Name:
Date:
13.1
Charles Darwin
Charles Darwin, a naturalist, was the first person to propose the theory of natural selection to explain evolution.
He did so in his book, On the Origin of Species by Means of Natural Selection. Darwin believed in evolution, that
evolutionary change was gradual, that natural selection was the mechanism for evolution, and that all life on
earth evolved from a few common ancestors.
A privileged childhood
Charles Darwin was born in
Shrewsbury,
England
on
February 12, 1809. His father
was a wealthy doctor, and his
grandfather
was
Josiah
Wedgwood, designer of the
famous
Wedgwood
china.
Although his mother died when
he was eight, Charles had a
happy childhood, cared for by
older siblings. As a boy, he loved
to collect specimens from nature,
especially beetles. At sixteen, he
went to Edinburgh to study medicine, but Charles did
poorly there. The following year he went to
Cambridge to study for the ministry; he graduated in
1831.
The HMS Beagle
After graduation, Darwin took a nonpaying job as a
naturalist on the ship, HMS Beagle. It was meant to
be a three-year trip to study the South American
coasts and some Pacific islands.
The trip lasted five years. Darwin studied rock
formations, fossils, and all living things wherever they
went. He noticed that the living things were similar to
fossils found nearby, but they were not the same. He
also noticed that living things from one place were
similar to, but not the same as, living things from other
places. For example, ostriches found in one part of
Argentina were different from ostriches found in
another part of that country, and both were different
from those found in Africa. He began to look for a way
to explain how these living things had changed.
For many years, Darwin led a double life. Publicly, he
studied things such as barnacles and crosspollination of plants. He published books about data
he had collected on the HMS Beagle. He received
many awards and honors and belonged to many
important scientific societies.
Privately, he worked on his theory of evolution. He
developed his theory about natural selection to
explain how living things change over time. Natural
selection is the process whereby individuals best
suited to an environment tend to survive, reproduce,
and have more progeny, while those less suited
decrease in population and even in some cases
become extinct. Over long periods of time, natural
selection could account for the variety of species
within a population of organisms, along with the
species found in the fossil records (extinct and nonextinct). He shared his ideas with a few friends, but he
did not publish them, fearing the firestorm that could
ensue. So, he quietly gathered evidence to support
his theory.
The Origin of the Species
In 1858, Darwin received a package that forced him to
take a stand. A young English scientist named Alfred
Russell Wallace sent him an outline of a theory about
evolution and natural selection. It was identical to
Darwin’s! He had to publish his theory or let Wallace
take the credit for something that he had worked on
for nearly twenty years.
Back in England
The Origin of the Species was published in 1859. The
book sold out immediately and was reprinted many
times during his lifetime. In it, Darwin wrote about the
evolution of plants and animals, based partly on
observations he made in the Galapagos Islands. He
left the sensitive topic of human evolution for two later
books.
Darwin returned to England in 1836 and married his
cousin, Emma Wedgwood in 1839. Unfortunately,
Darwin had gotten a tropical disease, later identified
as Chagas’s disease, from a beetle bite in South
America. It plagued him for the rest of his life.
Darwin died of heart problems in 1882. His wife
wanted to bury him in the countryside that he loved.
However, Parliament insisted that he be buried in
Westminster Abby near the grave of Sir Isaac
Newton.
Reading reflection
1.
Research: Darwin’s maternal grandfather was Josiah Wedgwood, the designer of famous Wedgwood
pottery. Use the library or the Internet to find information about his life and pictures of some of his work.
2.
What was Darwin’s first job after graduating from college?
3.
What were Darwin’s responsibilities on the HMS Beagle?
4.
What observation did Darwin make of living things and fossils found in the area?
5.
What observations did Darwin make regarding ostriches?
6.
In what way were Darwin’s observations regarding living things and fossils and his observations about
ostriches important?
7.
How did Darwin get Chagas’s disease? Research the symptoms of the disease.
8.
In what way did Darwin lead a double life?
9.
Why did Darwin put off publishing his theories of evolution and natural selection?
10. Why was it important that Darwin included his theory of natural selection in the book with his theory of
evolution?
11. Why do you suppose Darwin did not include his ideas about the evolution of man in his book The Origin of
the Species?
12. Research: After his death, a woman named Lady Elizabeth Hope claimed that Darwin renounced his
theory of evolution just before he died. Use the library or the Internet to find out the true story about what
Darwin said on his deathbed.
Page 2 of 2
Name:
Date:
13.2
Thomas Robert Malthus
Thomas Malthus, in his “Essay on the Principle of Population,” described the human struggle for existence. He
argued that the food supply could not keep up with the growth in human population, resulting in hunger,
sickness, and death from starvation. He thought that the population would outgrow the planet, unless excessive
growth was put in check by natural causes, misery (war and famine, for example), and moral restraint (which
included abstinence).
A wealthy family
Thomas Malthus was born
in 1766 to a wealthy country
family, the second son of
eight children. The family
estate was in Surrey,
England, near London.
Malthus was educated at
home by his father and a
number of tutors.
His father was a friend of
both
Jean-Jacques
Rousseau
and
David
Hume, two of the most important philosophers of their
day. Thomas probably grew up listening to long
philosophical debates in his family home.
Malthus graduated from Jesus College in Cambridge
in 1788 and became a minister in the Church of
England. In 1791, he earned his masters degree in
mathematics. While a minister for a church in a small
town near Surrey, he continued to live in his father’s
house. He participated in many lively intellectual
discussions there.
Writing down his ideas
In 1798, Malthus anonymously published a short
essay (approximately 50,000 words), called “An
Essay on the Principle of Population.” In 1803, he
published a longer second edition. Still not satisfied,
he continued to add new ideas until his fifth and final
edition was published. This edition was over 250,000
words and filled three volumes!
The essay
Thomas’ father and most of his peers were optimistic
about the future of mankind. Thomas, however,
disagreed. He believed that unless preventive
measures were taken, the human population would
grow faster than the food supply. He also claimed that
if there were too many workers, the wages would go
down (because the supply was greater than the need)
and food prices would rise (because the need would
be greater than the supply). Together, this would
result in poverty, hunger, and suffering. Thomas
predicted doom for mankind unless population growth
slowed. He recommended marrying later in life and
having fewer children. He himself did not marry until
he was thirty-eight and had only three children.
Malthus died in 1834.
Flaws in the theory
Malthus based his theory on the belief that human
population grows at a geometric rate (e.g., 2,4,8,16)
while production of food grows at an arithmetic rate
(e.g., 1,2,3,4,5). However, he never explained how he
figured this out.
Three things made Malthus’ predictions invalid for
most of the Western world. One was the Industrial
Revolution. It provided more jobs and a better
standard of living for most people. The second was a
number of scientific discoveries that allowed farmers
to produce more food. These discoveries resulted in
better fertilizers, better equipment, and more
knowledge about plants and animals. The third was
the use of new methods of birth control. Today,
Malthus’ predictions about poverty, hunger, and
overpopulation seem to hold true only in
underdeveloped countries where there is little access
to modern technology or scientific advancements.
Malthus’ influence
Two very important scientists were influenced by
Thomas Malthus’ ideas. Charles Darwin and Alfred
Russell Wallace were both working on their own
theories of evolution when they read Malthus’ essay.
Both scientists credited Malthus with influencing their
work. They read about animals producing more
offspring than could survive because of a lack of food.
They realized that due to natural differences, some
offspring would be better suited to survive than others.
This led both men to develop their individual theories
of natural selection and evolution.
Reading reflection
1.
Describe Thomas Malthus’ childhood.
2.
How did his childhood help to shape him as an adult?
3.
Why do you think that Malthus published his essay anonymously the first time?
4.
In what way did Malthus practice his own teachings?
5.
Explain in your own words what Malthus meant when he said that the population would increase at a
geometric rate while the food production would increase at an arithmetic rate.
6.
What possible flaw in his basic reasoning could cause his theory to be incorrect?
7.
List three factors that have affected the validity of Malthus’ theory about the principles of population.
8.
Who were Charles Darwin and Alfred Russell Wallace? How did Thomas Malthus influence them?
9.
Research: As a young man, Thomas Malthus was influenced by the discussions of his father’s friends. Find
out more about Jean-Jacques Rousseau and David Hume. Who were these men and what were their basic
beliefs? Share your findings with the class.
10. Although Thomas Malthus is considered an economist whose main concern was the fate of the poor, his
writings deal with a cause-and-effect relationship between population and food supply. Explain this causeand-effect relationship in your own words.
Page 2 of 2
Name:
Date:
Scientific Notation
14.1
A number like 95,800,000,000 (95 trillion, 800 billion) can take a long time to write, and an even longer time to
read. Because they frequently encounter very large numbers like this one (and also very small numbers, such as
0.000002, or two millionths), scientists developed a shorthand method for writing these types of numbers. This
method is called scientific notation.
A number is written in scientific notation when it is written as the product of two factors, where the first factor is
a number that is greater than or equal to 1, but less than 10, and the second factor is an integer power of 10. Some
examples of very large numbers written in scientific notation are given in the table below:
Scientific Notation
Standard Form
9.58 × 1010
95,800,000,000
5.2777 × 107
52,777,000
1.06 × 1015
1,060,000,000,000,000
9.99 × 104
99,900
Rewriting large numbers (given in scientific notation) in standard form:
Express 6.26 × 106 in standard form.
6.26 × 106 = 6,260,000
Move the decimal point (in 6.26) 6 places to the right. The exponent of the “10” is 6, giving us the number of
places to move the decimal. We know to move it to the right since the exponent (6) is a positive number.
Rewriting large numbers (given in standard form) in scientific notation:
Express 26,040,000,000 in scientific notation.
You need to rewrite this number so that it fits into the form:
10
26,040,000,000 × 10
Place the decimal point in 2 6 0 4 so that the number is greater than or equal to one but less than ten. This
gives the first factor (2.604). To get from 2.604 to 26,040,000,000, the decimal point has to move 10 places
to the right, so the power of ten is 10 (positive).
Page 2 of 3
14.1
1.
Fill in the missing numbers. Some will require converting scientific notation to standard form, while others
will require converting standard form to scientific notation.
Scientific Notation
a.
8.3 × 104
b.
1.256 × 102
c.
7.0102 × 1012
Standard Form
d.
99
e.
42,000
f.
110,000,000
g.
5.5 × 105
h.
1,000,500,000,000
Frequently, scientists also work with extremely small, but positive numbers. The mass of some atoms and
subatomic particles, or measurements of microscopic organisms often measure much less than one whole.
Scientific notation is used to represent these very small numbers. We use negative exponents to represent
numbers that are smaller than one whole in scientific notation. One example of such a small number is 0.0027
(27 ten thousandths).
Part I: rewrite small numbers (given in scientific notation) in standard form
•
Express 3.72 × 10-3 in standard form.
The exponent of the “10” is negative 3, giving us the number of places (3) and the direction (left, since the 3
is negative) to move the decimal point.
Part II: rewrite small numbers (given in standard form) in scientific notation
•
Express the number 0.0008 in scientific notation.
-4
0.0008 = 8 × 10
Place the decimal point in 8 so that the number is greater than or equal to one but less than ten. This gives the
first factor (8, or 8.0). To get from 8 to 0.0008, the decimal point has to move 4 places to the left, so the
power of ten is -4.
Page 3 of 3
14.1
1.
Fill in the missing numbers. Some will require converting scientific notation to standard form, while others
will require converting standard form to scientific notation.
Scientific Notation
a.
4.5 × 10-3
b.
2.1 × 10-4
c.
1.00122 × 10-1
Standard Form
d.
0.12
e.
0.00264
f.
761,000,000
g.
1.3 × 107
h.
2.
0.0020
Explain why the numbers below are not written in scientific notation, then give the correct way to write the
number in scientific notation.
Example: 11.6 × 105 is not written in scientific notation because the first factor (11.6) is greater than 10.
Since 11.6 × 105 = 1,160,000 (from moving the decimal point in 11.6 five places to the right), the correct
way to write this number in scientific notation is 1.16 × 106.
3.
a.
22 × 103
b.
1.0 × 1002
c.
10 × 104
Write the numbers in the following statements in scientific notation:
a.
Professional basketball’s all-time leading scorer made 38,387 points in his twenty-year career.
b.
He also holds the record for minutes played, with 57,446 minutes.
c.
In 2005, the U.S. population was about 297,000,000
d.
The mass of an electron is about 0.000 000 000 000 000 000 000 000 000 9108 grams.
e.
The unit commonly used to measure microorganisms is the micrometer. One micrometer equals 0.0001
centimeter.
f.
The population of California in 2005 was approximately 33,900,000.
g.
Earth is about 92,900,000 miles from the sun.
h.
In 2005, one right-fielder made a salary of $12,500,000 playing professional baseball.
Name:
Date:
14.1
Nicholas Steno
Nicholas Steno was a keen observer of nature at a time when many scientists were content to learn about the
world by reading books. Through dissection, Steno made important advances in the field of medicine. Later he
applied his observation skills to the field of geology, contributing three important principles that geologist use to
determine the order in which geological events occurred.
Steno’s childhood
Nicholas Steno was born in
1638
in
Copenhagen,
Denmark. He became ill at
age three and spent most
of his time indoors until age
six. He saw few children,
but spent time listening to
adults discuss religion.
Religion later became an
important part of his life.
Steno, the son of a
goldsmith,
had
skillful
hands like his father.
However, his skill was not in making jewelry. He was
an expert in dissecting animals to learn about
anatomy. He was fascinated by the structure of living
things.
Italian Duke Ferdinand sent the head to Steno for
dissection. Steno carefully observed the shark’s teeth.
They looked like glossopetrae or “tongue stones,” a
common stony item found inside rocks.
While we now know that these tongue stones are
fossilized remains of living things, in Steno’s time
many people believed tongue stones grew within
rocks, fell from the sky, or even fell from the moon.
Steno suggested a different explanation for the
tongue stones. He said they had once been actual
shark teeth! Now Steno started to think about how a
solid object, like a shark tooth, could get inside
another solid object, like a rock.
Three important principles
Based on his work, Steno came up with three
important principles of geology.
•
The principle of superposition describes that
layers of sediment settle on top of each other.
The oldest layers are on the bottom and the
younger layers on top.
•
The principle of original horizontality says that
sedimentary rock layers form in horizontal
patterns, even if they form on a bumpy surface
•
The principle of lateral continuity says that
sediment layers spread out until they reach
something that stops the spreading.
The young scientist
When Nicholas was not yet ten years old, his father
died. He spent his teen years living in Copenhagen
with a half-sister and her husband. Steno was smart,
curious, and a good listener. He gained the attention
of two scholars in Copenhagen.
The first, Ole Borch, welcomed Steno into his alchemy
laboratory. There, Steno watched as sediments
settled out of liquid solutions. He thought it was
interesting that even when the bottom of the jar was
bumpy, the sediments formed a smooth horizontal
layer on top of the bumpy surface.
Thomas Bartholin, a famous anatomist from the
University of Copenhagen, also mentored Steno.
Perhaps through this friendship, Steno developed a
keen interest in dissection and anatomy. In 1660, he
left Denmark to study medicine at the University of
Leiden in the Netherlands. There, through careful
dissection of mammals, he made discoveries related
to glands, ducts, the heart, brain, and muscles.
A shark’s tooth unlocks a mystery
In 1665, Steno moved to Italy. The following year,
fishermen there captured a great white shark. The
Steno explained that the shark teeth had been in soft
sediment that eventually hardened into a layer of
rock. Steno used his principles to write a book about
the geology of a region of Italy called Tuscany. Even
today, geologists use Steno’s principles to determine
the order in which geologic events occurred.
Father Steno
In 1675, Steno gave up science to become a priest.
He died in 1686 at the age of 48. In 1988, Pope John
Paul II beatified Steno, the first step in the process of
naming someone a saint. Today, the Steno Museum in
Denmark and craters on Mars and the moon bear his
name.
Reading reflection
1.
Name and describe briefly the three important principles of geology developed by Steno.
2.
How did most people at the time describe the origin of fossils?
3.
How did Steno explain the existence of tongue stones or shark teeth in the mountains?
4.
How did Steno’s medical background and skills help him with his geological discoveries?
5.
Observing is very important in science. What do you like to observe closely? What have you learned
through observation?
6.
Research: Steno’s father was a goldsmith and one of his teachers was interested in alchemy. What does a
goldsmith do? What is alchemy? How could these two fields have been helpful to Steno’s work?
Page 2 of 2
Name:
Relative Dating
Date:
14.2
Relative dating is a method used to determine the general age of a rock, rock formation, or fossil. When you use
relative dating, you are not trying to determine the exact age of something. Instead, you use clues to sequence
events that occurred first, then second, and so on. A number of concepts are used to identify the clues that
indicate the order of events that made a rock formation.
Relative dating concepts
The following situations illustrate relative dating concepts. Match each situation to the terms listed below the
graphic. Write the letter of each situation in the blank next to each term.
1.
Superposition _____
2.
Original horizontality _____
3.
Lateral continuity _____
4.
Cross-cutting relationships _____
5.
Inclusions _____
6.
Faunal succession _____
Page 2 of 3
14.2
Determining the order of events in a geologic cross-section
Helpful information: To answer some of the questions, you need to understand some terms: fault, metamorphic
rock, and intrusion. A fault is a region on Earth’s surface that is split in two pieces. In other words, a fault is a
crack on Earth’s surface. Metamorphic rocks are formed when one kind of rock is changed by heat and pressure.
When pressure is applied to layers of rock, the rock layers become wavy. An intrusion occurs when molten rock
pushes its way through a rock or rock layers.
1.
Use arrows to indicate the direction in which the following rock layers were compressed to make a
metamorphic rock.
2.
For the graphic at right, indicate the order in which the rock layers formed. Some
layers formed at the same time. What relative dating concepts did you use to
determine the order of the rock layers?
3.
Look carefully at the graphic below. Why is layer B smaller than layer A? Which
direction did the fault shift? How do you know?
4.
Two faults are shown in this geologic cross-section at right. Place the rock
layers and the two faults (A and B) in the order in which they happened.
Page 3 of 3
5.
This geologic cross section shows some rock layers that have undergone metamorphism. When did
the metamorphic event happen relative to the other features in the graphic?
6.
Did the intrusion in this cross-section happen before or after layer A was formed?
Justify your answer.
7.
Look at the two intrusions in this picture (below). Explain the appearances of the
top of each. Why is one top flattened while the top of the other intrusion is
rounded? Place the rock layers and intrusions in the order in which they happened.
8.
Examine this geologic cross-section.
a.
Why might the rock layers in this cross-section be wavy? Come up with an explanation.
b.
There are two fossils located at positions A and B. Which fossil is older? Justify your answer.
14.2
Name:
Date:
14.2
Alfred Wegener
Alfred Wegener was a man ahead of his time. He was an astronomer and a meteorologist, yet his greatest work
was in the field of earth science. His theory of plate tectonics is widely accepted today. Yet, in 1912 when he
proposed the idea, he was laughed at and ridiculed. It took fifty years for other scientists to find the evidence that
would prove his theory.
The young man
Alfred Wegener was born in
Berlin in 1880. He was the
son of a German minister
who ran an orphanage. As
a
boy,
he
became
interested in Greenland,
and as a scientist, he went
to Greenland several times
to study the movement of
air masses over the ice cap.
This was at a time when
most scientists doubted the
existence of the jet stream.
Just after his fiftieth birthday, he died there in a
blizzard during one of his expeditions.
Wegener graduated from the University of Berlin in
1905 with a degree in astronomy. Soon, however, his
interest shifted to meteorology. This was a new and
exciting field of science. Wegener was one of the first
scientists to track air masses using weather balloons.
No doubt, he got the idea from his hobby of flying in
hot air balloons. In 1906, he and his brother set a
world record by staying up in a balloon for over fiftytwo hours.
The search for evidence
In 1910 in a letter to his future bride, Wegener wrote
about the way that South America and Africa seemed
to fit together like pieces of a puzzle. To Wegener, this
was not just an odd coincidence. It was a mystery that
he felt he must solve. He began to look for evidence
to prove that the continents had once been joined
together and had moved apart.
Fossils of a small reptile had been found on the west
coast of Africa and the east coast of South America.
That meant that this reptile had lived in both places at
the same time millions of years ago. Wegener figured
that the only way this was possible was if the two
continents were connected when animals were alive.
They could not have traveled across the ocean.
There was also geological evidence. The rock
structures and types of rocks on the coasts of these
two continents were identical. Again, Wegener could
find no explanation for how this could have happened
by accident on opposite sides of the ocean. The rock
structures had to have been formed at the same time
and place under the same conditions.
A study of climates produced other evidence. Coal
deposits had been found in Antarctica and in England.
Since coal is formed only from plants that grow in
warm, wet climates, Wegener concluded that those
land masses must have once been near the equator,
far from their locations today.
Ridiculed and rejected
Wegener explained that all of the continents had been
part of one large land mass about 300 million years
ago. This super-continent was called Pangaea, a
Greek word that means “all earth.” It broke up over
time, and the pieces have been drifting apart ever
since. Wegener compared the drifting continents to
icebergs.
Wegener’s peers called his theory “utter rot!” Many
scientists attacked him with rage and hostility.
Wegener had two main problems. First, he was an
unknown outsider, not a geologist, who was
challenging everything that scientists believed at the
time. Second, he was not able to explain what caused
the continents to drift. While there seemed to be
evidence to show that they had indeed moved, he
could not identify a force that made it happen.
About fifty years after Wegener proposed his theory, a
scientist named Harry Hess made a discovery about
sea floor spreading that seemed to support
Wegener’s ideas. As a result, the theory of plate
tectonics was finally accepted by most scientists.
Reading reflection
1.
Explain the significance of Greenland in Wegener’s life.
2.
What world record did Wegener set in 1906?
3.
Why could Wegener be called an interdisciplinary scientist? Identify the fields of science of which he was
knowledgeable.
4.
Explain how the fossil of a small reptile provided evidence to help prove Wegener’s theory of drifting
continents.
5.
How did the discovery of coal deposits in England and Antarctica strengthen Wegener’s argument?
6.
Research: In his search for evidence to support his theory of drifting continents, Wegener studied the rock
strata in Karroo section of South Africa and the Santa Catarina section of Brazil. He also studied the
Appalachian Mountains in North America and the Scottish Highlands. Use a library or the Internet to
research these areas. What evidence do they provide for Wegener’s theory? Share your findings with the
class.
7.
What were the two main problems that Wegener faced when he tried to convince others that his theory of
drifting continents was valid?
8.
Research: Wegener and some colleagues drew maps of what they thought the world looked like at different
times as the super continent broke up and the continents drifted apart. Use a library or the Internet to find
pictures of these maps. Make a poster displaying Wegener’s vision of the world at
•
•
•
•
•
•
300 million years ago (Pangaea)
225 million years ago (Permian period)
200 million years ago (Triassic period)
135 million years ago (Jurassic period)
65 million years ago (Cretaceous period)
Today
Page 2 of 2
Name:
Date:
Averaging
14.3
The most common type of average is called the mean. To find the mean, just sum (add) all the data, then divide
the total by the number of items in the data set. This type of average is used daily by many people. Teachers and
students use it to average grades. Meteorologists use it to average normal high and low temperatures for a certain
date. Sports statisticians use it to calculate batting averages among many other things.
Jacob has had three tests so far in his English class. His grades are 88%, 73%, and 92%. What is his average test
grade?
1.
Find the sum of the data: 88 + 73 + 92 = 253
2.
Divide the sum (253) by the number of items in the data set (3): 253 ÷ 3 ≈ 84
3.
Solution: Jacob’s average (mean) test grade in English (so far) is about 84%
1.
The teachers at George Washington middle school were cleaning out their desks at the end of the year. Ms.
Johnston had 25 paper clips, Mr. Kraemer had 245 paper clips, Mrs. Ellington had 72 paper clips, and Mr.
Kennedy had 578. What was the average number of paper clips among the teachers?
2.
In the Elk Grove Unified school district, many languages are spoken by students at all of the schools. In the
middle schools, the following numbers of languages are spoken at each school: 31, 21, 23, 28, 23, 26, and
24. What is the average number of languages spoken by students at a middle school in the Elk Grove Unified
School District?
3.
During a locker cleaning session, Jimmy found he had 17 pencils, Sebastian had 2 pencils, Lola had 27
pencils, Andre had 11 pencils, Jonathon had 12 pens and 3 pencils, Madison had 39 pencils, and Phelipe had
26 pencils. What is the average number of pencils found in one locker among this group of friends?
4.
The payroll for one professional baseball team in the 2005 season was $55,869,262. There were 31 players
on the roster. What is the average yearly salary for a player on this team in 2005?
5.
Genise and her friends were shopping for jeans. They noticed quite a variety in the price. In one store, they
listed the prices of all the pairs of jeans: $22.99, $99.77, $35.00, $23.99, $112.25, $33.55, $22.99. What was
the average price of a pair of jeans in this store?
Name:
Geologic Time Periods
Date:
14.3
Write the name of the Era in the diagram below. Describe each era in your own words in the spaces on the next
page.
Page 2 of 2
14.3
Describe each era in your own words in the space below.