Transcript Section 2 Precambrian Time and the Paleozoic Era Chapter 9

Chapter 9
A View of Earth’s Past
Table of Contents
Section 1 Geologic Time
Section 2 Precambrian Time and the Paleozoic Era
Section 3 The Mesozoic and Cenozoic Eras
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Chapter 9
Section 1 Geologic Time
Objectives
• Summarize how scientists worked together to
develop the geologic column.
• List the major divisions of geologic time.
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Chapter 9
Section 1 Geologic Time
The Geologic Column
geologic column an ordered arrangement of rock layers that is
based on the relative ages of the rocks and in which the oldest
rocks are at the bottom.(6)(7)
• Evidence of changing conditions on Earth’s surface is recorded
in the rock layers of Earth’s crust.(1)
• The geologic time scale describes the sequence and length of
changes in earth’s crust. This outlines the development of Earth
and of life on Earth.(2)(3)
• No single area on Earth contained a record of all geologic time,
so scientists combined observations to create a standard
geologic column.(5)
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Chapter 9
Section 1 Geologic Time
The Geologic Column, continued
• Rock layers in a geologic column are distinguished by the types
of rock the layers are made of and by the kinds of fossils the
layers contain.(8)
• Fossils in the upper layers resemble modern plants and
animals.(9)
• Many of the fossils discovered in older, lower layers are from
species that look different from those living today and that have
been extinct for millions of years.(9)(10)
• 19th century scientists studied fossils and applied the principle
that old layers of rock are below young layers. (4)
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Chapter 9
Section 1 Geologic Time
The Geologic Column, continued
Using a Geologic Column
•
The first geologic columns developed used the average rates of
sediment deposition. (11)
•
To accurately determine ages of rock layers, scientist now use
radiometric dating. (12)
•
Scientists use geologic columns to estimate the age of rock layers that
cannot be dated radiometrically
•
To determine the layer’s age, scientists compare a given rock layer with
a similar layer in a geologic column that contains the same fossils or
that has the same relative position. (13)
•
If the two layers match, they likely formed at about the same time.(14)
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time
• The geologic history of Earth is marked by major
changes in Earth’s surface, climate, and types of
organisms. (15)
• Geologists use these indicators to divide the geologic
time scale into smaller units.
• Rocks grouped within each unit contain similar fossils
and each unit is generally characterized by fossils of
a dominant life-form. (16)
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time, continued
•The abbreviation Ma stands for
millions of years ago. (18)
•Answers for 19, 20, 21,
22, 23, 24, 25, 26, 27, 28,
29, 30, 31, 32,
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time, continued
Eons and Eras
• The largest unit of geologic unit of time is an eon.
Geologic time is divided into four eons: the Hadean
eon, the Archean eon, the Proterozoic eon, and the
Phanerozoic eon.(33) (34)
• The first three eons are part of a time interval
commonly known as Precambrian Time. This 4 billion
year interval contains most of Earth’s history.(35)
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time, continued
Eons and Eras
era a unit of geologic time that includes two or more periods(37)
• Dividing Precambrian time into smaller units is difficult because
very few fossils exist in early Precambrian rocks. (36)
• After Precambrian time the Phanerozoic eon began. This eon is
divided into smaller units of geologic time called eras.
• The first era of the Phanerozoic eon was the Paleozoic Era,
which lasted 292 million years.(38)(39)
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Section 1 Geologic Time
Divisions of Geologic Time, continued
Eons and Eras
• Paleozoic rocks contain fossils of a wide variety of marine and
terrestrial life forms.(42)
• After the Paleozoic Era the Mesozoic Era began and lasted
about 183 million years.
• Mesozoic fossils include early forms of birds and reptiles.
• The present era is the Cenozoic Era, which began 65.5 million
years ago. Fossils of mammals are common in Cenozoic
rocks.(43)(44)(45)
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time, continued
Eons and Eras
period a unit of geologic time that is longer than an epoch but
shorter than an era, what epochs are divided into.
epoch a subdivision of geologic time that is longer than an age but
shorter than a period, what periods are divided into. (48)
• Eras are divided into shorter time units called periods. Each
period is characterized by specific fossils and is usually named
for the location in which the fossils were first discovered.
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Chapter 9
Section 1 Geologic Time
Divisions of Geologic Time, continued
Eons and Eras
• Where the rock record is incomplete and deformed, a
detailed fossil record may be lacking to allow
scientists to divide period into shorter time units
called epochs. (49)
• Epochs may be divided into smaller units of time
called ages. (50)
• Ages are defined by the occurrence of distinct fossils
in the fossil record.(51)
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Chapter 9
Section 1 Geologic Time
Earth-History Clock
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Objectives
• Summarize how evolution is related to geologic
change.
• Identify two characteristics of Precambrian rock.
• Identify one major geologic and two major biological
developments during the Paleozoic Era.
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Evolution
evolution an inheritable change in the characteristics within a
population from one generation to the next; the development of
new types of organisms from preexisting types of organisms
over time(3)
• By examining rock layers and fossils, scientists have discovered
where the geologic history was recorded and evidence that
species of livings things have changed over time. (1)(6)
• Scientists call this process evolution.
• Information about the environment when the layer formed is the
kind of information scientists get form types of rock and fossils in
a rock layer. (2)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Evolution, continued
Evolution and Geologic Change
• Scientists think that evolution occurs by means of natural
selection. Evidence for evolution included the similarity in
skeletal structures of animals. This theory was proposed in 1859
by Charles Darwin. (4)
• Major geologic and climatic changes can affect the ability of
some organisms to survive.(5)
• By using geologic evidence, scientists try to determine how
environmental changes affected organisms in the past.
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Evolution, continued
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Section 2 Precambrian Time and
the Paleozoic Era
Evolution, continued
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Precambrian Time
Precambrian time the interval of time in the geologic
time scale from Earth’s formation to the beginning of
the Paleozoic era, from 4.6 billion to 542 million years
ago.(8)(10)
• The time interval that began with the formation of
Earth and ended about 542 million years ago is
known as Precambrian time, which makes up 88% of
Earth’s history.(9)(11)(12)
• A nebula is a large cloud or gases. (7)
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Section 2 Precambrian Time and
the Paleozoic Era
Precambrian Time, continued
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Precambrian Time, continued
• The Precambrian rock record is difficult to interpret,
because the rocks were damaged and therefore
could not be identified, therefore we do not know
much about what happened during that time. (13)
• Most Precambrian rocks have been so severely
deformed and altered by tectonic activity that the
original order of rock layers is rarely identifiable.
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Precambrian Time, continued
Precambrian Rocks
• Large areas of exposed Precambrian rocks, called
shields, exist on every continent. Formed from
volcanic activity, mountain building, sedimentation,
and metamorphism.(14) (15)
• Nearly half of the valuable mineral deposits in the
world occur in the rocks of Precambrian shields.(16)
• These valuable minerals include nickel, iron, gold,
and copper.(17)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
Precambrian Time, continued
Precambrian Life
• Fossils are rare in Precambrian rocks mostly because
Precambrian life-forms lacked bones, or other hard parts that
commonly form fossils, rock were very old, and many fossils
were probable destroyed as a result of volcanic activity, erosion,
folding and faulting.(18)
• One of the few Precambrian fossils that have been discovered
are stromatolites, which are reeflike deposits formed by bluegreen algae. They form in warm, shallow waters. (19)(20)
• The presence of stromatolite fossils in Precambrian rocks
indicates that shallow seas covered much of Earth during that
time.(21)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era
Paleozoic Era the geologic era that followed
Precambrian time and that lasted from 542 million to
251 million years ago.(22)(23)(24)
• Paleozoic rocks hold an abundant fossil record. The
number of plant and animal species on Earth
increased dramatically at the beginning of the
Paleozoic Era.
• Because of this rich fossil record, the Paleozoic Era
has been divided into seven periods.(28)
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The Paleozoic Era, continued
• When the Paleozoic Era began, Earth’s landmasses
were scattered around the world. (25)
• By the end of the Paleozoic Era, Earth’s landmasses
had collided to form the supercontinent, Pangaea.
(26)
• Paleozoic rock contain many fossils, while
Precambrian rocks do not. (27)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Cambrian Period
• The Cambrian Period is the first period of the Paleozoic Era.
• Land-dwelling plants and animals were not present. (35)
• Marine invertebrates thrived in the warm waters that existed
during this time.(30)
• Invertebrates lack a backbone. (32)
• The most common of the Cambrian invertebrates were trilobites.
Scientists use many trilobites as index fossils to date rocks to
the Cambrian Period.(34)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Cambrian Period
• The second most common animals of the Cambrian
Period were the brachiopods, a group of shelled
animals.(31)
• Fossils indicated that at least 15 different families of
brachiopods existed during this period.
• Other common Cambrian invertebrates include
worms, jellyfish, snails, and sponges.
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Ordovician Period
• During this period, populations of trilobites began to shrink, and
clamlike brachiopods and cephalopod mollusks became the
dominant invertebrate life-form.(37)
• Colonies of tiny graptolites also flourished in the oceans, and
the first vertebrates (animals with backbones) appeared.
(36)(38)
• The most primitive vertebrates were fish, which did not have
jaws or teeth and were covered with thick, bony plates. (39)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Silurian Period
• During the Silurian Period, echinoderms, relatives of
modern sea stars, and corals became more common.
• Scorpion-like sea creatures called eurypterids also
existed during this period.(40)
• Near the end of this period, the earliest land plants as
well as animals evolved on land.(41)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Devonian Period
• The Devonian Period is called the Age of Fishes because fossils
of many bony fishes were discovered in rocks of this period. (42)
• On type of fish, called a lungfish, had the ability to breathe air.
Another type of fish, Rhipidistians, were air-breathing fish that
had strong fins that may have allowed them to crawl onto the
land for short periods of time. (43)(45)
• The first amphibians were Ichthyostega. (44)
• Land plants, such as giant horsetails, ferns, and cone-bearing
plants also began to develop during this period.(46)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Carboniferous Period
• Carboniferous mean carbon bearing. (49)
• In North America, the Carboniferous Period is divided into the
Mississippian and Pennsylvanian Periods.(50)
• During this time, the climate was warm and humid, and forests
and swamps covered most of the world.(47)(48)
• Amphibians and fish continued to flourish, and the first
vertebrates that were adapted to live on land appeared as large
lizards.(52)
• Crinoids, a type of sea lily, are thought to be modern ancestor of
sea stars. (51)
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Chapter 9
Section 2 Precambrian Time and
the Paleozoic Era
The Paleozoic Era, continued
The Permian Period
•
The Permian Period marks the end of the Paleozoic Era, because a
mass extinction of a several life-forms occurred at the end of this
period.(53)(54)
•
During this time, the continents had joined to form Pangaea, and as a
result, the seas that covered the world retreated.(55)
•
Areas of desert and dry savanna climates developed on the northwest
side of mountains, and shallow inland seas disappeared. (56)
•
As the seas retreated, several species of marine life became extinct
such as eurypterids and trilobites. But, reptiles and amphibians
survived the environmental changes.(57)(58)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
Objectives
• List the periods of the Mesozoic and Cenozoic Eras.
• Identify two major geologic and biological
developments during the Mesozoic Era.
• Identify two major geologic and biological
developments during the Cenozoic Era.
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era
•
At the end of the Permian, 90% of marine organisms and 78% of land
organisms died.(1)(2)
mass extinction an episode during which large numbers of species
become extinct(3)
•
New life-forms appeared after the mass extinction due to readily
available resources and space. (4)
Mesozoic Era the geologic era that lasted from 251 million to 65.5 million
years ago; also called the Age of Reptiles.(5)(6)
•
Earth’s surface changed dramatically during the Mesozoic Era.
Pangaea broke into smaller continents, and the climate was warm and
humid and shallow seas and marshes covered much of the land.
Collisions of tectonic plates formed mountain ranges. (7)(8)(9)
•
Lizards, turtles, snakes and dinosaurs flourished during this era.(10)
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Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era, continued
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Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era, continued
The Triassic Period
•
The Mesozoic Era is known as the Age of Reptiles and is divided into
three periods: the Triassic, the Jurassic, and the Cretaceous
Periods.(11)(12)
•
Trees of the Triassic, called cycads, resembled today’s palm trees. (13)
•
The Triassic period marked the appearance of dinosaurs, the dominant
life-form. Most dinosaurs were about 4 m to 5 m long and moved very
quickly.(16)
•
Reptiles called ichthyosaurs lived in the oceans. The ammonite, a
marine invertebrate, was dominant, and serves as a Mesozoic index
fossil. (14)(15)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era, continued
The Jurassic Period
• Two major groups of dinosaurs evolved during the
Jurassic Period: the saurischians, or “lizard-hipped”
dinosaurs, and the ornithischians, or “bird-hipped”
dinosaurs.(17)(19)
• Brontosauruses, now called Apatosauruses were
saurischians and weighed up to 50 tons.
Stegosauruses, one of the best known ornithischians
and Pterosaurs were flying reptiles with skin-covered
wings and were also ornithischians.(18)(20)(21)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era, continued
The Cretaceous Period
• Among the common Cretaceous dinosaurs were the
Tyrannosaurus Rex (6m tall with teeth up to 15 cm long), the
armored ankylosaurs, the horned ceratopsians, and the duckbilled hadrosaurs.(22)(23)(24)(25)
• The earliest flowering plants, or angiosperms, appeared during
this period. The most common of these plants were magnolias
and willows.(26)
• Later, trees such as maples, oaks, and walnuts became
abundant.
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Section 3 The Mesozoic and
Cenozoic Eras
The Mesozoic Era, continued
The Cretaceous-Tertiary Mass Extinction
•
The Cretaceous Period ended in another mass extinction. No dinosaur
fossils have been found in rocks that formed after the Cretaceous
Period.(27)
•
One theory for the extinction of dinosaurs is that the continents moved
and there was increased volcanic activity that led to environmental
changes. (28)
•
Many scientists accept the impact hypothesis as the explanation for the
extinction of the dinosaurs. This hypothesis is that about 65 million
years ago, a giant meteorite crashed into Earth, spreading iridium all
over it.(28)(29)(30)
•
The impact of the collision raised enough dust to block the sun’s rays
for many years, resulting in a colder climate that caused plant life to die
and many animal species to become extinct.(28)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
Mass Extinction
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era
Cenozoic Era the current geologic era, which began 65.5 million years
ago and includes the present; also called the Age of Mammals(31)(32)
•
The earth’s continents moved to their present-day locations. (33)
•
During the Cenozoic Era, dramatic changes in climate have occurred.
As temperatures decreased during the ice ages, new species that were
adapted to life in cooler climates appeared and ice sheets covered onethird of Earth’s land at times.(34)
•
Mammals became the dominant life-form and underwent many
changes due to the cooler climates.(35)
•
The Cenozoic Era is divided into two periods: the Tertiary Period and
the Quaternary Period.
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Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Quaternary and Tertiary Periods
• The Tertiary Period includes the time before the last
ice age, and is divided into five epochs: The
Paleocene, Eocene, Oligocene, Miocene, and
Pliocene Epochs.(36)(38)
• The Quaternary Period began with the last ice age
and includes the present. (37)
• The Quaternary is divided into two epochs: The
Pleistocene and Holocene Epochs.(39)
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Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Paleocene and Eocene Epochs
• The fossil record indicates that during the Paleocene Epoch
many new mammals, such as small rodents and primates,
evolved.(40)
• Other mammals, including the earliest known ancestor of the
horse, first whales, flying squirrels, and bats, evolved during this
time.
• Worldwide, temperatures dropped by about 4ºC at the end of
the Eocene Epoch.(41)
• The Himalayas were uplifted due to the collision of the Indian
subcontinent with the Eurasian continent. (42)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Oligocene and Miocene Epochs
• During these epochs, the worldwide climate became
significantly cooler and drier. The modern Antarctic
icecap began to form and circumpolar currents
formed around Antarctica. The Mediterranean Sea
dried up and refilled several times.(43)(44)
• This climate change caused many early mammals to
become extinct. However largest known species of
deer, pigs, horses, camels, cats, and dogs flourished.
Also, the climate change favored grasses, conebearing, and hardwood trees. (43)(45)
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Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Pliocene Epoch
• During the Pliocene Epoch, predatory animals such
as bears, dogs, and cats, evolved into modern forms.
Herbivores, such as the giant ground sloth,
flourished.(46)
• Dramatic climatic changes occurred, and the
continental ice sheets began to spread. As a result,
much of Earth’s water became locked in ice. The
Bering land bridge and the Central American land
bridge formed, allowing various species to migrate
between the continents. (47)
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Pleistocene Epoch
• Began about 1.8 million years ago. (48)
• During the Pleistocene Epoch, ice sheets in Europe
and North America advanced and retreated several
times.
• Some animals had certain features that allowed them
to survive the cold climate, such as the thick fur that
covered woolly mammoths.
• Other species survived by moving to warmer regions,
while some species eventually became extinct.
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Pleistocene Epoch
• Fossils of the earliest ancestors of modern humans
were discovered in Pleistocene sediments.(49)
• Evidence of more-modern human ancestors indicated
that early humans may have been hunters.
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Chapter 9
Section 3 The Mesozoic and
Cenozoic Eras
The Cenozoic Era, continued
The Holocene Epoch
• The Holocene Epoch began 11,500 years ago as the
last glacial period ended. As the ice sheets melted,
sea level rose about 140 m, and the coastlines took
on their present shapes.(50)
• Modern humans developed agriculture and began to
make and use tools made of bronze and iron.
• If the entire history of the earth is pictured as
occurring in one year, the dinosaurs would have
disappeared on December 26.(51)
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Chapter 9
The Geologic Time
Scale
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Chapter 9
Similar Skeletal Structures of Mammals
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Chapter 9
Precambrian Time and the Paleozoic Era
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Chapter 9
The Mesozoic and Cenozoic Era
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Chapter 9
Fossil Evidence for Gondwanaland
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