystemRespiratory System Tadpoles use gills Tadpoles use gills to breathe to breathe Adult frogsAdult frogs breathe through breathe through lungs & lungs &

moist skinmoist skin (cutaneous respiration) (cutaneous respiration) GlottisGlottis is the opening into throat & lungs is the opening into throat & lungs

Respiratory SystemRespiratory System

Positive-pressure BreathingPositive-pressure Breathing See figure 42 – 9, pg 826See figure 42 – 9, pg 826 The floor of the mouth drops and the The floor of the mouth drops and the

nostrils open (air rushes in)nostrils open (air rushes in) The floor of the mouth is raised and the The floor of the mouth is raised and the

nostrils close ( air is pushed into the nostrils close ( air is pushed into the lungs)lungs)

Internal Frog Anatomy:Internal Frog Anatomy:

Excretory SystemExcretory System Carbon dioxide excreted through skin & Carbon dioxide excreted through skin &

lungs lungs KidneysKidneys filter blood & store urine in filter blood & store urine in

urinary bladderurinary bladder until leaves until leaves cloacacloaca

Internal Frog Anatomy:Internal Frog Anatomy: Nervous SystemNervous System Olfactory lobesOlfactory lobes at base of brain detect at base of brain detect smellssmells CerebrumCerebrum behind olfactory lobes behind olfactory lobes controls controls

musclesmuscles (voluntary activities of the body) (voluntary activities of the body) Optic lobesOptic lobes detect detect sightsight CerebellumCerebellum controls controls balance & coordinationbalance & coordination Medulla oblongataMedulla oblongata controls controls heart rate & heart rate &

breathingbreathing Cranial nervesCranial nerves connect brain & spinal cord, connect brain & spinal cord, Spinal nervesSpinal nerves branch off the spinal cord to branch off the spinal cord to

muscles & sensory receptors muscles & sensory receptors Tympanic membraneTympanic membrane and and columellacolumella detect detect

vibrations in the airvibrations in the air

Life cycle of a frog Life cycle of a frog including metamorphosisincluding metamorphosis

Mating embrace (amplexus); male’s sperm Mating embrace (amplexus); male’s sperm fertilizes female’s eggs externallyfertilizes female’s eggs externally

Eggs hatch and the tadpole is releasedEggs hatch and the tadpole is released Tadpole metamorphosis (stimulated by the Tadpole metamorphosis (stimulated by the

hormone thyroxine)hormone thyroxine) Metamorphosis:Metamorphosis:1.1. First lives off yolk stored in its bodyFirst lives off yolk stored in its body2.2. Gradually grows larger and develops three Gradually grows larger and develops three

pairs of gillspairs of gills

Life cycle of a frog Life cycle of a frog including metamorphosisincluding metamorphosis

Metamorphosis cont…Metamorphosis cont…3. Tadpole’s mouth opens, allowing it to feed3. Tadpole’s mouth opens, allowing it to feed4. Legs grow from the body, and the tail and gills 4. Legs grow from the body, and the tail and gills

disappeardisappear5. The mouth broadens, developing teeth and 5. The mouth broadens, developing teeth and

jawsjaws6. The lungs become functional 6. The lungs become functional 7. A small adult frog emerges from the water onto 7. A small adult frog emerges from the water onto

dry landdry land

Parental care in Parental care in AmphibiansAmphibians

Some species of poison dart frog lay eggs on the forest Some species of poison dart frog lay eggs on the forest floor and protect them, guarding the eggs from floor and protect them, guarding the eggs from predation and keeping them moist. The frog will urinate predation and keeping them moist. The frog will urinate on them if they become too dry. After hatching, a on them if they become too dry. After hatching, a parent (the gender depends upon the species) will parent (the gender depends upon the species) will move them, on its back, to a water-holding bromeliad. move them, on its back, to a water-holding bromeliad. The parent then feeds them by laying unfertilized eggs The parent then feeds them by laying unfertilized eggs in the bromeliad until the young have metamorphosed in the bromeliad until the young have metamorphosed

The females of some species sit on their eggs to keep The females of some species sit on their eggs to keep them moistthem moist

Poison Dart FrogPoison Dart Frog

Parental care in Parental care in AmphibiansAmphibians

Other frogs carry the eggs and tadpoles Other frogs carry the eggs and tadpoles on their hind legs or back (e.g. the on their hind legs or back (e.g. the midwife toads, midwife toads, Alytes spp.Alytes spp.). ).

Some frogs even protect their offspring Some frogs even protect their offspring inside their own bodies. The male inside their own bodies. The male Australian Pouched frog (Australian Pouched frog (Assa Assa darlingtonidarlingtoni) has pouches along its side in ) has pouches along its side in which the tadpoles reside until which the tadpoles reside until metamorphosis. metamorphosis.

Parental care in Parental care in AmphibiansAmphibians

The female Gastric-brooding frog (genus The female Gastric-brooding frog (genus RheobatrachusRheobatrachus) from Australia, now ) from Australia, now probably extinct, swallows its tadpoles, probably extinct, swallows its tadpoles, which then develop in the stomach. To which then develop in the stomach. To do this, the Gastric-brooding Frog must do this, the Gastric-brooding Frog must stop secreting stomach acid and stop secreting stomach acid and suppress peristalsis (contractions of the suppress peristalsis (contractions of the stomach). stomach).

Parental care in Parental care in AmphibiansAmphibians

Darwin’s frog(Darwin’s frog(Rhinoderma darwiniiRhinoderma darwinii) from ) from Chile puts the tadpoles in its vocal sac for Chile puts the tadpoles in its vocal sac for development. development.