amphibians lec.1.pdf

Amphibians
Amphibians
Copyright Cmassengale

Evolution of
Evolution of
Amphibians
Amphibians

"Amphibian" comes from the
"Amphibian" comes from the
Greek meaning "both life".
Greek meaning "both life".
Amphibians can live on water and
Amphibians can live on water and
on land.
on land.
Scientist infer that amphibians
Scientist infer that amphibians
evolved from lobe-finned fishes
evolved from lobe-finned fishes
called crossopterygians.
called crossopterygians.

Crossopterygian
Crossopterygian

Biologist conclude that amphibians appeared
Biologist conclude that amphibians appeared
during the late Devonian period, about 345
during the late Devonian period, about 345
million years ago.
million years ago.

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

Characteristics
Characteristics
of Amphibians
of Amphibians

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

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

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

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

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
They often bury themselves in
mud or leaves, emerging when
mud or leaves, emerging when
conditions are better.
conditions are better.

Such states of inactivity
Such states of inactivity
are known as known as:
are known as known as:
 Hibernation when it
Hibernation when it
occurs in the winter
occurs in the winter
Estivation when it occurs
Estivation when it occurs
in the summer
in the summer

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.

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

Classification of
Classification of
Amphibians
Amphibians

Biologists have identified about
Biologists have identified about
2,375 living species of amphibians
2,375 living species of amphibians
and have classified them into four
and have classified them into four
orders
orders
Anura – Frogs & Toads
Anura – Frogs & Toads
Urodela – Salamanders
Urodela – Salamanders
Trachystoma – Mud eels
Trachystoma – Mud eels
Apoda - Caecillians
Apoda - Caecillians

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

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

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

Siren
Siren

Apoda includes caecilians, a
Apoda includes caecilians, a
tropical, burrowing worm-like
tropical, burrowing worm-like
amphibians that is often
amphibians that is often
Legless
Legless

Anuran
Anuran
Characteristics
Characteristics

Frogs and toads comprise the
Frogs and toads comprise the
order Anura
order Anura
There are about 3,500 known
There are about 3,500 known
species of frogs and 300 kinds
species of frogs and 300 kinds
of toads
of toads
They are found on every
They are found on every
continent except Antarctica
continent except Antarctica

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

Some frogs and toads are climbers
Some frogs and toads are climbers
that dwell in trees or burrowers
that dwell in trees or burrowers
that live underground.
that live underground.

Toads and frogs have many
Toads and frogs have many
similarities in the way they look.
similarities in the way they look.
Some basic differences between
Some basic differences between
them are: toads have dry, warty
them are: toads have dry, warty
skin, while frogs have smooth, wet
skin, while frogs have smooth, wet
skin.
skin.

Both frogs and toads return to water to
Both frogs and toads return to water to
reproduce. In nearly all species eggs are
reproduce. In nearly all species eggs are
fertilized externally. The fertilized eggs
fertilized externally. The fertilized eggs
hatch into swimming larval forms called
hatch into swimming larval forms called
tadpoles
tadpoles

Urodelan
Urodelan
Characteristics
Characteristics

Salamanders, typical members of
Salamanders, typical members of
the Order Urodela, have elongated
the Order Urodela, have elongated
bodies, long tails, and smooth,
bodies, long tails, and smooth,
moist skin
moist skin

Compared to the anurans, salamanders
Compared to the anurans, salamanders
are less able to remain on dry land,
are less able to remain on dry land,
although some can live in dry areas by
although some can live in dry areas by
remaining inactive during the day
remaining inactive during the day

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

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

Apodan
Apodan
Characteristics
Characteristics

Caecilians, members of the Order
Caecilians, members of the Order
Apoda, compose a highly specialized
Apoda, compose a highly specialized
group of tropical burrowing
group of tropical burrowing
amphibians
amphibians

 These legless wormlike
These legless wormlike
creatures average 30 cm long,
creatures average 30 cm long,
but they can be up to 1.3m
but they can be up to 1.3m
long.
long.
 They have very small eyes and
They have very small eyes and
are often blind.
are often blind.
 They eat worms and other
They eat worms and other
invertebrates
invertebrates

The caecilian male deposits sperm
The caecilian male deposits sperm
directly into the female, and the
directly into the female, and the
female bears live young
female bears live young

Trachystoma
Trachystoma
Characteristics
Characteristics

The Order Trachystoma contains
The Order Trachystoma contains
three living species of mud eels,
three living species of mud eels,
or sirens
or sirens.
.
Sirens live in the eastern United
Sirens live in the eastern United
States and northeastern
States and northeastern
Mexico.
Mexico.

Frog External
Frog External
Anatomy
Anatomy

The frog's powerful hind legs are
The frog's powerful hind legs are
equally effective in jumping or
equally effective in jumping or
swimming. On land frogs sit with
swimming. On land frogs sit with
their hind legs folded against the
their hind legs folded against the
body, poised to jump at the first
body, poised to jump at the first
sign of danger
sign of danger.
.
Most frogs can make leaps many
Most frogs can make leaps many
times their body length
times their body length

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

Eyelids that can blink protect the
Eyelids that can blink protect the
frog's eyes from dust and
frog's eyes from dust and
dehydration
dehydration
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 eyelid
eyeball and joins the lower eyelid
This membrane keeps the eyelid
This membrane keeps the eyelid
moist and protects it when it is
moist and protects it when it is
under water
under water

Frogs have eardrums, or
Frogs have eardrums, or
tympanic membranes, which are
tympanic membranes, which are
circular structures located
circular structures located
behind each eye
behind each eye
Tympanic membrane

The frog's thick, moist skin
The frog's thick, moist skin
serves two important functions—
serves two important functions—
respiration and protection
respiration and protection
Glands secrete mucus to keep it
Glands secrete mucus to keep it
from drying up
from drying up

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

Some frogs, such as
Some frogs, such as Hyla
Hyla
versicolor,
versicolor, can change color in
can change color in
order to blend with the
order to blend with the
environment.
environment.
Count the
number of
frogs in the
picture?

Frog Internal
Frog Internal
Anatomy
Anatomy

Skeletal System
Skeletal System
The frog's spine has
The frog's spine has
nine vertebrae
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 helps
movement that helps
frogs catch prey
frogs catch prey

Skeletal System
Skeletal System
Posterior to this
Posterior to this
are seven trunk
are seven trunk
vertebrae, and
vertebrae, and
then a single sacral
then a single sacral
vertebra that
vertebra that
supports the hind
supports the hind
legs
legs
A long, slim bone
A long, slim bone
called the urostyle
called the urostyle
extends from the
extends from the
sacral vertebra
sacral vertebra

Skeletal System
Skeletal System
Bones of the pectoral
Bones of the pectoral
girdle, which form the
girdle, which form the
shoulders, connect to
shoulders, connect to
the front legs
the 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
ribs
ribs
The pelvic girdle
The pelvic girdle
connects to the hind
connects to the hind
legs
legs

Digestive System
Digestive System

Digestive System
Digestive System
Most frogs feed on insects, and their
Most frogs feed on insects, and their
digestive system is adapted to their diet
digestive system is adapted to their diet
A frog's tongue is an excellent insect
A frog's tongue is an excellent insect
catcher
catcher.
. The frog simply flicks out its
The frog simply flicks out its
long sticky tongue, curls it around its
long sticky tongue, curls it around its
prey, and pulls the insect back into its
prey, and pulls the insect back into its
mouth. Then the frog snaps its mouth
mouth. Then the frog snaps its mouth
shut and swallows
shut and swallows.
.

Digestive System
Digestive System
Frogs 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 perimeter
line the perimeter
of the upper jaw.
of the upper jaw.
Two patches of
Two patches of
vomerine teeth
vomerine teeth
project from
project from
bones in the roof
bones in the roof
of the mouth
of the mouth.
.

Digestive System
Digestive System
 Sometimes the frog
Sometimes the frog
blinks, pulls its eyes
blinks, pulls its eyes
inward, and presses them
inward, and presses them
against the roof of its
against the roof of its
mouth. This action helps
mouth. This action helps
push the food down its
push the food down its
throat
throat
 Digestion in frogs takes
Digestion in frogs takes
place in the alimentary
place in the alimentary
canal, which includes the
canal, which includes the
esophagus, stomach, small
esophagus, stomach, small
intestine, large intestine,
intestine, large intestine,
and cloaca
and cloaca

Circulatory System
Circulatory System
An 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 heart
does the fish's heart

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 deoxygenated
receives deoxygenated
blood from the body.
blood from the body.
Both the atria empty
Both the atria empty
into the ventricle, the
into the ventricle, the
main pumping chamber
main pumping chamber
of the heart.
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
body
body.
.
Blood to
body
Deoxygenated
blood
from body
R
Oxygenated
blood from
lungs

From the right atrium
From the right atrium
the blood enters the
the blood enters the
single ventricle. The
single ventricle. The
ventricle then
ventricle then
contracts, pumping
contracts, pumping
some blood to the
some blood to the
lungs to receive
lungs to receive
oxygen and some to
oxygen and some to
the rest of the body.
the 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
against the front side
of the heart
of the heart Copyright Cmassengale

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 three
immediately branch again into three
arches that carry blood to various
arches that carry blood to various
parts of the body.
parts of the body.
Deoxygenated blood travels in veins
Deoxygenated blood travels in veins
back to the right atrium from the
back to the right atrium from the
various regions of the body.
various regions of the body.
Oxygenated blood returns from the
Oxygenated blood returns from the
lungs to the left atrium via the
lungs to the left atrium via the
pulmonary veins
pulmonary veins

Respiratory System
Respiratory System
Tadpoles respire, or
Tadpoles respire, or
exchange carbon dioxide and
exchange carbon dioxide and
oxygen, through gills
oxygen, through gills

Respiratory System
Respiratory System
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 nostrils
closing its nostrils

Respiratory System
Respiratory 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 respiration
cutaneous respiration, or respiration
through the skin in both air and
through the skin in both air and
water, is very important, especially
water, is very important, especially
during estivation or hibernation.
during 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 only
Frogs use mouth breathing for only
a relatively small amount of their
a relatively small amount of their
respiration
respiration.
.

Excretory System
Excretory System
Urine and wastes from the digestive
Urine and wastes from the digestive
system are eliminated through the anus.
system are eliminated through the 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 conserve
Frogs that live mainly on land conserve
water by producing a small volume of
water by producing a small volume of
more concentrated urine.
more concentrated urine.

Excretory System
Excretory System
 Amphibians eliminate two primary types of metabolic
Amphibians eliminate two primary types of metabolic
waste products—carbon dioxide from respiration and
waste products—carbon dioxide from respiration and
waste compounds from the breakdown of foods
waste compounds from the breakdown of foods.
.
 Are the primary excretory organs and lie on either
Are the primary excretory organs and lie on either
side of the spine against the dorsal body wall. The
side of the spine against the dorsal body wall. The
kidneys filter nitrogenous wastes from the blood
kidneys filter nitrogenous wastes from the blood

The Nervous System
The Nervous System
The frog brain is more
The frog brain is more
complex than the fish brain,
complex than the fish brain,
enabling the frog to contend
enabling the frog to contend
with a more varied
with a more varied
environment.
environment.
The optic lobes, which
The optic lobes, which
control vision, lie behind the
control vision, lie behind the
cerebrum.
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 coordination
balance and coordination.
.

Nervous System
Nervous System
The medulla oblongata lies at the back
The medulla oblongata lies at the back
of the brain and joins the spinal cord.
of the brain and joins the spinal cord.
It controls organ functions.
It controls organ functions.
 Ten pairs of cranial nerves extend out
Ten pairs of cranial nerves extend out
directly from the brain.
directly from the brain.
The spinal cord transmits signals from
The spinal cord transmits signals from
all parts of the body to the brain and
all parts of the body to the brain and
from the brain back to the body.
from the brain back to the 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.

Reproductive System
Reproductive System
 Both male and female frogs
Both male and female frogs
have internal sex organs
have internal sex organs
 The male frog's foreleg
The male frog's foreleg
muscles and first fingers swell
muscles and first fingers swell
 These swellings help the male
These swellings help the male
maintain his grasp on the female
maintain 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
yellowish testes located near
the kidneys
the kidneys
 Sperm cells develop in the
Sperm cells develop in the
testes and pass through tubes
testes and pass through tubes
to the kidneys and urinary ducts
to the kidneys and urinary ducts
Male System

Reproductive System
Reproductive System
Female frogs a pair of
Female frogs a pair of
large, lobed ovaries
large, lobed ovaries
containing thousands of
containing thousands of
tiny immature eggs lie near
tiny immature eggs lie near
the kidneys
the 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

Reproductive System
Reproductive System
 The vast majority of eggs
The vast majority of eggs
and tadpoles are eaten by
predators such as fish,
birds, snakes, and turtles.
Some species of frogs
Some species of frogs
have
have
 The vast majority of eggs
The vast majority of eggs
birds, snakes, and turtles
. Amplexus

Metamorphosis
Metamorphosis
Newly hatched tadpoles live off
Newly hatched tadpoles live off
yolk stored in their bodies. They
yolk stored in their bodies. They
gradually grow larger and develop
gradually grow larger and develop
three pairs of gills.
three pairs of gills.
Tadpoles have a two-chambered
Tadpoles have a two-chambered
heart. Tadpoles can also regenerate
heart. Tadpoles can also regenerate
injured or lost body parts such as a
injured or lost body parts such as a
leg or tail.
leg or tail.
Legs grow from the body, and the
Legs grow from the body, and the
tail disappears.
tail disappears.

Metamorphosis
Metamorphosis
 The mouth broadens, developing
The mouth broadens, developing
teeth and jaws. A saclike
teeth and jaws. A saclike
bladder in the throat divides
bladder in the throat divides
into two sacs that become
into two sacs that become
lungs. The heart develops a
lungs. The heart develops a
third chamber.
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 tadpole are
The cells of the tadpole 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. Copyright Cmassengale

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