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Non-vertebrate Chordates,
Fishes, and Amphibians
Chapter 30
30-1 What is a chordate?
• All chordates show the
following traits at some
point in their lifetime:
1. Dorsal, hollow nerve cord
2. Notochord
3. Pharyngeal pouches
4. Tail beyond the anus
What is a chordate? (cont)
• The hollow nerve cord runs along the dorsal part of
the body.
• The notochord is a long, flexible rod that supports the
body.
– Found beneath the nerve cord
– May be replaced by bone (in vertebrates)
What is a chordate? (cont)
• Pharyngeal
pouches are paired
structures in the
throat region.
– In some chordates,
they open to the
outside of the body
and used for gas
exchange.
• All chordates have a
tail that extends
beyond the anus.
– It can contain bone
and muscle.
Mouse embryo
Most Chordates are Vertebrates
• About 96% of all
chordates are in the
subphylum Vertebrata.
• Most vertebrates have a
backbone.
• The anterior end of the
vertebrate backbone
develops into a brain.
• The backbone is made
of vertebrae.
• The backbone is part of
an endoskeleton.
Nonvertebrate Chordates
• Two groups of nonvertebrate chordates exist:
– Tunicates
– Lancelets
• Both are soft bodied marine organisms.
30-1 What is a fish?
• Fish are aquatic
vertebrates.
• Most have paired
fins, scales, and
gills.
• Fish were the first
vertebrates to evolve.
• The evolution of jaws
and the evolution of
paired fins were
important
developments during
the rise of the fishes.
The Evolution of Fish
• The earliest fish
were jawless,
armored with
bony plates
(about 400 million
yrs ago).
• Jaws allowed fish
better feeding
ability as well as
defense.
• Paired fins aided
movement and
provided more
control of
movement.
Doryaspis
Pacific Hagfish
Form & Function in Fish
• Fish can be herbivores,
carnivores, parasites,
filter feeders, and
detritus feeders.
• Most fish use gills for
gas exchange.
• Some fish have
specialized organs that
allow them to survive in
oxygen-poor water or in
areas where bodies of
water often dry up.
These specialized
organs serve as lungs.
African Lungfish
Fish Form & Function (Cont)
• Fish have a complete
digestive system
(alimentary canal).
• Fish have a closed
circulatory system with
a two chambered heart
that pumps blood.
• Fish are ectothermic.
• Most fish rid themselves
of nitrogenous wastes in
the form of ammonia
through the gills and
kidneys.
Fish Form & Function (Cont)
• Fish have well-developed nervous systems and highly
developed sense organs.
• The lateral line system can detect gentle currents
and vibrations in water with sensitive receptors.
Fish Form & Function (Cont)
• The swim
bladder is found
in bony fish.
• The swim bladder
is an internal, gasfilled organ that
can adjust the
buoyancy. It lies
just beneath the
back bone.
Fish Form & Function (Cont)
• Fish whose eggs hatch
outside the mother’s body
are oviparous. The embryos
obtain food from a yolk in the
egg.
• Fish that retain the eggs after
fertilization are called
ovoviparous. Embryos use
the yolk for nourishment. The
young are “born alive”.
• Viviparous animals develop
in the mother’s body and
obtain nourishment from the
mother’s body. (Fish are not
viviparous.)
Classification of Fish
• All living fish can be
classified into 3 groups:
1. Jawless fish (Agnatha)
2. Cartilaginous Fish
(Chondrichthyes)
3. Bony fish (Osteichthyes)
The Jawless Fish
• Jawless fish (Class
Agnatha) have no true
teeth or jaws.
• Their skeleton is made
of fibers and cartilage.
• They lack vertebrae and
retain their notochord as
adults.
• They have fish-like
bodies, no scales, and
unpaired fins.
• Two types: Hagfish &
Lampreys.
Hagfish
Lamprey
Cartilaginous Fish
• Belong to Class
Chondrichthyes.
• Includes sharks,
skates, rays.
• The skeleton is
entirely cartilage (no
bone).
• Possess tooth-like
scales.
• Gills are not
protected with bony
covering.
Bony Fish
• Belong to Class
Osteichthyes.
• Skeletons are made of
bone.
• Divided into two groups
– Ray-finned fish (have
bony spines or rays in the
fins)
• Perch
• Trout
Trout
– Lobe-finned fish (fleshy
fins have bones)
• Lungfish
• Coelocanth
Coelocanth
30-3 Amphibians
• An amphibian is a vertebrate
that, with some exceptions,
lives in water as a larva and on
land as an adult, breathes with
lungs as an adult, has moist
skin that contains mucus
glands, and lacks scales and
claws.
• The first amphibians probably
resembled lobe-finned fish
but had legs.
• There were challenges to
surviving on land
• Terrestrial vertebrates have to
breathe air, protect themselves
(and eggs) from drying out, and
support against the pull of
gravity.
Evolution of Amphibians
• Early amphibians evolved
several adaptations to
land:
– Bones in the limbs and
limb girdles became
stronger, permitting
better movement
– Lungs and breathing
tubes aided gas
exchange
– A sternum formed a
shield to support and
protect the internal
organs
• Most amphibians became
extinct at the end of the
Permian Period. Only 3
orders of small amphibians
still exist: frogs and toads,
salamanders, and
caecilians.
Amphibian Form & Function
• Tadpoles are typically
filter feeders or
herbivores; as adults they
become meat eaters.
• Amphibians have a
complete digestive
system.
• Respiration occurs
through the skin and gills
(tadpoles) or via the skin
and lungs (adults).
• Lungless amphibians use
the thin lining of the mouth
cavity and the skin.
Amphibian Form & Function
• Amphibians have a closed
circulatory system with a 3
chambered heart (two atria
and a ventricle).
• Amphibians are
ectothermic.
• A pair of kidneys removes
metabolic wastes from the
blood and form urine. Urine
can be stored in the urinary
bladder and excreted
through the cloaca.
Amphibian Form & Function
• Because amphibian
eggs lack a shell, the
eggs must be kept
moist.
• In most species,
females lay the eggs in
water. Fertilization is
external.
• Eggs are covered with
a sticky jelly.
• Most amphibians
abandon their eggs
after laying them.
Amphibian Classification
• Salamanders have long
bodies and tails. Most
have four legs. Adults and
larvae are carnivores.
• Frogs and toads share
their ability to jump. Frogs
tend to have long legs and
jump longer. Frogs are
more closely tied to water.
Adult frogs and toads lack
tails.
• Caecilians are legless
amphibians that live in
water or burrow in moist
soil.
Reptiles & Birds
Chapter 31
What is a reptile?
• A reptile is a vertebrate that
has dry, scaly skin, lungs,
and terrestrial eggs, with
several membranes.
• Reptilian skin is dry and
often covered with thick
scales.
• Scaly skin must be shed
periodically.
• Reptiles were the first
animals to lay shelled eggs
(amniote eggs).
• Reptiles evolved from
amphibian-like ancestors.
Reptile Form & Function
• Reptiles are ectothermic.
• Gas exchange is always via
lungs.
• Reptiles have a 3 chambered
heart with a partially divided
ventricle.
• Kidneys remove metabolic
wastes.
• All reptiles use internal
fertilization. Most males have a
penis-like organ that allows them
to deliver sperm into the female’s
cloaca.
• Reptiles are oviparous or
ovoviviparous.
• Legs have clawed toes.
Reptile Eggs
• The amnion is a fluidfilled sac that
surrounds and
cushions the embryo.
• The chorion regulates
gas exchange.
• The yolk sac contains
a nutrient-rich food
supply.
• The allantois stores
metabolic wastes.
• The shell is
impermeable to water
and to sperm.
• The amniote egg is
one of the most
important adaptations
to life on land.
Crocodile eggs
Reptile Classification
• There are four
surviving groups of
reptiles:
1. Lizards and Snakes
2. Crocodilians
3. Turtles and Tortoises
4. Tuataras
What is a bird?
• Birds are reptile-like
animals that maintain a
constant internal body
temperature. They have an
outer covering feathers;
two legs that are covered
with scales and are sued
for walking or perching;
and front limbs modified
into wings.
• The single most important
trait separating birds from
other vertebrates is
feathers.
Bird Feathers
• Feathers are made
mostly of protein
(keratin).
• Feathers help birds fly
and keep them warm.
• Preening allows birds to
rub oil on the feathers to
keep them water
resistant.
• Though all birds have
wings and feathers, not
all birds can fly.
Form & Function of Birds
• Birds are endothermic.
• The mouth lacks teeth and is
modified into a beak.
• Lacking teeth, birds have
specialized structures to help
digest food.
– A crop at the lower end of the
esophagus stores and
moistens food. It can also be
used to store nutrient rich food
to feed baby birds.
– The gizzard is a muscular
organ that may contain small
rocks to help grind food.
gizzard
Bird Form & Function
• Bird lungs have many air
sacs to increase gas
exchange.
• Birds have a 4
chambered heart and
are endothermic.
• Light-weight bones aid
flight.
• Birds that fly have only
one gonad and no
urinary bladder.
Bird Reproduction
• Both male and
female reproductive
tracts empty into the
cloaca.
• Bird eggs are
amniotic.
• Most birds incubate
their eggs until the
eggs hatch.
• Both parents may be
involved in raising the
offspring.
Bird Classification
• Nearly 30 orders of
birds exist.
• The largest order
of birds includes
the perching birds
(songbirds). There
are nearly 5000
species of
perching birds.
Mammals
Chapter 32
What is a mammal?
• Mammals have
milk producing
mammary glands.
• Mammals have
hair covering the
body.
• All breathe air with
lungs, have 4
chambered
hearts, and are
endothermic.
Mammal Form & Function
• Endotherms have a
much higher
metabolic rate than
other chordates.
• Hair and a layer of
subcutaneous fat
helps keep mammals
warm.
• Sweat glands help
cool the body. Panting
is a way that mammals
without sweat glands
can cool the body.
Mammal Form & Function
• High metabolic rates require
more food intake.
• Mammals can be
herbivores, carnivores, or
omnivores.
• Jaws and teeth are
specialized.
–
–
–
–
Incisors
Canines
Premolars
Molars
• Herbivores have a rumen
(stomach chamber) that
contains symbiotic bacteria
to digest the cellulose.
Mammal Form & Function
• All mammals use
lungs.
• A powerful muscle
called the diaphragm
aids breathing.
• Mammals have a
powerful 4 chambered
heart.
• Kidneys are used to
remove metabolic
wastes in the form of
urea.
Mammal Form & Function
• Mammals reproduce
by internal
fertilization.
• All offspring feed on
the mother’s milk.
• Offspring are cared
for by one or both
parents.
• Mammals are
classified into 3
groups based on
their mode of
development and
birth.
Mammal Diversity & Classification
• The three groups of
mammals are
1. Monotremes (egg
laying)
2. Marsupials
(pouched mammals)
3. Placentals
(develop in a uterus
and are nourished
by a placenta)
The Orders of Mammals
• Order Monotremata
– Egg laying
– Includes platypus and
echidna
• Order Marsupialia
– Pouched mammals
– Bear live young but at
a very early stage of
development
– Young complete
development in a
pouch (marsupium)
Orders of Mammals
• Order Insectivora
– Insect eaters
– Long narrow snout
– Sharp claws well
suited for digging
– Includes shrews,
hedgehogs, moles
• Order Sirenia
– Herbivores that live in
rivers and bays
– Large, slow-moving
aquatic mammals
– Manatees
Orders of Mammals
• Order Cetacea
– Adapted to life
underwater
– Have a blow hole
– Whales, dolphins,
porpoises
• Order Chiroptera
– Winged mammals
– Only mammals
capable of true flight
– Eat mostly insects and
fruit
– Bats
Orders of Mammals
• Order Rodentia
– Single pair of long,
curved incisors for
gnawing
– Mice, rats, voles,
squirrels, beavers,
gerbils
• Order Carnivora
– Have sharp canines
for catching prey
– Sharp claws
– Dogs, foxes, bears,
cats, walruses
Orders of Mammals
• Order Perissodactyla
– Odd toed hoofed
mammals
– Horses, tapirs,
rhinoceroses, zebras
• Order Artiodactyla
– Even toed hoofed
mammals
– Mostly large, grazing
animals
– Cattle, sheep, goats,
pigs, giraffes,
hippopotamus, camels,
deer
Orders of Mammals
• Order Lagomorpha
– Herbivores with two
pairs of incisors
– Adapted for running
and jumping
– Rabbits, hares
• Order Proboscidea
– Trunk-nosed mammals
– Elephants
Orders of Mammals
• Order Xenarthra
– Simple teeth without
enamel; some with no
teeth at all
– Sloths, anteaters,
armadillos
• Order Primata
– Highly developed
cerebrum and complex
behaviors
– Five digits on hands and
feet
– Lemurs, tarsiers, apes,
gibbons, humans