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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
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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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 are jawless vertebrates (agnathans)
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
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
• The lateral line system is a row of microscopic
organs sensitive to changes in the surrounding
water pressure – enables animal to detect
minor vibrations.
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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
Chondrichthyans (Sharks, Rays, and Their Relatives)
• Shark eggs are fertilized internally.
– Some species are oviparous (lay eggs that
hatch outside mother’s body)
– Some species are ovoviviparous (retain
fertilized eggs in oviduct – embryos are
nourished by yolk and develop into young that
are born after hatching in the uterus)
– Some species are viviparous (young develop
within the uterus – receive nutrients via
placenta)
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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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Swim Bladders in Fishes
• The swim bladder is a air sac that helps control the
buoyancy of the fish.
• The transfer of gases between the swim bladder and the
blood varies the inflation of the bladder and adjusts the
density of the fish.
–
So…as opposed to sharks, fishes can conserve energy by
remaining motionless.
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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
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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Amphibians
•
Class Amphibia
–
•
•
Is represented by about 4,800 species of organisms
Most amphibians
–
Have moist skin that complements the lungs in gas exchange
–
Are metamorphic
–
Have external fertilization where eggs lack a shell
Amphibian Groups:
–
Order Urodela: salamanders
–
Order Anura: frogs
–
Order Apoda: legless amphibians
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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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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 containing keratin 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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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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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
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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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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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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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
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