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Page 1: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

AmphibiansAmphibians

Page 2: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

Evolution of Evolution of AmphibiansAmphibians

Page 3: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

"Amphibian" comes from the "Amphibian" comes from the Greek meaning "both life". Greek meaning "both life". Amphibians can live on water Amphibians can live on water and on land. and on land.

Scientist infer that Scientist infer that amphibians evolved from amphibians evolved from lobe-finned fishes called lobe-finned fishes called crossopterygians.crossopterygians.

Page 4: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

CrossopterygianCrossopterygian

Page 5: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

Biologist conclude that amphibians Biologist conclude that amphibians appeared during the late Devonian appeared during the late Devonian

period, about 345 million years ago.period, about 345 million years ago.

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Crossopterygians had noCrossopterygians had no gills but they had gills but they had internal nostrils and a primitive lung that may internal nostrils and a primitive lung that may have enabled them then to respire for periods have enabled them then to respire for periods of time on land.of time on land.

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CharacteristiCharacteristics of cs of

AmphibiansAmphibians

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Amphibians are cold-blooded, Amphibians are cold-blooded, which means their blood which means their blood temperature rises and falls with temperature rises and falls with that of the surrounding that of the surrounding environmentenvironment

••

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They use gills, lungs, skin, and They use gills, lungs, skin, and mouth cavity in respiration.mouth cavity in respiration.

Page 10: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

They have moist, smooth, thin skin with They have moist, smooth, thin skin with no scales.Feet are webbed and the toes no scales.Feet are webbed and the toes

lack clawslack claws..

Page 11: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

Amphibians have many prominent Amphibians have many prominent characteristics that are adaptations to a life characteristics that are adaptations to a life spent both on land and in water:spent both on land and in water:They change from an aquatic larval stage to a They change from an aquatic larval stage to a terrestrial adultterrestrial adultform. This transformation is called form. This transformation is called metamorphosismetamorphosis

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Amphibians enter a state of Amphibians enter a state of dormancy or torpor when dormancy or torpor when conditions are unfavorable.conditions are unfavorable.They often bury themselves in mud They often bury themselves in mud or leaves, emerging when or leaves, emerging when conditions are better. conditions are better.

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Such states of Such states of inactivity are known as inactivity are known as

known as:known as: Hibernation when it Hibernation when it occurs in the winteroccurs in the winter

Estivation when it Estivation when it occurs in the summeroccurs in the summer

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Larvae have two-chambered hearts; Larvae have two-chambered hearts; adults have three-chambered hearts adults have three-chambered hearts and well-developed circulation.and well-developed circulation.

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Eggs lack multicellular membranes or Eggs lack multicellular membranes or shells. They are usually laid in water or shells. They are usually laid in water or in a moist environment and fertilized in a moist environment and fertilized externally.externally.

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Classification Classification of Amphibiansof Amphibians

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Biologists have identified Biologists have identified about 2,375 living species of about 2,375 living species of amphibians and have classified amphibians and have classified them into four ordersthem into four orders

Anura – Frogs & ToadsAnura – Frogs & Toads Urodela – SalamandersUrodela – Salamanders Trachystoma – Mud eelsTrachystoma – Mud eels Apoda - CaecilliansApoda - Caecillians

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Frogs and toads make up Frogs and toads make up the Order Anura ("without a the Order Anura ("without a

tail").tail").

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Salamanders and other Salamanders and other amphibians with legs and amphibians with legs and tails make up the Order tails make up the Order Urodela ("visible tail").Urodela ("visible tail").

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Page 21: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

..Some aquatic amphibians (mud Some aquatic amphibians (mud eels & sirens) belong to the eels & sirens) belong to the Order Trachystoma ("rough Order Trachystoma ("rough

mouth")mouth")

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SirenSiren

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Apoda includes caecilians, a Apoda includes caecilians, a tropical, burrowing worm-tropical, burrowing worm-

like amphibians that is like amphibians that is often often

Legless Legless

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Anuran Anuran CharacteristicsCharacteristics

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Frogs and toads comprise Frogs and toads comprise the order Anurathe order Anura

There are about 3,500 There are about 3,500 known species of frogs known species of frogs and 300 kinds of toadsand 300 kinds of toads

They are found on every They are found on every continent except continent except AntarcticaAntarctica

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Some types spend their entire Some types spend their entire life in or near water, but others life in or near water, but others live mainly on land and come live mainly on land and come

to the water only to mateto the water only to mate

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Some frogs and toads are Some frogs and toads are climbers that dwell in trees or climbers that dwell in trees or

burrowers that live burrowers that live underground.underground.

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Toads and frogs have many Toads and frogs have many similarities in the way they similarities in the way they

look. Some basic differences look. Some basic differences between them are: toads have between them are: toads have

dry, warty skin, while frogs dry, warty skin, while frogs have smooth, wet skin.have smooth, wet skin.

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Both frogs and toads return to Both frogs and toads return to water to reproduce. In nearly all water to reproduce. In nearly all

species eggs are fertilized species eggs are fertilized externally. The fertilized eggs externally. The fertilized eggs

hatch into swimming larval forms hatch into swimming larval forms called tadpolescalled tadpoles

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Urodelan Urodelan CharacteristicsCharacteristics

Page 31: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

Salamanders, typical members Salamanders, typical members of the Order Urodela, have of the Order Urodela, have

elongated bodies, long tails, elongated bodies, long tails, and smooth, moist skinand smooth, moist skin

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Compared to the anurans, Compared to the anurans, salamanders are less able to salamanders are less able to

remain on dry land, although some remain on dry land, although some can live in dry areas by remaining can live in dry areas by remaining

inactive during the dayinactive during the day

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Salamander lay their eggs in Salamander lay their eggs in water and like anurans they water and like anurans they hatch into swimming larvahatch into swimming larva

Salamander eggsSalamander eggs

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Other species can Other species can reproduce in damp land reproduce in damp land environments. Eggs laid on environments. Eggs laid on land hatch into miniature land hatch into miniature adult salamandersadult salamanders

Marbled SalamanderMarbled Salamander

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Apodan Apodan CharacteristicsCharacteristics

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Caecilians, members of the Caecilians, members of the Order Apoda, compose a highly Order Apoda, compose a highly

specialized group of tropical specialized group of tropical burrowing amphibiansburrowing amphibians

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These legless wormlike These legless wormlike creatures average 30 cm creatures average 30 cm long, but they can be up to long, but they can be up to 1.3m long.1.3m long.

They have very small eyes They have very small eyes and are often blind. and are often blind.

They eat worms and other They eat worms and other invertebratesinvertebrates

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The caecilian male deposits The caecilian male deposits sperm directly into the female, sperm directly into the female,

and the female bears live and the female bears live youngyoung

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Trachystoma Trachystoma CharacteristicsCharacteristics

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The Order Trachystoma The Order Trachystoma contains three living species contains three living species of mud eels, or sirensof mud eels, or sirens. .

Sirens live in the eastern Sirens live in the eastern United States and north United States and north eastern Mexico. eastern Mexico.

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Frog External Frog External AnatomyAnatomy

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The frog's powerful hind legs The frog's powerful hind legs are equally effective in jumping are equally effective in jumping or swimming. On land frogs sit or swimming. On land frogs sit with their hind legs folded with their hind legs folded against the body, poised to against the body, poised to jump at the first sign of dangerjump at the first sign of danger. .

Most frogs can make leaps Most frogs can make leaps many times their body many times their body lengthlength

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Frog's eyes also work equally well Frog's eyes also work equally well in or out of water. Because the in or out of water. Because the eyes bulge out from the head, the eyes bulge out from the head, the frog can stay submerged while frog can stay submerged while literally "keeping an eye out" for literally "keeping an eye out" for predatorspredators

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Eyelids that can blink protect Eyelids that can blink protect the frog's eyes from dust and the frog's eyes from dust and dehydrationdehydration

In addition to upper and lower eyelids, In addition to upper and lower eyelids, a third, transparent eyelid called a a third, transparent eyelid called a nictitating membrane covers each nictitating membrane covers each eyeball and joins the lower eyelideyeball and joins the lower eyelid

This membrane keeps the This membrane keeps the eyelid moist and protects it eyelid moist and protects it when it is under waterwhen it is under water

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Frogs have eardrums, or Frogs have eardrums, or tympanic membranes, tympanic membranes,

which are circular which are circular structures located behind structures located behind

each eyeeach eye

Tympanic membrane

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The frog's thick, moist skin The frog's thick, moist skin serves two important functionsserves two important functions— respiration and protection— respiration and protection

Glands secrete mucus to keep Glands secrete mucus to keep it from drying upit from drying up

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Some glands secrete foul-Some glands secrete foul-tasting or poisonous tasting or poisonous substances that protect the substances that protect the frog from enemiesfrog from enemies

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Some frogs, such as Some frogs, such as Hyla Hyla versicolor, versicolor, can change color can change color in order to blend with the in order to blend with the

environment.environment.

Count the number of

frogs in the picture?

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Frog Internal Frog Internal AnatomyAnatomy

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Skeletal SystemSkeletal System

The frog's spine The frog's spine has nine vertebraehas nine vertebrae

The cervical The cervical vertebra at the vertebra at the anterior end of the anterior end of the spine allows neck spine allows neck movement that movement that helps frogs catch helps frogs catch preyprey

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Skeletal SystemSkeletal SystemPosterior to this Posterior to this

are seven trunk are seven trunk vertebrae, and vertebrae, and then a single then a single sacral vertebra sacral vertebra that supports the that supports the hind legshind legs

A long, slim bone A long, slim bone called the urostyle called the urostyle extends from the extends from the sacral vertebrasacral vertebra

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Skeletal SystemSkeletal SystemBones of the pectoral Bones of the pectoral

girdle, which form the girdle, which form the shoulders, connect to shoulders, connect to the front legsthe front legs

They also provide the They also provide the primary protection to primary protection to the internal organs, the internal organs, since the frog has no since the frog has no ribsribs

The pelvic girdle The pelvic girdle connects to the hind connects to the hind legslegs

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Digestive SystemDigestive System

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Digestive SystemDigestive SystemMost frogs feed on insects, and Most frogs feed on insects, and

their digestive system is adapted their digestive system is adapted to their dietto their diet

A frog's tongue is an excellent A frog's tongue is an excellent insect catcherinsect catcher. . The frog simply The frog simply flicks out its long sticky tongue, flicks out its long sticky tongue, curls it around its prey, and pulls curls it around its prey, and pulls the insect back into its mouth. the insect back into its mouth. Then the frog snaps its mouth shut Then the frog snaps its mouth shut and swallowsand swallows. .

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Digestive SystemDigestive SystemFrogs have two Frogs have two

types of teeth types of teeth that hold on to that hold on to prey. A row of prey. A row of maxillary teeth maxillary teeth

line the line the perimeter of the perimeter of the upper jaw. Two upper jaw. Two

patches of patches of vomerine teeth vomerine teeth

project from project from bones in the roof bones in the roof

of the mouthof the mouth..

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Digestive SystemDigestive System Sometimes the frog Sometimes the frog

blinks, pulls its eyes blinks, pulls its eyes inward, and presses inward, and presses them against the roof them against the roof of its mouth. This of its mouth. This action helps push the action helps push the food down its throatfood down its throat

Digestion in frogs Digestion in frogs takes place in the takes place in the alimentary canal, alimentary canal, which includes the which includes the esophagus, stomach, esophagus, stomach, small intestine, large small intestine, large intestine, and cloacaintestine, and cloaca

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Circulatory SystemCirculatory SystemAn adaptation to the An adaptation to the

greater oxygen needs of greater oxygen needs of land animals is a more land animals is a more efficient circulatory efficient circulatory system than the fish's system than the fish's two-chambered heart. two-chambered heart.

The amphibian's three-The amphibian's three-chambered heart chambered heart partially mixes partially mixes oxygenated with oxygenated with deoxygenated blood and deoxygenated blood and pumps the blood pumps the blood throughout the body at throughout the body at higher pressure than higher pressure than does the fish's heartdoes the fish's heart

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The left atrium The left atrium receives oxygenated receives oxygenated blood from the lungs, blood from the lungs, and the right atrium and the right atrium receives receives deoxygenated blood deoxygenated blood from the body. from the body.

Both the atria empty Both the atria empty into the ventricle, the into the ventricle, the main pumping main pumping chamber of the heart. chamber of the heart.

In the ventricle In the ventricle oxygenated and oxygenated and deoxygenated blood deoxygenated blood mix partially and are mix partially and are pumped to the lungs pumped to the lungs and the rest of the and the rest of the bodybody..

Blood to body

Deoxygenated blood from bodyR

Oxygenated blood from lungs

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From the right atrium From the right atrium the blood enters the the blood enters the single ventricle. The single ventricle. The ventricle then contracts, ventricle then contracts, pumping some blood to pumping some blood to the lungs to receive the lungs to receive oxygen and some to the oxygen and some to the rest of the body. rest of the body.

The blood going to the The blood going to the body leaves the body leaves the ventricle through the ventricle through the conus arteriosus, a conus arteriosus, a large vessel that lies large vessel that lies against the front side of against the front side of the heartthe heart

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This vessel divides into a right and This vessel divides into a right and a left truncus arteriosus, which a left truncus arteriosus, which immediately branch again into immediately branch again into three arches that carry blood to three arches that carry blood to various parts of the body. various parts of the body.

Deoxygenated blood travels in Deoxygenated blood travels in veins back to the right atrium from veins back to the right atrium from the various regions of the body.the various regions of the body.

Oxygenated blood returns from Oxygenated blood returns from the lungs to the left atrium via the the lungs to the left atrium via the pulmonary veinspulmonary veins

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Respiratory Respiratory SystemSystem

Tadpoles respire, or Tadpoles respire, or exchange carbon dioxide exchange carbon dioxide and oxygen, through gillsand oxygen, through gills

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Respiratory Respiratory SystemSystem

Adult frogs lose the gills but can Adult frogs lose the gills but can respire in three ways: through respire in three ways: through the lungs, through the skin, and the lungs, through the skin, and through the mouth. through the mouth.

Respiration through the lungs is Respiration through the lungs is called pulmonary respiration. called pulmonary respiration.

A frog breathes by changing the A frog breathes by changing the volume and pressure of air in its volume and pressure of air in its mouth while either opening or mouth while either opening or closing its nostrilsclosing its nostrils

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Respiratory SystemRespiratory System Air moves from the throat to the Air moves from the throat to the

lungs through a slit-like passage lungs through a slit-like passage called the glottis.called the glottis.

Because the frog's lungs are small, Because the frog's lungs are small, cutaneous respiration, or cutaneous respiration, or respiration through the skin in respiration through the skin in both air and water, is very both air and water, is very important, especially during important, especially during estivation or hibernation. estivation or hibernation.

Oxygen can diffuse across the Oxygen can diffuse across the lining of the mouth and into the lining of the mouth and into the blood.blood.

Frogs use mouth breathing for Frogs use mouth breathing for only a relatively small amount of only a relatively small amount of their respirationtheir respiration..

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Excretory SystemExcretory SystemUrine and wastes from the digestive Urine and wastes from the digestive

system are eliminated through the system are eliminated through the anus. anus.

When a frog is in water, its permeable When a frog is in water, its permeable skin allows the water to enter its body. skin allows the water to enter its body.

Frogs that Frogs that live live primarily in water rid primarily in water rid themselves of excess water by themselves of excess water by excreting a large volume of very dilute excreting a large volume of very dilute urine.urine.

Frogs that live mainly on land Frogs that live mainly on land conserve water by producing a small conserve water by producing a small volume of more concentrated urine.volume of more concentrated urine.

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Excretory SystemExcretory System Amphibians eliminate two primary types of Amphibians eliminate two primary types of

metabolic waste products—carbon dioxide metabolic waste products—carbon dioxide from respiration and waste com pounds from from respiration and waste com pounds from the breakdown of foodsthe breakdown of foods. .

Are the primary excretory organs and lie on Are the primary excretory organs and lie on either side of the spine against the dorsal either side of the spine against the dorsal body wall. The kidneys filter nitrogenous body wall. The kidneys filter nitrogenous wastes from the bloodwastes from the blood

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The Nervous SystemThe Nervous SystemThe frog brain is more The frog brain is more

complex than the fish complex than the fish brain, enabling the frog to brain, enabling the frog to contend with a more varied contend with a more varied environment. environment.

The optic lobes, which The optic lobes, which control vision, lie behind control vision, lie behind the cerebrum.the cerebrum.

The cerebellum, a small The cerebellum, a small band of tissue lying at right band of tissue lying at right angles to the long axis of angles to the long axis of the brain, is the center of the brain, is the center of balance and coordinationbalance and coordination..

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Nervous SystemNervous SystemThe medulla oblongata lies at the The medulla oblongata lies at the

back of the brain and joins the spinal back of the brain and joins the spinal cord. It controls organ functions.cord. It controls organ functions.

Ten pairs of cranial nerves extend Ten pairs of cranial nerves extend out directly from the brain.out directly from the brain.

The spinal cord transmits signals The spinal cord transmits signals from all parts of the body to the from all parts of the body to the brain and from the brain back to the brain and from the brain back to the body. body.

The spinal nerves branch from the The spinal nerves branch from the spinal cord to various parts of the spinal cord to various parts of the body.body.

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Reproductive Reproductive SystemSystem

Both male and female frogs have Both male and female frogs have internal sex organsinternal sex organs

The male frog's fore leg muscles The male frog's fore leg muscles and first fingers swell and first fingers swell

These swellings help the male These swellings help the male maintain his grasp on the femalemaintain his grasp on the female

The reproductive system of the The reproductive system of the male frog includes two bean-male frog includes two bean-shaped creamy white or shaped creamy white or yellowish testes located near the yellowish testes located near the kidneyskidneys

Sperm cells develop in the testes Sperm cells develop in the testes and pass through tubes to the and pass through tubes to the kidneys and urinary ductskidneys and urinary ducts Male System

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Reproductive Reproductive SystemSystem

Female frogs a pair of Female frogs a pair of large, lobed ovaries large, lobed ovaries containing thou sands of containing thou sands of tiny immature eggs lie near tiny immature eggs lie near the kidneysthe kidneys

During the breeding season During the breeding season eggs enlarge, mature, and eggs enlarge, mature, and burst through the thin burst through the thin ovarian walls into the body ovarian walls into the body cavity. cavity.

They remain in structures They remain in structures called ovisacs until called ovisacs until ovulation is complete and ovulation is complete and then leave the body then leave the body through the cloacae through the cloacae opening.opening.

Female System

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Reproductive Reproductive SystemSystem

The vast majority of eggs The vast majority of eggs and tadpoles are eaten by and tadpoles are eaten by predators such as fish, predators such as fish, birds, snakes, and turtles. birds, snakes, and turtles. Some species of frogs Some species of frogs havehave

The vast majority of eggs The vast majority of eggs and tadpoles are eaten by and tadpoles are eaten by predators such as fish, predators such as fish, birds, snakes, and turtlesbirds, snakes, and turtles. .

Amplexus

Page 72: Amphibians. Evolution of Amphibians "Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land. "Amphibian" comes

MetamorphosisMetamorphosisNewly hatched tadpoles live off Newly hatched tadpoles live off

yolk stored in their bodies. yolk stored in their bodies. They gradually grow larger and They gradually grow larger and develop three pairs of gills. develop three pairs of gills.

Tadpoles have a two-Tadpoles have a two-chambered heart. Tadpoles can chambered heart. Tadpoles can also regenerate injured or lost also regenerate injured or lost body parts such as a leg or tail.body parts such as a leg or tail.

Legs grow from the body, and Legs grow from the body, and the tail disappears.the tail disappears.

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MetamorphosisMetamorphosis

The mouth broadens, The mouth broadens, developing teeth and jaws. A developing teeth and jaws. A saclike bladder in the throat saclike bladder in the throat divides into two sacs that divides into two sacs that become lungs. The heart become lungs. The heart develops a third chamber.develops a third chamber.

A hormone called thyroxin A hormone called thyroxin circulates throughout the circulates throughout the bloodstream and stimulates bloodstream and stimulates metamorphosis. metamorphosis.

The cells of the tad pole are The cells of the tad pole are genetically programmed to genetically programmed to respond to thyroxin at the respond to thyroxin at the appropriate stage of appropriate stage of development.development.

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