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BENEFITS AND TRADE-OFFS OF GENETICALLY MODIFIED ORGANISMS ACTIVITY 15

FIGURE 15.5: Rice blast fungus on rice plant introduced, consumers may feel safer when
Once genetic engineering was developed in the eating these foods. CRISPR is relatively easy to
1990s, scientists could now insert genes from use, is cheap, and generates results quickly. It
one organism into the genome of another to can be applied to a variety of organisms,
produce the desired result in just one including crop plants such as rice. These
generation. However, many consumers worry changes can be passed from one generation to
about the effects of eating foods that contain the next if the DNA of the organism’s sex cells
genes from other organisms. Recently, a new are altered.
technology called CRISPR was developed,
which allows researchers to modify organisms CRISPR has been used to create strains of rice
without introducing new DNA from other that are resistant to rice blast fungus. However,
organisms. CRISPR is an enzyme that acts like there are trade-offs to CRISPR. There is a small
a pair of molecular scissors, capable of cutting chance of CRISPR creating unintended changes
strands of DNA. With CRISPR, scientists can in non-target genes. Using CRISPR to make
edit specific genes of an organism and therefore disease-resistant crops may have future negative
change its traits. Since no new DNA is effects by decreasing biodiversity. Crops with
the edited genes may be more robust and
outlive other crop varieties, contributing to a
growing monoculture system of farming—and
monocultures are more vulnerable to future
environmental changes. For example, if all the
rice plants on a farm are genetically identical, a
new pathogen that is introduced to the
environment can very quickly wipe out the
entire harvest. Having a diversity of traits with
different plants resistant to different types of
pathogens causes a new disease to spread more
slowly and allows some plants to survive.

The effects of human interventions are not
always predictable, especially when it comes to
ecosystem challenges. Farmers need to consider
any unexpected changes that may happen in the
future, such as the introduction of new
pathogens or changes to the climate. Gene-
edited crops may survive current problems;
however, if these crops outlive all other crop
varieties, other risks need to be considered.

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

CASE STUDY 3

Fast-Growing Salmon

the aquaculture industry has long been their bodies to grow. Normally, the fish grow at
on the lookout for ways to grow fish faster while a certain rate, depending on environmental
spending less money. Industry leaders hope to conditions, including food availability. If the
meet the increasing demand for fish, increase genetic modification works as intended, the
profits, and reduce the environmental impact of growth rate of the genetically modified fish
fishing. In recent years, industry leaders have should increase so that the fish grow large
teamed up with genetic scientists to find ways to enough to be sold four times faster than
speed up fishes’ growth rates. Geneticists are unmodified salmon. Geneticists have succeeded
currently researching methods to genetically in producing this genetically modified salmon,
modify a number of farmed fish species, but, along with this success, there has been
including members of the salmonid family controversy.
(salmon and trout) and other commercially
important species like catfish and tilapia. One concern about genetically modified
salmon is that if they escape from their net
One promising idea involves inserting a pens, they could breed with wild salmon and
growth-hormone gene from the Pacific chinook make those salmon less fit. The escape of
salmon (Oncorhynchus tshawytscha) into the genetically modified salmon into the wild may
Atlantic salmon (Salmo salar). Like humans, have a serious impact on wild salmon and other
salmon produce a growth hormone that signals organisms that rely on salmon. Wild female

FIGURE 15.6: Net pens for growing farmed salmon are often built along the migration routes of wild salmon,
which poses a problem if the farmed salmon escape.
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BENEFITS AND TRADE-OFFS OF GENETICALLY MODIFIED ORGANISMS ACTIVITY 15

salmon are most likely to mate with larger that genetically modified salmon eat up to three
males. Studies have shown that in some fish times as much as the wild fish.
species, females mate more frequently with the
genetically modified males. Studies of Researchers continue to investigate the
genetically modified fish have also shown that possible damage that genetically modified
in some species, genetically modified males salmon might do to wild populations and how
breed offspring that do not survive as well in the to prevent these kinds of problems. Currently,
wild and are more likely to be eaten by genetically modified fish are only raised in
predators. This also prevents the unmodified closed containers on land to prevent them
wild males from having as many mating from breeding with wild populations.
opportunities, which depletes the wild Genetically modified salmon have been sold in
populations of fish. Canada since 2017, and in 2019 the FDA
approved fisheries to import, raise, and sell
A group of scientists at Purdue University in genetically modified salmon in the U.S.,
Indiana created a modified computer model to provided that they are labeled as a genetically
examine what would happen if 60 genetically modified organism.
modified fish were released into a population of FIGURE 15.7: Salmon spawning in a stream
60,000 wild fish. The scientists used a species of
fish called medaka. The computer model
predicted that if the genetically modified
medaka and wild medaka successfully
reproduced, within 30 generations the wild fish
would be extinct.

One option to prevent genetically modified
fish from disrupting wild populations is to
make them sterile. Salmon eggs may be treated
just after fertilization so that they grow into
sterile adult fish, but this technique is not always
100% effective.

Another concern is how much genetically
modified salmon eat. Some studies show that
they eat the same amount as wild salmon, and
therefore would not out-eat the wild fish if they
escaped. Other studies, however, have shown

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

CASE STUDY 4

Virus-Resistant Papaya

for years, the papaya ringspot virus has FIGURE 15.8: A healthy papaya

destroyed papaya crops in Central American FIGURE 15.9: A papaya with ringspot virus
and equatorial countries of the world. Once the crops where genes from one species were
virus infects a plant, an entire crop of papayas inserted into another. For example, a soy plant
can be ruined. Traditional methods to handle was modified with a Brazil nut gene in the
the disease include isolating papaya orchards to mid-1990s. In testing the genetically modified
prevent disease transmission, breeding soy, it was determined that the modified soy
naturally virus-resistant trees, and cross- could cause severe allergic reactions in people
protection. Cross-protection treats the papaya who were allergic to nuts, and so the project was
trees with a mild form of the virus so that the
trees develop immunity to it. All of these
techniques have had limited success and often
work best when combined. When nothing
works, the farmers’ only choice, if they want to
continue to grow papaya trees, is to move and
start new plantations in a virus-free area.

In 1998, a scientist at Cornell University in
New York State sequenced the genome of the
papaya virus. Once the genome was completed,
the gene that encodes for a protein in the coat of
the virus was identified and isolated. Scientists
used a gene gun to transport the gene and
implant it in papaya seedlings. These genetically
modified seedlings grew up to be papaya plants
that produced the papaya virus protein. Because
the plants produced the virus protein, the trees
developed immunity to infection by the virus,
similar to the way a vaccine works. This protects
the crops from ringspot virus and keeps the
crop profitable. Since the development of the
genetically modified papaya, many papaya
plantations in Hawaii have successfully grown
papaya crops without outbreaks of ringspot
infection.

A major concern with genetically modified
foods is that a person who eats them might have
an allergic reaction to the engineered protein.
This has happened in other genetically modified

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BENEFITS AND TRADE-OFFS OF GENETICALLY MODIFIED ORGANISMS ACTIVITY 15

terminated. Papayas, on the other hand, have Many farmers and scientists also worry that if
been exposed to the ringspot virus for years, everyone grows genetically modified papaya,
which causes them to contain the virus protein. there will be only one type of papaya grown.
This means that humans have been ingesting This makes the crop susceptible to devastating
the virus protein for years, and thus far there losses if a disease were to infect the crop. If all
are no documented cases of allergic reaction to the plants have the same genome, none would
the genetically modified papaya. be resistant to the disease. This problem occurs
Non-genetically modified papaya crops in whenever breeding leads to most crops having
Hawaii have become contaminated by very similar genomes, even when they are not
unintentional breeding with genetically genetically modified.
modified papaya crops. Some studies have
shown widespread contamination of
non-genetically modified papaya crops with the FIGURE 15.10: Hawaii is one
modified gene. This is a problem for Hawaiian location where genetically
farmers because some countries, modified papaya has been
including those in the European grown commercially.
Union, require strict labeling of all
genetically modified crops for HAWAII

Kauai

import. Scientists are currently Moloka’i HAWAII

researching the extent of the Oahu Maui

contamination and ways to prevent
its spread.

Hawai’i

Build Understanding 3299 SEPUP SGI Ecology SE
Figure: 3299EcoSB 18_07
1. Issue connection: Based on what youAgreenaddaaMneddCdoinscdu9s/9s.e5d in this
activity, what questions do you think communities should ask when
considering the sustainability of using a genetically modified
organism?

2. What are the benefits and trade-offs of planting crops that are
genetically modified to be herbicide resistant?

3. Policies about labeling genetically modified foods, such as genetically
modified papaya, vary from country to country. As of 2020, 64
countries—including the United States—require labels for all c7m0y0k9
c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps1 Maps2 Maps3 Maps4 Maps5
genetically modified foods and products. Certain countries will only
import foods that are certified 100% GM (genetic modification)-free.c60m30y100k0 c50m20y75k0 c15m90y90k0 c90m55y40k0
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c39 m7 y12 k0

In countries where labeling is mandatory, consumers often will not
buy products that are not certified GM-free. What are the trade-offs ofc15m10y0k85 c80m0y0k55
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labeling genetically modified foods? Explain at least two trade-offs.

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

4. Review the information on Student Sheet 2.3, “Genetics Case Study
Comparison.” What are the similarities and differences across the case
studies in regard to:
a. DNA?
b. genes?
c. proteins?
KEY SCIENTIFIC TERMS
CRISPR
gene
genetic modification
trade-off

Extension: Engineering Connections

CRISPR is being used to manage patients’ symptoms and could
potentially cure diseases that were once thought incurable—including
blood disorders, blindness, and cystic fibrosis. How can scientists use
gene-editing techniques such as CRISPR to potentially cure diseases?
Visit the SEPUP SGI Third Edition page of the SEPUP website at
www.sepuplhs.org/high/sgi-third-edition to read about how
scientists are using CRISPR to help patients.

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16 M EvoadluifaietidngOGrgeanneistimcaslly

farmer green’s neighboring farmers are facing the possibility

of an economic and social crisis. Over the last 40 years, the county’s
farmers have grown more soybeans and fewer other crops. The primary
crop they now grow is soybeans, but only a small percentage of the
soybeans are sold within the county for human and animal consumption.
Most are exported to other areas around the country, which contributes
significantly to the farmers’ economic and social well-being.
For the past several years, though, soybean production has been low due
to an ongoing drought. Last year, a virus, soybean mottling virus (SMV),
wiped out two-thirds of the already small soybean crop. SMV is
transmitted by aphids and causes plants to grow fewer leaves, smaller
pods, and fewer, if any, soybeans. A company called Genomics Unlimited
Inc. has offered to fund the growing of soybeans that are genetically
modified to protect against SMV. The genetically modified soybean, called
Soy*, has had a gene inserted from another plant that produces a
substance that deters aphids. As an advisor to the county government’s
Panel on Genetic Modification, Farmer Green’s job is to recommend what
action the government should take.

a b
FIGURE 16.1: Some viruses infect up to 94% of a healthy soybean field. The soybeans on the left are healthy (a),
while the soybeans on the right have contracted a virus (b).

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

Should the Panel on Genetic Modification approve the planting
of genetically modified soybeans in Farmer Green’s county?

Materials

FOR EACH STUDENT

Student Sheet 16.1, “Genetically Modified Soybean Study Comparison”

Procedure

1. Examine the following graphs. With your partner, discuss what the
graphs indicate about the sustainability of the county’s agriculture.
Write your ideas in your science notebook.

FIGURE 16.2: Bushels of soy
harvested over time"

Bushels of soy

1970 1975 1980 1985 1990 1995 2000 2005 2010 FIGURE 16.3: Profit from soy over
Year time

3422 SEPUP SGI Genetics SB
Figure: 3422GenSB 20_03
Agenda MedCond 9/9

Pro t from soy

1970 1975 1980Maps1 1985 1990 1995c7m0y0k9 2000 2005 2010
c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps2 Maps3 Maps4 Maps5

C-114 Year

c60 m30 y100 k0 c50 m20 y75 k0 c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

3422 SEPUP SGI Genetics SB c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

EVALUATING GENETICALLY MODIFIED ORGANISMS ACTIVITY 16

FIGURE 16.4: Crop diversity over
time

Crop diversity

1970 1975 1980 1985 1990 1995 2000 2005 2010
Year

3422 SEPUP SGI Genetics SB
FAig geu2nr.ed :Ras3cMe4i2aee2dndGCc“eoePnnrnSdoBo9p2t/eo09b_s0ao5lobky, Genomics Unlimited Inc. to Grow Soy*.” In your
record the benefits and trade-offs of the proposal,
based on the situation faced by Farmer Green’s county.

Proposal by Genomics Unlimited Inc. to Grow Soy*

Genomics Unlimited Inc. (GU) has developed a genetically modified
strain of soybean called Soy*. Their studies have shown that Soy* resists
infection by SMV. GU believes that if the county’s farmers raise Soy*, it
will restore soybean production to profitable levels.Maps1
c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps2 Maps3 Maps4 Maps5

GU proposes that half the soybean farmers in the county plant Soy* for
this year’s crops. Because the farmers have faced such problems with SMV,c60m30y100k0 c50m20y75k0 c15m90y90k0 c90m55y40k0
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c39 m7 y12 k0

GU will offer them a low price on the seed for this year. All of GU’s initial
effectiveness and safety testing has shown positive results, and thec15m10y0k85 c80m0y0k55
c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

company is confident that the modified seed will be a great help in solving
the county’s SMV problems.

3. Discuss with the class the benefits and trade-offs you noted. Be sure to
incorporate any information from earlier activities that you think is
relevant to this proposal.

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

Each member of your group will read one of the following four summaries
of scientific studies that have been done on Soy*. As a group, you will
analyze the data and conclusions in these summaries to help Farmer
Green make an evidence-based decision about whether to recommend
planting Soy* in the county.

4. With your group, decide who will read which summary.
5. As you read, consider the results of your assigned study, and record

your conclusions on Student Sheet 16.1, “Genetically Modified
Soybean Study Comparison.”

STUDY 1

Genetically Modified Soybeans—A Lab Study

Study time frame: 12 months (January 2008– repeated three times, for 120 days each. Results
December 2008) were averaged.

Research group: Genomics Unlimited Inc. Study results: See the graphs for Study 1.

Study objectives: Test the susceptibility of Soy*
(genetically modified soybeans) to SMV
transmitted by aphids (a common carrier of
SMV).

Study procedures: Twenty test Number of leaves FIGURE 16.5: Study 1: Number of leaves over time
greenhouses were set up, 10 to
grow unmodified soybeans and Soy* (control
10 to grow Soy*. Once a week, Soy* exposed to SMV
the number of leaves and unmodi ed soy (control)
soybean pods on each plant unmodi ed soy exposed to SMV
were counted. Half the
greenhouses for each type of Day 1 Day 30 Day 60 Day 90 Day 120
crop were exposed for two Time
months to aphids carrying
SMV. All plants were checked
once a week to determine if
they had contracted SMV. All
crops were watered and
fertilized regularly. Trials were

C-116 3422 SEPUP SGI Genetics SB
Figure: 3422GenSB 20_06
Agenda MedCond 9/9

EVALUATING GENETICALLY MODIFIED ORGANISMS ACTIVITY 16

Study conclusions: Soy* plants Number of soybean pods FIGURE 16.6: Study 1: Number of pods over time
are more resistant to SMV than
unmodified soy and have a Soy* (control)
higher yield than unmodified Soy* exposed to SMV
soy when exposed to SMV. No unmodi ed soy (control)
significant differences in growth unmodi ed soy exposed to SMV
and yield result when the plants
are not exposed to SMV.

Day 1 Day 30 Day 60 Day 90 Day 120
Time

3422 SEPUPFISGGUI GReEn1e6ti.c7s: SSBtudy 1: Percentage positive for SWV over timePercentage positive for SMV
Figure: 3422GenSB 20_07
Agenda MedCond 9/9 Soy* (control)

Soy* exposed to SMV
unmodi ed soy (control)
unmodi ed soy exposed to SMV

Day 1Maps1 Day 30Maps4 c7 m0 y0 k9 Day 60c0 m42 y92 k0c100 m0 y20 k70c25 m0 y15 k90 Day 90 Day 120

Maps2 Maps3 Maps5

Time c15 m90 y90 k0
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko

c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

3422 SEPUP SGI Genetics SB
Figure: 3422GenSB 20_08
Agenda MedCond 9/9

study 1:

c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90 C-117

Maps1 Maps2 Maps3 Maps4 Maps5

c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

STUDY 2

Genetically Modified Soybeans—A Field Study

Study time frame: 9 months (March Number of leaves FIGURE 16.8: Study 2: Number of leaves over time
2009–November 2009)
Research group: State Agricultural Soy* (control)
University Soy* exposed to SMV
unmodi ed soy (control)
unmodi ed soy exposed to SMV

Study objectives: Test the susceptibility
of Soy* (genetically modified soybeans)
to SMV transmitted by aphids (a
common carrier of SMV) in typical
growing conditions.

Study procedures: Four test fields were Day 1 Day 30 Day 60 Day 90 Day 120
set up, two to grow unmodified soybeans Time
and two to grow Soy*. Once a week, the
numbers of leaves and soybean pods on FIGURE 16.9: Study 2: Number of pods over timeNumber of soybean pods
each plant were counted. Half of each
type of crop was exposed to aphids 3FAi4gg2eu2nredS:Ea3PM4U2eP2dGSCGeonInGSdBe9n2/e09t_SSic0oos9yyS**B(ecxopnotsreodl) to SMV
carrying SMV. Crops were watered and unmodi ed soy (control)
fertilized regularly. Trials were repeated unmodi ed soy exposed to SMV
twice, for 120 days each. Results were
averaged.

Study results: See the graphs for Study 2.

Day 1 orca perch algae Day 120
otters urchins Day 90

Day 30 Day 60
Time

c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps1 Maps2 Maps3 Maps4 Maps5

FIGURE 16.10: Study 2: Percentage positive for SWV over time

c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0
c25 m0 y15 k90
c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

Percentage positive for SMV3Fi4g2u2reS:E3P4U2P2GSGenI GSBen2e0t_icSS1soo0yyS**B(control) SMV
exposed to m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6

c15 m10 y0 k85 c80

Agenda MedCond 9/9 unmodi ed soy (control)

unmodi ed soy exposed to SMV

C-118 Day 1 Day 30 Day 60 Day 90 Day 120
Time

EVALUATING GENETICALLY MODIFIED ORGANISMS ACTIVITY 16

STUDY 3

Genetically Modified Soybeans—A Field Study

Study time frame: 3 years (October Number of leaves FIGURE 16.11: Study 3: Number of leaves over time
2006–October 2009)
Research group: International Soy* (control)
Scientific Review Board Soy* exposed to SMV
Study objectives: Test the unmodi ed soy (control)
susceptibility of Soy* (genetically unmodi ed soy exposed to SMV
modified soybeans) and unmodified
beans to SMV transmitted by aphids Day 1 Day 30 Day 60 Day 90 Day 120
(a common carrier of SMV) in Time
difficult growing conditions.
Study procedures: Four test fields FIGURE 16.12: Study 3: Number of pods over time
were set up, two to grow unmodified
soybeans and two to grow Soy*. Soy* (control)
Once a week, the number of leaves
and soybean pods on each plant Number of soybean pods3422 SEPUP SGI GeneticSsoSyB* exposed to SMV
were counted. Half of each type of FAiggeunred:a3M42e2dGCeonnSdB92/09_1uu2nnmmooddii
crop was exposed for two months a ed soy (control)
year to aphids carrying SMV. Crops ed soy exposed to SMV
were given limited water to mimic
drought conditions. Crops were Day 1 Day 30 Day 60 c100 m0 y20 k70 c25 m0 y15 k90 Day 90 Day 120
grown in minimally fertilized soil to c7 m0 y0 k9 c0 m42 y92 k0
mimic poor soil conditions. Trials
were repeated nine times, for 120 Maps1 Maps2 Maps3 Maps4 Maps5
days each. Results were averaged.
Study results: See the graphs for Time
Study 3.
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

FIGURE 16.13: Study 3: Percentage positive for SWV over time

c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

F3i4g2u2reS:E3P4U2P2GSGenI GSBen2e0t_iSSc1oos3yyS**B11 (control) to SMV
exposed

Agenda MedCond 9/9 unmodi ed soy (control)
Positive for SMV
unmodi ed soy exposed to SMV

Day 1 Day 30 Day 60 Day 90 Day 120
Time

c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

STUDY 4

Genetically Modified Soybeans—Effects on Insects in a Lab Study

Study time frame: 18 months FIGURE 16.14: Study 4: Insects exposed to non-modified soy
(June 2007–December 2008)
Research group: International biological control (lady beetles and lacewings)
Society of Entomologists pollinators (honeybees)
Study objectives: Test the decomposers ( y larvae [maggots])
potential effects of Soy* other (painted lady butter ies)
(genetically modified soybeans)
on types of insects commonly Population count
found living in or near soybean
crops. Day 1 Day 30 Day 60 Day 90 Day 120
Study procedures: Eight insect Time
habitats, each populated with
one group of insects and one FIGURE 16.15: Study 4: Insects exposed to Soy*
type of soybean, were set up, as
shown in the following graphs. 3422 SEPUP SGI Genetics SB
Habitats were monitored, and AFiggeunred:a3M42e2dGCeonnSdB92/09_b1io5logical control (lady beetles and lacewings)
insect populations were counted
weekly. Plants were watered and pollinators (honeybees)
fertilized regularly to mimic decomposers ( y larvae [maggots])
ideal growing conditions. Trials other (painted lady butter ies)
were repeated four times, for 120
days each. Results were averaged. Population count

Study Results: See the graphs for
Study 4.

c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps1 Maps2 Maps3 Maps4 Maps5

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c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

Day 1 Day 30 Day 60 Day 90 Day 120

c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

Time

3422 SEPUP SGI Genetics SB
Figure: 3422GenSB 20_16
Agenda MedCond 9/9

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EVALUATING GENETICALLY MODIFIED ORGANISMS ACTIVITY 16

6. Share your notes with your group, and use their notes to complete
Student Sheet 16.1, “Genetically Modified Soybean Study
Comparison,” for the other three studies. Discuss your conclusions,
based on the information you now have for all four studies. Add
information or make edits to the conclusions on your Student Sheet,
based on your discussion.

7. Discuss any questions or thoughts you had while reading your
summary, and write them in your science notebook.

8. Discuss the original proposal with the class, following your teacher’s
instructions.

9. Based on the ideas you recorded on Student Sheet 16.1 and the
information from your class discussion, decide if Farmer Green should
support his neighbors in growing Soy*. In your science notebook,
write a report to the government Panel on Genetic Modification in
which you:

• state your recommendation to Farmer Green
• explain the benefits and trade-offs of your recommendation
• cite evidence from the summaries that supports your

recommendation

Build Understanding

1. Explain the similarities and differences in the experimental design of
the four studies on Soy*.

2. How might the differences in experimental design of the four studies
on Soy* affect each study’s outcomes and conclusions?

3. Describe how your recommendation will affect the social, economic,
and environmental sustainability of the county farmers.

4. Issue connection: What information should policymakers evaluate
when making decisions about genetically modified organisms?

KEY SCIENTIFIC TERMS

genetic engineering
trade-offs

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17 Alternatives to GMO Farming

the sustainability of food production is a major issue as greater
demand is placed on resources, such as land and water, to produce enough
food for a growing population. Genetic modification has quickly and
efficiently generated crops with traits that meet demands for more food,
such as saving crop plants like papaya from extinction and increasing crop
yields by modifying plants to tolerate changes in climate, resist pests, and
resist herbicides.

FIGURE 17.1: Special airplanes called crop dusters are sometimes used to spray fields with
chemicals that protect crops from damage.

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

However, farmers like Farmer Green are beginning to experience the
trade-offs of genetically modified organism use in terms of profit loss due
to transgene migration (such as superweeds), increased expenses to keep
their farm running well, and increased demand for unmodified foods by
consumers. In addition, changes in biodiversity as a result of practices like
monoculture with genetically modified crops can lead to decreases in crop
production over time.
To protect his future profits, Farmer Green has decided to join his local
agricultural board—the group responsible for making decisions about
what is planted in the region and any changes to farming practices that are
needed to promote sustainable food production and biodiversity. To
address the issue of superweeds, the board is considering four different
proposals to implement in the county. You are also a member of this board,
and you will need to vote on the proposal that you believe has the greatest
benefit for sustainable food production in your county.

Guiding Question

How can farmers support sustainable food production?

Materials

FOR EACH STUDENT

completed Student Sheet 2.3, “Genetics Case Study Comparison,” from
Activities 2, 5, and 15
completed Student Sheet 7.2, “Modeling Herbicide Resistance,” from
Activities 7, 9, and 10

Procedure

1. With your group, decide which student will read which of the four
proposals under consideration for sustainable food production. Work
by yourself to read your assigned proposal.

Proposal A: Superweed Removal

Superweeds are a significant problem for the sustainable production of
crops in our country. They pose a threat to the profits farmers can
make because they overgrow and shade out shorter crops like soy and
cotton, they decrease biodiversity by overtaking other weedy species
that support a diversity of pollinators, and they are resistant to several

C-124

ALTERNATIVES TO GMO FARMING ACTIVITY 17

common herbicides used by farmers in our county. Their numbers are
increasing, and superweeds are likely to spread to other neighboring
counties as well, with similar effects. We propose that farmers in our
county manually remove all weeds, especially superweeds, from their
fields periodically during each growing season. The cost of removing
weeds will be placed on the farmer who owns the field. No restrictions
will be placed on the continued growing and selling of genetically
modified crops.

Proposal B: Crop Separation

Transgene migration occurs when genetically modified crops are
grown in close proximity to their unmodified relatives, allowing sexual
reproduction through pollination (as in the case of superweeds). To
reduce the possibility of transgene migration occurring, we propose
that unmodified crops and genetically modified crops that are related
to one another be grown separately—at least 20 miles apart. A plan to
distribute crops across the county will be developed by the board, and
farmers will be instructed as to who can grow which type of crop.
Unmodified and genetically modified crops will be rotated every two
years so that each farmer will have an opportunity to grow more
profitable genetically modified crops during their rotation.

Proposal C: Diversifying Crops

Biodiversity is a critical element of sustainable food production. Across
the county, the majority of farms use a monoculture of genetically
modified crops to maximize profits. Monoculture has supported the
development of superweeds in our county and has decreased the
biodiversity necessary for the health of our crops over time. We
propose that each farmer must grow a minimum of four different crops
in their fields with a minimum of 25% being unmodified. Farmers can
determine which crops they will grow and where to place each crop
relative to the others.

Proposal D: Cooperative Growing

Several factors contribute to the sustainability of food production.
However, not all solutions consider the economic sustainability of
farming. Diversifying crops is essential for the health of both the crops
and the environment over time, but farmers must also benefit
economically from their work in order to continue growing food in our
county. We propose a cooperative growing system where farmers work
together to develop sustainable crops and share profits. For example,
Farmer A will grow a highly profitable genetically modified crop, and

C-125

GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

Farmers B and C will each grow a different unmodified crop that
protects biodiversity in our county. All three farmers will share the
profits of the crops at the end of each growing season to promote their
economic sustainability.
2. In your science notebook, make a chart like the one that follows. Fill in
the chart for your assigned proposal.

ECONOMIC SOCIAL E N V I R O N M E N TA L BENEFITS TRADE-OFFS
PROPOSAL OUTCOME OUTCOME OUTCOME
A
B
C
D

3. Present a summary of your proposal to the members of your group. As
your group members present the information about their proposals,
complete your chart.

4. Consider which proposal you think best supports sustainable food
production for Farmer Green’s county. In your science notebook,
record which proposal you would vote for and any evidence that
supports your decision. You can refer to your copies of Student Sheet
2.3, “Genetics Case Study Comparison,” and Student Sheet 7.1,
“Modeling Herbicide Resistance,” to gather additional evidence about
the benefits and trade-offs of genetically modified organisms to
support your decision.

5. Take part in a Walking Debate as a way to share your ideas with the
class about which proposal should have priority. Your teacher will
explain how to run the debate.

Build Understanding

1. Issue connection: Which proposal did you decide would best support
sustainable food production? Cite at least three pieces of evidence to
explain your reasoning, and state the trade-offs of your decision.

2. Describe three indicators you would recommend using to monitor the
success of the proposal over the next 10 years if your recommendation
from item 1 were implemented. These indicators can be any
observations that will help determine if the recommendation is
successful.

C-126

ALTERNATIVES TO GMO FARMING ACTIVITY 17

3. What social, economic, and environmental elements of sustainability
were involved in your considerations about which proposal to choose?

4. What scientific evidence influenced your considerations about which
proposal to choose?

KEY SCIENTIFIC TERMS

biodiversity
genetic modification
monoculture
transgene
trade-off

C-127



Unit Summary

Inheritance of Traits

Through sexual reproduction, which requires two parents, offspring inherit
half of their chromosomes—and therefore half of their genes—from each
parent. The parents produce gametes, such as sperm or eggs, through the
process of meiosis, which leads to genetic variation in gametes. When the
two gametes combine to form offspring, more genetic variation results.
Traits produced by an allele can be dominant or recessive. The genotype of
an organism is the combination of alleles that the organism has, and the
phenotype is the physical appearance or other characteristics produced by
those alleles. If an organism has two of the same alleles, it is homozygous
for that trait, and if it has two different alleles, it is heterozygous. Punnett
squares can be used to determine the probability of possible genotypes and
phenotypes of the offspring of two parent organisms.

Molecular Mechanisms

All cells (except red blood cells) contain DNA that is used to produce the
traits that make up an organism, such as appearance, blood type, certain
health conditions, and behavior. DNA contains genes that code for proteins
that bring about these traits. Cells undergo two phases of protein
synthesis—transcription and translation—to produce proteins. Which
proteins are produced depends on which genes are expressed or repressed
in the cell. New somatic cells produced by mitosis are also subject to genes
being expressed or repressed, which leads to differentiation of cells and,
ultimately, different cell types.

Genetically Modified Organisms

Genetic modification is a process used by scientists to change an
organism’s DNA. Typically, a gene from one organism is introduced into
the DNA of another for the purpose of providing the modified organism
with a new trait. For example, the gene from certain fish species that
helps them survive in freezing waters has been introduced into some

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GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

crop plants to help them withstand frost damage. With the advent of
CRISPR technology, genes can also be edited to include changes that
benefit the organism without adding DNA from other organisms.
Treatments that are now being developed for human diseases such as
sickle cell anemia and cystic fibrosis are using this new technology. No
DNA is introduced; instead, scientists edit the mutated genes to provide
relief from the symptoms of these genetic disorders.

Gene Flow

When cells reproduce and copies of genes are made, sometimes there are
random changes to the DNA called mutations. Mutations can be helpful,
harmful, or neutral, depending on how they affect the structure and
function of the protein coded by the gene. Some mutations are
purposefully introduced by genetic modification or selective breeding to
provide the offspring with new traits, such as drought tolerance or disease
resistance in plants.
Sometimes, modified genes unexpectedly spread into the environment.
This typically occurs when related species mate with one another and pass
on modified genes to their offspring. This can lead to significant impacts
that can have social, environmental, and economic trade-offs. For example,
when crops were modified with a gene for herbicide resistance and they
then mated with their weedy relatives, the offspring weeds were also
herbicide-resistant, which created economic and environmental issues for
farmers and the ecosystem.

C-130

FEEDING THE WORLD SUMMARY

KEY SCIENTIFIC TERMS inherit
karyotype
alleles meiosis
amino acid mitosis
asexual reproduction monoculture
biodiversity mRNA
biofuel mutations
centromere nondisjunction
chromatid parent cell
chromosomes phenotype
CRISPR polyploidy
crossing over protein
daughter cells protein synthesis
differentiation Punnett square
dihybrid cross recessive
diploid repressed (gene)
DNA RNA
dominant selective breeding
enzymes sexual reproduction
expressed (gene) somatic cells
gametes stem cells
gel electrophoresis superweed
gene expression trade-offs
genes traits
genetic engineering transcription
genetic modification transcription factor
genetically modified organisms transgene
(GMOs) transgene migration
genome translation
genotype tRNA
haploid
herbicide

C-131



EVOLUTION

MANAGING
CHANGE

EVOLUTION

Unit Issue

tuberculosis (tb) is a human disease caused by the bacterium

Mycobacterium tuberculosis (M. tuberculosis). It affects the lungs and
other parts of the body and can lead to severe illness and even death.
As many as a third of the people on Earth are infected with this
bacterium. In 2009, more people died from TB than in any previous
time in history. Yet, 9 out of 10 people have developed immunity to
this bacterium and do not get sick. If they were to take a TB test, the
result would be positive, but they would not have the disease and
could not pass it on to other people. Only 1 in 10 will develop active
TB, which is transmissible to other people.

Based on recent genetic evidence, researchers now believe that M.
tuberculosis has affected human populations for as long as 40,000
years. Researchers have evidence that the disease originated in Africa
and stayed with humans as they migrated to Europe and Asia.
Researchers think the original strain of the bacterium was a generalist
strain, infecting both humans and livestock such as sheep and cattle;
it then evolved to become two distinct specialized strains. One of
these strains evolved to become even more successful at infecting
people. This strain continues to evolve today, and human actions—
such as not completing a full course of prescribed antibiotics—are
likely the primary cause. A significant result of this evolution is
antibiotic resistance, which you will learn more about in this unit.

Other diseases caused by pathogens—diphtheria, smallpox, AIDS,
and influenza A, to name just a few—are also thought to have long
evolutionary histories. In some cases, researchers think that the
disease-causing pathogens may have originally infected animals

D-2

living with, or in close proximity to, humans. The pathogens then
evolved to infect humans. For example, the bacterium that causes
diphtheria is thought to have originated in domestic herbivores, such
as cows. The bacterium causing smallpox is thought to have
originated in camels. The virus causing AIDS is thought to have
originated in chimpanzees, and the virus causing influenza A is
thought to come from birds.

FIGURE A: Some animals that were the original hosts
for infectious diseases that now affect humans

D-3

In addition to the pathogens that have infected humans for hundreds,
thousands, and even tens of thousands of years, new diseases have
emerged or re-emerged more recently. For example, in 2015–2016, the
Zika virus became an epidemic. The geographic range of this virus is
typically limited to a narrow strip along the equator, but a mutation
occurred that allowed it to spread more widely. In 2019, a new
mutation in the spike protein of a coronavirus emerged and caused a
global pandemic. Some scientists think that human actions, including
land-use practices (such as deforestation), are at least partly responsible
for the growing rate of emerging and re-emerging diseases.
Figure B shows a map similar to the ones you observed in the very
first activity of this course, “Changing Landscapes” in Sustainability:
Changing Human Impact. This map shows areas experiencing

Tree cover
Tree cover loss

FIGURE B: Map of global tree cover and tree cover loss

D-4

deforestation and loss of biodiversity. Compare this map with the
one in Figure C, which shows scientists’ predictions about where
emerging diseases are likely to be found—the lighter the color, the
greater the probability. What patterns do you notice? What questions
do you have?
In this unit, you will explore some of these questions as well as an
overarching question: How do human activities affect the evolution of
other species, and what are the consequences for both biodiversity
and ourselves?

FIGURE C: Map showing where emerging diseases are likely to be found. The lighter the color, the greater the
probability of finding an emerging disease; the darker the color, the lower the probability.

D-5



1 Changing Environments

Investigative Phenomenon

FIGURE 1.1: Salamanders of the species Ensatina British
eschscholtzii in many colors and patterns. Clockwise from Columbia
top left: Large-blotched ensatina, Painted ensatina, Sierra
Nevada ensatina, Yellow-eyed ensatina, Monterey ensatina Washington
Oregon
All the individuals in these images are
members of one species of salamander, California
Ensatina eschscholtzii, found along the Pacific
Coast of North America (from British Columbia
down to Baja, Mexico), as shown in the map in
Figure 1.2. What do you notice about these
salamanders? What questions do you have?

FIGURE 1.2: Range map of the salamander Baja California
species Ensatina eschscholtzii

D-7

SEPUP SGI 3e Evolution

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

Understanding how wild populations of organisms evolve over time can be
challenging. Just as ecologists do, examining a population that is relatively
easy to study over extended periods of time can help us understand their
evolution. In the Ecology unit, you investigated one well-studied species—
the song sparrows on Mandarte Island—to understand the factors affecting
the birds’ population size and growth. In this activity, you will explore
changes in traits over time in another well-studied wild organism: the marine
iguana of the Galápagos Islands. But instead of having a wide range of colors
like the salamanders, iguanas show a tremendous range in body size.

Guiding Question

How do populations respond over time to a changing
environment?

FIGURE 1.3: Bartolome Island in the Galapagos Islands

D-8

CHANGING ENVIRONMENTS ACTIVITY 1

Procedure

Part A: Body Size and Reproduction

1. Read “Scientific Findings 1” to learn more about marine iguanas.

Scientific Findings 1

The marine iguana Genovesa Equator FIGURE 1.4: Map of
(Amblyrhynchus cristatus) Santiago
Galápagos Islands

is a single lizard species Baltra
found only in the Galápagos
Islands. It is unique among Rabida Santa Cruz
iguanas in that it feeds at sea
but lives on land. Marine Isabela Pinzon Santa Fe North
iguanas feed by grazing on Fernandina Santa Maria San Cristóbal America
algae growing on rocks in Española

the intertidal zone and
sometimes farther out to
sea. Marine iguanas have no
competitors, and they have virtually no native
predators. There are six populations of marine Equator South
iguanas, each living on a different island, GALAPAGOS America
ISLANDS

although individuals can swim between Paci c
islands. The iguanas’ body size, which is a Ocean

heritable trait, varies across the islands.

SEPUP SGI 3e Evolution
Figure: SGI Evo 1_3
MyriadPro Reg 9/Semibold 9.5

FIGURE 1.5: Male (upper left) and female marine iguanas
on land

FIGURE 1.6: Marine iguana under water
clinging to rock

D-9

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

2. Examine Figure 1.7 a–d, which shows data collected from marine
iguanas on two islands (Genovesa and Santa Fe), and describe what
you see in these graphs.

a) b)
Body size of females on Genovesa Island Body size of females on Santa Fe Island

70 70

60 60

50 50

Frequency
Frequency
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c) d)
Body size of males on Genovesa Island Body size of males on Santa Fe Island

70 70
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Body length (mm) Body length (mm)
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FIGURE 1.7 a–d: Body size of males and females on Genovesa and Santa Fe Islands

3. Use what you’ve learned so far to answer this question: What factors do
you think might be affecting the body size of male and female marine
iguanas on these two islands?

4. Read “Scientific Findings 2” to learn more about marine iguana
breeding behavior.

D-10
LabAids SEPUP SGI Evolution 3e
Figure: Evo3e SB 01_06a–f
MyriadPro Reg 9.5/11

CHANGING ENVIRONMENTS ACTIVITY 1

Scientific Findings 2

males: At the start of each breeding season, nearly 40% of the matings—and therefore
40% of the offspring produced on the island—
male iguanas compete among one another for in one year. Many of the smallest males didn’t
territories. Competition begins with head- mate at all.
bobbing displays and may escalate to head
butting and eventually to fighting. Larger females: Females iguanas choose a
males are better able to establish and defend
territories that are preferred by females. As a territory in which to dig their single nest, and
consequence, larger males are able to mate they mate only once during a breeding
with a greater number of females. The average season. Females lay between 1 and 6 eggs in
body length of males who were successful in their nest, and they may transfer up to 20% of
mating with females was 245 mm on their own body mass to their eggs. Larger
Genovesa Island and 400 mm on Santa Fe females are able to lay a greater number of
Island. One another island, researchers found eggs and thus produce a greater number of
that one male, the largest, accounted for offspring in each breeding season.

Survival (%) 5. Revisit Step 3 to see if your thinking has changed, based on these
findings.

Part B: Body Size and Changing Environments

6. Examine the graph in Figure 1.8, and describe what the data shows.

100
90
80
70
60
50
40
30
20
10
0
125 155 185 215 245 275 305 335 365 395 425

Body length (mm)

Survival Rate (%) on Genovesa, March 1991–March 1992 FIGURE 1.8: Survival rate vs.
Survival Rate (%) on Santa Fe Island, March 1990–March 1992 body size of marine iguanas,
1991–1992

D-11

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

7. Use what you’ve learned so far to answer this question: What factors do
you think might be causing this pattern of survival rate vs. body size?

8. Read “Scientific Findings 3” to learn more about marine iguanas.

Scientific Findings 3

Larger marine iguanas can feed more hour, that’s 20 hours of feeding per day,
efficiently than smaller iguanas, which means which, while technically possible, certainly
that they can get the food they need with less isn’t feasible. Thus, the very large iguana will
effort. For example, say that a small iguana not be able to maintain its body size and will
can eat at the rate of 1 food unit per hour, lose weight.
whereas a large iguana can eat at the rate of 2
food units per hour. The larger iguana is Smaller iguanas feed less efficiently than
feeding more efficiently—it can get more food larger iguanas—they have to work harder to
per unit of feeding effort. Larger iguanas are get the same amount of food as a larger
also stronger and can grip onto rocks while individual. They also have weaker grips and
feeding in strong currents. remain closer to shore, feeding on the algae
exposed during low tide. If they forage farther
However, the largest iguanas are less able to away from the shore, they run the risk of
maintain their body mass because they being swept out to sea.
cannot eat enough total algae to maintain
their size. For example, say that a very large However, smaller iguanas are better able to
iguana needs 40 food units per day to maintain their body mass because they need
maintain its body size. At 2 food units per less total algae. So, while they are less efficient
foragers, they don’t require as much total food.

9. Develop an initial explanation for factors affecting body size in marine
iguanas, and write this explanation in your science notebook.

10. Read “Scientific Findings 4” to learn more about El Niño events.

Scientific Findings 4

The galápagos islands are periodically affected upwelling, which results in a die-off of algae.
by El Niño–Southern Oscillation events. In 1991–1992, the Galápagos Islands
During a normal year, winds traveling from experienced a severe El Niño event.
west to east cause an upwelling of cold,
nutrient-rich water that gives rise to extensive To learn more about El Niño, see the
beds of algae. During an El Niño year, these background information at the end of this
winds reverse direction, preventing this activity.

D-12

CHANGING ENVIRONMENTS ACTIVITY 1

11. Use what you’ve learned so far to a Percentage of population25 March 1991
answer this question: What do you b 10020 N = 318
predict happened to the marine c 11015
iguana population as a result of the 12010Body length (mm)
1991–1992 El Niño event? Explain 130 November 1991
your prediction in your science 1405 N = 125
notebook. 1500
160Body length (mm)
12. Look at the graphs in Figure 1.9 a–e, 17025March 1992
which show body-length 18020N = 127
measurements of iguanas on 19015
Genovesa Island from just before the 20010Body length (mm)
El Niño event and at the end of the 210November 1992
event. The total population size, N, is 2205N = 48
shown next to each graph. What do 2300
these graphs show? Was your 240Body length (mm)
prediction in Step 11 supported? 25025March 1993
Explain your answer. 26020N = 39
27015
28010Body length (mm)

Percentage of population5
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e Percentage of population25
FIGURE 1.9 a–e: Marine iguana body 10020
length from before El Niño to after El Niño 11015
12010
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D-13

LabAids SEPUP SGI Evolution 3e
Figure: Evo3e SB 01_08a–e

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

Background Information: What Is El Niño?

El Niño is a climate pattern that consists of Chile. This process is known as upwelling.
unusual warming of surface waters in the During an El Niño event, the westward-
eastern tropical Pacific Ocean. El Niño can
also increase the speed and strength of ocean blowing trade winds weaken. These changes in
currents, impact the health of coastal air pressure and wind speed cause warm
fisheries, and change local weather patterns. surface water to move eastward along the
El Niño events occur about every two to Equator, from the western Pacific to the coast
seven years. However, these events are not of northern South America. Because of these
predictable. weaker trade winds, less upwelling of nutrient-
rich cold waters occurs in the eastern Pacific.
To understand the impact of El Niño, it’s Fish populations often die or migrate, resulting
important to be familiar with non-El Niño in serious consequences for the animals and
conditions in the Pacific Ocean. Normally, people who are dependent on them.
strong trade winds blow westward across the
ocean, pushing warm surface water toward During an El Niño event, widespread
the western Pacific, which borders Asia and climate changes can take place that are
Australia. sometimes severe. Rainfall increases
drastically in South America and can
Due to the warm trade winds, the sea contribute to coastal flooding and erosion.
surface is normally about .5 meter (1.5 feet) Drought threatens regions in Indonesia and
higher and 8°C (14.4°F) warmer in Indonesia Australia. These climatic events often lead to
than in South America. The westward serious economic, environmental, and social
movement of warmer waters causes cooler, consequences.
nutrient-rich waters to rise up toward the
surface on the coasts of Ecuador, Peru, and

Build Understanding

1. Construct an explanation for the evolution of body size in marine
iguanas. Be sure to account for the differences between the islands,
between males and females, and in times of differing food availability.

2. If algae were not limited, what do you predict would happen to the
iguana population and to individual iguanas?

3. If ocean temperatures continue to warm, how do you think body size
in marine iguanas will be affected?

4. Issue connection: The cats and dogs brought in by people are a
growing problem in the Galápagos Islands. What effect might these
populations have on the evolution of marine iguanas?

D-14

CHANGING ENVIRONMENTS ACTIVITY 1

KEY SCIENTIFIC TERMS

adaptation
competition
evolution
natural selection
population

Extension

Major weather patterns like El Niño can affect the evolution of species.
Ancient El Niño-like weather patterns were a major driver in
environmental changes that helped shape human evolution. But what
evidence do scientists have for explaining the powerful effects of these
weather patterns? Visit the SEPUP SGI Third Edition page of the SEPUP
website at www.sepuplhs.org/high/sgi-third-edition to read articles about
how weather patterns helped create humanity.

D-15



2 Increasing Temperatures

in the last activity, you investigated how the body size of marine

iguanas evolves over relatively short periods of time, due to changes in the
environment. When food is abundant, larger body size is favored by
natural selection, but when food is scarce, a medium body size is more
adaptive. In the case of the marine iguanas, El Niño events have been the
major source of environmental change affecting the population. But
scientists are now wondering how climate change, including warming
ocean temperatures, will affect these iguanas. In fact, the effects of global
warming on many different kinds of organisms are now being investigated
across the globe. Of particular concern from a sustainability perspective is
how plants will adapt to increasing temperatures. Because people rely on
plants for so many things—including food, medicine, energy, and shelter—
predicting how plants will evolve to climate change is essential. In this
activity, you will measure the rate of photosynthesis in aquatic plant species
under different temperature conditions. You will then make connections
between your results and how a changing climate may affect sustainability.

FIGURE 2.1: Aquatic plants growing below the surface of the water

D-17

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

How might increasing temperatures affect populations of
aquatic plants over time?

Materials

FOR THE CLASS

2 digital scales
2 plastic cups (weigh boats)
supply of baking soda
supply of tap water
cold water bath (4°C)
room-temperature water bath (20°C–24°C)
warm water bath (40°C)

FOR EACH GROUP OF FOUR STUDENTS

4 capped plastic vials
2 sprigs of Ludwigia
2 sprigs of Elodea
plastic cup
SEPUP stir stick
permanent marker
masking tape
195-mL graduated cup
scissors
timer (or stopwatch)

FOR EACH STUDENT

Student Sheet 2.1, “Experimental Results”
chemical splash goggles

SAFETY

Wear chemical splash goggles while working with chemicals.
Be cautious when working with live organisms. If there are
any spills, or if substances come in contact with your skin,
notify your teacher immediately, and wash with soap and water.
Wash your hands at the end of the investigation.

D-18

INCREASING TEMPERATURES ACTIVITY 2

Procedure

1. Read “Plant Diversity at Lake Clancy,” a scenario about a fictitious lake.
As you read, think about the following questions:

• What do you notice about the data?
• What do you think is happening to the aquatic plants in Lake Clancy?
• What will happen to the population of aquatic plants in Lake Clancy

if this weather trend continues?

2. Discuss with your group your responses to the questions in Step 1.

Plant Diversity at Lake Clancy 20Number of plants (thousands)
18
Lake Clancy, a spring-fed lake, is about 100m to Number of days16
200m across, roughly the size of two football 14
fields, and and about 10 meters deep at its 12
deepest point. Many species of birds use the 10
lake as a rest stop on their migratory paths, and
the lake is home to a variety of aquatic plant 8
species. The temperature of the lake remains 6
relatively stable throughout the year, with 4
warmer water at the surface and cooler water at 2
the bottom. 0

In the past five years, scientists who study the 1980 1985 1990 1995 2000 2005 2010 2015 2020
aquatic environment of Lake Clancy noticed
that the historically diverse population of plants Year
growing in and around the lake has changed. FIGURE 2.2: Aquatic plant populations of Lake Clancy
The rim of the lake was known to grow thick
with Elodea plants, and the bottom of the lake 120
contained Ludwigia plants. However, in recent
years, the population of Elodea seems to be 100
decreasing, whereas the submerged Ludwigia
plants are increasing in number and are seen 80
nearer to the surface of the lake than ever before.
Scientists who study Lake Clancy wonder if the LabA6i0ds SEPUP SGI Evolution 3e
surviving Ludwigia plants have a trait that Figure: Evo3e SB 02_03
protects them when growing in warmer water. Myri4a0dPro Reg 9.5/11

Scientists did not detect any changes in 20 Elodea
chemical pollutants in the water, but they did Ludwigia
record more days over 40°C (104°F) each
summer over the past 20 years, with the highest 0
number of hot days in the past 10 years. The 1980 1985 1990 1995 2000 2005 2010 2015 2020
scientists wonder if increasing temperatures
could be affecting the plant populations growing Year
in Lake Clancy.
FIGURE 2.3: Number of days above 40°C

D-19

LabAids SEPUP SGI Evolution 3e
Figure: Evo3e SB 02_02

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

3. Prepare to conduct your investigation on the rate of photosynthesis in
aquatic plant species under different temperatures by deciding which
group members will perform the following roles:

• Timer
• Bubble counter for Elodea
• Bubble counter for Ludwigia
• Data recorder

4. Obtain 2.5 g of baking soda in your plastic cup, and 100 mL of water in
your graduated cup. Add the water to the baking soda in the plastic
cup, and use the stir stick to stir thoroughly until the water looks clear.

5. Use scissors to cut an 8- to 10-cm segment from each aquatic plant,
and add each segment to a vial, with the cut side of the stem facing
toward the opening of the vial.

6. Fill the two vials with the baking soda–water solution. Make sure that
the plant segments are fully submerged, as shown in Figure 2.4, and
that the stems aren't pressing up against the wall of the vial. Cap the
vials. Use masking tape and a marker to mark the cap of each vial with
the name of the plant species that it will contain (Elodea and Ludwigia,
respectively).

FIGURE 2.4

D-20
LabAids SEPUP SGI Evolution 3e
Figure: Evo3e SB 2_04

INCREASING TEMPERATURES ACTIVITY 2

7. Take a control reading by having the bubble counters
count the number of bubbles generated by the plant
segment over 10 seconds, 30 seconds, and 60 seconds
with just the room lights on (not a grow light or direct
sunlight). Record the data on Student Sheet 2.1,
“Experimental Results.” Refer to Figure 2.5 to see what
bubbles coming out the end of a plant look like.

8. Place the vials in the room temperature water bath as
instructed by your teacher.

9. Repeat Steps 5–7.

10. Place your vials in your group’s other assigned water bath.

11. Leave your vials in the baths for 5 minutes. Then collect FIGURE 2.5
your data by counting the number of bubbles produced
in 60 seconds in each vial. Record your data on Student
Sheet 2.1.

12. Discuss your data with the class, according to your teacher’s
instructions.

Build Understanding LabAids SEPUP SGI Evolution 3e
Figure: Evo3e SB 2_05

1. Arjun suspects that the aquatic plants died when they were placed in
the 40°C water bath during the activity, and that is why photosynthesis
stopped. However, Ava thinks that the plants just shut down
photosynthesis for a little while to protect themselves from the heat.
What experimental steps could they take to determine if the plants are
alive or dead?

c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps2
Scientists studying the survival of aquatic plants in Lake ClancyMaps1 Maps3 Maps4 Maps5

2. noticed that some individuals appeared to be unaffected by thec60m30y100k0 c50m20y75k0 c15m90y90k0 c90m55y40k0

c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c39 m7 y12 k0

warming water, while others of the same species died when c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

temperatures became too extreme. What could explain the scientists’
observation? What might happen to the plant population over time?

3. The aquatic plants at Lake Clancy provide important resources to the
animals and invertebrates that depend on the lake, such as shelter and
food. How might changes to the aquatic plant populations in the lake
affect the other species who live there?

4. Issue connection: If global warming continues to increase, how might
this impact humans and our reliance on the process of photosynthesis
for the production of food crops? How might this relate to the three
pillars of sustainability?

D-21

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

KEY SCIENTIFIC TERMS

climate change
competition
photosynthesis
species

D-22

3 Social Behavior

you have seen how competition for resources, both biotic and
abiotic, can affect the evolution of structural traits (such as body size) and
metabolic traits (such as the rate of photosynthesis) in populations. In this
activity, you will explore another type of trait that can evolve in response to
environmental factors: behavior. Specifically, you will investigate social
behavior among black-tailed prairie dogs.

Guiding Question

What other traits can evolve in response to environmental
conditions?

FIGURE 3.1: Black-tailed prairie dogs live in prairie
dog towns. They use alarm calls to warn one another
of predators.

D-23

EVOLUTION SCIENCE & GLOBAL ISSUES: BIOLOGY

Procedure

Part A: Black-Tailed Prairie Dogs

1. As you watch the video about black-tailed prairie dogs, write down
everything you notice about the prairie dogs and their environment.
Also write down any questions you have, based on these observations.

2. Discuss with your partner why prairie dogs might vocalize. What do
you think is the function of these calls?

3. Read the following passage, “Prairie Dogs.”

Prairie Dogs

Prairie dogs are large ground time standing watch. When a
squirrels that live in prairie dog prairie dog spots a predator, it
towns. Within each town are sometimes sounds an alarm by
territories held by groups called emitting a high-pitched bark. The
coteries. Prairie dogs are prey to individual issuing this alarm is
aerial predators, including hawks simultaneously alerting other
and owls, and to ground prairie dogs that a predator is
predators, such as coyotes and nearby and making itself more
badgers. When above ground, noticeable to the predator. Thus,
prairie dogs spend much of their alarm-calling is risky to the caller.

4. Develop an initial argument for how alarm-calling could be an
adaptation that evolved, even if the behavior increases the caller’s risk
of predation.

FIGURE 3.3 : Black-tailed prairie dog giving an alarm call (left) and yipping prairie dog pup (right)
D-24