El Cajon Valley High School Understanding a Unique Earth Questions

1General Science 1A
Credit 1
NAME:____________________
Rev. 5/5/21
WELCOME TO GENERAL SCIENCE IA
Understanding a Unique Earth
This course will introduce you to processes that continue to
make Earth a unique planet that supports life as we know it.
You will learn about the history and formation of Earth,
plate tectonics, Earth’s internal processes, our solar system,
and the universe. You will use the knowledge you have
gained in the course to analyze data, form an opinion, and
defend your opinions based on scientific evidence.
Course at a Glance
Credit
Title
Focus
1A
History of
Earth
Students will understand that life on our planet is a complex process
that has coevolved with Earth’s systems over billions of years. They
will examine the different stages of geologic time to construct a
timeline of Earth’s formation and history.
2A
Modeling
Plate
Tectonics
Students will understand how Earth’s internal processes cycle matter
by thermal convection, and be able to model the layers of Earth’s
interior. They will explain how plate tectonics and continental drift
affect Earth’s surface and ocean floor features.
3A
Earth’s
Internal
Processes
4A
Dating the
Geosphere
5A
Stars and the
Universe
Students will understand that Earth’s internal processes shape Earth’s
surface features. They will relate the process of plate tectonics and
Earth’s internal processes to the development of mountains and
volcanoes, and the occurrence of earthquakes.
Students will understand how the past and current movements of
Earth’s crust can be used to explain the age of crustal rocks. They will
be able to evaluate evidence from ancient Earth materials to construct
an account of Earth’s formation and the different ages of Earth’s
crustal layers.
Students will understand that the Big Bang Theory is based on
astronomical evidence. They will describe how stars, over their life
cycles, produce elements. They will explain how nuclear fusion in our
Sun releases energy in the form of radiation.
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NAME:____________________
Course Information
Teacher Contact Information
Supervising Teacher –
Science Teacher –
Phone Number –
Phone Number –
E-mail –
E-mail –
Hours Available –
Hours Available –
Tutoring Hours –
Days and Times –
Tutor Names –
Grading Scale
Mark
A
B
C
D
INC
Indicator
Points
Value
100 –
90%
89 –
80%
79 –
70%
69 –
60%
59 –
0%
Performance Task
40
Quiz
Homework
20
40
Total
100
Student Support Icons
Title
Icon
Description
Review
Activity
This provides the students with a reminder that they need to answer questions.
Technology
Guides students through the tasks and assignments that require the use of
technology and manipulatives.
Reading
This icon lets the students know they will be completing a reading activity.
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NAME:____________________
CREDIT 1A: HISTORY OF EARTH
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly, and accurately.
Lesson
Title
INTRODUCTION
1.1
The Formation of Earth
1.2
The Geologic Time Scale
1.3
The Precambrian and The Paleozoic
Era
1.4
The Mesozoic and Cenozoic Eras
PERFORMANCE TASK
QUIZ
Assignments

 Connect to Video
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Where Did Earth’s Water Come From?
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 History in Rocks
 Analysis Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Investigating Paleozoic Fossils
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Weighing the Evidence for a Mass Extinction –
On Land
 Review Questions


Credit Materials



Materials
Pen/Pencil
HMH Earth Science
Textbook (optional)
Packet



Technology Needs
Internet
Computer
HMH Online Resources
(optional)
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NAME:____________________
CREDIT 1A: INTRODUCTION
Read “Where Did Earth Come From?” and watch the video “The Sun & The Earth: Crash Course Big History
#3” below. Then answer the essential question.
Where Did Earth Come From?
The Big Bang Theory is the current and most widely accepted theory for the expansion of the universe. The
Big Bang Theory states that billions of years ago all of the matter in the universe was compressed into an
extremely small volume. Then, around 14 billion years ago, a sudden event called the big bang sent this matter
and energy outward in all directions. As the universe expanded, some of the matter began to collect together as
it collided. Solar nebulas, which are rotating clouds of gas and dust, began to form. Scientists believe our solar
system formed from one of these solar nebulas around 4.6 billion years ago. Energy from collisions and
increasing gravity caused the center of this solar nebula to get hotter and denser until hydrogen atoms began to
fuse together. This fusion is what marked the birth of our sun, and is what powers it today. As the sun formed
in the center of the solar nebula, planets began to form as well. Because of the sun’s gravity, the rocky planets
Mercury, Venus, Earth, and Mars formed closer to the sun, and the gas giants Jupiter, Saturn, Uranus, and
Neptune formed further away. As these rocky planets formed, the heavier elements sank to the center forming
layers. As the heavier elements sank toward the core of Earth, the lighter elements began to form a layer that
started cooling to form a crust. Early Earth was very hot and molten, containing no solid rock. This crust
formed the solid rock of Earth’s surface. This solid Earth was still very different from what we see today. It
took billions of years of volcanic activity, impacts from meteors and comets, and a newly forming atmosphere
to make conditions perfect for life to form on Earth.
An essential question is something that allows you to explore the content of the credit. Before you answer the
question watch the video. Then answer the essential question to the best of your ability. You will revisit it at
the end of the credit to see if your answer has evolved.
Video: The Sun & The Earth: Crash Course Big History #3 (14:32)

“The Sun & The Earth: Crash Course Big History #3.” YouTube. CrashCourse, 2 Oct. 2014. Web. 13 May 2015.
Essential Question
Hypothesize on what you imagine Earth looked like before life began. What surface features might you see?
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LESSON 1.1: THE FORMATION OF EARTH
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly, and accurately.
Learning Goals for this Lesson
 Explain the nebular hypothesis of the origin of the solar system.
 Describe how planets form.
 Describe the formation of the land, the atmosphere, and the oceans of Earth.
Lesson Assignments
 Connect to Essential Question
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Where Did Earth’s Water Come From?
 Review Questions
Engage
Connect to Essential Question
What objects make up Earth’s solar system?
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Explore
Exploration Activity
As Earth’s surface formed and the crust slowly cooled into solid masses, there would have been many frequent
volcanic eruptions. These eruptions would have spewed out gases, such as sulfur dioxide (SO2), making the
atmosphere different than the one we know today. Examine the two pictures below. Use them to answer the
following questions. Use the key to the right of the picture to identify the gases.
Chemical
Symbol
Chemical
Name
NH3
Ammonia
H2 O
Water
N2
CO2
Nitrogen
gas
Carbon
Dioxide
Ar
Argon
SO2
Sulfur
Dioxide
CH4
Methane
O2
Oxygen
gas
1. What gases existed in early Earth’s atmosphere that still exist today?
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2. Which gases exist today, but were absent from early Earth’s atmosphere?
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3. What are some differences between the land formations you see in the two pictures? What effects could
these have on the differences in the atmospheres?
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
How Did the Solar System Form?
The solar system consists
of the sun, planets, dwarf
planets, and other bodies.
All of these bodies orbit
the sun. Planets are the
main bodies that orbit the
sun. Scientists have
debated the origins of the
solar system for a long
time. Many scientists
once thought that the sun
formed first, and then
threw off the materials
that became the planets.
In 1796, a mathematician
named Pierre-Simon,
marquis de Laplace, had
another idea. His idea is
now called the nebular
hypothesis. Most
scientists today think the nebular hypothesis is the best description of how the solar system formed.
Laplace’s nebular hypothesis states that the sun and the planets formed at about the same time. They formed out
of a rotating cloud of gas and dust called a nebula. The nebula from which our sun and planets formed is called
the solar nebula. About 5 billion years ago, the strength of gravity near the solar nebula increased. This
probably occurred because of a nearby supernova or other forces.
Energy from collisions and pressure from gravity made the center of the solar nebula hotter and denser. When
the temperature at the nebula center became high enough, hydrogen fusion began. The star that we call the sun
formed. About 99% of all the matter that was in the solar nebula now makes up the sun.
1. What is the relationship between the solar nebula and the solar system?
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How Did the Planets Form?
While the sun was forming at the center of the solar nebula, planets were forming in the outer parts of the
nebula. During the early stages of planet formation, only small bodies called planetesimals existed. Some
planetesimals joined together, forming larger bodies called protoplanets. The gravitational pull of the
protoplanets attracted other planetesimals. These planetesimals collided with the protoplanets, and the masses
combined. Eventually, the protoplanets became very large and formed the planets and moons. The features of a
newly formed planet depended on the distance between the protoplanet and the sun. The protoplanets that
became Mercury, Venus, Earth, and Mars were close to the sun. These planets are small, so they did not have
enough gravitational pull to hold onto some of their gases. Other lighter elements may have been blown or
boiled away by the sun. As the denser material sank to the planet centers, layers formed. Today the inner
planets have solid surfaces. They are smaller, denser, and rockier than the outer planets.
Four other protoplanets became Jupiter, Saturn, Uranus, and Neptune. These planets formed in the cold, outer
regions of the nebula. They did not lose their lighter elements, such as helium and hydrogen. They also kept
ices, such as water, methane, and ammonia ice. At first, thick ice layers surrounded small cores of heavy
elements. Intense heat and pressure in the interiors made the ices melt and form layers of liquid and gas. Today,
the outer planets are called gas giants because they are large and are made up mostly of gases. Uranus and
Neptune are also sometimes called ice giants. Gas giants have low density, and are larger than the inner planets.
Pluto was once known as the ninth planet, but scientists now classify Pluto as a dwarf planet. Like a planet, a
dwarf planet is a spherical body. Unlike a planet, a dwarf planet has not cleared other objects from the path of
its orbit.
How Did Solid Earth Form?
When Earth first formed, it was very hot. Three sources of energy contributed to the high temperatures:
 Energy was produced when the planetesimals that formed the planets collided with each other.
 The increasing weight of the outer layers compressed the inner layers, which generated energy.
 Radioactive materials were very abundant when Earth formed. These materials give off radiation, which
warms the rock around them.
Earth’s center is a dense core composed of heavy elements. A thick layer of rock called the mantle surrounds
the core. The outer layer is a thin crust of rock. These layers formed through a process called differentiation.
During differentiation, dense materials sink and less dense materials rise, forming layers. Eventually, Earth’s
surface cooled enough for solid rock to form. Earth’s surface continued to change as a result of heat in Earth’s
interior. The surface also changed because of impacts and through interactions with the newly forming
atmosphere.
2. How did Earth’s layers develop?
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How Did Earth’s Atmosphere Form?
Like solid Earth, Earth’s atmosphere formed through the process of differentiation. Earth’s early atmosphere
was made up mostly of hydrogen and helium. The sun heated the gases, allowing them to escape Earth’s
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gravity. The solar wind probably blew away the gases. As Earth’s surface continued to form, volcanic eruptions
occurred much more frequently than they do today. The eruptions released large amounts of gases, such as
water vapor, carbon dioxide, nitrogen, methane, sulfur dioxide, and ammonia. This process, known as
outgassing, formed a new atmosphere. Solar radiation caused the ammonia and some of the water vapor in the
atmosphere to break down. Some of the oxygen released during the breakdown formed ozone. The ozone
collected high in Earth’s atmosphere and blocked some ultraviolet radiation, which is harmful to living things.
Organisms that could survive in Earth’s early atmosphere developed. Some of these organisms, such as
cyanobacteria and green plants, used carbon dioxide for photosynthesis. This process released oxygen. Over
time, the amount of oxygen in the atmosphere increased. About 2 billion years ago, the percentage of oxygen in
the atmosphere increased rapidly. It has not changed very much since then.
3. How did the process of outgassing help shape Earth’s atmosphere?
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How Did Earth’s Oceans Form?
Some scientists think part of Earth’s water came from space. Icy bodies, such as comets, collided with Earth.
Water from these bodies became part of Earth’s atmosphere. As Earth cooled, water vapor condensed to form
rain. The rain collected on Earth’s surface to form the first oceans. The first oceans were probably made of
fresh water. Over millions of years, rainwater fell to Earth. The water dissolved many solids and carried them to
the oceans. As water evaporated from the oceans, some chemicals combined to form salts. This process made
the oceans more and more salty. Carbon dioxide from the atmosphere dissolves in the oceans. When carbon
dioxide levels in the atmosphere decrease, more heat can escape into space. Over Earth’s history, the
concentration of carbon dioxide in the atmosphere has increased and decreased periodically. As a result, Earth
has had climates that were warmer and cooler than today’s climate.
4. How do scientists think Earth’s oceans formed?
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5. In this section, you have learned about the formation of Earth’s land, atmosphere, and oceans. Which
components of Earth’s current composition make it capable of supporting life?
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Allison, Mead A., et al. “Chapter 27: Planets of the Solar System/Section 1: Formation of the Solar System.” Holt McDougal Earth Science Interactive Reader, Holt
McDougal, a Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 407–412.
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Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Solar System 101 (4:10)

Where is Earth in our solar system? Where are the rest of the planets located?
In this interactive virtual investigation, you will get to explore our universe and see how
gravity played a role in forming it.
“Solar System 101 | National Geographic” YouTube. National Geographic, 30 Aug 2017. Web. 26 Apr 2021.
How Was Planet Earth Formed? (3:27)

How did the Earth develop into the rocky planet that we know today? This video will
explain how the different layers of the Earth formed.
“Less Than Five – How Was Planet Earth Formed?” YouTube. Astronimate, 20 Dec 2016. Web. 26 Apr 2021.
Why Is There Air? (4:34)

“Why Is There Air?” YouTube. DNews, 27 June 2014. Web. 14 May 2015.
Why is there air? This video will discuss where Earth’s atmosphere came from and why it is
different from the atmospheres of other planets in our solar system.
Where Did Earth’s Water Come From? (2:59)

“Where Did Earth’s Water Come From?” YouTube. MinuteEarth, 7 Feb. 2014. Web. 18 Sept. 2014.
Was Earth’s water delivered from comets and meteor impacts? Watch this video
for evidence regarding this hypothesis about the origin of Earth’s water.
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Elaborate
Where Did Earth’s Water Come From?
Water has some unique properties and is essential for life on Earth. But where did Earth’s water come from? In
the following excerpts from two articles, you will read about evidence for different hypotheses regarding the
origins of Earth’s water. As you read the information, answer the questions that accompany them.
In trying to understand the formation of the early Earth, some researchers have suggested that the planet was
dry and inhospitable to life until icy comets pelted the earth and deposited water on the surface.
Wendy Panero, associate professor of earth sciences at Ohio State, and doctoral student Jeff Pigott are
pursuing a different hypothesis: that Earth was formed with entire oceans of water in its interior, and has
been continuously supplying water to the surface via plate tectonics ever since.
Researchers have long accepted that the mantle contains some water, but how much water is a mystery. And,
if some geological mechanism has been supplying water to the surface all this time, wouldn’t the mantle have
run out of water by now?
Because there’s no way to directly study deep mantle rocks, Panero and Pigott are probing the question with
high-pressure physics experiments and computer calculations.
“When we look into the origins of water on Earth, what we’re really asking is, why are we so different than
all the other planets?” Panero said. “In this solar system, Earth is unique because we have liquid water on
the surface. We’re also the only planet with active plate tectonics. Maybe this water in the mantle is key to
plate tectonics, and that’s part of what makes Earth habitable.”
Gorder, Pam F. “Study Hints That Ancient Earth Made Its Own Water—Geologically.” The Ohio State University News Room. Ohio State University, 17 Dec. 2014.
Web. 25 Feb. 2015.
Water molecules were surely part of the dusty swirl that coalesced into the Sun and its planets beginning
about nine billion years after the Big Bang. But Earth’s early history, including epochs with high ambient
temperatures and no enveloping atmosphere, implies that surface water would have evaporated and drifted
back into space. The water we encounter today, it seems, must have been delivered long after Earth formed.
Faced with this conundrum, astronomers realized that there are two ready-made sources: comets and
asteroids, the solar system’s gravel strewn among planetary boulders. The primary difference between the
two is that comets typically have a greater concentration of ingredients that vaporize when heated,
accounting for their iconic gaseous tails. Both comets and asteroids can contain ice. And if, by colliding with
Earth, they added the amount of material some scientists suspect, such bodies could easily have delivered
oceans’ worth of water. Accordingly, each has been fingered as a suspect in the mystery.
Greene, Brian. “How Did Water Come to Earth?” Smithsonian.com. Smithsonian Magazine, May 2013. Web. 25 Feb. 2015.
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1. According to the first article, where did Earth’s water come from? What evidence does this article give
to support this?
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2. According to the second article, where did Earth’s water come from? What evidence does this article
give to support this?
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3. After reading both articles, where do you think Earth’s water came from? Use evidence from the
articles to support your reasoning.
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Evaluate
Review Questions
Answer the following questions.
1. Explain the nebular hypothesis.
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2. Describe how our solar system developed.
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3. Why are the outer planets more gaseous than the inner planets?
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LESSON 1.2: THE GEOLOGIC TIME SCALE
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly, and accurately.
Learning Goals for this Lesson
 Summarize how scientists worked together to develop the geologic column.
 List the major divisions of geologic time.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 History in Rocks
 Analysis Questions
Engage
Connect to Prior Knowledge
What are some ways that we measure time?
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Explore
Exploration Activity
The geologic time scale represents the chronological order of Earth’s history. It is organized by major events
and changes that have occurred. These events are based on fossil and geological records. The geologic time
scale is divided by a series of units based on where specific rocks or fossils are found. The three basic units of
time include eras, periods, and epochs. Each is measured in millions of years (Ma). Examine the following
geologic time scale. Then answer the questions below.
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1. What are the different eras in the geologic time scale?
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2. Approximately how many millions of years did each last?
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3. When did oceans first appear?
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4. During which period did the atmosphere reach its current oxygen rich state?
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5. During which period did land organisms appear? How many millions of years ago did this take place?
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6. During which period did the first primates appear? During which period did humans appear?
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
What Is a Geologic Column?
Earth’s surface is always changing. The layers of rock in Earth’s crust record these changes. Scientists study
these rock layers to learn about Earth’s history. No one area on Earth has a complete record of Earth’s history.
Therefore, scientists from around the world share what they learn from the rock record. These scientists
developed a standard order of rock layers called a geologic column. The oldest rocks are at the bottom of the
column. The more recent rocks are at the top of the column. In a geologic column, different layers hold
different types of rock and fossils. Fossils in the upper layers look like modern plants and animals. Many fossils
in the lower, older layers are from extinct plants and animals. Scientists can use geologic columns to estimate
the ages of rock layers. Scientists compare a layer of rock with a similar layer in a geologic column. The layers
they compare may be in the same position relative to other layers. They may have the same fossils. If the two
rock layers match, they probably formed around the same time.
1. Where on a geologic column would you most likely find fossils of extinct organisms? Explain your
answer.
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2. How can scientists use a geologic column to determine a rock layer’s age?
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What Are the Divisions of Geologic Time?
Scientists use what they have learned from rocks and fossils to create a geologic time scale. The geologic time
scale identifies major events in Earth’s past. It also summarizes changes in Earth’s surface, climate, and
organisms over time. Scientists use these changes to divide the geologic time scale into smaller units. Fossils
from certain organisms characterize each unit of geologic time.
The largest unit of geologic time is an eon. Geologic time has four eons, as shown on page 15. The first three
eons are part of Precambrian time. Precambrian time lasted 4 billion years. It makes up most of Earth’s
history. After Precambrian time, the Phanerozoic Eon began. Eons are divided into shorter units of time called
eras. Eras are divided into shorter units of time called periods. Each period has specific types of fossils.
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Periods are usually named for the place where the fossils were first found. For example, the Jurassic Period is
named for the Jura Mountains in Europe. Sometimes periods are divided into shorter units called epochs.
Scientists make this division only if there is enough information from the fossil record. Epochs can be divided
into even shorter units called ages. Scientists need a detailed fossil record to mark ages.
3. List the following units of time from shortest to longest: age, eon, epoch, era, period, year.
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4. What is needed by scientists to divide an epoch into ages?
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Allison, Mead A., et al. “Chapter 9: A View of Earth’s Past/Section 1: Geologic Time.” Holt McDougal Earth Science Interactive Reader, Holt McDougal, a Division
of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 123–126.
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Four Ways To Understand the Earth’s Age (3:44)

Sneideman, Joshua M. “Four Ways to Understand the Earth’s Age – Joshua M. Sneideman.” YouTube. TED-Ed, 29 Aug. 2013.
Web. 12 Sept. 2014.
How old is the Earth? In this video the age of the Earth is compared to one calendar
year to show how extremely old Earth is compared to us humans.
Crash Course Big History: The Evolutionary Epic
(14:33)

“Crash Course Big History: The Evolutionary Epic | Big History Project.” YouTube. Big History Project, 5 Sept. 2014. Web.
19 Sept. 2014.
What did life look like during the different periods of the geologic time scale? This
video explores the different periods of the geologic time scale.
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Elaborate
History in the Rocks
Geologists have learned a lot about the geologic history of Earth. They have studied the arrangement of rock
layers. They have also studied the arrangement of fossils in the rock layers. Fossils give clues about the
environment in which the organism that made the fossil lived. Scientists can also find the ages of the fossilbearing rocks in which fossils are found because the ages of many fossils have been found through radiometric
dating of associated igneous rocks. Radiometric dating, fossil age, and rock arrangement are all used to tell what
changes have happened in the arrangement of the rock layers through geologic time. In this lab, you will
discover how the geologic history of an area can be told by studying the arrangement of fossils and rock layers.
Directions:
Study the fossils shown in Figure A. Note their placement in related groups and the geologic periods in which
the organism that made the fossil lived. Select one of the four rock columns shown in Figure B. This figure
shows how some of these fossils may happen in a series of rock layers. Record the number of the column you
are using __________.
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Using Figures A and B on the previous page, answer the following questions.
1. List the fossil names from your column in order from bottom to top.
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2. Do the fossils in your column appear in the order of geologic time?
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3. Do the fossils in your column appear in order of geologic periods? If not, which periods are missing?
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Evaluate
Analysis Questions
Answer the following questions.
1. What might have happened that would explain the order in which fossils were found in each of the rock
columns? (Hint: What can happen to rock layers that could cause them to appear out of order?)
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2. Study column 3 in Figure B. Note that there is a rock layer that has no fossils between two rock layers
that have fossils. Hypothesize on how this might have happened?
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3. Describe what the area you live in might have been like when the organisms in your chosen column
lived.
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Mead, Allison, et al. “Skills Practice Lab: History in the Rocks.” Holt McDougal Online, Holt McDougal, a Division of Houghton Mifflin Harcourt Publishing Co,
2010, my.hrw.com/sh2/es10/teacher/osp/hqx/data/chap09/section01/dscl_a.pdf.
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LESSON 1.3: THE PRECAMBRIAN AND THE
PALEOZOIC ERA
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly, and accurately.
Learning Goals for this Lesson
 Summarize how evolution is related to geologic change.
 Identify the major biological and geological events of Precambrian time.
 Identify the major biological and geological events of the Paleozoic Era.
 List the periods of the Paleozoic Era.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Investigating Paleozoic Fossils
 Review Questions
Engage
Connect to Prior Knowledge
How could physical changes to Earth, such as an ice age or rising sea levels, lead to physical changes in
organisms?
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
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Explore
Exploration Activity
The timeline of the Earth above lists the relative geologic eras to scale. During the Precambrian between 4
billion and 3.8 billion years ago the early Earth began to cool which allowed water vapor to condense and fall as
rain. Once liquid water was present, organic compounds could be formed from inorganic compounds. There
are multiple hypotheses on how these organic molecules formed, and how the first living cells arose, but once
life was present on Earth it began to transform the planet. Some of the most common fossils of Precambrian
time are cyanobacteria. Cyanobacteria are unicellular (single celled) organisms that are photosynthetic. They
take in carbon dioxide gas and release oxygen gas into the atmosphere similar to modern day plants.
Answer the questions below.
1. How old is the Earth?
_______________________________________________________________________________________
_______________________________________________________________________________________
2. Did unicellular or multicellular life appear first? How do you know?
_______________________________________________________________________________________
_______________________________________________________________________________________
3. What are cyanobacteria?
_______________________________________________________________________________________
_______________________________________________________________________________________
4. How did cyanobacteria contribute to the evolution of multicellular organisms like the plants and animals
we see today?
_______________________________________________________________________________________
_______________________________________________________________________________________
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
What Is Evolution?
Earth’s history is recorded in rock layers. The fossils from each layer show which species of organisms existed
when the layer formed. Scientists study and compare fossils from different times in Earth’s history. By
studying fossils, scientists have discovered evidence that species have changed over time. Scientists use the
term evolution to describe this change. Evolution is the process in which new species develop from existing
species. Scientists find evidence for evolution when they compare fossils to living organisms.
Geologic and climatic changes affect the ability of many organisms to survive. Scientists use evidence from
rocks and fossils to find out how environmental changes affected organisms in the past. The fossil record
shows that some species survived environmental changes but that some species disappeared. Scientists study
fossils to find out why some species changed over time and why some stayed almost the same. They also try to
find out why species became extinct.
1. What is evolution?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. How do geologic changes affect evolution?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Why Do Scientists Know Relatively Little About Precambrian Time?
Most scientists agree that Earth formed about 4.6 billion years ago. Earth formed as part of a cloud of dust, or
nebula. Over time, particles from the cloud formed Earth and other planets. The formation of Earth was the
beginning of Precambrian time. Precambrian time lasted about 4 billion years and makes up about 88% of
Earth’s history. Scientists do not know much about what happened during Precambrian time. Geologic changes
have deformed the rock layers from the time. The layers are not in their original order. Thus, the rock record is
hard to interpret, or understand.
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Earth has many areas of exposed, or uncovered, Precambrian rocks. These areas are called shields. Precambrian
shields result from millions of years of geologic changes. Precambrian rocks have very few fossils.
Precambrian organisms did not have hard parts such as bones or shells that fossilize easily. Precambrian rocks
are also very old. Volcanic eruptions, erosion, and movement of tectonic plates probably destroyed most
Precambrian fossils. Scientists have discovered a few Precambrian fossils. The most common fossils are
cyanobacteria. These fossils are found in stromatolites, or reef-like deposits that form in water. Scientists have
also discovered Precambrian fossils of marine worms and jellyfish.
3. What are two characteristics of Precambrian rocks?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Why do scientists not divide Precambrian time into smaller units based on the fossil record?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
What Changes Happened in the Paleozoic Era?
The Paleozoic Era began 542 million years ago and ended 251 million years ago. When the Paleozoic Era
began, many small continents were scattered over Earth. By the end of the Paleozoic Era, the smaller continents
had moved and collided, or crashed into each other. This movement formed the supercontinent Pangaea. The
collisions lifted large areas of land and formed mountain ranges. Paleozoic rocks have many fossils. These
fossils show that the number of plant and animal species increased during the Paleozoic Era. Scientists have
used the detailed fossil record to divide the Paleozoic Era into six periods: Cambrian, Ordovician, Silurian,
Devonian, Carboniferous, and Permian.
Many marine, or sea, organisms appeared during the Cambrian Period. The warm, shallow waters on Earth
were perfect for marine invertebrates, or animals without backbones. The most common Cambrian
invertebrates were trilobites. Scientists use many kinds of trilobite fossils as index fossils. Cambrian
invertebrates also included brachiopods, a kind of animal with a shell. Many kinds of brachiopods lived during
this period, but very few exist today. Worms, jellyfish, snails, and sponges also existed during the Cambrian
Period.
During the Ordovician Period, brachiopods and other marine organisms, such as graptolites, became more
common. At the same time, the number of trilobite species decreased. By this period, vertebrates had appeared.
Vertebrates are animals with backbones. The earliest vertebrates were fish. Fish in the Ordovician Period did
not have jaws or teeth. Their bodies had thick, bony plates.
Vertebrate and invertebrate marine life thrived during the Silurian Period. Corals and relatives of modern sea
stars became more common. Eurypterids, shown below, also lived during this period. Near the end of the
Silurian Period, early land plants and animals evolved.
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The Devonian Period is called the Age of Fishes. Rocks from this period hold fossils of many bony fish. One
group of fishes, lungfish, could breathe air. Another group of fishes, rhipidistians, may have used their strong
fins to crawl on land. Early amphibians, such as the ancestors of modern frogs, probably evolved from
rhipidistians. Land plants, such as ferns, also appeared during this period.
During the Carboniferous Period, Earth’s climate was generally warm. Humidity was often very high. Forests
and swamps covered much of the land. Over many millions of years, these forests and swamps became coal
deposits. These coal deposits exist today in places such as Pennsylvania and Ohio. In North America, scientists
divide the Carboniferous Period into the Mississippian Period and the Pennsylvanian Period. Amphibians and
fish thrived during the Carboniferous Period. Crinoids were common ocean animals. Insects such as giant
cockroaches and dragonflies were common land animals. Near the end of the period, early reptiles, which
looked like large lizards, appeared.
The Permian Period is the last period in the Paleozoic Era. Many environmental changes happened during this
period. By the start of the Permian Period, the continents had joined to form Pangaea. New mountain ranges
formed, and areas of dry land developed. The warm, shallow seas became smaller. The environmental changes
caused a mass extinction of Paleozoic organisms. In a mass extinction, a very large number of species becomes
extinct at about the same time. As the seas became smaller, there were fewer habitats for marine species. During
the mass extinction at the end of the Permian Period, most marine invertebrates, such as trilobites, died out.
However, fossils show that many reptiles and amphibians survived the changes. Animals from these groups
dominated Earth for millions of years after the Paleozoic Era.
5. How did Pangea form?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
6. What may have caused the explosion of life during the Cambrian Period?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Allison, Mead A., et al. “Chapter 9: A View of Earth’s Past/Section 2: Precambrian Time and the Paleozoic Era.” Holt McDougal Earth Science Interactive Reader,
Holt McDougal, a Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 127-132.
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Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
The Grand Canyon: Evidence of Earth’s Past (2:51)
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.nautiloid/the-grandcanyon-evidence-of-earths-past/
WGBH. “The Grand Canyon: Evidence of Earth’s Past.” PBS LearningMedia. NOVA, 2006. Web. 19 May 2015.
How can scientists study the Precambrian and Paleozoic Era? In this video you will see
how the Grand Canyon gives a glimpse into the past with rock layers that are up to 1.7
billion years old.
Cambrian Explosion (13:07)
http://www.pbslearningmedia.org/resource/11dae54b-299a-4b45-a964d574e8dc3320/cambrian-explosion/
“Cambrian Explosion.” PBS LearningMedia. Shape of Life, 2014. Web. 19 May 2015.
What was the Cambrian explosion? This video focuses on fossilized organisms found in
the Burgess Shale formation of the Canadian Rockies. It discusses their evolution and
sudden arrival during the beginning of the Paleozoic Era.
NOVA scienceNOW: Mass Extinction (4:50)
http://www.pbslearningmedia.org/resource/oer09.sci.life.evo.massextinct/mass-extinction/
WGBH. “NOVA ScienceNOW: Mass Extinction.” PBS LearningMedia. NOVA, 2009. Web. 19 May 2015.
What could have caused the mass extinction during the Permian Period at the
end of the Paleozoic Era? This video will explore the evidence for different
hypotheses to discover what may have caused this mass extinction.
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Elaborate
Investigating Paleozoic Fossils
Background:
Unlike Precambrian rocks, Paleozoic rocks hold vast amounts of fossils. Plant and animal life flourished and
evolved into many different species during the Paleozoic Era. Many species that we see present today evolved
from ancestral species that were present during the Paleozoic Era. This rich fossil record has given scientists an
insight into what life may have looked like between 250 million to 500 million years ago.
Examine the following fossils and compare them to some present day organisms. Use your observations to
answer the questions.
During the early Paleozoic Era organisms called
trilobites flourished in the warm, shallow seas. They
went extinct toward the end of the Permian period.
During the mid-Paleozoic Era organisms called
eurypterids lived in shallow lagoons. Eurypterids
had one pair of legs for swimming and four or five
pairs of legs for walking.
Horseshoe crabs like the one in this picture are alive
in the oceans today. They can be found in warm
shallow ocean waters with soft sandy or muddy
bottoms.
Different species of scorpions, like the one in this
picture, are found throughout the world. They are
characterized by their 4 pairs of legs, a pair of
pinchers, and a curved tail ending with a venomous
stinger.
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Toward the end of the Paleozoic Era organisms
called crinoids were common in the oceans. They
were marine animals that attached to rocks or the
ocean bottom.
These sea lilies are marine animals that inhabit the
Earth’s oceans today. They attach to rocks on the
sea floor with a stalk. They feed by filtering
particles with their tentacle-like arms.
Analysis:
1. Compare the trilobite fossil and the horseshoe crab. What do you notice that is similar about them?
What do you notice that is different?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. Compare the eurypterid fossil and the scorpion. What do you notice that is similar about them? What
do you notice that is different?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. Compare the crinoid and the sea lilies. What do you notice that is similar about them? What do you
notice that is different?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Develop a hypothesis to explain why you think eurypterids developed legs even though they lived on the
ocean floor.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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Evaluate
Review Questions
Use the diagram below to answer the following questions.
1. During which period did the first vertebrates appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. During which period did land plants appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. During which period did the first animals appear on land? What type of organisms were they? Estimate
the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. During which period did the supercontinent Pangea form? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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LESSON 1.4: THE MESOZOIC AND CENOZOIC
ERAS
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly, and accurately.
Learning Goals for this Lesson
 List the periods of the Mesozoic and Cenozoic Eras.
 Identify the major biological and geological events of the Mesozoic Era.
 Identify the major biological and geological events of the Cenozoic Era.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Weighing the Evidence for a Mass Extinction – On Land
 Review Questions
Engage
Connect to Prior Knowledge
Hypothesize on a possible way that the mass extinction at the end of the Mesozoic Era contributed to mammals
becoming the dominant life-forms during the Cenozoic Era.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
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Explore
Exploration Activity
The Mesozoic Era began after the Permian mass extinction that happened at the end of the Paleozoic Era. Even
though a mass extinction of a large number of life occurred, fossils indicate that reptiles and amphibians were
able to survive the environmental changes that killed off so many other species. The Mesozoic Era is also
known as the Age of Reptiles because of the success of these reptiles and amphibians. Use the timeline above to
answer the following questions.
1. During which Period did the supercontinent Pangea begin to break apart? Estimate the date in millions
of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
2. During which Period did mammals first appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
3. During which period did the first primitive birds appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
4. During which period did the first modern birds appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
5. About how many millions of years ago (Ma) did dinosaurs become extinct?
_______________________________________________________________________________________
_______________________________________________________________________________________
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The Cenozoic Era began after the Cretaceous-Tertiary mass extinction at the end of the Mesozoic Era.
Dramatic climate changes occurred as continental ice sheets spread across nearly one-third of Earth’s land.
New species that were better adapted to life in cooler climates appeared. Mammals became the dominant lifeform. Because of their success, the Cenozoic Era is known as the Age of Mammals. The Cenozoic Era
continues on today into the present. Use the timeline above to answer the following questions.
6. By what Epoch had most modern mammal families appeared? Estimate the date in millions of years
(Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
7. During what Epoch did the first hominids appear? Estimate the date in millions of years (Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
8. During what Period and what Epoch did modern humans appear? Estimate the date in millions of years
(Ma).
_______________________________________________________________________________________
_______________________________________________________________________________________
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Explain
As you complete the reading, answer the questions in the space provided.
Reading
What Changes Happened During the Mesozoic Era?
During a mass extinction, large numbers of species become extinct around the same time. At the end of the
Permian Period, more than 70% of land organisms and 90% of marine organisms became extinct. The Mesozoic
Era followed this mass extinction. The mass extinction left space and resources for the species that survived.
During the Mesozoic Era, many new species evolved.
During the Mesozoic Era, Pangaea broke into smaller continents. Shallow seas and marshes covered much of
the land. In general, the climate was warm and humid. The conditions were good for reptiles. Lizards, turtles,
crocodiles, snakes, and many dinosaurs thrived during the Mesozoic Era. This era is often called the Age of
Reptiles. The Mesozoic Era left a rich fossil record. Based on the fossil record, scientists divide the Mesozoic
Era into three periods: Triassic, Jurassic, and Cretaceous.
Many dinosaur species lived during the Triassic Period. Some dinosaurs were the size of squirrels. Others were
nearly 30 m long. Most dinosaurs were about 2 m to 5 m long and moved quickly. Reptiles called ichthyosaurs
lived in the oceans during the Triassic Period. New marine invertebrates evolved, such as the ammonite. On
land, small mammals appeared in the forests.
Dinosaurs became the dominant organism during the Jurassic Period. Fossil records show that two major
groups of dinosaurs evolved. Scientists distinguish the dinosaurs in these groups by their hip bones. The
Jurassic Period also had flying reptiles, such as the pterosaur. The pterosaur flew on skin-covered wings, like
modern bats do. Jurassic rocks also show evidence of early birds, such as Archaeopteryx.
Dinosaurs continued to dominate Earth during the Cretaceous Period. Tyrannosaurus rex was almost 6 m tall,
which made it one of the largest carnivores from this time. Its sharp teeth were up to 15 cm long. The armored
ankylosaurs and the horned ceratopsians were other dinosaurs of the Cretaceous Period. Flowering plants, or
angiosperms, evolved during this period. Angiosperms include magnolia and willow trees. Later, trees such as
maples, oaks, and walnuts became common. Angiosperms are the dominant type of land plant today.
The Cretaceous Period ended in a mass extinction that included the dinosaurs. Some scientists think that
changes such as volcanoes and continental shifts caused the extinction. However, many scientists use the impact
hypothesis to explain the mass extinction. According to the impact hypothesis, an asteroid crashed into Earth
65 million years ago. The crash threw dust into the air. The dust blocked the sun and caused Earth’s climate to
cool. Many species could not survive the cooler climate. Over time, the dust settled over Earth and formed a
layer of sediment. This sediment was full of the element iridium. Iridium is common in asteroids, but
uncommon in rocks on Earth.
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1. What is one major geologic development during the Mesozoic Era?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. What do many scientists think caused the mass extinction of the dinosaurs?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. How could you identify the boundary between the Cretaceous and Tertiary Periods in a rock sample?
Explain your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
What Changes Happened During the Cenozoic Era?
The Cenozoic Era began 65 million years ago after the mass extinction at the end of the Mesozoic Era. Earth
had many climate changes during the Cenozoic Era. At times, ice sheets covered almost one-third of Earth’s
land. New species that could survive in cool climates appeared. Mammals became the dominant organisms.
Thus, the Cenozoic Era is called the Age of Mammals. The Cenozoic Era is divided into two periods: the
Tertiary and the Quaternary. These periods are divided into seven epochs: the Paleocene, Eocene, Oligocene,
Miocene, Pliocene, Pleistocene, and Holocene.
During the Paleocene Epoch, many new mammal species evolved. The first primates also evolved during this
time. The tarsier is a modern primate with ancestors from the Paleocene Epoch.
During the Eocene Epoch, the first horses, whales, flying squirrels, and bats appeared. Small reptiles continued
to thrive. At the end of the Eocene Epoch, Earth’s climate cooled further.
During the Oligocene Epoch, continents collided and formed the Himalayas in Asia. Earth’s climate became
cooler and drier. Many early mammals became extinct. However, large species of deer, pigs, horses, camels,
cats, and dogs survived. Marine invertebrates, such as clams and snails, continued to thrive. Grasses and
hardwood trees flourished in this climate.
The Miocene Epoch had changes in currents and sea levels. The largest known land mammals existed during
this epoch. Miocene rocks contain fossils of horses, camels, deer, rhinoceroses, pigs, raccoons, wolves, and
foxes. They also contain fossils of saber-toothed cats, which are now extinct.
During the Pliocene Epoch, predators such as bears, dogs, and cats evolved into their modern forms. Modern
horses also appeared. Near the end of the Pliocene, climate changes caused the ice sheets to grow. As more
water froze, sea levels fell. A land bridge appeared between Eurasia and North America. Changes in Earth’s
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crust formed a land bridge between North and South America. Organisms moved between the continents on
these land bridges.
During the Pleistocene Epoch, ice sheets changed in size many times. Some animals, such as the woolly
mammoth, had thick fur that helped them survive the cold climate. Other species survived by moving to warmer
areas. Some species became extinct. Pleistocene rocks have fossils of early modern humans. Cave paintings
suggest that early humans may have been hunters.
The Holocene Epoch began about 11,500 years ago as the last glacial period ended. The Holocene continues
today. As the ice sheets melted, sea levels rose. Coastlines took on their present shapes. In the early Holocene
Epoch, modern humans began to farm and use tools made of bronze and iron.
4. What do the start of the Mesozoic Era and the start of the Cenozoic Era have in common?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
5. What is one major geologic development during the Cenozoic Era?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Allison, Mead A., et al. “Chapter 9: A View of Earth’s Past/Section 3: The Mesozoic and Cenozoic Eras.” Holt McDougal Earth Science Interactive Reader, Holt
McDougal, a Division of Houghton Mifflin Harcourt Publishing Co., 2010, pp. 133-138.
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Dinosaur Supremacy – Walking With Dinosaurs – BBC (3:59)

“Dinosaur Supremacy – Walking With Dinosaurs – BBC.” YouTube. BBC Earth, 4 Aug. 2012. Web. 26 Sept. 2014.
What allowed dinosaurs to begin appearing during the Triassic Period? This video will
show how a combination of speed and agility gave early dinosaurs an evolutionary edge.
The Smell of Prey – Walking with Dinosaurs in HQ – BBC (2:48)

“The Smell of Prey – Walking with Dinosaurs in HQ – BBC.” YouTube. BBC Earth, 9 Nov. 2012. Web. 26 Sept. 2014.
What top predatory dinosaurs had evolved by the Jurassic Period? This video will show
how dinosaur species had evolved to become top predators, but also had evolved
defenses against predators.
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Reptiles of the Skies – Walking with Dinosaurs in HQ – BBC (4:31)

“Reptiles of the Skies – Walking with Dinosaurs in HQ – BBC.” YouTube. BBC Earth, 9 Nov. 2012. Web. 26 Sept. 2014.
How did dinosaurs conquer the skies during the Cretaceous Period? This video will
show how some dinosaur species evolved special adaptations for flight.
Microraptor – Flying Dinosaur – Planet Dinosaur – BBC (4:00)

“Microraptor – Flying Dinosaur – Planet Dinosaur – BBC.” YouTube. BBC Earth, 24 May 2013. Web. 26 Sept. 2014.
How did feathers begin evolving in dinosaurs? This video will show how primitive
feathers were used for gliding from tree to tree.
Asteroid attack 1 – an answer? – What Really Killed the Dinosaurs?
– BBC (3:08)

“Asteroid Attack 1 – an Answer? – What Really Killed the Dinosaurs? – BBC.” YouTube. BBC Earth, 24 Aug. 2011. Web. 26 Sept.
2014.
What caused the mass extinction at the end of the Cretaceous Period? This video will
investigate the K-T boundary to try and discover what caused this mass extinction.
Age of Mammals – Global Processes (3:11)

“Age of Mammals – Global Processes.” YouTube. NHMLA, 9 Aug. 2010. Web. 29 Sept. 2014.
How has the Earth changed over the past 65 million years? This video will show continents
moved, climate changed, and mammals evolved.
Primeval Kill – BBC (4:04)
https://www.youtube.com/watch?v=saplHLrMC0&list=PL22E84F0E32D9C37D&index=5
“Primeval Kill – BBC.” YouTube. BBC Worldwide, 19 Oct. 2007. Web. 30 Sept. 2014.
How do scientist think predators like sabretooth cats hunted during the Pleistocene Epoch?
This video will explore what life was like during this time.
The Last of the Mammoths | Natural History Museum (3:47)

“The Last of the Mammoths | Natural History Museum.” YouTube. Natural History Museum, 29 Aug. 2014. Web. 30 Sept. 2014.
Why did the woolly mammoth go extinct? Watch this video to see what
may have been the cause of the mammoth’s extinction.
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Elaborate
Weighing the Evidence for a Mass Extinction – On Land
Introduction:
The Cretaceous (K) and Tertiary (T) boundary on the geologic time scale marks the end of the Cretaceous
Period and the beginning of the Tertiary Period. The element iridium is common in asteroids but not on Earth.
There is a thin layer of iridium found in the soil along the K-T boundary. The iridium-rich clay layer at the K-T
boundary is found at the bottom of the ocean in soil 66 million years old, and in the K-T clay layer and rocks
that were part of the land at the time. The fossils in those rock layers reveal what happened to land species
during the mass extinction event. In this activity, you will examine the evidence for a mass extinction based on
the diversity of plants found in rock layers below and above the K-T boundary.
For more information on the K-T boundary and mass extinction you can watch the following video.
The Day the Mesozoic Died (33:43)
http://media.hhmi.org/biointeractive/films/The_Day_The_Mesozoic_Died.html
“The Day the Mesozoic Died.” The Day the Mesozoic Died. Howard Hughes Medical Institute, 2014. Web. 25 Sept. 2014.
The diagram to the right and
the accompanying table show
the diversity of plants in the
late Cretaceous and early
Tertiary periods as determined
by leaf fossils found in rock
layers from the Raton Basin
formation of Colorado and
New Mexico. The fossils have
been grouped in “phases” of
changing diversity. The rock
layers from the late Cretaceous,
labeled Phase 1, show fossils of
leaves from palm trees and
other plant species that live in
tropical climates. The K-T clay
layer is shown by the dotted
line between Phase 1 and Phase
2. Phase 5 corresponds to about
1.5 million years after the K-T
boundary.
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Using the diagram and information above, answer the following questions.
1. Which phase has the most leaf diversity?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. Which phase has the least leaf diversity?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. Does leaf diversity increase or decrease between phases 2 and 3? What about in subsequent phases?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Using multiple sentences, describe the overall picture of changes in plants throughout the 2-million-year
period represented in the diagram. Be sure to include the following terms in your description: mass
extinction, Cretaceous Period, K-T boundary.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Adapted from Colvard, Mary. “Weighing the Evidence for a Mass Extinction-On Land.” BioInteractive. Ed. Laura Bonetta, Eriko Clements, Susan Dodge, and Vivi
Vajda. Howard Hughes Medical Institute, July 2014. Web. 02 June 2015. .
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Evaluate
Review Questions
Answer the following questions.
1. Describe two hypotheses for the Cretaceous-Tertiary mass extinction.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
2. Suppose that you are a geologist who is looking for the boundary between the Cretaceous and Tertiary
Periods in a rock outcrop. What would you look for to determine the location of the boundary? Explain
your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
3. Explain how the ice ages affected animal life during the Cenozoic Era.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
4. Describe the worldwide environmental changes that set the stage for the Age of Mammals.
_______________________________________________________________________________________
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Revisit the essential question, did your answer change? Why or why not?
Essential Question
Hypothesize on what you imagine Earth looked like before life began. What surface features might you see?
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39
General Science 1A
Credit 1
Learning Goal for this Credit
Communicate scientific information clearly, thoroughly and accurately.
Lesson
1.1
Title
The Formation of Earth
1.2
The Geologic Time
Scale
The Precambrian and
The Paleozoic Era
1.3
1.4
The Mesozoic Era
Learning Goals For Each Lesson

Explain the nebular hypothesis of the origin of the solar system.

Describe how planets form.

Describe the formation of the land, the atmosphere, and the oceans of Earth.

Summarize how scientists worked together to develop the geologic column.

List the major divisions of geologic time.

Summarize how evolution is related to geologic change.

Identify the major biological and geological events of Precambrian time.

Identify the major biological and geological events of the Paleozoic Era.

List the periods of the Paleozoic Era.

List the periods of the Mesozoic and Cenozoic Eras.

Identify the major biological and geological events of the Mesozoic Era.

Identify the major biological and geological events of the Cenozoic Era.
General Science Rubric
Credit Grading
Responses to Packet
and Questions
40 pts.
Performance Task
40 pts.
Quiz
20 pts.
4
 My responses in
my packet show
clear reasoning and
use of evidence.
3
 My responses in
my packet show
basic reasoning and
use of evidence.
2
 My responses in
my packet show
basic reasoning but
limited evidence to
support it.
1
 My answers to the
questions in my
packet are either
unscientific or
overly simplistic,
and have limited
evidence.
 I completed some
of the expectations
of the assignment
to show what I
know.
 I completed some
of the expectations
but struggled to
show what I know.
 I made connections
to other ideas
within and across
science credits.
 I completed all of
the expectations of
the assignment to
thoroughly show
what I know.
 My explanation is
clear and supported
by valid scientific
evidence.
 I mainly completed
the expectations of
the assignment to
show what I know.
 My explanation is
supported by
scientific evidence.
 My explanation is
simplistic or basic
and supported by
limited scientific
evidence.
 My explanation is
not supported by
scientific evidence.
Students receive 2 points per correct response.
___x 10 = ___/40
___x 10 = ___/40
___x2 = ___/20
Total:
___/100
41
General Science 1A
Credit 1