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LESSON
LESSONPLANS
PLANS
PAGES 1–4
Discussion
BACK FROM THE DEAD
Ask students: How do you think scientists decide which species
to try to revive? (For instance, DNA may be available only from
certain species.) Would you be more in favor of bringing some
species back than others? What would influence your decision?
ASSESSMENT PACKAGE
Assessments are tailored to different science disciplines and
the Common Core State Standards. All four files can be found at
the end of this document.
BIOLOGY/COMMON CORE: PERSUASIVE WRITING
WHAT DO YOU THINK?
standards
Use this work sheet to help students write a wellsupported opinion essay about whether or not
scientists should resurrect extinct species.
NATIONAL SCIENCE EDUCATION StandardS:
Grades 5-8: Reproduction and heredity
Grades 9-12: Molecular basis of heredity
NEXT GENERATION SCIENCE STANDARDS:
LS3A: Inheritance of traits
Common Core State Standard:
READING INFORMATIONAL TEXT: 1. Write arguments to
support claims using sufficient evidence.
CHEMISTRY: READING COMPREHENSION
FIGHTING FUNGUS
Students read a passage and answer questions
about how a chemical imbalance caused the
extinction of the gastric-brooding frog and many
other amphibians.
Objective
Understand how scientists are using biotechnology to try to
bring extinct animals back to life.
EARTH SCIENCE: READING COMPREHENSION
A MAMMOTH EXTINCTION
Lesson
1. Project the PDF of the article, “Back From the Dead,” on a
Have students read a passage and answer
questions about how a warming climate may
have contributed to the disappearance of woolly
mammoths.
whiteboard and/or print the article for students (see next four
pages). Ask students: What does the word extinct mean? (No
individuals of a species remain alive.)
2. Ask students how scientists might bring an extinct
species back to life. Then enlarge the diagram “How to Make a
Mammoth” on page 2. Have a volunteer read the steps.
PHYSICS: READING COMPREHENSION
ZAPPING CELLS
An electric current helps cloned eggs to grow. Use
this reading passage to help students learn about
electricity in the human body.
3. Read the text beneath the article’s headline. “Should scientists bring extinct species back to life?” Poll the class and
record the results. Ask students for reasons supporting their
opinions; record them on the note.
4. Have the class read the article silently. Afterward, repeat the
poll about whether scientists should revive extinct species. Are
the results different now? Ask the students to explain why they
changed their minds or kept the same opinion.
5. Have students write an essay that states and supports their
opinion after reading the article.
resources
• VIDEO EXTRA: Watch a video about bringing species back
from extinction at: www.scholastic.com/scienceworld.
• Check out the teacher resources at this interactive website
about cloning and other aspects of genetics:
http://learn.genetics.utah.edu/content/tech/cloning/.
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Back from
the
Dead
Jon Foster/National Geographic Stock
Should scientists bring extinct species back to life?
1
Science World • www.scholastic.com/scienceworld
U
ntil the 1980s, Australia was home
to a very odd amphibian: the
gastric-brooding frog. The strange
thing about this frog was that the
female laid her eggs in water, and
once the male fertilized them, she swallowed
the eggs whole. Her tadpoles grew inside
her stomach. When the baby frogs were fully
developed, the mother burped them out of
her mouth!
This strange species fascinated scientists.
But soon after researchers discovered gastricbrooding frogs in the early 1980s, a fungal
infection wiped all of them out. The species
became extinct.
Now, three decades later, the gastricbrooding frog may come back to life.
Scientists are trying to use biotechnology—
the artificial manipulation of living things—to
resurrect the baby-burping frog, as well as
species that have been extinct much longer.
“Just imagine looking at a saber-toothed
cat, or a woolly mammoth, or a giant ground
sloth—things our ancestors saw,” says Hank
Greely, a bioethicist at Stanford University in
California. “That’s plausible now.”
natural disasters, disease outbreaks, or
climate change.
“All of these ‘de-extinction’ projects are
focused on trying to increase the complexity
and diversity of the natural world,” says Mike
Archer, a paleontologist at the University
of New South Wales in Australia. Archer is
leading the team that’s trying to bring back
the gastric-brooding frog.
When Archer set out to revive the frog
5 years ago, the first thing he needed was an
intact nucleus from one of its cells. Nuclei
contain an organism’s DNA. This chemical
carries the hereditary information that
determines an animal’s traits.
Scientists have been using nuclei from
living animals to create clones, or genetically
identical copies, of those animals for many
years (see Cloning Timeline, p. 3). But when
an animal dies, its cells decompose and the
DNA inside its nuclei begins to break down.
Philippe Psaila/SCIENCE SOURCE (EGG); Fernando G Baptista,/National Geographic Stock (bottom)
A pipette injecting
genetic material
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DNA
Transfer: Under
a microscope, a
researcher injects
an egg with genetic
material to create a
clone.
EGG
Reviving a Species
Why bring back extinct species? One
reason is to increase biodiversity, which has
declined in many areas as species die off.
When an ecosystem has a wide variety of
animals and plants, there’s a better chance
that at least some of them will survive
SUBSCRIBER
S
ONLY
A pipette
holding the
egg in place
How to Make a WOOLLY Mammoth
Scientists may be able to use a frozen cell from a mammoth that’s been dead for thousands of years to bring the
species back from extinction. An elephant—the mammoth’s closest living relative—would carry the baby clone.
mammoth
nucleus
Isolate the
nucleus of a
viable mammoth cell
from a frozen carcass.
1
elephant
egg
Remove the
nucleus from the
egg of an elephant
and replace it with the
mammoth nucleus.
2
Chemically
or electrically stimulate
the cell to make
it begin dividing.
3
Place the egg
in the uterus
of an elephant. It
will take almost two
years to develop.
4
If the
pregnancy
is successful, the
elephant gives birth
to a baby mammoth.
5
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2
This makes cloning an extinct species much
harder than cloning a living one.
Luckily, back in the 1970s, another
scientist had frozen some gastric-brooding
frog tissue and saved it. Archer examined
cells from the frozen sample and was excited
to find that their nuclei appeared intact.
The next step was to find an egg. In
traditional cloning, scientists take an egg
cell from a female of the same species and
remove its nucleus. Then they replace it with
the nucleus of a regular cell from the body
of the individual they want to clone. When
the egg starts to divide, the new cells contain
copies of the donor animal’s DNA.
But no one had saved any gastric-brooding
frog eggs. That meant Archer had to try
De-Extinction Plans
So far, none of the eggs have grown past
the embryo stage into baby frogs. Archer and
his colleagues aren’t sure why. But if they can
solve that problem, says Archer, “I’m hopeful
that within a few years we should have this
frog back.”
Archer’s attempt is the farthest along, but
other teams of scientists want to use similar
techniques to bring back other extinct
species, like the woolly mammoth. These
hairy relatives of elephants roamed the frozen
tundra of Siberia until they died out about
5,000 years ago. Scientists have found many
cloning
TIMELINE
Scientists first cloned
animals more than 60
years ago. Since then,
breakthroughs in cloning
technology have brought
them closer to being able
to revive extinct species.
3
1952
Scientists create the first cloned animal—a
tadpole—by extracting a cell nucleus from
a developing embryo and inserting it into
an egg that has had its nucleus removed.
Science World • www.scholastic.com/scienceworld
1996
Dolly the sheep, the first mammal cloned
using the body cell of an adult animal, is
born in Scotland. Dolly becomes famous
and brings lots of attention to cloning.
Ria Novosti/AFP/Getty Images (top); Thinkstock (1952); Jeff J Mitchell UK/Reuters (1996)
MAMMOTH
MUMMY: This baby
mammoth’s body,
discovered under
permafrost in
Siberia in 2007,
still had some DNA
inside.
something else: inserting
the cell nucleus of the
extinct frog into the egg of
another species. He started
collecting eggs laid by great
barred frogs, a common
species in Australia.
Over the next few years,
Archer’s team injected thousands of great barred frog
eggs with gastric-brooding
frog nuclei. None of them
grew. But the researchers
kept trying and adjusting
their technique.
Finally, about two years
ago, one of the eggs started
dividing. When Archer tested
the growing ball of cells, or
embryo, he found gastricbrooding frog DNA inside.
“That told us that the
extinct animal’s DNA was driving the development of a new frog,” he says.
ANT Photo Library/SCIENCE SOURCE (frog); George Laycock/SCIENCE SOURCE (pigeon); STR New/Reuters (2001); San Diego Zoo (2003); Wikimedia Commons (2009)
scientists working on
buried mammoth fossils
these projects should
and, in a few cases, the
be very careful. Many of
frigid conditions have
the environments that
helped preserve some
extinct species once
DNA. A group of South
inhabited have changed
Korean and Russian
since they lived there,
researchers hopes to use
he says. If a long-gone
this material to bring
species is reintroduced,
mammoths back to life
it could become an
one day (see How to
COMING BACK? The gastricinvasive species that
Make a Woolly
brooding frog, now extinct,
birthed babies through its mouth.
upsets the current
Mammoth, p. 2).
ecosystem.
Ben Novak, a bioloSome conservationgist at the University
GONE FOR NOW:
Passenger pigeons
ists also worry that if
of California, Santa
were hunted to
scientists can bring
Cruz, wants to use
extinction in the 1800s.
extinct animals back,
genetic techniques to
no one will care about
bring back the extinct
keeping endangered
passenger pigeon. These
species from becoming
sleek, gray-blue birds
extinct in the first place.
used to flock over the
“If this were to
Northeastern U.S. in
undercut efforts to
groups of a billion or
conserve currently
more. But by the late
existing species, that
1800s, they had been
would be a tragedy,” says Greely.
hunted to extinction by trappers who sold
Archer doesn’t think that will happen. In
them for people to eat. Bringing them back
fact, he says, the cloning techniques scientists
would help restore biodiversity to the forest
develop to bring back extinct species could
ecosystems in which they lived, says Novak.
be used to breed endangered animals too.
Many of the species scientists want to
Ethical Concerns
bring back became extinct because people
Technology may have made it possible
hunted them or ruined their habitats, argues
to bring back extinct species. But does that
Archer. Humans even helped spread the
mean it’s a good idea?
fungus that killed off gastric-brooding frogs.
Hank Greely, the Stanford bioethicist,
“They shouldn’t be gone, and we did
studies the ethical implications of technoloit,” says Archer. “I think we have a moral
gies like cloning. He thinks de-extinction
responsibility to try to fix what we broke.”
has many potential benefits, including
—Mara Grunbaum
helping ecosystems recover. But Greely says
2001
Researchers clone the first domestic
cat. The kitten is named CC, for “Copy
Cat.” Some companies begin offering
to clone pets—but it’s very expensive.
2003
Cells from a dead banteng, a type of
wild Asian cattle, produce a healthy
cloned calf—raising hope that cloning
can help save endangered species.
Core
Question
Should scientists
try to bring back
extinct species?
Cite evidence
from the article
to support your
opinion.
2009
Scientists report that they used frozen
cells to clone the bucardo, an extinct
Spanish goat. But the clone, born with
lung defects, lived only seven minutes.
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4
BIOLOGY/common core: persuasive writing
Name:
what do you think?
In “Back From the Dead,” you learned that scientists are trying to bring extinct species back to life. Not all scientists believe
it is a good idea to resurrect organisms that have died out. Use this work sheet to write an opinion essay explaining your view
about whether scientists should bring extinct species back to life. Use facts from the article to support your opinion.
Step 1. State your opinion. (Clearly state your opinion about whether scientists should try to bring species back from
extinction.)
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
Step 2. Gather supporting evidence. (Provide at least two arguments that support your opinion. Consider the benefits
or dangers of reviving extinct species.)
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
Step 3. Summarize the topic. (Write a brief summary for people who aren’t familiar with the science of bringing back
extinct species.)
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
Step 4. Write your essay on a separate piece of paper:
• Introduce the reader to the topic with your summary.
• Write a paragraph that states your opinion and includes your supporting arguments. Be sure to include relevant details.
• Conclude by briefly restating your opinion.
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chemistry: READING COMPREHENSION
Name:
FIGHTING FUNGUS
In “Back From the Dead,” you read about scientists who are trying to bring extinct species back to life. One species they
are trying to revive is the gastric-brooding frog. This frog was driven to extinction in part by a fungal infection that causes
a deadly chemical imbalance. Read the following passage to learn about this chemical killer and how scientists hope to
stop it from wiping out other species of amphibians. Then answer the questions that follow.
FATAL FUNGUS
A microorganism is killing off many of the world’s amphibians. The chytrid fungus
(Batrachochytrium dendrobatidis) has infected at least 200 species. Many of those species have
already become extinct. Can scientists stop this killer?
The chytrid fungus kills by causing a chemical imbalance. Healthy amphibians absorb water
and chemicals called electrolytes through their skin. Electrolytes are charged particles that carry
electrical signals to the body’s cells. These electric pulses are critical to the functioning of nerves,
muscles, and the heart.
The chytrid fungus prevents amphibians from properly taking in electrolytes through their skin.
Scientists have found that infected frogs have low levels of potassium and sodium ions. Without
these electrolytes to help carry electrical signals to the heart, the frogs die.
There is some promising news: A bacterium called Janthinobacterium lividum appears to protect
amphibians against the deadly fungus. The bacterium produces a chemical that prevents the
growth of the chytrid fungus. J. lividum already exists on the skin of many amphibians. Scientists
are considering ways to introduce the protective microbe to other amphibian populations.
QUESTIONS
1. Roughly how many amphibian species have been
infected with the chytrid fungus?
A 2
B 200
C 2,000
D all of them
4. How does Janthinobacterium lividum protect
amphibians?
A It produces electrolytes for amphibians to use.
B It kills all other bacteria in the area.
C It prevents the growth of the chytrid fungus.
D It removes electrolytes from amphibians’ skin.
2. Which of the following is NOT true?
5. Which of the following sentences is best
A Amphibians absorb water through their skin.
B The chytrid fungus is critical to the functioning of
nerves and muscles.
C Electrolytes carry electrical signals in the body.
D A lack of electrolytes can be deadly to frogs.
3. Use context clues to choose the best definition
for absorb.
A release
B reduce
C feel
D take in
supported by information in the passage?
A There is no hope for saving the world’s amphibians.
B Janthinobacterium lividum will protect all amphibians
from the chytrid fungus.
C The chytrid fungus is a big problem for amphibians, but
scientists may find a way to fight it.
D Scientists are not concerned about the effects of the
chytrid fungus on amphibians.
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earth: READING COMPREHENSION
Name:
A MAMMOTH EXTINCTION
In “Back From the Dead,” you read about scientists who are trying to bring extinct species back to life. Many factors can
cause a species to disappear. Read the following passage to learn about evidence for what may have killed off woolly
mammoths. Then answer the questions that follow.
MAMMOTH MYSTERY
What caused woolly mammoths to vanish from the planet? Many scientists blame the
extinction of the species on overhunting by humans. But new findings indicate that another factor
also played a role in their demise.
Mammoths once roamed most of northern North America and Siberia. Fossil evidence
suggests that these hairy, elephantlike animals completely disappeared roughly 10,000 years
ago. That’s around the same time that humans first moved into North America and began hunting
them.
But researchers now believe hunting wasn’t the only thing killing off mammoths. By looking
at the ages of fossilized mammoth bones, scientists can tell that mammoth populations were in
decline before people arrived. The likely culprit: a warming climate.
The extinction of woolly mammoths coincided with the end of a glacial period, a time when
Earth’s climate was cool and large sheets of ice covered much of Earth’s surface. As the climate
warmed, new types of plants replaced the cold-weather grasses that the giant herbivores ate.
Many mammoths may have starved because their digestive systems weren’t adapted to break
down the new plants.
QUESTIONS
1. When did woolly mammoths disappear?
A about 10,000 years ago
B at the end of a glacial period
C at roughly the same time humans moved into North
America
D all of the above
2. Which of the following is an opinion?
A Mammoths disappeared roughly 10,000 years ago.
B A glacial period is a time when large ice sheets cover
much of Earth’s surface.
C Mammoths ate cold-weather grasses.
D Humans should not have hunted mammoths.
3. Use context clues to choose the best definition
for coincided with.
A caused
B had nothing to do with
C happened at the same time as
D prevented
4. Which of the following is NOT thought to have
contributed to the extinction of woolly mammoths?
A Earth’s climate changed.
B Earth’s temperature cooled.
C The plants in North America changed.
D Humans hunted mammoths.
5. Which of the following best describes the
author’s main purpose in writing this article?
A to provide readers with interesting information about
mammoths
B to explain how humans can drive animals to extinction
C to describe how Earth’s climate changed 10,000 years
ago
D to explain what scientists think drove woolly mammoths
to extinction
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physics: READING COMPREHENSION
Name:
ZAPPING CELLS
In “Back From the Dead,” you read that one way scientists coax cells into dividing is by using electric current. Read the
passage below to learn about electricity in the body and how electrical therapy could play an important role in medicine.
Then answer the questions that follow.
IT’S ELECTRIC
Electricity powers many devices, but did you know that the human body is an electric machine too?
Electricity plays an important role in our muscular and nervous systems.
Scientists first began learning about electricity in the body in the late 1700s. That’s when an Italian
researcher named Luigi Galvani found that he could make the legs of a dead frog twitch by bringing
them into contact with an electric current.
Today, biologists know that an animal’s nerves form a network that transmits electrical signals
throughout the body. A nerve cell does this by allowing positively charged ions to enter the cell. The
charge from the ions flows along the nerve cell until it reaches the end, and then the signal moves to
the next nerve cell. When the signal reaches a muscle cell, positively charged ions enter it. The ions
cause proteins inside the cell to change shape. That makes the muscle cell contract, and a body part
moves—just like Galvani’s frog legs.
Some researchers have recently found that electricity may help certain cells regenerate after an
injury. Rat nerve cells that have been cut regrow more quickly when they are exposed to a mild electric
current. After more testing, electrical therapy could someday help people recover from nerve injuries.
QUESTIONS
1. Which role does electricity play in biological
systems?
A transmitting nerve signals
B causing muscle contractions
C speeding nerve repair after injury
D all of the above
2. Which of the following statements is NOT
supported by the passage?
A The human body uses electricity.
B Nerve cells transmit electrical signals.
C If you touch a dead frog, you’ll feel an electric shock.
D A mild electric current can aid healing.
3. Use context clues to choose the best definition
for regenerate:
A contract
B regrow
C spark
D bend
4. According to the passage, which statement best
describes what happens when a nerve cell transmits
an electrical signal?
A Positively charged ions enter the cell.
B The nerve cell contracts.
C You feel a tingling sensation.
D all of the above
5. Which statement best describes the purpose of
the last paragraph?
A to persuade doctors to use electrical therapy on their
patients
B to explain how the study of electricity in the body could
help people
C to reassure people that nerve injuries can be repaired
D to entertain readers with an amusing story
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