Fishes and Amphibians
Chapter 28
Section 28.1
What is a fish?
• Fishes, like all vertebrates, are classified in the
phylum Chordata.
• Fishes belong to the
subphylum Vertebrata.
What is a fish?
• In addition to fishes,
subphylum Vertebrata
includes amphibians,
reptiles, birds, and
mammals.
What is a fish?
• In vertebrates, the embryo’s notochord is
replaced by a backbone in adult animals.
• All vertebrates are bilaterally symmetrical,
coelomates that have endoskeletons,( made
of cartilage or bone) closed circulatory
systems, nervous systems with complex
brains and sense organs, and efficient
respiratory systems.
• * is a tough, flexible material
Section 1
Fishes and Amphibians
Fishes
Neural Crest
 A neural crest is a group of cells that
develop from the nerve cord in vertebrates.
 Portions of the brain and skull, certain
sense organs, and some nerve fibers are
some of the structures that develop from
the neural crest.
Key Characteristics of Modern Fishes
• Despite the variation – all fish have Gills,
single loop blood circulation, and a backbone.
1.Fish breathe using gills
• Fish have gills made up of feathery gill
filaments that contain tiny blood vessels
through which gases enter and leave the
blood.
Gill Filaments
Fishes breathe using gills
• As a fish takes water in
through its mouth,
water passes over the
gills and then out
through gill slits at the
side of the fish.
Gill Filaments
• Gill cover= operculum
• Oxygen and carbon
dioxide are exchanged
through the capillaries in
the gill filaments. In a
countercurrent
flow.(=blood flows in one
direction and water in the
opposite direction.)
Water
Artery
Capillary networks
in filament Gill
filaments
Vein
Water
2. Single-loop blood circulation• Blood is pumped from the heart to the capillaries in the
gills.
• From the gills, blood passes to the rest of the body and
then returns to the Heart.
• a.) Sinus Venous- collection chamber- reduces the
resistance of blood flow into the heart.
• b.) Atrium- delivers blood to ventricle
• c.) Ventricle- forces blood to flow through the gills and
eventually to the rest of the body.
• d.) Conus arteriosus- smoothes the pulsations and
adds still more force.
• Lungfishes are an exception they have a double loop.
Fishes have two-chambered hearts
Aorta
Gills
Heart
Capillary
network
5. Reproduction
• Although the method may vary, all fishes
reproduce sexually.
• Fertilization and development is external in
most fishes.
• Eggs and sperm can be released directly into
the water, or deposited in more protected
areas, such as on floating aquatic plants.
• A yolk sac within each egg contains nutrients
the developing embryo will need for growth.
Fishes reproduce sexually
• Most bony fishes have external fertilization
and development.
• This type of external
reproduction in fishes
and some other animals
is called spawning.
Salmon spawning
Fishes reproduce sexually
• Cartilaginous fishes have internal fertilization.
• Skates deposit fertilized eggs on the
ocean floor.
• Some female sharks and rays carry
developing young inside their bodies.
• A few species of sharks lay eggs.
• During mating, the male uses two organs
called claspers to insert sperm into the
female.
Fishes reproduce sexually
• In some bony fishes, such as guppies and
mollies, fertilization and development is
internal.
• Most fishes that produce millions of eggs
provide no care for their offspring after
spawning.
• Some fishes, such as the mouth-brooding
cichlids, stay with their young after they
hatch.
Most fishes have paired fins
• Fishes in the classes Chondrichthyes
and Osteichthyes have paired fins.
• Fins are fan-shaped
membranes that are
used for balance,
swimming, and
steering.
3. Vertebral column (backbone)
• made of either cartilage or bone
• Surrounds the spinal cord
• Brain is encased with the skull or cranium.
4. KidneysNephrons- are tube-like units that regulate the
body’s salt and water balance and remove
metabolic wastes from the blood.
Freshwater fish excrete large amounts of urine
compared to marine fish due to osmosis and ion
exchange.
* to make up for the water they lose by osmosis,
marine fish drink sea water & pump out excess
ions out of their bodies.
Most fishes have paired fins
• Fins are attached to and supported by the
endoskeleton and are important in locomotion.
Most fishes have paired fins
• The paired fins of fishes foreshadowed the
development of limbs for movement on land
and ultimately of wings for flying.
Pectoral
fin
Caudal
fin
Dorsal
fins
Anal
fin
Pelvic
fins
Fishes have developed sensory systems
• The lateral line system is a line of fluid-filled
canals running along the sides of a fish that
enable it to detect movement and vibrations
in the water.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Fishes have developed sensory systems
• Fishes have eyes
that allow them to
see objects and
contrasts between
light and dark in the
water as well.
• Some fishes that live
in areas of the ocean
where there is no
light may have
reduced, almost
nonfunctional eyes.
Fishes have developed sensory systems
• Some fishes also have an extremely
sensitive sense of smell and can detect
small amounts of chemicals in the water.
• Sharks can follow a trail of blood through
the water for several hundred meters.
Section 1
Fishes and Amphibians
Scales
 There are four types of fish scales.
 Placoid scales -made
 Ctenoid scales- tooth
of tooth like material and
like a comb
 Cycloid scalesmade of bone and
skin
are rough and heavy
(shark)
 Ganoid scales-made
of enamel and bone
Jaws evolved in fishes
Gill arches
Gill slits
Jawless, filter-feeding fish
Skull
Jaws
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
• The gill arches evolved to form the jaw!!
Jaws evolved in fishes
Gill arches
Gill slits
Gill arches
Gill slits
Skull
Jawless, filter-feeding fish
Beginning of jaw formation
Fish with jaws
• Jaws also allowed early fishes to prey on a
greater variety of organisms.
• The advantage of jaws is that they enable
an animal to grasp and crush its prey with
great force
Jaws
Jaws evolved in fishes
• Sharks have up to 20 rows of teeth that
are continually replaced.
• Their teeth point
backwards to prevent
prey from escaping
once caught.
Jaws evolved in fishes
• Sharks are among the most streamlined
of all fishes and are well adapted for life
as predators.
Most fishes have bony skeletons
• Bony fishes, a successful and widely
distributed class, differ greatly in habitat,
size, feeding behavior, and shape.
Classes of fishes
Fishes
Class
Organisms
Characteristics
Myxini
Hagfishes
Jawless, cartilaginous
skeleton, gills
Cephalaspidomorphi
Lampreys
Chondrichthyes
Sharks, skates, rays
Jawless, cartilaginous
skeleton, gills
Jaws, cartilaginous skeleton, paired
fins, gills, scales, internal fertilization
Osteichthyes
Lobe-finned fishes,
ray-finned fishes
Jaws, bony skeleton, paired fins,
gills, scales, swim bladder
Bony fishes have separate vertebrae
that provide flexibility
• The evolution of a backbone composed of
separate, hard segments called vertebrae was
significant in providing the major support
structure of the vertebrate skeleton.
• Separate vertebrae provide great flexibility.
Bony fishes
evolved swim
bladders
• A fish with a
swim bladder
can control its
depth by
regulating the
amount of gas
in the bladder.
Swim bladder
Bony fishes evolved swim bladders
• Some fishes remove gases from the swim
bladder by expelling them through a special
duct that attaches the swim bladder to the
esophagus.
• In fishes that do not have this duct their swim
bladders empty when gases diffuse back into
the blood.
A Bony
Fish
Lateral line system
Swim bladder
Kidney
Urinary bladder
Scales
Reproductive organ
Fins
Stomach
Intestine
Liver
Heart Gills
Section 28.2
Diversity of fishes
• Fishes range in size from the tiny dwarf goby
that is less than 1 cm long, to the huge whale
shark that can reach a length of about 15 m—
the length of two school buses.
Whale shark
Agnathans are jawless fishes
• Lampreys and
hagfishes belong to
the superclass
Agnatha.
Lamprey
• The skeletons of agnathans, as well as of
sharks and their relatives, are made of a
tough, flexible material called cartilage.
• Lampreys and Hagfish have a notochord in
all stages of their life. (even adulthood)
Agnathans are jawless fishes
• A hagfish has a toothed mouth and feeds on
dead or dying fishes.
• It can drill a hole into a fish and suck out the
blood and insides.
• Parasitic lampreys use their suckerlike
mouths to attack other fishes.
• They use their sharp teeth to scrape away the
flesh and then suck out the prey’s blood.
Sharks and rays are cartilaginous fishes
• Sharks, skates, and rays belong to the class
Chondrichthyes.
• These fishes, like agnathans,
possess skeletons composed
entirely of cartilage.
• Sharks are perhaps the
most well-known predators
of the oceans.
Sharks and rays are cartilaginous fishes
• Like sharks, most rays are predators and
feed on or near the ocean floor.
• Ras have flat bodies
and broad pectoral fins
on their sides.
Sharks and rays are cartilaginous fishes
• By slowly flapping their toes up and down,
rays can glide as they search for mollusks
and crustaceans along the ocean floor.
Subclasses of bony fishes (see p. 831)
• Scientists recognize two subclasses of bony
fishes—the lobe-finned fishes, including
lungfishes, and the ray-finned fishes.
• The lobe-finned fishes are represented by
seven living species: six species of
lungfishes, which have both gills and
lungs, and the coelacanth.
• Each fin consists of a long, fleshy
muscular lobe that is supported by a
central core of bones.
• A third group (now extinct) - Is the
tetrapod
Subclasses of bony fishes
• In the ray-finned fishes,
such as catfish, perch,
salmon, and cod, fins are
fan-shaped membranes
supported by stiff spines
called rays.
• Teleosts- have highly
mobile fins
• Very thin scales
• Completely symmetrical
tails
• 95% of all ray finned fish
are teleosts.
Perch
Evolution of Fishes
• Scientists have identified fossils of fishes
that existed during the late Cambrian
Period, 500 million years ago.
• At this time, ostracoderms (OHS trah koh
durmz), early jawless fishes, were the
dominant vertebrates on Earth.
Origins of Fishes
Heterostracah
Anaspid
Cephalaspid
Origins of Fishes
• Bone provides a place for muscle
attachment, which improves locomotion.
• In ancestral fishes, bone that formed into
plates provided protection as well.
Origins of Fishes
• Scientists hypothesize that the jawless
ostracoderms were the common ancestors
of all fishes.
• Modern cartilaginous and bony fishes evolved
during the mid-Devonian Period.
• Lobe-finned fishes, such as coelacanths
(SEE luh kanths), are another ancient group,
appearing in the fossil record about 395
million years ago.
Key Characteristics of Amphibians
• Legs- most have 4,
Caecilians have none.
• Amphibians have thin,
moist skin (cutaneous
respiration)
• Lungs- is an internal ,
baglike respiratory
organ.
-In the larval form
they have gills not
lungs.
4. Double Loop circulation
• Two large veins called pulmonary veins return
oxygen rich blood from the lungs to the heart.
• The evolution of the three-chambered heart
in amphibians ensured that cells received the
proper amount of oxygen.
• Blood from both chambers then moves to
the third chamber, (=ventricle) which pump
oxygen-rich blood to body tissues and
oxygen-poor blood back to the lungs and
skin so it can pick up more oxygen.
5. Partially Divided Heart
• In the three-chambered heart of amphibians,
one chamber receives oxygen-rich blood
from the lungs and skin, and another
chamber receives oxygen-poor blood from
the body tissues. (=atrium) divided into left
and right sides.
•A dividing wall known as the septum
separates the atrium into a right and left.
6. Cutaneous Respiration- amphibians
have thin, moist skin which they
use to supplement their oxygen content.
Frogs and toads belong to the order Anura
• Frogs and toads are amphibians with no tails.
• Frogs have long hind legs and smooth,
moist skin.
Frog
Toad
Frogs and toads belong to the order Anura
• Toads have short legs and bumpy, dry skin.
• Adult frogs and toads are predators that eat
invertebrates, such as insects and
worms.(=carnivorous)
Frog
Toad
• Because the skin of an amphibian must stay
moist to exchange gases, most amphibians
are limited to life on the water’s edge or
other moist areas.
Frogs and toads belong to the order Anura
• Most frogs and toads spend part of their
life cycle in water and part on land.
• They breathe through lungs or through
their thin skins.
• Declining numbers of frog species, or
deformities in local frogs, sometimes
indicate the presence of pollutants in
the environment.
Eyes
A Frog
Tympanic membrane
Backbone
Fat bodies
Intestine
Tongue
Vocal cords
Lungs
Heart
Calls
Liver
Legs
Frogs and toads belong to the order Anura
• Frogs and toads also have vocal cords that are
capable of producing a wide range of sounds.
Vocal cords are sound-producing bands of
tissue in the throat.
Reproduction in Frogs
• Fertilization in most amphibians is external,
and water is needed as a medium for
transporting sperm.
• Amphibian eggs lack protective membranes
and shells and must be laid in water or other
moist areas.
Amphibians undergo metamorphosis
Fertilized eggs
Adult frog
Young, legless
tadpoles live
off yolk stored
in their bodies.
Young frogs have
structures
needed for life on land.
Tadpoles with legs feed on plants in the
water.
Metamorphosis of a Frog
•
•
•
•
•
•
Tadpole
-Herbivore
-Gills
- tail
-no legs
2 Chambered
heart
•
•
•
•
•
•
Adult
-Carnivore
-Lungs
-no tail
-legs
3 chambered heart
Amphibians undergo metamorphosis
• Young salamanders resemble adults, but, as
aquatic larvae, they have gills and usually
have a tail fin.
• Most adult salamanders
lack gills and fins.
• They breathe through
their moist skin or with
lungs.
Amphibians undergo metamorphosis
• Completely terrestrial salamander species do
not have a larval stage; the young hatch as
smaller versions of adults.
• Most salamanders
have four legs for
moving about, but a
few have only two
front legs.
Amphibians are ectotherms
• An ectotherm (EK tuh thurm) is an animal
that has a variable body temperature and
gets its heat from external sources.
• Because many biological processes
require particular temperature ranges in
order to function, amphibians become
dormant in regions that are too hot or
cold for part of the year.
Mudpuppy
Salamanders belong to the order Caudata
• A salamander has a long,
slender body with a neck
and tail.
• Salamanders resemble
lizards, but have smooth,
moist skin and lack claws.
Salamanders belong to the order Caudata
• They range in size
from a few centimeters
in length up to 1.5 m.
The young hatch from
eggs, look like small
salamander adults, and
are carnivorous.
Caecilians belong to the order Gymnophiona
• Caecilians are burrowing amphibians, have
no limbs, and have a short, or no tail
(=wormlike)
• Caecilians are primarily tropical animals
with small eyes that often are blind.
• They eat earthworms and other invertebrates
found in the soil.
• All caecilians have internal fertilization.
Challenges of life on land
• Amphibians first appeared about 360
million years ago.
• Amphibians probably evolved
from an aquatic tetrapod around
the middle of the Paleozoic Era.
Challenges of life on land
• Able to breathe through their eyes,
butt, or fingers, amphibians became, for
a time, the dominant vertebrates on land.
Challenges of life on land