Chapter 40
Amphibians
Section 1 Origin and Evolution of
Amphibians
Section 2 Characteristics of Amphibians
Section 3 Reproduction in Amphibians
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Describe the three preadaptations involved
in the transition from aquatic to terrestrial
life.
Describe two similarities between
amphibians and lobe-finned fishes.
List five characteristics of living
amphibians.
Name the three orders of living
amphibians, and give an example of each.
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
 Preadaptations - are adaptations in an
ancestral group that allow a shift to new
functions which are later favored by natural
selection.
Lobe-finned fishes had several preadaptations
that allowed them to transition to life on
land.





______________
_______________________________________
__________________
___________________
_____________________
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Characteristics of Early Amphibians
Amphibians and lobe-finned fishes share many anatomical
similarities, including:
 similar skull
 similar vertebral column
 similar bone structure in fins and limbs
 early amphibians had a large tail fin and lateral line canals
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Diversification of Amphibians
About ______ million years ago
amphibians split into two main
evolutionary lines.
One line included ancestors of
reptiles, the other line included the
ancestors of modern amphibians.
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Diversification of Amphibians
Today there are about 4,500 species of
amphibians belonging to three orders:
_________ - includes frogs and toads
___________ - includes salamanders
and newts
______________ - includes caecilians
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Modern amphibians share several key
characteristics
 Most change from an aquatic larval stage to a terrestrial
adult form, in a transformation called metamorphosis.
 Most have moist, thin skin with no scales.
 Feet, if present, lack _________ and often are webbed.
 Most use gills, lungs, and skin in respiration.
 Eggs lack multicellular membranes or shells, are usually
laid in water, and are usually fertilized
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Order Anura
Order includes ______ and ________.
Members may be fully aquatic, fully
terrestrial, or amphibious.
Most reproduce in water, laying eggs that
hatch into swimming larvae called
___________.
Larvae are _________. Adults are
_____________ and will eat any animal they
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can capture.
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Order Caudata
Includes ___________ (may also be called newts).
Members may be fully aquatic, fully terrestrial,
or amphibious.
Many reproduce in water. Some reproduce on
land, with no swimming larval stage.
Larvae and adults are
___________________.
Some have no lungs, and respire through their
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skin only.
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
Order Gymnophiona
 Includes ____________ (legless amphibians that resemble
small snakes).
 Most are burrowing. They have small eyes beneath skin
or bone, and are often blind.
 All are ________________.
 All are thought to have internal fertilization.
 Some lay eggs which the female guards, others develop
inside the female.
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Chapter 40
Section 1 Origin and Evolution of
Amphibians
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Chapter 40
Section 2 Characteristics of
Amphibians
 Relate the structure of amphibian skin to the types of habitats in
which amphibians can survive.
 Identify three adaptations for life on land shown by the skeleton
of a frog.
 Sequence the flow of blood through an amphibian’s heart.
 Describe how a frog fills its lungs with air.
 Describe the digestive and excretory systems of amphibians.
 Discuss an amphibian’s nervous system.
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Chapter 40
Section 2 Characteristics of
Amphibians
Amphibian skin serves two important
functions:
Respiration - The skin is permeable to gases and
water. ____________________secrete a lubricant that
keeps the skin moist in air.
Protection - The skin protects amphibians from
infection and secretes a _______________ or
______________ mucus that protects amphibians
from predators.
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Chapter 40
Section 2 Characteristics of
Amphibians
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Chapter 40
Section 2 Characteristics of
Amphibians
A strong skeleton supports the body of amphibians against the
force of gravity.
 Vertebrae ______________ to form a strong, rigid structure.
 Strong limbs assist with standing and walking.
 _____________ and ____________ girdles transfer weight to the
limbs.
 Skeletons of frogs are specialized for jumping and landing.
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Chapter 40
Section 2 Characteristics of
Amphibians
 _______________add strength to
the forelimbs and hind limbs.
 Thick arm bones and pectoral
girdle absorb shock of landing.
 Long hind legs allow frogs to
jump farther.
 Lengthened pelvic girdle and
fused vertebrae add support.
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Chapter 40
Section 2 Characteristics of
Amphibians
The circulatory system is divided into
______ loops.
_____________circulation - carries
deoxygenated blood from the heart to
the lungs and back to the heart.
______________ circulation - carries
oxygenated blood from the heart to the
body and back to the heart.
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Chapter 40
Section 2 Characteristics of
Amphibians
___________ chambered heart:
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Chapter 40
Section 2 Characteristics of
Amphibians
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Chapter 40
Section 2 Characteristics of
Amphibians
Amphibians use two forms of
respiration
____________respiration - respiration
through the lungs
____________ respiration - respiration
through the skin
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Chapter 40
Section 2 Characteristics of
Amphibians
Amphibians use positive pressure breathing, shown
below.
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Chapter 40
Section 2 Characteristics of
Amphibians
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Chapter 40
Section 2 Characteristics of
Amphibians
 Includes the pharynx, esophagus, stomach, liver,
gallbladder, small intestine, large intestine, and cloaca.
 The upper part of the small intestine is called the
________________.
 The coiled middle portion of the small intestine is the
_________.
 A membrane that holds the small intestine in place is
called the ___________________.
 Waste materials are stored in the cloaca and exit the body
through the ________.
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Chapter 40
Section 2 Characteristics of
Amphibians
Accessory Glands
The liver produces _______, which is
stored in the gallbladder and helps
break down _____.
The ______________ secretes enzymes
that help break down food into
particles that can be absorbed by the
blood.
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Chapter 40
Section 2 Characteristics of
Amphibians
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Chapter 40
Section 2 Characteristics of
Amphibians
The ___________ are the primary
excretory organ, and filter
nitrogenous wastes from the blood.
Wastes combined with water are
known as urine_______.
Urine flows from the kidneys to the
cloaca and then to the
_________________, which branches
off the cloaca.
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Chapter 40
Section 2 Characteristics of
Amphibians
 The ______________ lobes are
larger in amphibians than in
fish.
 The _______________ is
responsible for behavior and
learning.
 The ______________process
information from the eyes.
 The __________ is responsible
for muscular coordination.
 The ___________controls heart
rate and respiration rate.
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Chapter 40
Section 2 Characteristics of
Amphibians
Sense Organs -
 Larvae have a _______________, most adults do not.
 The eyes are covered by a ___________________, a
transparent moveable membrane that protects the
eye.
 Sound is detected by the ________________.
 Sounds are transmitted to the inner ear by the
_______________, or eardrum, and the _____________, a
small bone that extends between the tympanic
membrane and the inner ear.
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Chapter 40
Section 3 Reproduction in
Amphibians
Explain how a male frog attracts a
female of the same species.
Discuss the reproductive system of a
frog.
Describe the life cycle of a frog.
Describe the changes that occur during
metamorphosis in frogs.
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Chapter 40
Section 3 Reproduction in
Amphibians
Males attract females with a mating
call.
Females only respond to males of the
same species.
The male clings to the female in an
embrace called ______________.
Eggs and sperm are released into the
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Chapter 40
Section 3 Reproduction in
Amphibians
Reproductive system
Male - includes two bean-shaped
testes located near the kidneys that
produce sperm during the breeding
season.
Female - includes a pair of large
ovaries containing thousands of tiny
immature eggs. During the
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Chapter 40
Section 3 Reproduction in
Amphibians
 When the eggs hatch, a tadpole is released.
 The tadpole grows and slowly changes from an aquatic
larva into an adult in a process called _______________.
 Metamorphosis is controlled by a hormone called
______________.
 Some amphibians do not produce _____________ and
remain in the larval stage their entire life.
 Some amphibians do not have a larval stage and hatch
from the egg as small versions of the adult.
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Chapter 40
Section 3 Reproduction in
Amphibians
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Chapter 40
Section 3 Reproduction in
Amphibians
Parental care increases the likelihood that the offspring
will survive.
 Some species guard their eggs until they hatch.
 Some species sit on their eggs to prevent them from
drying out.
 The male Darwin’s frog carries the eggs in his vocal
sacs until the larvae finish metamorphosis.
 Female gastric brooding frogs swallow their eggs and
the larvae mature in the stomach.
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Chapter 40
Standardized Test Prep
1. The forelimbs of vertebrates evolved
from which structures in lobe-finned
fishes?
A. anal fin
B. pelvic fin
C. pectoral fins
D. pectoral girdle
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Chapter 40
Standardized Test Prep
1. The forelimbs of vertebrates evolved
from which structures in lobe-finned
fishes?
A. anal fin
B. pelvic fin
C. pectoral fins
D. pectoral girdle
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Chapter 40
Standardized Test Prep
2. Amphibians must lay eggs in water
primarily for what reason?
F. The eggs are not laid in nests.
G. The eggs need oxygen from water.
H. The eggs need protection from
predators.
J. The eggs do not have multicellular
membranes and a shell.
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Chapter 40
Standardized Test Prep
2. Amphibians must lay eggs in water
primarily for what reason?
F. The eggs are not laid in nests.
G. The eggs need oxygen from water.
H. The eggs need protection from
predators.
J. The eggs do not have multicellular
membranes and a shell.
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Chapter 40
Standardized Test Prep
3. Metamorphosis must take place before
amphibians are able to do what?
A. swim
B. live on land
C. respire with gills
D. feed themselves
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Chapter 40
Standardized Test Prep
3. Metamorphosis must take place before
amphibians are able to do what?
A. swim
B. live on land
C. respire with gills
D. feed themselves
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Chapter 40
Standardized Test Prep
The figure below shows a longitudinal
section, ventral view, of a frog heart. Use
the figure below to answer question 4.
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Chapter 40
Standardized Test Prep
4. Identify the source of blood flow in the
section of the heart labeled 1.
F. the body
G. the aorta
H. the lungs
J. both lungs and body
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Chapter 40
Standardized Test Prep
4. Identify the source of blood flow in the
section of the heart labeled 1.
F. the body
G. the aorta
H. the lungs
J. both lungs and body
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Chapter 40
Standardized Test Prep
5. Anura : frogs :: Gymnophiona :
A. toads
B. newts
C. caecilians
D. salamanders
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Standardized Test Prep
5. Anura : frogs :: Gymnophiona :
A. toads
B. newts
C. caecilians
D. salamanders
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Chapter 40
Standardized Test Prep
The figure below shows an artist’s
rendering of Ichthyostega. Use the figure
to answer the question that follows.
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Chapter 40
Standardized Test Prep
6. Ichthyostega is an early amphibian.
Which of the following characteristics is
most likely to help it live on land?
F. fishlike tail
G. seven-toed feet
H. four strong limbs
J. lateral-line canals on the head
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Chapter 40
Standardized Test Prep
6. Ichthyostega is an early amphibian.
Which of the following characteristics is
most likely to help it live on land?
F. fishlike tail
G. seven-toed feet
H. four strong limbs
J. lateral-line canals on the head
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Chapter 40
Standardized Test Prep
Modern amphibians are a diverse
group, but they do have some
common characteristics.
Describe five key characteristics
shared by modern amphibians.
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Chapter 40
Standardized Test Prep
Modern amphibians are a diverse
group, but they do have some
common characteristics.
Describe five key characteristics
shared by modern amphibians.
Answer: Metamorphosis from larva
to adult; moist, thin skin; clawless
feet; respiration with lungs, skin,
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Chapter 40
Standardized Test Prep
Base your answers to parts A & B on
the information below.
Frogs breathe by a positive pressure
system.
Part A Describe how frogs move air
into their lungs. Which part of
inhaling is “positive pressure?”
Part B Describe how frogs move air
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Chapter 40
Standardized Test Prep
Answer:
Part A The mouth floor drops, sucking air
in. The nostrils seal and the mouth floor
lifts (positive pressure), which forces air
into the lungs.
Part B: The body wall muscles and lung
elasticity force lung air into the mouth,
which makes the floor drop. The floor then
lifts to force air out of nostrils.
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