Transcript Chapter 40 Amphibians Table of Contents Section 1 Origin and Evolution of Amphibians Section 2 Characteristics of Amphibians Section 3 Reproduction in Amphibians.

Chapter 40
Amphibians
Table of Contents
Section 1 Origin and Evolution of Amphibians
Section 2 Characteristics of Amphibians
Section 3 Reproduction in Amphibians
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Objectives
• 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.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Adaptation to Land
• 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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bone structure
pouches in digestive tracts for gas exchange
nostrils
higher metabolism
efficient hearts
Chapter 40
Section 1 Origin and Evolution of
Amphibians
From Fin to Limb
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Adaptation to Land, continued
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
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Characteristics of Early Amphibians
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Adaptation to Land, continued
Diversification of Amphibians
• About 300 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.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Adaptation to Land, continued
Diversification of Amphibians
Today there are about 4,500 species of amphibians
belonging to three orders:
• Anura - includes frogs and toads
• Caudata - includes salamanders and newts
• Gymnophiona - includes caecilians (legless
tropical amphibians)
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Modern 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 claws 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 externally.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Characteristics of Amphibians
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Visual Concept
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Modern Amphibians, continued
Order Anura
• Order includes frogs and toads.
• Members may be fully aquatic, fully terrestrial, or
amphibious.
• Most reproduce in water, laying eggs that hatch
into swimming larvae called tadpoles.
• Larvae are herbivores. Adults are carnivorous
and will eat any animal they can capture.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Modern Amphibians, continued
Order Caudata
• Includes salamanders (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 carnivorous.
• Some have no lungs, and respire through their
skin only.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Modern Amphibians, continued
Order Gymnophiona
• Includes caecilians (legless amphibians that
resemble small snakes).
• Most are burrowing. They have small eyes
beneath skin or bone, and are often blind.
• All are carnivorous.
• All are thought to have internal fertilization.
• Some lay eggs which the female guards, others
develop inside the female.
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Phylogenetic Diagram of Amphibians
Chapter 40
Section 1 Origin and Evolution of
Amphibians
Types of Amphibians
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Visual Concept
Chapter 40
Section 2 Characteristics of
Amphibians
Objectives
• 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.
Chapter 40
Section 2 Characteristics of
Amphibians
Skin
Amphibian skin serves two important functions:
• Respiration - The skin is permeable to gases and
water. Mucous glands secrete a lubricant that
keeps the skin moist in air.
• Protection - The skin protects amphibians from
infection and secretes a foul-tasting or poisonous
mucus that protects amphibians from predators.
Chapter 40
Section 2 Characteristics of
Amphibians
External Structure
of a Frog
Chapter 40
Section 2 Characteristics of
Amphibians
Skeleton
A strong skeleton supports the body of amphibians against
the force of gravity.
• Vertebrae interlock to form a strong, rigid structure.
• Strong limbs assist with standing and walking.
• Pectoral and pelvic girdles transfer weight to the limbs.
• Skeletons of frogs are specialized for jumping and landing.
Chapter 40
Section 2 Characteristics of
Amphibians
Skeleton, continued
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Fused bones add strength to the
forelimbs and hind limbs.
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Thick arm bones and pectoral
girdle absorb shock of landing.
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Long hind legs allow frogs to
jump farther.
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Lengthened pelvic girdle and
fused vertebrae add support.
Chapter 40
Section 2 Characteristics of
Amphibians
Circulatory System
The circulatory system is divided into two loops.
• Pulmonary circulation - carries deoxygenated
blood from the heart to the lungs and back to the
heart.
• Systemic circulation - carries oxygenated blood
from the heart to the body and back to the heart.
Chapter 40
Section 2 Characteristics of
Amphibians
Circulatory System, continued
Three chambered heart:
Chapter 40
Section 2 Characteristics of
Amphibians
Amphibian Heart Structure
Chapter 40
Section 2 Characteristics of
Amphibians
Frog Heart and Double-Loop Circulation
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Visual Concept
Chapter 40
Section 2 Characteristics of
Amphibians
Respiration
Amphibians use two forms of respiration
• Pulmonary respiration - respiration through the
lungs
• Cutaneous respiration - respiration through the
skin
Chapter 40
Section 2 Characteristics of
Amphibians
Respiration, continued
Amphibians use positive pressure breathing, shown below.
Chapter 40
Section 2 Characteristics of
Amphibians
Amphibian Lung Structure
Chapter 40
Section 2 Characteristics of
Amphibians
Respiration in Amphibians
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Visual Concept
Chapter 40
Section 2 Characteristics of
Amphibians
Digestive System
• Includes the pharynx, esophagus, stomach, liver,
gallbladder, small intestine, large intestine, and cloaca.
• The upper part of the small intestine is called the
duodenum.
• The coiled middle portion of the small intestine is the ileum.
• A membrane that holds the small intestine in place is called
the mesentery.
• Waste materials are stored in the cloaca and exit the body
through the vent.
Chapter 40
Section 2 Characteristics of
Amphibians
Digestive System, continued
Accessory Glands
• The liver produces bile, which is stored in the
gallbladder and helps break down fat.
• The pancreas secretes enzymes that help break
down food into particles that can be absorbed by
the blood.
Chapter 40
Section 2 Characteristics of
Amphibians
Internal Structure of a Frog
Chapter 40
Section 2 Characteristics of
Amphibians
Excretory System
• The kidneys 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 urinary bladder, which branches off
the cloaca.
• Nitrogenous wastes are converted from ammonia
to urea, which is highly concentrated and helps
conserve water.
Chapter 40
Section 2 Characteristics of
Amphibians
Nervous System
• The olfactory lobes are larger
in amphibians than in fish.
• The cerebrum is responsible
for behavior and learning.
• The optic lobes process
information from the eyes.
• The cerebellum is responsible
for muscular coordination.
• The medulla oblongata
controls heart rate and
respiration rate.
Chapter 40
Section 2 Characteristics of
Amphibians
Nervous System
Sense Organs -
• Larvae have a lateral line, most adults do not.
• The eyes are covered by a nictitating membrane, a
transparent moveable membrane that protects the eye.
• Sound is detected by the inner ear.
• Sounds are transmitted to the inner ear by the
tympanic membrane, or eardrum, and the columella, a
small bone that extends between the tympanic
membrane and the inner ear.
Chapter 40
Section 2 Characteristics of
Amphibians
Anatomy of a Frog
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Visual Concept
Chapter 40
Section 2 Characteristics of
Amphibians
Anatomy of a Frog (part 2)
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Visual Concept
Chapter 40
Section 3 Reproduction in
Amphibians
Objectives
• 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.
• Identify two examples of parental care in
amphibians.
Chapter 40
Section 3 Reproduction in
Amphibians
Courtship and Fertilization
• 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 amplexus.
• Eggs and sperm are released into the water.
• Fertilization is external.
Chapter 40
Section 3 Reproduction in
Amphibians
Courtship and Fertilization, continued
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 breeding season the eggs mature.
Chapter 40
Section 3 Reproduction in
Amphibians
Life Cycle
• 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.
• Metamorphosis is controlled by a hormone called
thyroxine.
• Some amphibians do not produce thyroxine 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.
Chapter 40
Life Cycle
of a Frog
Section 3 Reproduction in
Amphibians
Chapter 40
Section 3 Reproduction in
Amphibians
Amphibian Life Cycle
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Visual Concept
Chapter 40
Section 3 Reproduction in
Amphibians
Parental Care
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.