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SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

HAWAII

Kauai contained only 37% fishmeal and 12% fish oil,
all of which they obtained from sustainable
Moloka’i fisheries or from canneries or other businesses

Oahu Maui HAWAII

that process caught fish for human
consumption. The remaining protein in the
food comes from agricultural protein and grains.
Kailua- Hawai’i While this is a better solution than the original
Kona food, it still uses a lot of resources and is one area

Hawai’i FIGURE 16.6: Map of Hawaii of the fishery that is still a sustainability challenge.

Great Escapes
A big problem with open-net pens everywhere
is that they attract predators. Seals and dolphins
farmed fish introducing genes that would be new have been known to rip open aquaculture net
to the wild fish populations. The farm went pens, freeing fish to escape—some right into the
through a rigorous permitting process, and even mammals’ jaws. This has prompted farmers to
set some of its fishery-management policies to be install detection devices to prevent escapes. But
stricter than required by the state and federal despite these efforts, escapes will occur. This
LabAids SEPUPgoSvGeIrEncomloegnyts3.eThe yellowtail farmers set up a presents two main problems: first, escaped fish
FMigyuriraed:PErcooR3eegSswyB9is.l15td6e/1m_a10n6dwhkeepret a few adult fish are caught in the may carry parasites and viruses that infect wild
as brood stock (the fish who lay and populations, and second, escaped farm fish
fertilize eggs) in tanks at the land-based hatchery might introduce new species to the local
to spawn offspring. The larval offspring are then ecosystems that could become invasive.
fed a special type of zooplankton, which is also
raised at the hatchery. Once the young fish have For the Hawaiian yellowtail farm, however, this
been weaned onto a commercial feed and are is less of a threat. Escapes have been rare at the
large enough, they are moved to the open-ocean farm, and when they do happen, the concerns
pens to grow until they are big enough to be are not as significant as they might be. Farmed
harvested and sold. fish often have more parasites than wild fish
because they live in such close conditions. The
The Food Challenge Hawaiian farm carefully controls the fish’s diet,
The yellowtail is carnivorous, and the adults feed and the open ocean location means that waterMaps1
c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

Maps2 Maps3 Maps4 Maps5

exclusively on other fish. Initially the Hawaiian constantly moves through the pens, helping to
c15m90y90ck0ontrol parasites in the fish farms. Studies of
farm used a dried food that was approximatelyc15m90y90k0 c90m55y40k0 nearby wild populations of yellowtail have not
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko

c60 m30 y100 k0 c50 m20 y75 k0 c39 m7 y12 k0

80% fishmeal and oil from wild-caught fish. This shown any increase in parasites. And the fear of
did not meet the criteria the farm had set for
being sustainable. Something had to change.c15m10y0k85 c80m0y0k55 c0 m0 y0 k6 c25m0y15newk90 species being introduced to the wild
c12 m7 y0 k0

Through consultation with scientists and population is also not a concern; because the
environmentalists, the Hawaiian farmers worked brood stock are from the wild population, the
with their feed company to develop a food thatc60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 farmed fish are separated by only one generation.
c39 m7 y12 k0

FIGURE 16.7: Hawaiian yellowtail food web

phytoplankton zooplankton small bony sh yellowtail (Seriola rivoliana)
squid

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

CASE STUDY 3

Using Maximum Sustainable Yield to Determine Fishery Regulations

t h e co n c e p t o f maximum sustainable rates of individual fish, survival rates, and
yield (MSY) was first introduced in the 1930s reproductive rates. Knowing how fast a fish
and has been used in various fisheries grows, when it can reproduce, and how long it
throughout the world since then. MSY is a type normally survives helps determine how fast the
of mathematical model that incorporates population can grow or replenish. Once this is
information about a resource to determine how known, a fishery can calculate how much of the
much of that resource can be used while fish population can be harvested sustainably.
keeping the resource sustainable. Think back to
the model incorporating carrying capacity in New Zealand’s Orange Roughy Fishery
Activity 2: Population Growth Models, which
showed that a population is growing most The Hoplostethus atlanticus fish used to be
rapidly when it is halfway to the carrying called the slimehead fish and was considered
capacity. That is the point when the population too ugly to catch and sell. But in the 1970s,
is most productive. Fisheries managers who use fishers from New Zealand began catching
an MSY approach attempt to determine that them to sell for fish sticks and fillets and
point in a population’s growth because it will started calling them orange roughy to make
yield the greatest sustainable harvest. them more appealing to consumers. Orange
roughy form large spawning groups, often on
Determining the MSY for a fishery requires top of seamounts (underwater mountains),
incorporating population growth rates, growth which makes them easy targets for fishers. Just

Production (tonnes) 100,000
90,000
80,000 1980 1985 1990 1995 2000 2005 2010
70,000
60,000
50,000
40,000
30,000
20,000
10,000
0
1975

FIGURE 16.8: Orange roughy production 1975–2010

LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 16_08
A-11M0 yriadPro Reg 9.5/11

SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

in New Zealand, catches of the fish went from the orange roughy, along the top of a seamount.
less than 10,000 tonnes per year in 1979 to While this is very efficient in terms of catching a
over 90,000 tonnes per year at the fishery’s fish like the orange roughy, it can cause a lot of
peak in 1990. However, the population of damage to the surrounding ecosystem. The
orange roughy decreased dramatically after seamounts and other places that orange roughy
that peak and is currently below 10,000 tonnes tend to gather are often covered in corals and
per year. The same trend was seen in other other species that are damaged by or caught up
orange roughy fisheries throughout the world, in the bottom-trawling nets. This damage to the
and in some cases the fisheries collapsed orange roughy’s habitat means that it, along
completely. The fisheries had been relying on with the other species being harmed, may take
an MSY model, so what went wrong? even longer to recover.

Understanding the Orange Roughy Can Maximum Sustainable Yield
Be Used Effectively?
When the orange roughy fishery was established
in the 1970s, little was known about this deep- Other fisheries that use MSY as part of their
water species. It was thought that the fish lived management strategy have had much more
up to 30 years, and because they were found in success, including the dolphinfish (Coryphaena
such large groups on the seamounts, scientists hippurus), or mahi-mahi, fishery off the coast of
believed that they were a very productive Ecuador. This fishery uses drifting longlines
species that could easily replenish. The MSY for (very long fishing lines with multiple hooks
the orange roughy was set using those towed behind fishing boats) and fishes for
assumptions, which turned out to be very several large open-ocean fish species, including
wrong. As technology improved, scientists mahi-mahi, at certain times of the year.
learned that orange roughy grow very slowly Scientists have been able to collect accurate data
and are not able to reproduce until they are at showing that mahi-mahi is a fast-growing fish
least 20 years old. When they are ready to and can reproduce when it is less than a year
reproduce, they gather in large groups and old. The fishery used data on population growth
spawn at the same time. They do not reproduce rates, growth rates of individual fish, survival
every year, and it turns out that they are the rates, and reproductive rates to set careful
longest-lived commercially fished species limits, using the MSY strategy for their fishery,
known. It is estimated that the orange roughy and they frequently revisit and readjust the
on average lives 125 to 150 years, and one MSY based on what they learn from their
specimen caught off New Zealand was ongoing data collection. They continually
estimated to be over 230 years old. monitor the size of the population, particularly
to be sure that there are plenty of fish to
This data meant that the orange roughy fishery reproduce and replenish the population. One
had to reevaluate how they determined their challenge they do face is unintended harvesting
MSY. It also meant that it may take many years of other species, particularly sharks and other
for the orange roughy population to recover. slow-growing open-ocean fish. The fishery’s use
of the MSY as part of their management
Another sustainability challenge the orange strategy is still fairly new, but scientists and
roughy fishery is facing is their method of researchers who monitor fisheries have found
fishing: bottom trawling. This method of fishing
drags a net along the sea floor—or, in the case of

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

16,000

14,000

12,000

10,000

Catch (t) 8,000

6,000

4,000

2,000

0 2002 2004 2006 2008 2010 2012 2014 2016 2018
2000

FIGURE 16.9: Mahi-mahi production 2003–2018

thatLFsiagobuAfraeidr:sEthcSoEe3PseUtrPSaBSteG1g6I y_E0cios9lwogoyrk3eing and the the numbers of fish being harvested. The orange
fisheMryyrisaedePmrosRseugst9a.5in/1a1ble. roughy example is a case where inaccurate and
incomplete data led to unsustainable harvesting,
The lessons learned from using the MSY whereas the mahi-mahi example is a case where
approach is that it relies on accurate, current accurate and relatively complete data have
data to establish the initial model and that the allowed for sustainable harvesting of this fish
population being harvested must be monitored over a period of time.
frequently so that adjustments can be made to

Dolphin sh

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

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

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

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SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

CASE STUDY 4

Restricted Fishing Areas: The Tabu Tradition in Fiji

i n t h e i s l a n d s of Fiji in the South Pacific FIGURE 16.10: Fishers of all ages in Fiji
Ocean, fishing has long been part of the
traditional culture. According to Fijian custom, kind of fishing. The hope was that these tabu
coastal areas called qoliqoli (pronounced go-lee areas would provide a safe area for fish and
go-lee) are owned by communities and are other species to reproduce and grow and that
passed down from generation to generation. as the populations in these areas recovered,
Members of the community fish in their there would be a spillover effect: They would
qoliqoli both to feed themselves and their spread past the tabu boundaries to repopulate
families and to catch fish to sell. It is customary the surrounding areas where fishing was still
that when the chief of a community dies, a tabu allowed.
(pronounced tam-boo) is placed on a part of the
qoliqoli out of respect for the community At first, five tabu areas were set up by different
leader. This tabu means that no fishing of any communities. These areas showed signs of
kind is allowed in that area for 100 days. After success, with increased catches in the areas
100 days the area can be fished again, and the around the tabus. Other communities joined in,
community harvests fish to hold a feast to end and today a network of more than 400
the period of mourning. Typically after 100 days communities comprises the Fiji Locally
of closure, the tabu area has a more abundant Managed Marine Areas (FLMMA).
harvest than before.
Challenges to the Tabus
Modern Uses of the Tabu Tradition
Not everyone in the communities agrees with
In the late 1990s, fisheries were at a crisis point the restrictions imposed by the FLMMA. Some
due to overfishing. Simultaneously, many of the find them too restrictive, and there have been
cultural traditions such as the tabu were no disagreements about the penalties, such as fines,
longer being observed. The coral reefs
surrounding the islands were dying, there were
fewer fish, and those that were present were
smaller; other species that were fished
commercially, such as sea urchins and sea
cucumbers, were also in serious decline.

Fijian communities began to come together to
investigate reviving the culture of the tabu but
with some modifications. Several communities
decided to form committees to oversee their
qoliqoli and to institute regulations based on
tradition. Tabus were set up but were modified
to be long-term or permanent. The tabus
generally closed 10%–20% of the qoliqoli to any

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

FIGURE 16.11: Fishing in Fiji

associated with breaking the tabu. Additionally, can find a larger harvest. However, ongoing
the amount of success associated with the tabus studies of tabus within the FLMMA have shown
has varied; some areas have seen good recovery that areas with active tabus generally show signs
for the ecosystem and the associated fisheries, of ecosystem recovery, and many Fijians hope
but others have not. There have also been that the FLMMA will continue to help rebuild
problems with poachers coming in at night and their fisheries.
targeting the tabu areas where they know they

Build Understanding

1. Issue connection: How can case studies, such as the four in this activity,
help suggest solutions for communities facing sustainability challenges?
What other factors might need to be considered?

2. Issue connection: Choose one of the fisheries models from the case
studies in this activity. If this model was implemented with the Avril Gulf
tuna fishery:
a. What types of indicator data could be used to monitor the
environmental, economic, and social impacts?
b. What criteria and constraints would be appropriate to include?

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SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

KEY SCIENTIFIC TERMS

aquaculture
ecosystem
marine reserve

Extension

From a mathematical perspective, the MSY for a population is when the
population size is at the exact point where the population growth rate is
highest. Revisit the logistic growth model from Activity 2: Population
Growth Models to determine the growth rates for a hypothetical
population of 100 fish with a carrying capacity of 1,000 and a
maximum per capita growth rate, r, of 0.6. Examine what happens
when you change the starting population size, the carrying capacity,
and/or r. Visit the SEPUP SGI Third Edition page of the SEPUP website
at www.sepuplhs.org/high/sgi-third-edition, and follow your teacher’s
instructions to access this simulation.

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17 Making Sustainable boundary of Avril Gulf shing area
Fisheries Decisions

it’s been 10 years since the tuna fishery closed in the Avril

Gulf, but the fishery has still not recovered. Your group has been given
$500,000 by the Avril Gulf Wildlife Protection Agency. The agency has made
the decision to consider two strategies: creating a marine reserve to protect
the Avril Gulf tuna, or opening aquaculture farms to farm tuna near the Avril
Gulf’s shore. They are funding your group to plan, implement, and monitor
one of these strategies.
Your group will choose a strategy, develop a monitoring plan with specific
constraints and criteria to determine if your plan is successful, and then
monitor the implementation of your strategy for 10 years to determine its
effects on the sustainability of the Avril Gulf tuna fishery. After 10 years, you
will determine if the agency should continue with your strategy and
monitoring plan, adapt it, or choose another strategy.

Guiding Question

Which fisheries-management strategy is the best choice for
the sustainability of the Avril Gulf tuna industry?

N

Avril Atlantic
Ocean

KEY proposed marine Scale
reserve 0 20 40

proposed aquaculture kilometers
open net pens

FIGURE 17.1: Map of Avril Gulf

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LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 16_12

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Materials

FOR EACH GROUP OF FOUR STUDENTS

set of 6 Fishery Indicator cards

FOR EACH STUDENT

Student Sheet 16.1, “The Avril Gulf Tuna Fishery,” from Activity 16
Student Sheet 17.1, “Tracking Indicators”

Procedure

1. Obtain a set of the Fishery Indicator cards. With your group, lay out
the cards on the table, and review the information they provide about
the Avril Gulf tuna fishery.

2. Decide with your class which strategy each group will implement: the
aquaculture operation or the marine reserve.

3. With your group, predict what each indicator might show if your
strategy were used in the Avril Gulf. Record your thoughts in the
“Predicted Outcome” column on Student Sheet 17.1, “Tracking
Indicators.”

4. Develop a plan with your group to monitor the fishery indicators. You
have been allocated a budget of $500,000.

• Determine what criteria and constraints you will use to determine if

your strategy has improved the sustainability of the Avril Gulf tuna
fishery.

• Choose which of the six indicators on Student Sheet 17.1 you will

monitor. The cost per indicator is either $125,000 for 5 years of
monitoring or $250,000 for 10 years of monitoring.
5. Record your plan in your science notebook.
6. Ask your teacher for the data collected as part of your monitoring plan.
7. With your group, review the data.
8. On Student Sheet 17.1, record the “Observed Outcome” for each
indicator you monitored. Compare the results with the criteria and
constraints you developed. Be prepared to share your plan and the
outcomes with the other groups who implemented your strategy.

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MAKING SUSTAINABLE FISHERIES DECISIONS ACTIVITY 17

9. Follow your teacher’s instructions to share your plan and outcomes
with the other groups. As groups share their results, use Student Sheet
17.1 to record evidence about the results of each strategy for any
indicators you did not monitor.

10. Write a report to the Avril Gulf Wildlife Protection Agency on whether
the agency should continue to use the strategy your group investigated.

If you recommend continuing the strategy, include the following in
your report:
– Your recommendation
– The strategy you used and what you learned in the initial 10-year
monitoring process
– What criteria and constraints you included in your 10-year plan,
and if they were or were not met
– Which indicators you monitored, what they showed, and what
changes you recommend in regard to indicator monitoring
– The trade-offs of continuing the strategy, including how it will
affect the three pillars of sustainability (economic, social, and
environmental)
– How well you predict the strategy might reestablish the wild fish
population.

If you recommend not continuing the strategy, include the following in
your report:
– Your recommendation
– The strategy you used and what you learned in the initial 10-year
monitoring process
– What criteria and constraints you included in your 10-year plan,
and if they were or were not met
– Which indicators were monitored and what they showed
– The trade-offs of stopping the strategy, including how it will affect
the three pillars of sustainability (economic, social, and
environmental)
– Why you think the strategy will not reestablish the wild fish
population

Be sure to include evidence from this activity and Activity 16:
Sustainable Fisheries Case Studies to support your recommendation.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Build Understanding

1. Which fisheries-management strategy appears to be the most
sustainable for the Avril Gulf tuna fishery? Explain why.

2. What other design options and strategies might the communities near
the Avril Gulf consider implementing to meet the challenge of the
declining fishery?

3. How do you think it would affect the ecosystem if the communities
near the Avril Gulf continued fishing spotted flying fish instead of
Avril Gulf tuna?

4. Revisit the investigative phenomenon for this learning sequence:
Ecosystem health can vary. What have you learned about human
activities related to aquatic ecosystems over the last several activities
that might help explain the pattern of where endangered and
threatened ecosystems are found across the world?

5. Describe two sustainability challenges that your own community is
facing.
KEY SCIENTIFIC TERMS
ecosystem
fisheries management
population
sustainability

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Unit Summary

Population Growth

All populations of organisms have the ability to grow exponentially, yet
most do not do this. Factors that limit population growth include both
biotic factors (competition, predation, parasitism, etc.) and abiotic factors
(rainfall, temperature, sunlight, etc.). To determine if a population of
organisms is growing, declining, or stable, scientists must be able to assess
population size and make comparisons at different points in time. Because
it is rarely possible to count every individual, scientists use different
methods to estimate population size, including quadrat sampling and
mark-and-recapture sampling. Scientists rely on models to make
predictions of population growth and to estimate the carrying capacity (K)
of a population in a particular habitat. Many of these estimates and models
rely on mathematics and computational thinking.

Ecosystems and Patterns of Species Diversity

Populations of organisms are part of an ecological community made up of
many different species. An ecosystem includes both this entire ecological
community and the abiotic environment. Ecosystems can exist at many
different spatial scales, from nearly global to microscopic. They are defined
by their components, the interactions among the components, and the
boundary of the system. Species are not distributed randomly across
ecosystems. Instead, patterns of species diversity across ecosystems can be
predicted and explained by a number of different factors, such as topography
and precipitation in terrestrial ecosystems, and depth and light levels in
aquatic ecosystems.

Energy and Matter Flow Through Ecosystems

All organisms need energy and matter from food to survive and reproduce.
Organisms obtain matter and energy in one of two ways: Either they make
their own food (producers), or they ingest food stored within the bodies of
other organisms (consumers). Most producers use the cellular process of
photosynthesis to react carbon dioxide and water in the presence of

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

sunlight to produce oxygen and glucose (sugar). However, some
producers—like those in hydrothermal vent communities—use chemical
energy to drive chemosynthesis. All organisms use the process of cellular
respiration to convert food into useful matter and energy.
Species in an ecosystem are connected to one another, directly or
indirectly, through feeding relationships. These relationships can be
organized into food webs, which track the flow of energy and matter
through the ecosystem. Though matter cycles through an ecosystem, the
flow of energy from one feeding level to the next is inefficient. This is
because most of the energy is transferred to the abiotic components of the
ecosystem as thermal energy, instead of being stored in the bodies of
organisms as chemical energy.

Ecosystems and the Carbon Cycle

The biosphere comprises all living organisms. The biosphere interacts with
Earth’s other systems (hydrosphere, atmosphere, and lithosphere) through
the exchange of carbon released through cellular respiration or stored
through photosynthesis. The greatest exchange of carbon is between the
biosphere and the atmosphere, which is made even greater through human
activity. Earth’s greatest storage of carbon is in the lithosphere.

Disruptions to Ecosystems

Ecosystems can be disrupted by a variety of factors, including both abiotic
factors (fires, changes in water temperature, etc.) and biotic factors (diseases,
the introduction of a new species, the elimination of a species, etc.). Some of
these disruptions are naturally occurring, and others are anthropogenic
(human-caused). The ability of an ecosystem to withstand or recover from a
disruption depends on many factors, including the length of the disruption,
the size of the disruption, and the overall resilience of the ecosystem prior to
the disruption. A healthy ecosystem that experiences a temporary, small
disruption is more likely to be resilient than an unhealthy ecosystem that
experiences a long-term, large-scale disruption.

Developing Sustainable Ecological Issues

Humans rely on many kinds of natural resources, including biodiversity.
Harvesting natural resources may cause a decline in their populations and
a disruption to the ecosystem. To continue relying on natural resources,
people must first understand their impact on these resources and then
develop sustainable strategies and solutions for minimizing or mitigating

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LIVING ON EARTH SUMMARY

any negative impacts. Sustainable solutions may take many forms,
depending on the particular situation. Finding a sustainable solution
requires identifying the criteria for success, planning how to address the
constraints that limit options, and recognizing the three pillars of
sustainability (environmental, economic, and social).

KEY SCIENTIFIC TERMS fishery
food webs
abiotic gross productivity
anthropogenic hydrosphere
aquaculture inbreeding
atmosphere interaction
biological diversity intrinsic growth rate (r)
biomass lithosphere
biosphere marine reserve
biotic matter
boundary net productivity
brood parasites photosynthesis
carbon cycle population
carrying capacity (K) producers
cellular respiration resilient
chemosynthesis resistant
component scale
constraints stable
consumers sugar
criteria sustainability
disruption system
ecological efficiency system model
ecosystem trophic levels
energy
exponential growth
fisheries management

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IMPROVING
GLOBAL
HEALTH

CELLS

CELLS

Unit Issue

health is often thought about as a personal issue based on a
person’s genetics, behavior, and environment. It is also a sustainability
issue that is affected by the interaction of environmental, social, and
economic factors and is increasingly shaped by emerging global
patterns, due in part to climate change. Over the last 100 years, world
average surface temperature increased by approximately 0.6 °C, with
about two-thirds of that warming occurring since 1975. Scientists are
concerned about the effects on human health as a result of such
changes. The World Health Organization estimated the increase in the

FIGURE A: Estimated Deaths from Climate Change in 2000

Climate change
deaths per million

0–2
2–40
40–80
80–120

B-2

number of deaths per million people in the year 2000 as a result of
climate change, as shown in Figure A. In what ways do you think a
changing climate could affect human health? What do you think this
map might look like today?
Some impacts could be beneficial. For example, less severe winter
weather could reduce deaths attributable to cold. Even so, most
scientists anticipate that there will be greater negative impacts on
human health. Scientists are studying the spread of diseases, such as
malaria, that are transmitted by organisms that thrive in warmer
climates. They project that rising temperatures will result in an
increase in extreme weather events, such as heat waves and floods,
and will also affect food production, air quality, and water supply.
What are the challenges to human health in a changing world? In this
unit, you will investigate how human health is increasingly subject to
emerging global patterns, including extreme heat events, changes in
the frequency of diseases, and climate effects on the food supply.

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1 Survival Needs

very hot days and heat wav e s are a natural part of the day-to-day
variation in weather. However, many places around the world are
increasingly experiencing periods of hotter-than-average days and nights,
resulting in more heat-related illnesses and deaths. A series of unusually hot
days with temperatures higher than average for a particular time and place is
known as an extreme heat event. In 2019, an extreme heat event led to the
hottest recorded temperatures in many parts of Europe. Parts of France,
Germany, and the Netherlands reached temperatures of over 105°F (40°C),
and more than 1,500 people died from heat-related illness in France alone.

Investigative Phenomenon

Human health is increasingly affected by you observe? Why do you think people die

emerging global patterns such as extreme in extreme heat? What effect do you think

heat events, which are expected to happen extreme heat has on the human body? In

with more frequency both around the globe the next activities, you will investigate how

and in the United States. The following different conditions, such as extreme heat,

graph shows the number of deaths due to affect human health and how the human

extreme weather events in the U.S. What do body responds to these changes.

U.S. WEATHER FATALITIES 30 YEAR AVERAGE FOR 1991 2000

140 138
FIGURE 1.1: U.S. Weather-
120 Related Fatalities (30-Year
Average for 1991–2020)
100
85 69

80

60 46
40 39
20 35
27

0 Winter Cold N/A N/A
Flood Lightning Tornado Hurricane Heat Wind Rip

Currents

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

What is most necessary to keep the human body functioning
in extreme heat?

Materials

FOR EACH GROUP OF FOUR STUDENTS

Student Sheet 1.2, “An Expert Opinion”
set of 13 Survival Item cards

FOR EACH STUDENT

Student Sheet 1.1, “Ranking Survival Items”

Procedure

1. Read the following scenario.

It is mid-morning in August, and your plane has just crash-landed
in the desert of the southwestern United States. Nobody is
seriously hurt, but the pilot was unable to notify anyone of your
position before the crash, and all technology has been destroyed.
The immediate area is flat and barren, except for some cactus
plants. The last weather report indicated that the temperature
would reach 43°C (109°F). You are dressed in lightweight clothing—
short-sleeved shirt, pants, socks, and sneakers.

FIGURE 1.2: One of four deserts
in the southwestern U.S.
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SURVIVAL NEEDS ACTIVITY 1

2. With your group, read each Survival Item card aloud. Make sure that
everyone in your group agrees about what each item is.

3. Work by yourself to rank the items in what you think is their order of
importance for survival, with 1 being the most important and 13 being
the least important. Record your rankings in Table 1.1 on Student
Sheet 1.1, “Ranking Survival Items.”

4. When everyone in your group has completed their individual rankings,
work together to come to a consensus on the five most important items
in order of their importance to survival. Share your point of view by
discussing why you ranked one item higher than another.

5. Record your group’s top five survival items, in order of importance, in
Table 1.2 on Student Sheet 1.1. In column 2, explain your reasoning:
Why is this item so important for survival? How would you use this
item to survive?

6. Look over Student Sheet 1.2, “An Expert’s Opinion.” Record the
expert’s ranking of the survival items on Student Sheet 1.1 and
compare his ranking with your own.

7. Discuss the following questions with your group. Remember to listen
to and consider other group members’ ideas. If you disagree with
anyone in your group, explain why you disagree.

• Which items did you rank differently from the expert? Why?
• What surprised you about the expert’s rankings?
• Is there any item that you think was necessary for survival that was

not on the list? How would this item have helped you to survive?

• What are some possible reasons that someone might die from

extreme heat? (Think about what is happening in the human body.)

• Based on the expert’s rankings, which body function or functions

are the most important to maintain in order to survive?

Build Understanding

1. Would you have ranked the items differently if your plane had crashed
in a location in the Arctic, with average summer temperatures of
−10°C to 10°C (14°F to 50°F)? Explain your thinking.

2. In this activity, the desert survival scenario was used as a model for an
extreme heat event. In what ways was this scenario a good model for
an extreme heat event? In what ways was this scenario different from
what might occur in an extreme heat event?

B-7

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

3. A feedback loop is a process where a change in a system triggers a
certain result.

a. What do you think happens inside your body during extreme heat?
In other words, what does your body do to keep cool?

b. What kind of feedback loop do you think is happening inside your
body to help keep you cool?

4. Look again at the graph of weather-related fatalities in the
introduction. Do you predict that the number of heat-related deaths in
the future will increase, decrease, or stay the same? Support your
prediction with at least two pieces of evidence.

5. Issue connection: The effects of heat on local temperatures depend
on the environment. Temperatures in cities are often a few degrees
higher than their surrounding rural areas, a phenomenon known as
an urban heat island effect.
According to the U.S.
Environmental Protection
Agency, temperatures in U.S.
cities can be as much as 12°C
(22°F) higher than surrounding
areas. Look at the photo in
Figure 1.3, which was taken with
a thermal camera.

• What do you observe?

• What effect do you think this

could have on human health?

• What does this mean for global
sustainability?
FIGURE 1.3: Thermal photo of Tower Bridge, London, England

KEY SCIENTIFIC TERMS

extreme heat event
feedback loop
function
sustainability

B-8

2 Everyday Hydration

although the human body can survive up to three weeks without
food, it can survive only a few days without water. This is because the body
constantly loses water through excreting it as urine to remove wastes.
Perspiration also leads to water loss. About 60% of the human body is
water. Much of that water is found inside cells, while the rest is in the blood
and between the cells in tissues.
In most of the United States, people can stay hydrated by turning on the tap
for clean drinking water. In contrast, in some parts of the U.S. and the
world, a significant portion of a person’s day can be spent gathering water.
Yet, people in both situations may face dehydration. One reason for this is
that the human body can become dehydrated more quickly than most
people think. It takes only a 2% loss of total water content for a person to
start feeling thirsty. At this point, the body is already in a state of
dehydration. How is this affecting the body’s cells and tissues? In this
activity, you will investigate the effects of hydration levels on plant cells,
which will serve as a model for the effects on human cells.
Note: If you need to review basic concepts about cells, tissues, and organs,
you will find a short reading at the end of this activity.

FIGURE 2.1

B-9

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

How does a lack of water affect an organism?

Materials

FOR EACH GROUP OF FOUR STUDENTS

dropper bottle of 5% salt solution
dropper bottle of distilled water
pair of scissors
paper towel

FOR EACH PAIR OF STUDENTS

2 microscope slides
2 coverslips
pair of forceps (tweezers)
microscope
slice of red onion

SAFETY

Always carry a microscope properly with both hands: one
hand underneath, and one hand holding the microscope arm.
Be careful when using the scissors and handling the coverslips.
Coverslips are very fragile. If one breaks, do not touch the broken
glass. Inform your teacher immediately about any broken coverslips.

Procedure

Part A: Dehydration In People and Plants

1. Think of an occasion when you were really thirsty for a period of time.
Read the following questions, and share your responses with your group.

• What symptoms did you experience?
• What do you think was happening inside your body to cause these

symptoms?

B-10

EVERYDAY HYDRATION ACTIVITY 2

FIGURE 2.2: Plant A and Plant B

2. Look at the images of plants in Figure 2.2. Discuss the questions that
follow with your group.

• Which plant appears dehydrated? Explain your reasoning.
• What do you think is happening inside the plant’s tissues and cells

to cause it to wilt?

Part B: Dehydration in Cells

3. Review how to focus a microscope by reading the following
information. If needed, your teacher will provide additional guidance.

Focusing a Microscope

Be sure that your microscope is set on the lowest magnification before
placing your slide onto the microscope stage. Place the slide on the
microscope stage. Center the slide so that the sample is directly over
the light opening, and adjust the microscope settings as necessary. If
the microscope has stage clips, secure the slide in position so that it
does not move.

Observe the sample. Focus first eyepiece
with the coarse-focus knob, and
then adjust the fine-focus knob.

After switching to a higher coarse-focus objectives
magnification, be careful to knob stage clips
adjust the focus with the stage
fine-focus knob only.
diaphragm
Return to low magnification ne-focus light source
before removing the slide from knob
the microscope stage.

3377 SEPUP SGI Cell SB B-11
Figure: 3377CellSB 02_01
Mryriad Pro 9/9

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

4. With a partner, obtain a slice of onion, and use forceps or your
fingernail to peel off the very thin inner layer of the onion.

5. Place 1–2 drops of water on a clean slide, and place your piece of onion
in the water on the slide.

6. Carefully place a coverslip over the piece of onion. Begin by
holding the coverslip at an angle over the water droplet, and then
gradually lower the coverslip to avoid introducing any air bubbles,
as shown in Figure 2.3.

FIGURE 2.3: Placing the coverslip

7. B33e77sSuErPeUPtShGaI tCeylloSuB r microscope is set on the lowest magnification (the
sAFhiggoeunrredt:ae33Ms7te7CdoeCblolSnjBde0c93/t_9i0v2e) before placing your slide on the microscope stage.
Center the slide so that the specimen is directly over the light opening,
and adjust the microscope settings as necessary.

Hint: To check that you are focused on the material that is on the slide,
move the slide slightly while you look through the eyepiece. The
material that you are focused on should move at the same time you
move the slide.

8. Observe the material on the slide.
Hint: If the material on the slide is too bright to see, reduce the amount

of light on the slide. Do this by slightly closing the diaphragm under
the stage. Move the slide so that one or several cells are near the center
of your view.
9. Without moving the slide (which can usually be secured with stage
clips), switch to medium magnification (usually 10×). Adjust the
microscope settings as necessary. Slowly focus up and down by
turning the fine-focus knob.
10. Without moving the slide, switch to the highest magnification (usually
40×). Be careful not to smash the objective against the slide! Adjust the
microscope settings as necessary. Slowly focus up and down, using
only the fine-focus knob. You will see several layers of onion cells.
Hint: If the material on the slide is too dark to see, increase the amount
of light on the slide. Do this by slightly opening the diaphragm under
the stage.

B-12

EVERYDAY HYDRATION ACTIVITY 2

11. Select one cell to draw in your science notebook at high magnification.
Use the information in “Microscope Drawing Made Easy” to help you.

Microscope Drawing Made Easy

Below is a picture taken through a microscope of the alga Spirogyra. The diagram
to the right shows what a biologist or biological illustrator might draw and how
they would label the drawing.

Spirogyra (algae) x 400

chloroplast

cell wall

3377 SEPUP SGI Cell SB
Figure: 3377CellSB 03_01
Agenda MedCond 9/9

Some Tips for Better Drawings
• Use a sharp pencil and have a good eraser available.
• Try to relax your eyes when looking through the eyepiece. You can cover one eye or

learn to look with both eyes open. Try not to squint.
• Look through your microscope at the same time you do your drawing. Look through

the microscope more than you look at your paper.
• Don’t draw every small thing on your slide. Just concentrate on one or two of the

most common or interesting things.
• You can draw things larger than you actually see them. This helps you show all the

details you see.
• Keep written words outside the circle.
• Use a ruler to draw the lines for your labels. Keep lines parallel— do not cross one

line over another.
• Remember to record the level of magnification next to your drawing.

B-13

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

12. Return to the lowest magnification, and remove the slide from the
microscope.

13. Repeat Steps 4–12, but first add 1–2 drops of salt solution. Do this by
placing a few drops of salt solution along one side of the cover slip, as
shown in Figure 2.4. Then place the edge of a small piece of paper towel
on the opposite edge of the cover slip. This will draw the salt solution
across the slide. (If nothing happens, add 1–2 more drops.) On your cell
drawing, label areas of higher and lower concentrations of water.

FIGURE 2.4: Placing the paper towel

14. When you finish your observations, throw away the onion pieces, rinse
the slides and coverslips, and pat them dry with a paper towel. You may
also need to wipe off any salt water that spilled on the microscope stage.

Part C: Dehydration In People

15. Look at Table 2.1, which shows the recommended daily water
consumption for humans in liters per day. Identify how much water
you should be drinking each day.

Note: 1 liter is almost 34 ounces, or the equivalent of about four glasses
of water.

TABLE 2.1: Recommended Daily Water Consumption as Liquid

AGE RECOMMENDED DAILY WATER CONSUMPTION (L/DAY)
4–8 years 1.2
9–13 years 1.6 (female), 1.8 (male)
14–18 years 1.8 (female), 2.6 (male)
Adults 2.2 (female), 3.0 (male)

16. Work with your group to design an experiment to determine if you are
drinking enough water—if your average daily intake meets the
recommended amount. Think about the following questions as you
design your experiment:

• What is the purpose of your experiment?
• What is your hypothesis?

B-14

EVERYDAY HYDRATION ACTIVITY 2

• What is your procedure? How would you collect the data?
• Would you conduct more than one trial? Explain.
• How will the data you gather help you make a conclusion?

17. Share your experimental design with your class. Discuss limitations in
the accuracy, precision, reliability, and reproducibility of your data.

accuracy: how closely a measurement or calculation conforms to
the correct (or actual) value

precision: how close repeated measurements are to one another

reliability: how consistently a method measures something

reproducibility: obtaining the same results using the same
method

Extension

What happens when you add more water to the plant cells treated with salt
water? Repeat Procedure Step 13 with distilled water to find out. Record
your observations. What did you observe? What do you think happened
inside the cells?

Build Understanding

1. In organisms, water can flow between the inside and outside of a cell.
In this activity, adding salt water to the slide created a high-salt
environment outside the plant cell. What happened to the onion cells
when you added the salt water? Support your answer with
observations and/or drawings from your experiment.

2. Adding salt water to the plant cell modeled what happens to cells
during dehydration.
a. Why do you think plants wilt when their cells become dehydrated?
b. In Activity 1: Survival Needs, one of the survival items was salt
pills. Based on what you learned in this activity, would salt pills be
a useful survival item in extreme heat? Why or why not?

B-15

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

3. Human cells also respond to changes in the amount of water in the
environment. Look at the drawing of normal red blood cells in Figure
2.5. Which drawing—A or B—do you think represents red blood cells
in a state of dehydration? Explain your reasoning and support your
answer with evidence from this activity.

Normal red blood cells A B

FIGURE 2.5: Normal red blood cells, A, B
SGI Cells
Figure: SGI3e Cells SB 2_7

M4y.r iaIndPwrohSaetmwibaoylsdd9o.5es your body function to maintain optimum hydration
levels?

5. Issue connection: About 1.2 billion people (almost one-fifth of the
world’s population) live in areas where water is scarce. Cities that are at
high risk of running out of water in the future include Miami, Florida;
Mexico City, Mexico; São Paulo, Brazil; London, United Kingdom;
Cape Town, South Africa; Cairo, Egypt; Bangalore, India; Jakarta,
Indonesia; Beijing, China; Tokyo, Japan; and Melbourne, Australia.

Look at Figure 2.6, which compares daily water use by local residents
and by tourists in 21 countries.
a. Do you think countries should limit the number of tourists at
popular destination sites? Support your answer with evidence, and
identify the trade-offs of your decision.
b. Explain how this issue is a sustainability issue and how it relates
to the three pillars of sustainability (social, economic, and
environmental).

Normal red blood cells A B
SGI Cells
BFMi-gy1ur6iraed: PSrGoI3SeemCeibllos lSdB92.5_7

EVERYDAY HYDRATION ACTIVITY 2

1000 Local use (tourism deducted)
900 Tourism use
800
700 Liters per person per day
600
500
400
300
200
100
0

Australia GerFramanFcinjyieIndoInnedsiiaa JamIitaaclyaNePSwihilniZMgeapMJlaapealaipxaypinosnacriesoaned STrihaLSilapananikdna
China KingdUoAmE
Egypt

United

FIGURE 2.6: Graph of Local Vs. Tourist Water Use

KEY SCIENTIFIC TERMS

accuracy

cell
dehydration
LOCAL VSh.yTdOraUtiRoInST WATER USE
organ
LabAids SEpPrUePciSsGioI Cnells 3e
Figure: Celrlsel3ieabSBili0t2y_08
MyriadProrReepgro9.d5/u1c1ibility

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

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

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

B-17

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Review and Refresh: Cell Structure and Function

Parts of a Cell compartment within the cell. It is separated
from the rest of the cell by a nuclear membrane.
From observing many kinds of cells in The nucleus contains the majority of the genetic
thousands of organisms, biologists have information of the cell and directs the cell’s
discovered that some structures are found in all activities, including growth and reproduction.
or nearly all cells. These structures are so
common that they are usually included in Most cells have tiny structures—some of
models or drawings of a “typical” cell. Every which can just barely be seen with a light
kind of cell, whether a bacterium or a cell from microscope—that help them do many jobs.
a giant oak tree, has a cell membrane that These structures are called organelles, or “little
separates the cell from its environment (see organs.” Organelles are often surrounded by
Figure 2.7). The cell membrane acts as a barrier their own specialized membranes. The nucleus
to control what enters or leaves the cell. is one example of an organelle. The organelles
Everything that enters or leaves the cell must that convert most of the energy from food into
cross this membrane. usable energy are called mitochondria (plural;
the singular is mitochondrion). Mitochondria
The material enclosed by the cell membrane is use oxygen to complete the process of cellular
called the cytoplasm, which means “cell respiration, converting the energy stored in
material.” In the cytoplasm, the cell uses food for the cell’s use. For this reason,
substances from food for two purposes: to build mitochondria are sometimes called the cell’s
new cell substances and structures and to begin power plant. Different types of cells have
the first steps in cellular respiration. Cellular different numbers of mitochondria, ranging
respiration is the process by which an organism’s from one to thousands. Cells that need a lot of
cells break down glucose and release energy that energy, such as muscle cells, have more
can be used for life functions, such as mitochondria than cells with low energy
movement and growth. requirements.

Many cells contain a small dark center, called Some of the jobs performed by organelles are
a nucleus. The cells of both multicellular and described in Table 2.2.
unicellular organisms (except for bacteria) have
a cell nucleus. The nucleus is a small

FIGURE 2.7: Animal and Plant Cell Models

ANIMAL CELL PLANT CELL
cell membrane cytoplasm
nucleus cell wall
nuclear cell membrane
membrane mitochondria
cytoplasm
nucleus
vacuole
chloroplasts

mitochondria

EVERYDAY HYDRATION ACTIVITY 2

TABLE 2.2: Cell Structures and Functions

STRUCTURE NAME AND FUNCTION(S) STRUCTURE NAME AND FUNCTION(S)

Cell membrane Cytoskeleton
Controls what enters the cell Is the long thread-like or tubular
strands involved in the movements
Allows the internal cell of cells and of materials within cells
environment to differ from
the external one Supports and anchors some
structures within cells

Cytoplasm Vacuole
Stores substances and can
3842 T-7-2 (Cell) SB Is the location of many reactions contribute to the breakdown of
Figure: T-7-2 Fig04_02 that take place in the cell 3842 T-7-2 (Cell) SB wastes
Figure: T-7-2 Fig04_09
Legacy Sans Std Med 10/11.5 Legacy Sans Std Med 10/11.5

Nucleus Lysosomes
3842 T-7-2 (Cell) SB Stores genetic material and directs Break down wastes and toxins
Figure: T-7-2 Fig04_03 the activities of the cell
Legacy Sans Std Med 10/11.5 3842 T-7-2 (Cell) SB
Figure: T-7-2 Fig04_10
Legacy Sans Std Med 10/11.5

Nuclear membrane Vesicles
Separates the nucleus from the Carry materials from one location
3842 T-7-2 (Cell) SB in the cell to another location, or to
3842 T-7-2 (Cell) SB cytoplasm Figure: T-7-2 Fig04_1t1he cell membrane
Figure: T-7-2 Fig04_04 Legacy Sans Std Med 10/11.5
Legacy Sans Std Med 10/11.5

Cell wall Ribosomes
Provides support and protection 3842 T-7-2 (Cell) SB Produce proteins
Figure: T-7-2 Fig04_12
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Figure: T-7-2 Fig04_05
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Mitochondria Endoplasmic reticulum
3842 T-7-2 (Cell) SB Are the sites of the reactions of
Figure: T-7-2 Fig04_06 aerobic respiration, which uses Is involved in the production
Legacy Sans Std Med 10g/lu1c1o.5se obtained from food and
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oxygen to produce energy for the with
cells and tissues

Chloroplast Golgi apparatus
Is the site of photosynthesis, which Modifies and sorts proteins and
uses light as a source of energy lipids before they are transported
3842 T-7-2 (Cell) SB for producing sugars from carbon 3842 T-7-2 (Cell) SB to their final locations in the cell
Figure: T-7-2 Fig04_07 dioxide and water Figure: T-7-2 Fig04_14
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3842 T-7-2 (Cell) SB B-19
Figure: T-7-2 Fig04_15
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Figure: T-7-2 Fig04_08
Legacy Sans Std Med 10/11.5

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

A plant cell’s structure is a little different from an together to perform a specific function. Tissues
animal cell’s structure. In addition to the cell are organized into layers, fibers, clumps, or
membrane, a plant cell has a cell wall that provides other arrangements. Muscle and blood are
additional structural support and stability to a examples of animal tissues.
plant cell. Green plants also have organelles called
chloroplasts, which absorb light and use its energy An organ is a group of tissues organized into a
along with water and carbon dioxide to produce structure that performs a specific function. The
sugars for the cell. This whole process is called stomach, heart, and lungs are examples of organs
photosynthesis. Some other organisms, such as in many animals. These organs have specialized
algae, also have chloroplasts and photosynthesize. functions, such as digesting food, pumping
Plant cells, like animal cells, have mitochondria blood, and absorbing oxygen from the air.
that use oxygen and nutrients to generate energy.
In all organisms, several organs work together
Levels of Organization to form an organ system. Animal systems include
the digestive, respiratory, and circulatory systems.
In multicellular organisms, cells are organized In both plants and animals, organ systems work
into tissues—a group of similar cells that work together to maintain the organism’s normal
functions.

Figure 2.8: Levels of Organization: Human and Plant
Note: These diagrams are not drawn to scale.

Organism Organ system Organ Tissue Cell Organelles
(digestive system)

Shoot
system

Root Organ system Organ Tissue Cell Organelles
system (digestive system)

Organism
B-20 SGI 3e SB Fig 7.1

3 Homeostasis Disrupted

globally, life expectancy has increased by more than 28 years

between 1950 and 2019: from 45 years in 1950 to 73 years in 2019. It
increased by more than six years just from 2000 to 2019! Sadly, this data
does not include the impact of the COVID-19 pandemic that began 2020.
In 2021, life expectancy decreased both in the U.S. and globally.
Increasingly, changing global patterns, such as the spread of new diseases,
are affecting human health around the world. Disruptions to the
homeostasis of the human body can be caused by disease or can result in
disease. A disease is any breakdown in the structure or function of an
organism. Infectious diseases, like malaria, are illnesses caused by viruses
or bacteria that people spread to one another through contact with
contaminated surfaces, bodily fluids, and blood products; through insect
bites; or through the air. Noninfectious diseases, like cancer, cannot be
transmitted from one person to another and are caused by such factors as
the environment, genetics, and aging.

Investigative Phenomenon

CElixTmphaeattretCsfaoBrrlrayInmLcyermeCahesaeDniingseiTnaigcseks HHeeaaltthaWnAadlveSer:ttasKyIeseIsnpudeHodyoDdrsruartiendg

LifeCstaysDleeisssoeCafosNneotGrniblionubfteaecltltyiooRuissing DLaoncgaelrFoluosoLdewvaetlesroCf aBrarcietes ria

These headlines highlight the effect of changing global patterns
on human health. What news about human health and global
change has been reported where you live? How does your body
work to keep you healthy in these changing environments?

B-21

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

What happens when disease disrupts a body’s normal
functioning?

Materials

FOR EACH STUDENT

Student Sheet 3.1, “Case Studies”
Student Sheet 3.2, “Modifying a Model”
12–20 sticky notes

Procedure

1. Use Student Sheet 3.1, “Case Studies,” and the Read, Think, and Take
Note strategy to help you understand the reading:

• Stop at least three times during each section of the reading to mark

on a sticky note your thoughts or questions about the reading. Use
the following guidelines to start your thinking:

Read, Think, and Take Note Guidelines

As you read, use a sticky note from time to time to:

• Explain a thought or reaction to something you read
• Note something in the reading that is confusing or unfamiliar
• List a word from the reading that you do not know
• Describe a connection to something you’ve learned or read previously
• Make a statement about the reading
• Pose a question about the reading
• Draw a diagram or picture of an idea of connection

• After writing a thought or question on a sticky note, place it next to

the word, phrase, sentence, diagram, drawing, or paragraph in the
reading that prompted your note.

• After reading, discuss with your partner the thoughts and questions

you had while reading.
2. Discuss the reading with your class.

B-22

HOMEOSTASIS DISRUPTED ACTIVITY 3

Reading

Introduction: The Human Body Regulates Itself

A person’s external environment can change in many ways. For example, it
can be very hot or very cold. Access to drinking water can be difficult or
easy. One reason that people survive is that they adapt to the environment
by wearing appropriate clothing, drinking water, and using heating and
cooling indoors. But even without such actions, the human body can
survive in a range of conditions. This is because the human body works to
maintain stable internal conditions. The body’s ability to maintain internal
conditions within a healthy range is known as homeostasis. Body
temperature, blood sugar levels, and hydration levels are three examples of
internal conditions that are regulated through homeostasis.
The human body has feedback mechanisms that respond to changing
conditions to maintain homeostasis. One mechanism is a negative feedback
loop, in which the body recognizes a change and brings conditions back to
normal. (A positive feedback loop is one where the body recognizes a change
and stimulates more of the same response, such as in childbirth or when
blood clots.) Body temperature is regulated through a negative feedback
loop, as shown in Figure 3.1. The human body generates enough thermal
energy through cellular respiration and other chemical reactions in cells to
raise the body temperature. Thermal energy is a form of energy that causes

Maintaining Human Body Temperature

Body temperature falls Body temperature rises

Blood vessels constrict so Blood vessels dilate,
that heat is conserved. resulting in heat loss to
Sweat glands do not the environment. Sweat
secrete uid. Shivering glands secrete uid. As
(involuntary contraction of the uid evaporates, heat
muscles) generates heat, is lost from the body.
which warms the body.

Heat is retained Heat is lost to the environment

Normal body temperature
FIGURE 3.1: Maintaining Human Body Temperature

B-23

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

increases in temperature, so the human body uses it to maintain temperature
homeostasis. Body temperature would rise approximately 1°C per hour if the
body did not transfer excess heat to the environment, such as through
evaporation of perspiration. Different body systems interact to maintain this
homeostasis. In the case of body temperature, the cardiovascular, respiratory,
integumentary (skin and related structures), nervous, and muscular systems
work together.
The following three case studies describe ways in which feedback loops
function within the human body to maintain homeostasis and how illness
can disrupt this homeostasis.

CASE STUDY 1

Body Temperature Homeostasis and Heatstroke

The average normal internal body temperature is releases heat less effectively when it is hot
37°C (98.6°F). It is normal for human body outside. A person can help their body maintain
temperature to fluctuate within a range around homeostasis by drinking fluids and staying in a
that temperature. Anything above 38°C (100.4°F) cooled indoor environment. However, in some
is considered a fever and can be a sign that the cases, these options are not available or are not
human body is fighting off an infection. A fever is enough. Small children, the elderly, and certain
a normal response to infection; the body is simply other groups—including people with chronic
readjusting its temperature set point, like changing diseases, low-income populations, outdoor
the set temperature on a thermostat. Many workers, and people engaged in intense athletic
microbes are sensitive to high temperatures, and a activities on hot days—are at a higher risk for
heat-related illness.
fever can help to reduce
the growth of these Effects of Heatstroke on Homeostasis
disease-causing
organisms. But if the Heat stress describes a range of heat-related
body temperature rises disorders that occur when the body fails to lose
above 39.5°C (103°F), heat to maintain its normal core temperature.
the results can be One of the most serious is heatstroke, a
serious. condition that can occur when the body
temperature rises above 40°C (104°F), usually as
When extreme a result of a long exposure to high temperatures
heat events occur, or physical exertion in high temperatures. It is
temperature most common in the summer months.
homeostasis cannot be
maintained by normal With heatstroke, the normal mechanisms for
bodily processes alone. controlling body temperature break down as the
The human body core body temperature rises. The brain becomes
too hot to function normally and no longer
FIGURE 3.2

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HOMEOSTASIS DISRUPTED ACTIVITY 3

FIGURE 3.3: Projected Increase in Number Increase from 2019 to 2050 in number
of Hot Days Per Year (2019–2050) of days per year when it feels like 90°F+

Seattle 9 0–19 Total 90+ heat
20–34 index days per year
35–39 predicted by 2050
40–44
45–56

San Francisco 10 Denver 35 Minneapolis 49 Boston 41
Los Angeles 56 Phoenix 161 Detroit 47
San Diego 44 New York 51
Chicago Philadelphia 68
59 Baltimore 79
Washington 79
St. Louis 95

Dallas 137 Atlanta 104

Houston 158

Gulf of Mexico Tampa
177

Miami
178

sends signals that maintain the feedback loop. suffering from heatstroke typically requires
The body stops sweating, which can lead to a emergency medical treatment because the body’s
further rise in core body temperature. As you ability to maintain homeostasis has been
saw in Figure 3.1, a negative feedback loop helps overwhelmed.
maintain temperature homeostasis in a healthy
individual. In an individual suffering from Restoring Homeostasis
heatstroke, many of these mechanisms no
longer function, and the body temperature The risk of heatstroke can be reduced by
SGI Cells continues to rise. preparing for hot weather. People should
Figure: SGI3e CSeyllsmSpBt3o_m04s of heatstroke include high body wear appropriate clothing, drink lots of water,
MyriadPro Setmemibpoeldra9t.u5/r1e2, /c1o8nfusion or delirium, nausea and and avoid strenuous activity during the
vomiting, hot and/or dry skin, rapid breathing, hottest part of the day. When heatstroke
increased heart rate, and headache. Untreated occurs, it requires emergency treatment to
heatstroke can quickly damage the brain, heart, cool down the body. This may include
kidneys, and muscles. The damage worsens the immersing the person in cold water or an ice
longer treatment is delayed, increasing the risk of bath, use of evaporative cooling, and the use
serious complications or death. A person of medications to relax muscles.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Challenges to Prevention and Treatment Preventive measures can reduce the effects
of extreme heat events. For example,
Human exposure to extreme heat is increasing communities can educate the public about
due to changes in climate. Extreme temperature health risks associated with heat and provide
events are increasing in their frequency, duration, air-conditioned cooling centers. With
and magnitude worldwide. Between 2000 and planning and outreach, the number of
2016, the number of people exposed to heat fatalities associated with heat can be reduced.
waves increased by around 125 million. The map
in Figure 3.3 shows the projected increase in the
number of hot days in the U.S. by 2050.

CASE STUDY 2

Blood Sugar Homeostasis and Diabetes

Another example of a negative feedback loop that maintain normal blood sugar
in the human body is the control of blood sugar homeostasis.
(glucose). When blood sugar rises, receptors in
the body sense a change. The pancreas then A person with diabetes mellitus cannot
secretes insulin into the blood to lower blood regulate their blood sugar, mainly because the
sugar levels. Once blood sugar levels reach pancreas does not release enough insulin.
homeostasis, the pancreas stops releasing Diabetes is a noninfectious disease that affects
insulin. When blood sugar is low, the pancreas people of all ages and from all countries. The
releases glucagon to increase blood sugar World Health Organization reports that the
levels. Figure 3.5 models the feedback loops world is experiencing a global diabetes
epidemic. Global diabetes prevalence is
FIGURE 3.4 estimated to increase substantially, from 463
million people in 2019 to 700 million by 2045.

The number of young people with diabetes is
increasing especially rapidly.

Effect of Diabetes on Homeostasis

Diabetes disrupts the body’s ability to process
sugars and is caused by a breakdown in the
normal functioning of certain cells. There are
two common types of diabetes, both of which
involve high levels of glucose in the blood.
The first, type 1 diabetes, occurs when the
body’s immune system destroys the cells in
the pancreas that produce insulin, the
hormone that regulates the level of glucose in
the blood. Type 2 diabetes occurs either when

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HOMEOSTASIS DISRUPTED ACTIVITY 3

Maintaining Human Blood Sugar Levels

Blood glucose Blood glucose
level rises. level falls.

PANCREAS HOMEOSTASIS PANCREAS

Beta cells in pancreas (glucose levels 90mg/100mL) Alpha cells in pancreas
release insulin into release glucagon.
the blood. Set Point
GLUCAGON
INSULIN

LIVER LIVER

Body cells take up glucose. Liver takes up Liver breaks down
glucose and stores glycogen and
it as glycogen. releases glucose.

Blood glucose Blood glucose
level declines. level rises.

FIGURE 3.5: Maintaining Human Blood Sugar Levels

the body does not produce enough insulin or of toes, feet, or legs. Any of these can result in
iwnhsuenlinFMSsiGp.gyIFureCiraoceed:lirPlSfsriGeocIx3SceeameCmleilblpslosllSadeBr9,e3.t5_h/n51e2o/t1m8reemspbornadniensgotfoliver disability.

cells have protein receptors that recognize Restoring Homeostasis
insulin and activate the glucose transport
protein that moves glucose into the cell. If the Both type 1 and type 2 diabetes disturb the
normal balance of glucose within and outside
receptors cannot recognize insulin, the liver the cell. This in turn leads to other problems of
cells do not take up glucose from the blood.Maps1
c0 m42 y92 k0metabolism that further disrupt homeostasisc7m0y0k9
c100 m0 y20 k70 c25 m0 y15 k90

Maps2 Maps3 Maps4 Maps5

Consequently, cells cannot access glucose to get and cause complications that may lead toc0m30y70k0
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

the energy they need, and glucose will build up disability or death. People with type 1 diabetes
c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

in the blood. must give themselves regular insulin injections
Blood glucose tests can detect diabetes in
very early stages, before symptoms appear. The and carefully monitor their blood sugar levels
and intake of carbohydrates. Some people with
early symptoms of diabetes include excessive type 2 diabetes require insulin shots, while
urination, thirst, hunger, weight loss, changes
in vision, fatigue, and possibly coma. Diabetes- others take an oral medication and follow a
healthy diet. The more carefully that people
related complications that may develop over a with diabetes maintain their blood glucose
number of years include blindness, kidney
failure, coronary heart disease, stroke, and levels within the normal range, the lower the
risk of serious health consequences from either
serious infections that may lead to amputation type of diabetes.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Approximately 90% of the people around the diabetes could reduce the occurrence of this
world with diabetes have type 2 diabetes. Excess disease by 35%–58%.
body weight and lack of physical activity
increase the risk of developing type 2 diabetes. The causes of the immune reactions that lead
Previously, type 2 diabetes was observed mostly to type 1 diabetes are unknown, although there
in adults, but today it is common in children as is evidence that genetic and environmental
well. Actions that people can take to help factors may increase the risk of developing type
prevent or control type 2 diabetes include: 1 diabetes. There are currently no preventive
measures, but careful management of blood
• maintaining a healthy body weight sugar and insulin levels can help to mitigate the
• exercising with moderate intensity on side effects.

most days of the week Challenges to Prevention and Treatment

• avoiding tobacco use Diabetes has serious social and economic impacts
on afflicted individuals, their families, and the
Regular blood tests can be given to at-risk health-care system, including effects on people’s
individuals to detect elevated levels of blood ability to work and the costs of treatment. Body
sugar that predict type 2 diabetes. Early weight is an important risk factor for development
detection and treatment reduce the chance of of type 2 diabetes. Although losing weight and
developing diabetes and the serious exercising reduce the risk of this disease—and
complications, such as reduced life sometimes reverse its course—making lifestyle
expectancy, that may follow. World health changes is difficult. This is a key challenge to
experts estimate that lifestyle changes by preventing type 2 diabetes.
people at high risk of developing type 2

CASE STUDY 3

Hydration Homeostasis and Severe Diarrhea

Your body is highly attuned to the amount of causes approximately 40% of all cases of severe
water you consume. If you drink when you’re diarrhea in infants worldwide. More than 85% of
thirsty, you’re likely getting enough water in rotavirus deaths occur in Asia and Africa. It is
your body on a daily basis. Figure 3.6 models a transmitted in contaminated water or food,
negative feedback loop showing how the human airborne droplets, and contact with
body maintains the water content of blood contaminated surfaces. Safe water, sanitation,
within a healthy range. and refrigeration of food are important for
controlling rotavirus transmission.
Severe diarrhea disrupts this homeostasis.
Globally, only a few infectious diseases cause the Effect of Rotavirus on Homeostasis
majority of deaths for children younger than five
years old. Rotavirus, with the severe diarrhea it When a person has diarrhea, their large
causes, is one of them. Rotavirus is a virus that intestine does not function properly and is not
infects the cells that line the small intestine. It absorbing water from the food mixture

B-28

HOMEOSTASIS DISRUPTED ACTIVITY 3

Water content of Water content of
the blood LOW the blood HIGH

Too much salt Too much
or sweating water drunk

Brain produces more Water content of Brain produces
water-regulating the blood normal less water-regulating
hormone hormone
Low volume of water
High volume of water reabsorbed by kidney
reabsorbed by kidney

Urine output Urine output
LOW HIGH

(small volume of (large volume of
concentrated urine) dilute urine)

FIGURE 3.6: Maintaining Fluid Levels in Human Blood

SGI Cells
entFMeigyruriirnaedg:PSrfGorI3oSeemmCeitblhlosleSdBs93m.5_/0a178ll intestine. This results
in more water being excreted in the feces and • Body temperature may not stay regulated.
less water being absorbed into the body. This • Electrolytes in the blood become unbalanced.
disrupts homeostasis because, with an • Joints may not work properly.
inadequate supply of water, blood pressure • Blood pressure may increase or decrease.

dsaeMfcerleyaacisanersrt.yaCoieunlltsibndoogdnyoFptlrhuoacivedesseeLnseotuhvgaeht dlwseapitenenrdtHooun msaenvTehrBeeslvyoommopidttoinmgs, foefvreor,taavbidruoms iinnfaelcptiaoinn,inancldude
water. Without enough water, systems in the watery diarrhea over several days. The virus
body change. Cells shrink, and the brain infects and kills the cells in the small intestine
signals the body to urinate less. Normally, that absorb nutrients and water. As a result,
kidneys flush out waste from human blood. unabsorbed nutrients and water leave the body
Without enough water to function properly, rapidly in loose stools and vomit. The infected
the kidneys use more energy, and their tissues person becomes weak and dehydrated. These
can be damaged. Without adequate water symptoms are usually milder in adults, who
intake, kidneys, as well as other organs, can normally recover.
cease to function. Currently, there is no drug treatment for
A lack of water can also impact other bodily rotavirus infection. Only oral or intravenous
functions. Without adequate water intake: rehydration with electrolytes is prescribed to

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

FIGURE 3.7 elements that boost the immune system, and
breastfeeding eliminates the need for infants to
maintain homeostasis of water and salts in eat food or take in drinks that may be
the blood. contaminated. However, for HIV-positive
mothers, breastfeeding is not a good option for
Challenges to Prevention and Treatment preventing rotavirus in their infants because
breast milk can transmit HIV. In these cases, it
Exclusive breastfeeding is a strategy for is safer to feed babies a breast milk
preventing diarrheal infections, including replacement, such as infant formula.
rotavirus, in infants up to six months old.
Exclusive breastfeeding means that the baby In 2007, a vaccine became available to prevent
ingests no food or drink besides its mother’s rotavirus infection, and widespread distribution
breast milk. The baby may be given vitamins, of the vaccine could be a major boost for
minerals, or medicines but no water. Breast prevention of the disease. The World Health
milk contains nutrients, antibodies, and other Organization now recommends that the
rotavirus vaccine be administered to infants as
soon as possible after six weeks of age.
Currently there are two major roadblocks to
global use of a rotavirus vaccine. First, more
vaccines are going to countries where rotavirus
is much less of a problem than to those with the
greatest need for the vaccine. This is partly a
matter of the relatively high cost of the
vaccine—about $20 or more per child. Second,
the rotavirus vaccines, like many vaccines, must
be kept refrigerated to prevent their spoiling—a
difficult task in remote tropical and subtropical
areas of the world that do not have a reliable
supply of electricity.

Extension 1

Interested in finding out more about how infectious diseases affect
human health? Your teacher can provide you with Student Sheet 3.3:
Case Study: Malaria, an additional case study on malaria, a vector-borne
disease. A vector is an organism that does not cause the disease itself but
spreads disease-causing microbes from one host to another. In the case of
malaria, the vector is a mosquito. It can carry the single-celled organism
that causes malaria, and infect a person when it bites them. You can add
an additional row to the table on Student Sheet 3.2 to record information
about this disease.

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HOMEOSTASIS DISRUPTED ACTIVITY 3

Build Understanding

1. What factors could make a person more at risk for having their body’s
homeostasis disrupted?

2. Humans are warm-blooded and are able to regulate their body
temperature internally. Think about how cold-blooded animals such as
snakes and lizards regulate their body temperature. Draw a model of a
feedback loop to show how a cold-blooded animal regulates its body
temperature outdoors. Be sure to include labels and a written
explanation that describes what is happening in your drawing.

3. Think about what you considered the most important items for survival
in Activity 1: Survival Needs. Based on what you now know about how
your body functions, explain how two of these items would help your
body maintain homeostasis. Be sure to address different levels of
organization in your body and how your body systems interact.

4. Take another look at the image on Student Sheet 3.2, “Modifying the
Model.”
a. Modify this image to show what happens to blood cells and skin
tissue when fluid levels in the body change. Be sure to label and
explain your modifications. Note that you do not need to stay
within the lines of the image.
b. Identify where in the model a person is likely to be thirsty, as well
as not thirsty.

5. Issue connection: Figure 3.8 shows the global disease burden by
region in 1990 and 2017. Disease burden is a measure of years of
healthy life lost from illness, injury, and other factors.
a. Improving global health is a sustainability goal. How successful
have people been in achieving this goal? Support your answer with
evidence from the maps.
b. How do you think the COVID-19 pandemic that began in 2020 has
affected this trend?
c. What type of global health initiatives do you think would have the
greatest impact on improving global health? Explain your
reasoning.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

FIGURE 3.8: Global Disease Burden by Region, 1990 and 2017
Roser, M., & Ritchie, H. (2017). Global Disease Burden by Region, 1990 and 2017.
Published online at OurWorldinData.org. Retrieved from: https://ourworldindata.org/
burden-of-disease
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HOMEOSTASIS DISRUPTED ACTIVITY 3

KEY SCIENTIFIC TERMS

disease
homeostasis
infectious
model
negative feedback loop
noninfectious
sustainability
thermal energy
vector

Extension 2

Are you curious about how other diseases affect the body’s ability to
maintain homeostasis? Think about what questions you still have, and do
additional research to see what you can find out. Visit the SEPUP SGI Third
Edition page of the SEPUP website at www.sepuplhs.org/high/sgi-third
-edition for links to more information and a journal article. You can use
Student Sheet 3.4, “Evaluating Websites,” to guide you in examining the
resources you find.

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