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Chapter 32
Introduction to Vertebrates
Table of Contents
Section 1 Vertebrates in the Sea and on Land
Section 2 Terrestrial Vertebrates
Section 3 Evolution of Primates
Section 4 The Genus Homo
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Objectives
• Identify the key characteristics of vertebrates.
• Describe two adaptations found in early fishes.
• Identify the relationship of fishes to amphibians.
• Summarize the key adaptations of amphibians for
life on land.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Adaptations of Vertebrates
• Vertebrates are chordates with a backbone. They
take their name from the individual segments, called
vertebrae, that make up the backbone.
• In most vertebrates, the backbone completely
replaces the notochord found in invertebrate
chordates.
• The backbone provides support for and protects a
dorsal nerve cord. It also provides a site for muscle
attachment.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Vertebrate Skeleton (Cat)
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Adaptations of Vertebrates, continued
• Vertebrates share a number of other characteristics,
including segmentation, bilateral symmetry, and two
pairs of jointed appendages, such as limbs or fins.
• The tissues of vertebrates compose organs. In turn,
the organs compose organ systems.
• Vertebrate organ systems tend to be more complex
than the organ systems found in invertebrates.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Major Vertebrate Organ Systems
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
The First Vertebrates
• The first chordates evolved about 550 million years
ago. According to the fossil record, the first
vertebrates appeared about 50 million years later.
• The first vertebrates were fishes. Unlike most of the
fishes you are familiar with, the earliest fishes, called
agnathans, had neither jaws nor paired fins.
• Within another 50 million years, jawless fishes had
diversified into a great variety of species.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolutionary
Relationships
Among
Chordates
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Fishes
This phylogenetic tree shows the relationship of the
early fishes to later fishes and amphibians.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Fishes, continued
• About 430 million years ago, the acanthodians, or
spiny fishes, appeared. Acanthodians had strong
jaws with jagged, bony edges that served as teeth,
enabling them to hold onto prey.
• Jaws are thought to have evolved from gill arch
supports made of cartilage a lightweight, strong,
flexible tissue.
• About 20 million years after the acanthodians
appeared, the placoderms, jawed fishes with
massive heads armored with bony plates, evolved.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Jaws
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Origin of Jaws
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Fishes, continued
Sharks and Bony Fishes
• About 400 million years ago, sharks and bony fishes
appeared.
• Most sharks and bony fishes have streamlined
bodies that are well adapted for rapid movement
through the water.
• Bony fishes have a skeleton made of bone, which is
heavier and less flexible than cartilage. Bony fishes
have a swim bladder, which compensates for this
weight.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Swim Bladder in Bony Fish
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Modern Fishes
• Today there are more fishes than any other group of
vertebrates, both in terms of numbers of individuals
and numbers of species.
• Today’s fishes belong to one of three major groups:
the agnathans, the cartilaginous fishes, and the bony
fishes.
• Bony fishes make up about 95 percent of modern fish
species. Because bony fishes are adapted to many
different environments, they vary greatly in size,
color, and shape.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Amphibians
• The first group of vertebrates to live on land were the
amphibians, which appeared about 370 million years
ago.
• Amphibians probably evolved from a group of bony
fishes called lobe-finned fishes.
• The pattern of bones in an amphibian’s limbs bears a
strong resemblance to that of a lobe-finned fish.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
From Fin to Limb
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Amphibians, continued
The “Age of Amphibians”
• Amphibians increased greatly in numbers during the
Carboniferous period. During this time, which begins
what is called the ―age of amphibians,‖ the number of
amphibian families increased from 14 to about 34.
• In the Permian period that followed, amphibians
reached their greatest diversity, increasing to 40
families.
• By the middle Permian, 60 percent of all amphibian
species were living in dry environments.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Evolution of Amphibians, continued
Adaptations for Life on Land
• A number of major adaptations allowed some species
to successfully invade land.
1. Legs. Legs support the body’s weight as well as
allow movement from place to place.
2. Lungs. On land, lungs carry out gas exchange.
3. Heart. Land animals tend to have higher metabolic
rates than aquatic animals. The structure of the
vertebrate heart allows oxygen to be delivered to
the body efficiently.
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Characteristics of Early Amphibians
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Chapter 32
Section 1 Vertebrates in the Sea
and on Land
Modern Amphibians
• All of today’s amphibians are descendants of the
amphibians that survived into the Jurassic period.
• They are found in aquatic and moist habitats
throughout the temperate and tropical regions of the
world.
• Frogs and toads make up the largest, and probably
the most familiar, group of modern amphibians.
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Chapter 32
Section 2 Terrestrial Vertebrates
Objectives
• Summarize why dinosaurs became the dominant
land vertebrates.
• Contrast ectotherms with endotherms.
• Identify the dinosaurlike and the birdlike features of
Archaeopteryx.
• Summarize why mammals replaced dinosaurs.
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Chapter 32
Section 2 Terrestrial Vertebrates
Early Reptiles
• Fluid loss is a problem for all terrestrial animals, that
is, animals that live on land. The adaptations that
permitted amphibians to live on land further
developed in reptiles.
• Two very important adaptations for terrestrial life
evolved in reptiles. Reptiles were the first animals to
have skin and eggs that are both almost watertight,
and they differ from amphibians in this respect.
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Chapter 32
Section 2 Terrestrial Vertebrates
Early Reptiles, continued
This phylogenetic tree shows the presumed relationship
of early reptiles to the animals that evolved from them.
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Dinosaurs
• Beginning about 235 million years ago, dinosaurs
dominated life on land for roughly 150 million years.
They evolved from the thecodonts, an extinct group
of crocodile-like reptiles.
• One factor that affected dinosaur evolution was the
movement of the continents, which radically altered
Earth’s climate.
• When the dinosaurs first appeared, all of Earth’s
landmasses were joined in a single supercontinent
called Pangaea.
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Chapter 32
Section 2 Terrestrial Vertebrates
Breakup of Pangaea
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Chapter 32
Section 2 Terrestrial Vertebrates
Continental Drift (Pangaea)
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Dinosaurs, continued
Triassic Dinosaurs
• By the end of the Triassic period, small, carnivorous dinosaurs
were very common and had largely replaced the thecodonts.
There are at least three reasons why dinosaurs were so
successful:
1. Legs positioned directly under the body provided good
support for the dinosaur’s body weight, enabling dinosaurs to be
faster and more agile runners than the thecodonts.
2. Dinosaurs were well adapted to the dry conditions found in
Pangaea during the late Triassic period.
3. At the end of the Triassic period a large meteorite struck
northeastern Canada. Thecodonts and many other species
became extinct, but the dinosaurs survived.
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Dinosaurs, continued
The Jurassic Period—The Golden Age of Dinosaurs
• The Jurassic period is considered the golden age of
dinosaurs because of the variety and abundance of
dinosaurs that lived during this time.
• They included the largest land animals of all time, the
sauropods. Sauropods were the dominant herbivores of
the Jurassic period.
• By the late Jurassic period, a new type of dinosaur had
evolved. These dinosaurs, the carnivorous theropods,
stood on two powerful legs.
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Dinosaurs, continued
Were Dinosaurs Warmblooded?
• Ectothermic animals, such as today’s reptiles, have
metabolisms that are too slow to produce enough heat to warm
their bodies.
• Mammals and birds are endothermic animals. They maintain a
high, constant body temperature by producing heat internally.
• For a long time it was thought that dinosaurs were ectotherms.
However, new evidence indicates that at least some dinosaurs
were endotherms.
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Chapter 32
Section 2 Terrestrial Vertebrates
Comparing Endotherms and Ectotherms
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Dinosaurs, continued
The Cretaceous Extinction
• 65 million years ago, all dinosaurs abruptly
disappeared from the fossil record.
• Most scientists now agree that the major contributing
cause was the impact on Earth of one or more
meteorites or asteroids.
• Such an impact would have thrown large amounts of
material from Earth’s surface into the atmosphere. This
would have blocked sunlight and created a prolonged
cold period.
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Chapter 32
Section 2 Terrestrial Vertebrates
Mass Extinction
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Birds
• The earliest known bird is Archaeopteryx.
Archaeopteryx was about the size of a crow and
shared many features with small theropods.
• Archaeopteryx had a dinosaurlike skeleton, but
birdlike wings and feathers.
• By the early Cretaceous period, only 15 million years
after Archaeopteryx lived, a variety of birds with many
of the features of modern birds had evolved.
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Chapter 32
Section 2 Terrestrial Vertebrates
Modern Birds
• There are more species of birds than of any other
terrestrial vertebrate.
• Birds live in a wide variety of environments and differ
greatly in appearance. While most birds have wings
and can fly, some birds such as the ostrich have
wings and do not fly.
• Most birds consume small, energy-rich meals of
fruits, seeds, worms, or insects.
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Chapter 32
Section 2 Terrestrial Vertebrates
Modern Reptiles
• Of the 16 orders of reptiles known to have existed,
only four remain today. The turtles have the most
ancient origins and have changed very little since
before the time of the dinosaurs.
• The vast majority of living reptiles belong to the
second group to evolve—snakes and lizards.
Tuataras belong to the third group.
• The fourth line of living reptiles—crocodiles and their
relatives, including the familiar alligators—appeared
on Earth much later than the first three groups.
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Mammals
• The first mammals appeared about 220 million years
ago, just as the dinosaurs were evolving from
thecodonts.
• It is most likely that mammals were descendants of
the therapsids, an extinct order of reptiles that were
probably endotherms.
• Mammals are the only vertebrates that have fur and
mammary glands.
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Chapter 32
Section 2 Terrestrial Vertebrates
Therapsids
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Mammals, continued
• Early mammals, such as
Eozostrodon, were
small—about the size of
mice.
• They were insect-eating
tree dwellers that were
active at night.
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Chapter 32
Section 2 Terrestrial Vertebrates
Characteristics of Early Mammals
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Chapter 32
Section 2 Terrestrial Vertebrates
Evolution of Mammals, continued
Diversification of Mammals
• In the Tertiary period, mammals rapidly diversified,
taking over many of the ecological roles once
dominated by dinosaurs.
• The largest land mammals reached their peak during
the last ice age (about 2 million to 10,000 years ago).
• Today, there are more than 4,500 species of
mammals, and they inhabit virtually every habitat on
Earth. They are found in jungles, deserts, and on
polar ice.
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Chapter 32
Section 2 Terrestrial Vertebrates
Modern Mammals
• Modern mammals other than monotremes show one
of two patterns of development.
1. Marsupials. Marsupial young are born at a very
immature stage and complete their development in
their mother’s pouch (called a marsupium).
2. Placentals. Placental mammals develop within
their mother’s body and are nourished by an organ
called the placenta.
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Chapter 32
Section 3 Evolution of Primates
Objectives
• Name two unique features of primates.
• Contrast prosimians with monkeys.
• Distinguish monkeys from apes.
• Describe the evolutionary relationship between
humans and apes.
• Identify the evidence that indicates human ancestors
walked upright before their brains enlarged.
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Chapter 32
Section 3 Evolution of Primates
Characteristics of Primates
• A primate is a member of the mammalian order
Primates, which includes prosimians, monkeys, apes,
and humans. The first primates had:
1. Grasping hands and feet
2. Forward orientation of the eyes
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Chapter 32
Section 3 Evolution of Primates
Types of Primates
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Chapter 32
Section 3 Evolution of Primates
Characteristics of Primates, continued
Prosimians
• According to the fossil record, the modern primates
that most closely resemble early primates are the
prosimians.
• A prosimian is a member of a group of mostly nightactive primates that live in trees.
• Modern prosimians include lorises, lemurs, and
tarsiers.
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Chapter 32
Section 3 Evolution of Primates
Nonhuman Primates
• About 36 million years ago, a revolution occurred in
how primates live. Many primate species became
diurnal.
• Diurnal animals are active during the day, and they
sleep at night.
• The evolution of a diurnal pattern gave primates more
opportunities to feed and enabled them to better
detect predators.
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Chapter 32
Section 3 Evolution of Primates
Comparing Diurnal and Nocturnal
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Chapter 32
Section 3 Evolution of Primates
Nonhuman Primates, continued
Monkeys
• Feeding mainly on fruits and leaves, monkeys were
among the first primates to have opposable thumbs.
• An opposable thumb—such as your own—stands
out at an angle from the other fingers and can be
bent inward toward them to hold an object.
• This gives the hand a greatly increased level of
ability to manipulate objects.
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Chapter 32
Section 3 Evolution of Primates
Nonhuman Primates, continued
Apes
• Apes, which share a common ancestor with
monkeys, first appeared about 30 million years ago.
• Modern apes include gibbons, orangutans, gorillas,
and chimpanzees.
• Apes have larger brains with respect to their body
size than monkeys, and none of the apes have tails.
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Chapter 32
Section 3 Evolution of Primates
Nonhuman Primates, continued
This phylogenetic
tree represents the
theoretical
evolutionary
relationships
between modern
apes and humans.
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Chapter 32
Section 3 Evolution of Primates
Clues to Human Ancestry
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Chapter 32
Section 3 Evolution of Primates
Early Hominids
• Hominds are primates that walk upright on two legs.
• Hominids are members of the group that led to the
evolution of humans.
• According to the fossil record, hominids first
appeared on Earth about 5 million to 7 million years
ago.
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Chapter 32
Section 3 Evolution of Primates
Hominid
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Chapter 32
Section 3 Evolution of Primates
Comparing Bipedal and Quadrupedal
Movement
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Chapter 32
Section 3 Evolution of Primates
Early Hominids, continued
Australopithecines
• The early hominids best represented by fossil finds
belong to the group known as australopithecines.
• Their fossil remains indicate that australopithecines
walked upright on two legs; thus they are classified
as hominids.
• The brains of australopithecines had a slightly greater
volume, relative to body weight, than the brain of an
ape.
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Chapter 32
Section 3 Evolution of Primates
Comparison of Gorilla and Australopithecine
Skeletons
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Chapter 32
Section 3 Evolution of Primates
Comparing Gorillas and Australopithecine
Skeletons
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Chapter 32
Section 3 Evolution of Primates
Early Hominids, continued
Other Early Hominids
• In the past few years, scientists have discovered
fossils of hominids that indicate that the hominid line
extends back past 6 million years.
• Over the last 6 million years, a variety of different
hominids have existed, with more than one species
living at one time.
• As new fossils are found, our picture of the root of the
human phylogenetic tree may come into sharper
focus.
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Chapter 32
Section 3 Evolution of Primates
Hominids in the Fossil Record
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Chapter 32
Section 4 The Genus Homo
Objectives
• Compare H. habilis with australopithecines.
• Describe the characteristics of Homo erectus.
• Describe the evidence that suggests that H. sapiens
evolved in Africa.
• Compare Neanderthals with modern humans.
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Chapter 32
Section 4 The Genus Homo
Early Members of the Human Genus
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Chapter 32
Section 4 The Genus Homo
Homo habilis
• Our genus, Homo, is composed of at least three
species. Of these three, modern humans, Homo
sapiens sapiens, is the only surviving species.
• The first members of the genus Homo appeared on
Earth more than 2 million years ago. Because of its
association with tools, this hominid was named Homo
habilis. The Latin word homo means ―man,‖ and the
Latin word habilis means ―handy.‖
• Fossils indicated that Homo habilis lived in Africa for
about 500,000 years and then became extinct.
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Chapter 32
Section 4 The Genus Homo
Homo erectus
• Homo erectus was larger than Homo habilis—about
1.5 m (5 ft) tall. Homo erectus also had a large brain
of about 1,000 cm3 (60 in.3).
• Homo erectus evolved in Africa and migrated into
Asia and Europe.
• Homo erectus survived for more than 1 million years.
The species disappeared about 200,000 years ago,
as early modern humans emerged.
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Chapter 32
Section 4 The Genus Homo
Theory of Hominid Migration
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Chapter 32
Section 4 The Genus Homo
Homo sapiens
• Homo sapiens is the only surviving species of the
genus Homo. The name Homo sapiens is from the
Latin homo, meaning ―man,‖ and sapiens, meaning
―wise.‖
• Homo sapiens is a newcomer to the hominid family.
• Early Homo sapiens left behind many fossils and
artifacts, including the first known paintings.
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Chapter 32
Section 4 The Genus Homo
Homo sapiens, continued
African Origins?
• In the past, some scientists proposed that
independent Homo erectus groups living in Africa,
Europe, and Asia interbred and that Homo sapiens
thus arose as a new species at the same time all
over Earth.
• Most scientists, however, argue that Homo sapiens
appeared in one place (Africa) and then migrated to
Europe and Asia, where the species gradually
replaced Homo erectus.
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Chapter 32
Section 4 The Genus Homo
Homo sapiens, continued
Homo sapiens in Europe
• Members of the species Homo sapiens, called
Neanderthals, first appeared in Europe about
130,000 years ago. The Neanderthals were short and
powerfully built.
• Neanderthals became more and more abundant in
Europe and Asia, and by 70,000 years ago, they had
become fairly common.
• Neanderthals were the first hominids to show
evidence of abstract thinking.
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Chapter 32
Section 4 The Genus Homo
Neanderthals
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Chapter 32
Section 4 The Genus Homo
Homo sapiens, continued
Modern Homo sapiens
• About 34,000 years ago, the European Neanderthals
were abruptly replaced by Homo sapiens of modern
appearance.
• These early humans are thought to have evolved first
in Africa and then migrated to Europe and Asia.
• Early modern humans lived by hunting. They had
complex patterns of social organization, and they
probably used language.
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Chapter 32
Standardized Test Prep
Multiple Choice
The drawings below show two extinct animals. Use the
drawings to answer questions 1–3.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
1. The colored bones in the drawings are examples of
A.
B.
C.
D.
gill arches.
vertebrae.
homologous structures.
vestigial structures.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
1. The colored bones in the drawings are examples of
A.
B.
C.
D.
gill arches.
vertebrae.
homologous structures.
vestigial structures.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
2. Which statement about the evolution of these
animals is most likely correct?
F. The lobe-finned fish evolved from the amphibian.
G. The amphibian evolved from the lobe-finned fish.
H. Both animals evolved from an earlier species of
amphibian.
J. Both animals evolved from different, unrelated
ancestors.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
2. Which statement about the evolution of these
animals is most likely correct?
F. The lobe-finned fish evolved from the amphibian.
G. The amphibian evolved from the lobe-finned fish.
H. Both animals evolved from an earlier species of
amphibian.
J. Both animals evolved from different, unrelated
ancestors.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
3. These animals belong to the same
A.
B.
C.
D.
family.
order.
class.
phylum.
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Chapter 32
Standardized Test Prep
Multiple Choice, continued
3. These animals belong to the same
A.
B.
C.
D.
family.
order.
class.
phylum.
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