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Chapter 34
Vertebrates
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mammalia
(mammals)
Reptilia
(turtles, snakes,
crocodiles, birds)
Amphibia
(frogs, salamanders)
Dipnoi
(lungfishes)
Actinistia
(coelacanths)
Actinopterygii
(ray-finned fishes)
Chordates
Craniates
Vertebrates
Gnathostomes
Osteichthyans
Lobe-fins
Tetrapods
Amniotes
Chondrichthyes
(sharks, rays, chimaeras)
Cephalaspidomorphi
(lampreys)
Myxini
(hagfishes)
Cephalochordata
(lancelets)
Urochordata
(tunicates)
Echinodermata
(sister group to chordates)
Hypothetical Phylogeny of Chordates
Milk
Amniotic egg
Legs
Lobed fins
Lungs or lung derivatives
Jaws, mineralized skeleton
Vertebral column
Head
Brain
Notochord
Figure 34.2
Ancestral deuterostome
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Vertebrates
• By the end of the Cambrian period, some 540
million years ago
– An astonishing variety of animals inhabited
Earth’s oceans
• One of these types of animals
– Gave rise to vertebrates, one of the most
successful groups of animals
• There are approximately 52,000 species of
vertebrates
– Which include the largest organisms ever to
live on the Earth
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Vertebrates
• The animals called vertebrates
– Get their name from vertebrae, the series of
bones that make up the backbone
Figure 34.1
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Chordates
• Chordates have a notochord and a dorsal,
hollow nerve cord, post-anal tail, and
pharyngeal slits during some part of their
development
– Vertebrates are a subphylum of the phylum
Chordata
• Chordates are bilaterian animals that belong to
the clade of animals known as Deuterostomia
• Two groups of invertebrate deuterostomes, the
urochordates and cephalochordates, are more
closely related to vertebrates than to
invertebrates
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Derived Characters of Chordates
• All chordates share a set of derived characters
– Although some species possess some of these
traits only during embryonic development
Dorsal,
hollow
nerve cord
Muscle
segments
Brain
Notochord
Mouth
Anus
Muscular,
post-anal tail
Figure 34.3
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Pharyngeal
slits or clefts
Notochord
• The notochord
– Is a longitudinal, flexible rod located between
the digestive tube and the nerve cord
– Provides skeletal support throughout most of
the length of a chordate
• In most vertebrates, a more complex, jointed
skeleton develops
– And the adult retains only remnants of the
embryonic notochord
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Dorsal, Hollow Nerve Cord
• The nerve cord of a chordate embryo
– Develops from a plate of ectoderm that rolls
into a tube dorsal to the notochord
– Develops into the central nervous system: the
brain and the spinal cord
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Pharyngeal Slits or Clefts
• In most chordates, grooves in the pharynx
called pharyngeal clefts
– Develop into slits that open to the outside of
the body
• These pharyngeal slits
– Function as suspension-feeding structures in
many invertebrate chordates
– Are modified for gas exchange in aquatic
vertebrates
– Develop into parts of the ear, head, and neck
in terrestrial vertebrates
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Muscular, Post-Anal Tail
• Chordates have a tail extending posterior to the
anus
– Although in many species it is lost during
embryonic development
• The chordate tail contains skeletal elements
and muscles
– And it provides much of the propelling force in
many aquatic species
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Tunicates – Invertebrate Chrodates
•
Tunicates, subphylum Urochordata belong to the deepest-branching
lineage of chordates are marine suspension feeders commonly called
sea squirts
•
Tunicates most resemble chordates during their larval stage which may
be as brief as a few minutes
Notochord
Dorsal, hollow
nerve cord
Tail
Excurrent
siphon
Incurrent
siphon
Muscle
segments
Intestine
Stomach
Atrium
Pharynx with slits
Figure 34.4c
(c) A tunicate larva is a free-swimming but
nonfeeding “tadpole” in which all four
chief characters of chordates are evident.
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Tunicates – Invertebrate Chrodates
• As an adult a tunicate draws in water through
an incurrent siphon, filtering food particles
Incurrent
siphon
to mouth
Excurrent
siphon
Excurrent
siphon
Atrium
Pharynx
with
numerous
slits
Tunic
Anus
Intestine
Esophagus
Stomach
Figure 34.4a, b
(a) An adult tunicate, or
sea squirt, is a sessile
animal (photo is
approximately life-sized).
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(b) In the adult, prominent
pharyngeal slits function
in suspension feeding,
but other chordate
characters are not obvious.
Lancelets – Invertebrate Chrodates
•
Lancelets, subphylum Cephalochordata are named for their bladelike
shape. Lancelets are marine suspension feeders that retain the
characteristics of the chordate body plan as adults.
Tentacle
2 cm
Mouth
Pharyngeal slits
Atrium
Notochord
Digestive tract
Atriopore
Dorsal, hollow
nerve cord
Segmental
muscles
Anus
Tail
Figure 34.5
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Craniates
• Craniates are chordates that have a head
• The origin of a head
– Opened up a completely new way of feeding
for chordates: active predation
• Craniates share some common characteristics
– A skull, brain, eyes, and other sensory organs
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Derived Characters of Craniates
• One feature unique to craniates is the neural
crest, a collection of cells that appears near the
dorsal margins of the closing neural tube in an
embryo
Dorsal edges
of neural plate
Neural
crest
Neural
tube
Ectoderm
Ectoderm
Notochord
(a) The neural crest consists of
bilateral bands of cells near
the margins of the embryonic
Figure 34.7a, b
folds that form the neural tube.
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Migrating neural
crest cells
(b) Neural crest cells migrate to
distant sites in the embryo.
Neural Crest Cells
• Neural crest cells give rise to a variety of
structures, including some of the bones and
cartilage of the skull
(c) The cells give rise to some
of the anatomical structures
unique to vertebrates, including
some of the bones and cartilage
of the skull.
Figure 34.7c
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Hagfishes
• The least derived craniate lineage that still survives is class
Myxini, the hagfishes
• Hagfishes are jawless marine craniates that have a
cartilaginous skull and axial rod of cartilage derived from
the notochord but lack vertebrae
Slime glands
Figure 34.9
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Derived Characteristics of Vertebrates
• Vertebrates are craniates that have a backbone
• During the Cambrian period
– A lineage of craniates evolved into vertebrates
• Vertebrates have
– Vertebrae enclosing a spinal cord
– An elaborate skull
– Fin rays, in aquatic forms
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Lampreys
• Lampreys
– Represent the oldest living lineage of
vertebrates
– Have cartilaginous segments surrounding the
notochord and arching partly over the nerve
cord
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Lampreys
• Lampreys are jawless vertebrates inhabiting
various marine and freshwater habitats
Figure 34.10
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Origins of Bone and Teeth
• Mineralization
– Appears to have originated with vertebrate
mouthparts
• The vertebrate endoskeleton
– Became fully mineralized much later
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Gnathostomes
• Gnathostomes are vertebrates
that have jaws
Gill slits
• Today, jawless vertebrates
– Are far outnumbered by those
with jaws
• Gnathostomes have jaws
– That evolved from skeletal
supports of the pharyngeal
slits
Figure 34.13
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Cranium
Mouth
Skeletal rods
Gnathostomes
• Other characters common to gnathostomes
include
– Enhanced sensory systems, including the
lateral line system
– An extensively mineralized endoskeleton
– Paired appendages
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Chondrichthyans (Sharks, Rays, and Their Relatives)
• Members of class Chondrichthyes
– Have a skeleton that is composed primarily of
cartilage
• The cartilaginous skeleton
– Evolved secondarily from an ancestral
mineralized skeleton
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Sharks & Rays
• The largest and most diverse subclass of
Chondrichthyes includes the sharks and rays –
having streamlined bodies and acute senses
(a) Blacktip reef shark (Carcharhinus melanopterus).
Fast swimmers with acute senses, sharks have
paired pectoral and pelvic fins.
(b) Southern stingray (Dasyatis americana).
Most rays are flattened bottom-dwellers that
crush molluscs and crustaceans for food. Some
rays cruise in open water and scoop food into
Figure 34.15a, b their gaping mouth.
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Pectoral fins
Pelvic fins
Ray-Finned Fishes and Lobe-Fins
• The vast majority of vertebrates
– Belong to a clade of gnathostomes called
Osteichthyes (BONY FISHES)
• Nearly all living osteichthyans
– Have a bony endoskeleton
• Aquatic osteichthyans
– Are the vertebrates we informally call fishes
– Control their buoyancy with an air sac known
as a swim bladder
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Fishes
• Fishes breathe by drawing water over four or
five pairs of gills located in chambers covered
by a protective bony flap called the operculum
Dorsal fin
Swim bladder
Nostril
Spinal cord
Brain
Cut edge of
operculum Gills
Heart
Figure 34.16
Gonad
Urinary
Anus bladder
Liver
Kidney
Stomach Pelvic fin
Intestine
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Adipose fin
(characteristic of
trout)
Caudal
fin
Anal fin
Lateral
line
Ray-Finned Fishes
• Class Actinopterygii, the ray-finned fishes
includes nearly all the familiar aquatic
osteichthyans
(a) Yellowfin tuna (Thunnus
albacares), a fast-swimming,
schooling fish that is an important
commercial fish worldwide
(b) Clownfish (Amphiprion
ocellaris), a mutualistic
symbiont of sea anemones
Figure 34.17a–d
(c) Sea horse (Hippocampus
ramulosus), unusual in
the animal kingdom in that
the male carries the young
during their embryonic
development
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(d) Fine-spotted moray eel
(Gymnothorax dovii), a
predator that ambushes
prey from crevices in its
coral reef habitat
Lobe-Fins
• The lobe-fins, class Sarcopterygii
– Have muscular and pectoral fins
– Include coelacanths, lungfishes, and tetrapods
Figure 34.18
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Tetrapods
• Tetrapods are gnathostomes that have limbs
and feet
• One of the most significant events in vertebrate
history
– Was when the fins of some lobe-fins evolved
into the limbs and feet of tetrapods
• Tetrapods have some specific adaptations
– Four limbs and feet with digits
– Ears for detecting airborne sounds
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The Origin of Tetrapods
• In one lineage of lobe-fins the fins became
progressively more limb-like while the rest of
the body retained adaptations for aquatic life
Bones
supporting
gills
Figure 34.19
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Tetrapod
limb
skeleton
Amphibians
• Class Amphibia
– Is represented by about 4,800 species of
organisms
• Most amphibians
– Have moist skin that complements the lungs in
gas exchange
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Urodela
• Order Urodela
– Includes salamanders, which have tails
(a) Order Urodela. Urodeles
(salamanders) retain their tail as adults.
Figure 34.21a
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Anura
• Order Anura
– Includes frogs and toads, which lack tails
(b) Order Anura. Anurans, such as
this poison arrow frog, lack a tail as adults.
Figure 34.21b
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Apoda
• Order Apoda
– Includes caecilians, which are legless and
resemble worms
(c) Order Apoda. Apodans, or caecilians,
are legless, mainly burrowing amphibians.
Figure 34.21c
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Amphibians
• Amphibian means “two lives”
– A reference to the metamorphosis of an
aquatic larva into a terrestrial adult
(b) The tadpole is
an aquatic
herbivore with
a fishlike tail and
internal gills.
(a) The male grasps the female, stimulating her to
release eggs. The eggs are laid and fertilized in
water. They have a jelly coat but lack a shell and
Figure 34.22a–c would desiccate in air.
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(c) During metamorphosis, the
gills and tail are resorbed, and
walking legs develop.
Amniotes
• Amniotes are tetrapods that have a terrestrially
adapted egg
• Amniotes are a group of tetrapods
– Whose living members are the reptiles,
including birds, and the mammals
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A Phylogeny of Amniotes
Saurischians
Dinosaurs
Lepidosaurs
Archosaurs
Synapsids
Diapsids
Reptiles
Ancestral
amniote
Figure 34.23
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Derived Characters of Amniotes
• Amniotes are named for the major derived character
of the clade, the amniotic egg
– Amniotic eggs contain specialized membranes that
protect the embryo (leathery shell) – the shell prevents
desiccation of the embryo
– The amniotic egg removes the need to return to water
for reproduction – the embryonic membrane allows for
gas and waste exchange; food supplies are stored in
yolk; and the amnion protects the embryo in a fluid
filled cavity from mechanical shock
– In amniotes, there is more efficient reproduction with
internal fertilization – fewer gametes required
– New hatchlings are more fully developed in amniotes
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Amniotes
• The extraembryonic membranes have various
functions
Extraembryonic membranes
Allantois. The allantois is a disposal
sac for certain metabolic wastes produced by the embryo. The membrane
of the allantois also functions with
the chorion as a respiratory organ.
Amnion. The amnion protects
the embryo in a fluid-filled
cavity that cushions against
mechanical shock.
Chorion. The chorion and the membrane of the
allantois exchange gases between the embryo
and the air. Oxygen and carbon dioxide diffuse
freely across the shell.
Yolk sac. The yolk sac contains the
yolk, a stockpile of nutrients. Blood
vessels in the yolk sac membrane transport
nutrients from the yolk into the embryo.
Other nutrients are stored in the albumen (“egg white”).
Embryo
Amniotic cavity
with amniotic fluid
Yolk (nutrients)
Albumen
Shell
Figure 34.24
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Adaptations in Amniotes
• Amniotes also have other terrestrial
adaptations
– Such as relatively impermeable skin and the
ability to use the rib cage to ventilate the lungs
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Reptiles
• The reptile clade includes the tuatara, lizards,
snakes, turtles, crocodilians, birds, and the
extinct dinosaurs.
• Reptiles have scales that create a waterproof
barrier and lay shelled eggs on land
Figure 34.25
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Reptiles
• Most reptiles are ectothermic
– Absorbing external heat as the main source of
body heat
• Birds are endothermic
– Capable of keeping the body warm through
metabolism
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Evolution of Reptiles
• The other major living lineage of lepidosaurs
– Are the squamates, the lizards and snakes
• Lizards
– Are the most numerous and diverse reptiles,
apart from birds
Figure 34.27b (b) Australian thorny devil
lizard (Moloch horridus)
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Snakes
• Snakes are legless lepidosaurs
– That evolved from lizards
(c) Wagler’s pit viper (Tropidolaemus wagleri), a snake
Figure 34.27c
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Turtles
• Turtles
– Are the most distinctive group of reptiles alive
today
• Some turtles have adapted to deserts
– And others live entirely in ponds and rivers
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Turtles
• All turtles have a boxlike shell
– Made of upper and lower shields that are fused
to the vertebrae, clavicles, and ribs
Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina)
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Alligators and Crocodiles
• Crocodilians
– Belong to an archosaur lineage that dates
back to the late Triassic
Figure 34.27e (e) American alligator (Alligator mississipiensis)
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Reptiles Have Waterproofed Skin
• Reptiles have several adaptations for terrestrial
living not generally found in amphibians:
– Scales containing keratin waterproof the skin –
helping prevent dehydration in dry air.
– This adaptation permits life on terrestrial
habitats and provides mechanical and
chemical protection of the body
– They have well-developed lungs so they are
better able to exchange gases with their
atmosphere (air instead of water)
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Birds
• Birds are archosaurs
– But almost every feature of their reptilian
anatomy has undergone modification in their
adaptation to flight
• Many of the characters of birds
– Are adaptations that facilitate flight
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Flight in Birds
• A bird’s most obvious adaptations for flight are
its wings and feathers
Finger 1
(b) Bone structure
Palm
(a) wing
Finger 2
Forearm
Wrist
Finger 3
Shaft
Vane
Shaft
Figure 34.28a–c
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Barb
Barbule
Hook
(c) Feather structure
The Origin of Birds
• Birds probably descended from theropods
– A group of small, carnivorous dinosaurs
• By 150 million years ago feathered theropods had evolved
into birds
• Archaeopteryx remains the oldest bird known
Wing claw
Toothed beak
Airfoil wing with
contour feathers
Figure 34.29
Long tail with
many vertebrae
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Flight in Birds
• The demands of flight have rendered the
general body form of many flying birds similar
to one another
(b) Mallards. Like many bird species,
the mallard exhibits pronounced color
differences between the sexes.
(c) Laysan albatrosses. Like most birds,
Laysan albatrosses have specific
mating behaviors, such as this
courtship ritual.
(d) Barn swallows. The barn swallow is a member of
the order Passeriformes. Species in this order are
called perching birds because the toes of their feet
can lock around a branch or wire, enabling the bird
Figure 34.30b–d
to rest in place for long periods.
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Foot Structure in Birds
• Foot structure in bird feet shows considerable
variation
Perching bird
(such as a
cardinal)
Grasping bird
(such as a
woodpecker)
Figure 34.31
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Raptor
(such as a
bald eagle)
Swimming bird
(such as a duck)
Mammals
• Mammals are amniotes that have hair and
produce milk
• Mammals, class Mammalia are represented by
more than 5,000 species
– Mammary glands, which produce milk are a
distinctively mammalian character
– Hair is another mammalian characteristic
– Mammals generally have a larger brain than
other vertebrates of equivalent size
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Early Evolution in Mammals
• The jaw was remodeled during the evolution of
mammals from nonmammalian synapsids
– And two of the bones that formerly made of the
jaw joint were incorporated into the
mammalian middle ear
Jaw joint
Key
Jaw joint
Dentary
Angular
Squamosal
Articular
Quadrate
Dimetrodon
Morganucodon
(a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate
and articular, form part of the jaw joint. In Morganucodon, the lower jaw is reduced to a single bone,
the dentary, and the location of the jaw joint has shifted.
Middle ear
Stapes
Eardrum
Inner ear
Middle ear
Inner ear
Eardrum
Stapes
Sound
Sound
Incus (evolved
from quadrate)
Malleus (evolved
from articular)
Figure 34.32a, b
Morganucodon
Dimetrodon
(b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated
into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in
this evolutionary remodeling are evident in a succession of fossils.
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Monotremes
• Monotremes are a small group of egg-laying
mammals consisting of echidnas and the
platypus
Figure 34.33
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Marsupials
• Marsupials include opossums, kangaroos, and koalas
• A marsupial is born very early in its development and
completes its embryonic development while nursing within
a maternal pouch called a marsupium
(a) A young brushtail possum. The young of
marsupials are born very early in their
development. They finish their growth
while nursing from a nipple (in their
mother’s pouch in most species).
Figure 34.34a
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Convergent Evolution in Marsupials
• In Australia, convergent evolution has resulted
in a diversity of marsupials that resemble
eutherians in other parts of the world
Marsupial mammals
Plantigale
Marsupial mole
Eutherian mammals
Deer mouse
Mole
Sugar glider
Flying squirrel
Wombat
Woodchuck
Tasmanian devil
Kangaroo
Figure 34.35
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Wolverine
Patagonian cavy
Eutherians (Placental Mammals)
• Compared to marsupials
– Eutherians have a longer period of pregnancy
• Young eutherians
– Complete their embryonic development within
a uterus, joined to the mother by the placenta
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Major Eutherian Orders
MAIN
CHARACTERISTICS
ORDERS
AND EXAMPLES
Lay eggs; no
nipples; young
suck milk from
fur of mother
Monotremata
Platypuses,
echidnas
ORDERS
AND EXAMPLES
Proboscidea
Elephants
Koala
Long, muscular
trunk; thick,
loose skin; upper
incisors elongated
as tusks
Tubulidentata
Aardvark
African elephant
Teeth consisting of
many thin tubes
cemented together;
eats ants and termites
Aardvark
Aquatic; finlike
forelimbs and
no hind limbs;
herbivorous
Sirenia
Manatees,
dugongs
Embryo completes
development in
pouch on mother
Marsupialia
Kangaroos,
opossums,
koalas
Echidna
MAIN
CHARACTERISTICS
Hyracoidea
Hyraxes
Rock hyrax
Short legs; stumpy tail;
herbivorous; complex,
multichambered
stomach
Manatee
Xenarthra
Sloths,
anteaters,
armadillos
Reduced teeth or
no teeth; herbivorous
(sloths) or carnivorous
(anteaters,
armadillos)
Rodentia
Squirrels,
beavers, rats,
porcupines,
mice
Chisel-like, continuously
growing incisors worn
down by gnawing;
herbivorous
Red squirrel
Tamandua
Lagomorpha
Rabbits,
hares, picas
Chisel-like incisors;
hind legs longer than
forelegs and adapted
for running and
jumping
Primates
Lemurs,
monkeys,
apes,
humans
Golden lion
tamarin
Jackrabbit
Carnivora
Dogs, wolves,
bears, cats,
weasels, otters,
seals, walruses
Sharp, pointed canine
teeth and molars for
shearing; carnivorous
Perissodactyla
Horses,
zebras, tapirs,
rhinoceroses
Hooves with an
even number
of toes on each
foot; herbivorous
Chiroptera
Bats
Frog-eating bat
Bighorn sheep
Cetaceans
Whales,
dolphins,
porpoises
Figure 34.36
Pacific whitesided porpoise
Hooves with an
odd number of toes
on each foot;
herbivorous
Indian rhinoceros
Coyote
Cetartiodactyla
Artiodactyls
Sheep, pigs
cattle, deer,
giraffes
Opposable thumbs;
forward-facing eyes;
well-developed
cerebral cortex;
omnivorous
Aquatic; streamlined
body; paddle-like
forelimbs and no
hind limbs; thick
layer of insulating
blubber; carnivorous
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Eulipotyphla
“Core insectivores”: some
moles, some
shrews
Adapted for flight; broad
skinfold that extends
from elongated fingers
to body and legs;
carnivorous or
herbivorous
Diet consists mainly
of insects and other
small invertebrates
Star-nosed
mole
Primates
• The mammalian order Primates include lemurs,
tarsiers, monkeys, and apes
– Humans are members of the ape group
• Most primates have hands and feet adapted for
grasping
• Primates also have
– A large brain and short jaws
– Forward-looking eyes close together on the face,
providing depth perception
– Well-developed parental care and complex social
behavior
– A fully opposable thumb
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Hominoids
• The hominoids consists of primates informally
called apes
(a) Gibbons, such as this Muller's gibbon, are
found only in southeastern Asia. Their very
long arms and fingers are adaptations for
brachiation.
(b) Orangutans are shy, solitary apes that live in the rain
forests of Sumatra and Borneo. They spend most of
their time in trees; note the foot adapted for grasping
and the opposable thumb.
Figure 34.40a–e
(d) Chimpanzees live in tropical Africa. They
feed and sleep in trees but also spend a
great deal of time on the ground. Chimpanzees
are intelligent, communicative, and social.
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(e) Bonobos are closely
related to chimpanzees
but are smaller. They
survive today only in the
African nation of Congo.
(c) Gorillas are the largest apes: some
males are almost 2 m tall and weigh
about 200 kg. Found only in Africa, these
herbivores usually live in groups of up to
about 20 individuals.
Hominoids
• Hominoids
– Diverged from Old World monkeys about 20–
25 million years ago
• Humans are bipedal hominoids with a large
brain
• Homo sapiens is about 160,000 years old
– Which is very young considering that life has
existed on Earth for at least 3.5 billion years
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Derived Characters of Hominids
• A number of characters distinguish humans
from other hominoids
– Upright posture and bipedal locomotion
– Larger brains
– Language capabilities
– Symbolic thought
– The manufacture and use of complex tools
– Shortened jaw
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings