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PHOTOSYNTHESIS AND THE ENVIRONMENT ACTIVITY 12

2. Explain how the variable you tested affected the rate of photosynthesis
in spinach. Support your answer with evidence from your experiment.

3. Share and discuss your experimental results with your class. As a class,
determine the following:
a. What variable (or variables) increased the rate of photosynthesis?
b. What variable (or variables) decreased the rate of photosynthesis?

4. Which variables that you investigated in this activity do you think
affect nutritional sustainability? Explain your thinking.

5. Go to Appendix J: Science as a Human Endeavor in the Student Book
to review the nature and limitations of science. Use the information in
this appendix to describe how your investigation is consistent with the
nature of science and why it falls within the field of science.

6. Issue connection: Figure 12.4 shows how worldwide protein
consumption has changed over time (per capita refers to the average
per person). How would understanding the variables affecting plant
photosynthesis helpCaHdAdNrGesEsIgNloPbRaOlTpErIoNteCiOnNsSuUsMtaPinTaIObNility?

PER CAPITA OVER TIME
120

100

g/capita/day 80 Developed
Developing
60 World

40

20

0 1973–1985 1985–1997 1997–2009 2009–2011
1961–1973

FIGURE 12.4: Change in Per Capita Protein Consumption Over Time

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

KEY SCIENTIFIC TERMS

accuracy
photosynthesis
precision
reliability
reproducibility
sustainability

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13 Feeding the World’s Population

global changes are projected to affect the supply and quality of FIGURE 13.1
food. For example, crops are sensitive to changes in temperature,
precipitation, and carbon dioxide concentrations in the atmosphere.
Scientists from the University of Minnesota analyzed data from around the
world to see how crop yields varied with precipitation and temperature. In
some cases, slight decreases in crop yields resulted in about 1% fewer
consumable food calories per year. That represents about 35 trillion
calories each year, enough to provide more than 50 million people with a
daily diet of over 1,800 Calories. But not all the changes were negative:
Some crop yields increased in some locations.
In the next several activities, you will continue to build on your knowledge
of photosynthesis and cellular respiration from the Ecology unit. You will
begin by investigating and analyzing evidence about food production, and
discussing the trade-offs of possible solutions.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

How are global changes affecting the food supply?

Materials

FOR EACH STUDENT

Student Sheet 13.1, “Summarizing the Data”
Student Sheet 13.2, “Analyzing the Data”

Procedure

1. Follow your teacher’s instructions for reading and summarizing one or
more of the following data sets. Use Student Sheet 13.1, “Summarizing
the Data,” to record your understanding of each data set and any
questions you have.

DATA SET 1

Global Demand for Food

To feed the approximately 10 billion 10
people who will live on the planet by
2050, the United Nations Food and Crop Yield (tonnes per hectare) 8
Agriculture Organization forecasts
that crop production may need to 6
increase by 60%. Other studies
project an even greater increase in 4
crop demand (around 100%), as
increasing meat consumption results 2
in greater demand for feed crops.
Figure 13.2 shows crop yields in the 0 1990 2010 2030 2050
past (beginning in 1960) and future 1970 Rice Wheat Soy
projections (through 2050).
Corn

Projected Required

FIGURE 13.2: Global Crop Yields Vs. Demand
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FEEDING THE WORLD’S POPULATION ACTIVITY 13

DATA SET 2

Changing Crop Yields

Figure 13.3 shows the projected percentage sweet potato, soybean, groundnut, sunflower,
change in the yields of 11 major crops (wheat, and rapeseed) from 2046 to 2055, compared
rice, maize [corn], millet, field pea, sugar beet, with 1996–2005.

PROJECTED CHANGES IN CROP YIELDS BETWEEN PRESENT AND FUTURE

Percentage change in yields between present and future
–50 –20 0 20 50 100
FIGURE 13.3: Projected Changes in Crop Yields Between Present and Future

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DATA SET 3

Projected Changes in California’s Crops

California produces over a third of the United percentage change in yields of various crops
States’ vegetables and two-thirds of its fruits and grown in California over time.
nuts. Figure 13.4 shows the projected

20 Alfalfa 20 Sa ower 20 Corn
10 10 10
2040 2060 2080 2100 2040 2060 2080 2100 2040 2060 2080 2100
0 0 0
–10 –10 –10
–20 –20 –20
–30 –30 –30

2020 2020 2020

Percent Change (%) 20 Tomato 20 Rice 20 Wheat
10 10 10
2040 2060 2080 2100 2040 2060 2080 2100 2040 2060 2080 2100
0 0 0
–10 –10 –10
–20 –20 –20
–30 –30 –30

2020 2020 2020

20 Cotton 20 Sun ower Higher emissions scenario
10 10 Lower emissions scenario
2040 2060 2080 2100 2040 2060 2080 2100
0 0
–10 –10
–20 –20
–30 –30

2020 2020

FIGURE 13.4: Crop Yield Response to Warming in California’s Central Valley

LabAids SEPUP SGI Cells 3e
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CROP YIELD RESPONSE TO WARMING IN CALIFORNIA’S CENTRAL VALLEY
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FEEDING THE WORLD’S POPULATION ACTIVITY 13

DATA SET 4

Crop Yields in Temperate Vs. Tropical Regions

Figure 13.5 compares the changes in the yields happen to crop yields with an increase in global
of corn, wheat, and rice in temperate vs. tropical temperatures of 1°C, 1.5°C, and 2°C.
regions. The x-axisPshRoOwJEsCwThEaDt CisRpOrPojYeIcEtLeDd tCoHANGE WITH CHANGES IN GLOBAL TEMPERATURE

60 Temperate Regions Corn Tropical Regions

Corn yield change (%) 40 60Corn yield change (%) 12 3
40
20 20

0 0
–20
–20 –40
–60
–40

–60 12 3

60 Wheat

Yield Change (%) 40 60Wheat yield change (%)
40
Wheat yield change (%) 20 20

0 0
–20
–20 –40
–60
–40
12 3
–60 12 3
Rice
Rice yield change (%) 60 Rice yield change (%)
40 60
20 40
20
0
–20 0
–40 –20
–60 –40
–60
12 3
12 3

Global Temperature Increase from 1850

FIGURE 13.5: Projected Crop Yield Changes with Changes in Global Temperature B-91
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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

DATA SET 5

Positive Effects of Increased Carbon Dioxide Levels

Plants use carbon dioxide to make sugars, increase the amount of carbohydrates the plant
carbohydrates, and other carbon-containing produces. Scientists investigating the effect of
molecules. More carbon dioxide in the increasing carbon dioxide alone on agricultural
atmosphere can improve the crop yields in some plants found a fertilization effect on wheat, rice,
areas if other conditions needed for plant growth and soybeans. An increase in carbon dioxide can
(such as water availability) are right. While increase the productivity of wheat by 11.5% and
beneficial effects can be offset by extreme corn by 8.4%. At some point, the positive effects
weather, drought, or heat stress, higher carbon level off and an increase in carbon dioxide does
dioxide levels can stimulate plant growth and not provide much additional benefit.

1.5 Soy
Wheat

1.4 Rice

Relative Yield 1.3

1.2

1.1

Corn

1.0
280 320 360 400 480 520 560

Parts Per Million
FIGURE 13.6: Projected Effect of Increasing Carbon Dioxide Levels on Crop Yield

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Source: https://www.globalwarming-sowhat.com/

FEEDING THE WORLD’S POPULATION ACTIVITY 13

DATA SET 6

Food Consumption

The energy provided by food to people in
developing countries has changed over time, as
shown in Figure 13.7. (This graph was first
introduced in Activity 9, “Global Nutrition.”)

Population in developing countries (millions) 8,000 < 2,000 kcal/person/day 2,000–3,000 kcal/person/day 7,671
7,000 2,000–2,500 kcal/person/day > 3,000 kcal/person/day 3,362
6,000
5,000 6,839 4,069
4,000 240
3,000 5,218 5,879 2,631 2050
2,000 711 2,261
1,000 4,099
281 2,233
0 1,559
1,166
1,850 2,047 3,489
480 2,349
1990/1992 227 104 683
2005/2007 2015 2030

FIGURE 13.7: Per Capita Consumption

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

DATA SET 7

Summary of 70 Food Production Studies

An analysis of more than 70 studies on the effects Rice, a main source of calories in developing
of changes in global climate on food production countries, is projected to reduce in global yield
found that there would be a decrease in corn by an average of 3.2% per degree Celsius, much
production by the four major producers: United less than maize and wheat. India is projected to
States, China, Brazil, and India. These four be impacted the most, with a 6.6% decline per
countries are responsible for two-thirds of global degree Celsius. The losses for Indonesia,
corn production. For wheat, the average Bangladesh, Vietnam, and China (which
estimated decrease in global yield is 6.0% per produces approximately one-third of the world’s
degree Celsius—though China, the largest wheat rice) are smaller.
producer in the world, is projected to decline by
only 2.6% per degree Celsius.

Brazil CORN WHEAT
China (IN PERCENT PER °C) (IN PERCENT PER °C)
India
Russia –5.5 —
United States –8.0 –2.6
–5.2 –9.1
–7.8
— –5.5
–10.3

TABLE 13.1: Projected Crop Yield Per Degree of Warming

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FEEDING THE WORLD’S POPULATION ACTIVITY 13

DATA SET 8

Effects of Carbon Dioxide on Nutritional Levels

Higher carbon dioxide levels can affect the magnesium, copper, sulfur, phosphorus, and
protein, vitamin, and mineral content of crops. nitrogen—are also expected to decrease with
Researchers found that plants’ protein content more carbon dioxide in the atmosphere. For
will likely decrease significantly if carbon example, a zinc deficit in food crops could affect
dioxide levels reach 540–960 parts per million 150–200 million people. As carbon dioxide
(ppm). The current level is approximately 412 levels rise, the openings in plant shoots and
ppm and is projected to reach these higher leaves shrink, so they lose less water. It appears
levels by 2100. Studies show that barley, wheat, that plants then lose water more slowly, slowing
potatoes, and rice have 6%–15% lower down water movement in their tissues and
concentrations of protein when grown at these drawing in less nitrogen and minerals from the
higher carbon dioxide levels, although the soil. Vitamin B levels in crops may drop as well
protein content of corn and sorghum does not because nitrogen in plants is critical for
decline significantly. However, food crops could producing these vitamins. In one study, rice
lose enough key nutrients to cause a protein grown with elevated carbon dioxide
deficiency in an estimated 150 million people. concentrations contained 17% less vitamin B1
This is in addition to the number of people who (thiamine), 17% less vitamin B2 (riboflavin),
already experience nutritional deficiencies. 13% less vitamin B5 (pantothenic acid), and
30% less vitamin B9 (folate) than rice grown
The concentrations of important under current carbon dioxide levels.
micronutrients—such as iron, zinc, calcium,

Build Understanding

1. How are global changes likely to affect food quality and supply?
Support your answer with evidence from this activity.

2. What questions do you still have about plants, plant growth, and food
production?

3. Issue connection: There are several proposed solutions to addressing
the future food needs of the world’s population, including making
croplands more productive through improved nutrient and water
management, and developing strains of crops that can grow more
productively in different environments.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Here are two proposed solutions that involve individual actions:

• Changing individual diets: About 62% of crop production is for

food, 35% is used for animal feed, and 3% is harvested for fuel and
other industrial uses. Shifting more crop production toward food
(and away from animal feed) could potentially add about 50% more
calories to the global food supply. This would require a decrease in
the amount of meat consumed globally.

• Reducing food waste: Approximately 24% of the food calories

produced are wasted during consumption or are lost in the supply
chain. Cutting waste and losses by half would close 22% of the gap
between calories available today and those needed by 2050. This
would require making choices so that little or no food is thrown away.
Explain what actions you are willing to take to address food
availability. Include evidence that supports how your decision would
address food availability and the trade-offs that are required.
4. Issue connection: How are changes to the global food supply likely
to affect the three pillars of sustainability (environmental, economic,
and social)?
KEY SCIENTIFIC TERMS
nutritional sustainability

Extension

What is the latest research on climate effects on food quality and supply? Visit
the SEPUP SGI Third Edition of the SEPUP website at www.sepuplhs.org/
high/sgi-third-edition for links to more information and a journal article.

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14 Investigating Cellular Respiration

people need food for energy. Some plants convert sugars to

complex carbohydrates (starch) or fats that can be stored in plant stems,
roots, and seeds. Plants use these stored substances when needed to
provide energy for processes such as reproduction. People take advantage
of these stored substances when they eat these foods, which contribute to
nutritional sustainability. Certain plant organs—such as the parts of
onions, carrots, parsnips, turnips, and potatoes that people use as food—
store sugars and starches for when the plant needs them to provide energy
through cellular respiration. Some seeds, such as nuts, store both starches
and fats.

a b
FIGURE 14.1: Root vegetables (a) and peanuts (b)

In previous activities, you observed evidence of photosynthesis performed
by the green parts of plants. You have seen that plant leaves conduct
photosynthesis in the light. In this activity, you will use another part of a
plant—a bean—to investigate cellular respiration. Beans are good for this
purpose because they do not contain chloroplasts, so their cells don’t

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

csoenedducocattphotosynthesis. This means that any changes in carbon dioxide
levels must be caeumsebdryboy cellular respiration. The beans used in this activity
have been germinated—they have sprouted and are starting to grow. You
will dfeosoidgnstoyroeur own investigation to test how changing one variable in the
environment affects the rate of cellular respiration of sprouted beans.

seed coat

embryo

food store

FIGURE 14.2: Germinated Bean

Guiding Question

How do various factors in the environment affect the rate of
cellular respiration in plants?

MaterialsSGI Cells
Figure: SGI3e Cells SB 14_02
MyriadPro 9.5
FOR EACH GROUP OF FOUR STUDENTS

4 transparent sealable cups

4 plastic disc inserts

4 8-ounce foam cups c7 m0 y0 k9 c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90

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masking tape

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timer

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

partially completed Student Sheet 10.1, “Anticipation Guide: Energy and
Matter from Food,” from Activity 10
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chemical splash goggles

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INVESTIGATING CELLULAR RESPIRATION ACTIVITY 14

SAFETY

Wear chemical splash goggles when working with chemicals.
Do not touch the mixture or bring it into contact with your eyes or
mouth. Wash your hands thoroughly with soap after completing the
procedure.

The indicator used in this activity, phenol red, will stain skin and
clothing. If you get it on your skin or clothing, immediately flush the
area with water.

Procedure

Part A: Collecting Evidence that Beans Respire

1. Make a table like Table 14.1 in your science notebook. Observe your
teacher’s demonstration of the color of the phenol red solution in the
presence and absence of carbon dioxide. Use your observations to
complete the table.

TABLE 14.1: Phenol Red Indicator

Before After

Color

Carbon dioxide present?

2. In your group, set up an investigation to confirm that beans respire.
a. Place a plastic disc insert in the plastic cup to keep the beans out of
the liquid, as shown in
Figure 14.3, and place a
few beans on the insert.
Be sure to handle the
beans carefully so you
don’t break off the
sprouts!

FIGURE 14.3: Investigation Setup

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

b. Prepare your indicator solution by adding 25 drops of phenol red
to 145 mL of water in a plastic cup and swirling the solution to mix
it. You will use this indicator to determine whether there is any
evidence that beans respire.

c. Pour enough indicator solution into the bottom of each cup so that
it is just below the plastic disc insert.

d. Set up a control. Use masking tape and a permanent marker to
label each cup appropriately.

e. Fix the lids on the cups tightly to prevent any gas from escaping.
f. Observe the beans for 15 minutes (or longer, if recommended by

your teacher). Record your results and conclusions in your science
notebook.

Part B: What Variables Affect Bean Respiration?

4. With your group, discuss changing global conditions that might affect
the rate of cellular respirations by beans. Choose a variable to test,
based on these changing conditions.

5. Design your experiment, including answers to the following questions:

• What is the purpose of your experiment?
• What variable are you testing?
• What variables will you keep the same?
• What control or controls will you need to set up?
• What is your hypothesis?
• Will you collect qualitative and/or quantitative data? How will these

data help you make a conclusion?

• What are the steps in your procedure?
• How many trials will you conduct?

6. Make a data table that has space for all the data you need to record. You
will fill it in during your experiment.

7. Obtain your teacher’s approval of your experiment design.
8. Conduct your experiment, and record your results.
9. Follow your teacher’s instructions to clean up and dispose of your

materials properly.
10. Follow your teacher’s instructions for how you will share your results

with the class.

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INVESTIGATING CELLULAR RESPIRATION ACTIVITY 14

Build Understanding

1. What variable did you test? Explain why you chose this variable and
what results you predicted in your hypothesis.

2. What other variables did your class test? How did these other variables
affect the rate of respiration?

3. Think about all the investigations done by your class on the beans.
a. What conclusions can you draw based on the results? Be sure to
explain how the data collected supports your conclusions.
b. How confident are you of these results and your class’s conclusions?
What would make the results more accurate, precise, reliable, and
reproducible?

4. Do you think cellular respiration in humans and other mammals is
affected by any variables? Explain your ideas.

5. Some plants lose their leaves in the fall and cannot perform
photosynthesis without them. Explain, based on what you learned in
this activity, why many plants are able to survive over the winter.

6. Return to Student Sheet 10.1, “Anticipation Guide: Energy and Matter
from Food,” from Activity 10, and complete the “After” column for
statements 1–5.

7. Issue connection: Review Data Sets 5 and 8 from Activity 13.
a. Based on Data Sets 5 and 8 and the results of this investigation,
how might global changes that increase temperatures affect the
food supply?
b. What might happen to the sustainability of the food supply as a
result of global climate changes?

KEY SCIENTIFIC TERMS

accuracy
cellular respiration
photosynthesis
precision
reliability
reproducibility
sustainability

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15 Energy for Life

the processes that use energy in your body—such as making new
proteins, sending signals in the brain, and causing muscles to move—
require a readily available supply of chemical energy. Figure 15.1 shows the
typical energy needs for 16–18-year-olds. Notice how calorie needs vary
with a person’s level of physical activity.

ESTIMATED CALORIE NEEDS PER DAY FOR AGES 16 18

Calorie Needs 4,000 Male
3,000 Female
2,000

1,000

Sedentary Moderately Active Active

Activity Level

FIGURE 15.1: Estimated Calorie Needs Per Day for Ages 16–18

You observed that stored energy in oxygen and glucose can be released as
thermal energy when oxygen and glucose react during the process of
combustion. But plants, animals, and humans can’t use thermal energy to
run the processes that keep their cells, tissues, and organs alive and
functioning. They also cannot directly use the energy stored in oxygen and
glucose. Instead, all organisms use cellular respiration to transfer the
energy stored in oxygen and glucose to a usable form. In this activity, you
will learn more about how the reaction of sugar and oxygen during cellular
respiration provides plants, animals, and you with usable energy.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

The carbohydrates, proteins, and fats that provide the calories in food are
all carbon-containing molecules, with a carbon backbone. One of the
simplest carbon-containing molecules is methane, CH4. Methane is a
component of natural gas and is an excellent fuel. Like food molecules, it
reacts with oxygen to produce carbon dioxide and water. In Part A of this
activity, you will track the energy change from the reaction of methane
with oxygen to see how a chemical reaction can release energy.

Guiding Question

How does cellular respiration produce usable energy?

Materials

FOR EACH GROUP OF FOUR STUDENTS

molecular model set containing the following:
18 white "atoms"
8 black "atoms"
8 red "atoms"
1 blue "atom"
34 straight gray "bonds"
6 curved gray "bonds"

FOR EACH STUDENT

partially completed Student Sheet 10.2, “Cellular Respiration Model,”
from Activity 10
Student Sheet 15.1, “Tracking Energy in a Chemical Reaction”
6–10 sticky notes

Procedure

Part A: Tracking Energy From Food

1. With your group, examine the molecular model set and the
following key:

• Each colored sphere represents atoms of one element, as shown in

Table 15.1.

• A single straight gray connector between atoms represents a single

bond.

• Two curved gray connectors represent a double bond.

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ENERGY FOR LIFE ACTIVITY 15

TABLE 15.1: Key to Atom Models

ELEMENT COLOR OF MODEL ATOMS NUMBER OF CONNECTIONS
Carbon black PER ATOM
Hydrogen white 4
Nitrogen blue 1
Oxygen red 3
2

A chemical bond, or bond, is a force that holds atoms together in
molecules. Scientists have calculated the average amount of energy
transfer when certain bonds are broken or formed. Table 15.2 shows the
average energy values for four bonds that are important in food molecules.

TABLE 15.2: Average Bond Energies

BOND ENERGY UNITS TRANSFERRED ENERGY UNITS TRANSFERRED
C–H TO BREAK THE BOND WHEN BOND FORMS
C=O 413 required 413 released
H–O 745 required 745 released
O=O 467 required 467 released
498 required 498 released

2. With your partner, discuss any patterns you see in the data, and record
your ideas in step 1 on Student Sheet 15.1, “Tracking Energy in a
Chemical Reaction.”

3. Use Student Sheet 15.1 and the molecular model set to model the
rearrangements of bonds in a chemical reaction and to calculate the
energy transfer that takes place.

4. Review the graphs and your response to Procedure Step 12 from
Activity 10: Burning Calories. Do your results from Student Sheet 15.1
support or conflict with your response to Step 12? Be prepared to share
your ideas with the class.

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Part B: How Does Cellular Respiration Make Energy From Food Useful?

5. Think about how the process of cellular respiration compares to the
process of burning food as you complete the following reading. As you
read, use the Read, Think, and Take Note strategy:

• 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.

Reading

Cellular Respiration And Usable Energy

Aerobic Cellular Respiration
Aerobic cellular respiration refers to respiration in the presence of oxygen.
The first steps of cellular respiration begin in the cytoplasm, and the
reactions that require oxygen take place in mitochondria. You have already
determined that the process of cellular respiration in the human body has
some parallels with burning a piece of food in a laboratory. When people
refer to “burning” calories, they are referring to breaking down food all the
way to carbon dioxide and water for energy, because none of the food burned
for energy increases body weight. Both combustion of food in the presence
of pure oxygen and cellular respiration in the presence of oxygen in air are

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ENERGY FOR LIFE ACTIVITY 15

chemical reactions that have the same inputs and outputs. These inputs and
outputs can be summarized in the equation in Figure 15.2.

Glucose ϩ Oxygen Carbon dioxide ϩ Water
ϩ

Energy

FIGURE 15.2: Equation for Cellular Respiration in the Presence of Oxygen

Energy is included on the right side of the equation when it is released by a
reaction. A dotted arrow is used in the figure to distinguish it from matter.
In Part A of this activity, you modeled how energy stored in oxygen and a
carbon-containing substance is released as they react and rearrange to
form new molecules.

To get food to burn, you needed to first get things started by transferring a
small amount of thermal energy from a lit match to the food. This gave the
system a small energy boost that started the combustion reaction. In
cellular respiration, special proteins in the cells called enzymes bring the
oxygen and sugar together, so this thermal energy boost isn’t needed.

With the beans in Activity 14: Investigating Cellular Respiration, you
observed that cellular respiration doesn’t rapidly release the large amounts
of thermal energy that are released by combustion. This is because cellular
respiration breaks down sugar molecules in many small steps, each of
woxhyigcehnr.eSFLleoiagabmusAreeeisd:osaCfSestElmlhPsiU3asPelelSSnaBGmeI1rCog5e_yul0lnis2st3roeeflethaseetdotaasl energy stored in sugar and
thermal energy, which helps to
maintainMtyermiapdPerroatRuerge9h.5o/m11eostasis. But the rest of the energy from cellular

FIGURE 15.3 B-107

CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

respiration is converted into chemical energy, which is energy stored in the
bonds of molecules. ATP is the main molecule used for storing and
carrying energy in cells. Over 30 molecules of ATP can be produced with
the energy released per glucose molecule during cellular respiration in the
presence of oxygen. ATP and similar molecules provide the energy for
every chemical reaction that requires energy in your cells.

Even when you are sleeping, you need energy for the chemical reactions
that keep you alive. Some of these chemical reactions take place in all cells.
For example, cells from bacteria, plants, animals, and humans all need ATP
as a source of energy to make new proteins and to divide. In your muscle
cells and your heart, much of the ATP is used for contraction. In your
brain, some of the energy is used to make signal molecules and to send
them from one cell to another. So, although the energy needs of different
organisms and different cells overlap, they aren’t exactly the same.

Figure 15.4 shows estimated averages of the amount of energy from cellular
respiration used by the human body for three main activities over the
course of a day:

• Resting metabolism (the chemical Digesting and
metabolizing
reactions that keep your brain and
other organs, including your heart food
and lungs, going when you are at rest) 10%

• Physical activity
• Digesting and metabolizing food

These activities vary somewhat from
person to person and from day to day.
Physical activity Resting metabolism
30% 60%
Anaerobic Cellular Respiration

Although all organisms conduct some
form of cellular respiration, not all
organisms use oxygen. Some
organisms are able to survive in the
absence of oxygen because they
conduct anaerobic respiration.
Anaerobic cellular respiration takes
place in the cytoplasm of the cell and
does not use oxygen to break down FIGURE 15.4: Human Energy Use

sugars. In fact, the first stage of aerobic cellular respiration does
not require oxygen either, but the mitochondria in humans,
animals, and plants use oxygen to continue breaking down
food and releasing more energy.
LabAids SEPUP SGI Cells 3e
Figure: Cells 3e SB 15_03
MyriadPro Reg 9.5/11

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ENERGY FOR LIFE ACTIVITY 15

Some organisms are able to survive using just the first (anaerobic) steps of
respiration. For example, organisms such as yeast conduct fermentation, a
process that partially breaks down sugars to produce ethyl alcohol, carbon
dioxide, and the energy stored in ATP. Other organisms, such as the
bacteria in yogurt, break down sugars to produce lactic acid and ATP.
In humans, anaerobic cellular respiration can take place for short periods
of time when enough oxygen isn’t delivered to the tissues. This most often
occurs in muscles during intense exercise. Red blood cells, which lack
mitochondria, also conduct anaerobic respiration. The partial breakdown
of sugars to produce ethyl alcohol or lactic acid produces far less ATP per
glucose than aerobic respiration.
Some prokaryotes (organisms without nuclei) don’t react sugars with
oxygen, but instead react sugars with other substances that play a role
similar to oxygen’s in breaking down the sugars.

Build Understanding

1. Prepare a Venn diagram like the one in Figure 15.5, and use it to
compare the chemical reactions of combustion and aerobic cellular
respiration.

FIGURE 15.5: Venn Diagram for Combustion and Aerobic Cellular Respiration

COMBUSTION CELLULAR
RESPIRATION

2. What are the similarities and differences between anaerobic and
aerobic respiration?

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

3. You learned in the Ecology unit that aerobic cellular respiration plays
an important role in the cycling of matter and the flow of energy in
ecosystems. Do you think that anaerobic respiration performs a
similar function? Explain your thinking.

4. Return to the model you began on Student Sheet 10.2, “Cellular
Respiration Model.”
a. Complete the model by filling in the energy graph for cellular
respiration on the bottom half of the Student Sheet.
b. Add arrows, labels, and a caption to your model to identify:

• the changes in matter during cellular respiration
• the changes in energy during cellular respiration
• what causes the changes in energy and matter to take place
• why there is an overall release of energy from cellular respiration

5. Think about what you have learned about photosynthesis, respiration,
and energy transfer in the Ecology unit and this unit. Which of the
following graphs do you think best represents the flow of energy
during photosynthesis? ExplaiRnEyAoCuTrIOanNsEwNeEr.RGY CHANGES

A B
Reactants
Stored Reactants
Energy
Stored
Energy

Products Products

Reaction Time (Progress) Reaction Time (Progress)

C Products D
Products
Stored
Energy Stored
Energy
Reactants
Reactants

Reaction Time (Progress) Reaction Time (Progress)
FIGURE 15.6: Reaction Energy Changes
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ENERGY FOR LIFE ACTIVITY 15

KEY SCIENTIFIC TERMS

aerobic cellular respiration
anaerobic cellular respiration
atom
ATP
bond
chemical bond
chemical energy
energy
molecule
thermal energy

Extension

Use a computer simulation to investigate how photosynthesis and cellular
respiration meet the energy needs of all organisms. In what ways are these
processes similar or different? Visit the SEPUP SGI Third Edition website at
www.sepuplhs.org/high/sgi-third-edition to get started.

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16 Matter for Cells

in activity 10: burning calories and Activity 15: Energy for Life,

you investigated how organisms use food for energy. From these activities
and Activity 9: Global Nutrition, you’ve determined that an organism
needs food for more than energy: Food must also provide the matter that
an organism needs to build and maintain its cells, tissues, and organs. In
addition to carbohydrates, this matter includes proteins and fats.
Consider your own need for matter from food. Young people who are
growing are building muscle, bone, and other tissues as they increase in
body mass. Their cells need matter to build new tissues and grow. Even in
adults, certain cells are continually replaced. The average life of some of
these cells is shown in Table 16.1.

TABLE 16.1: Average Life of Selected Cell Types

CELL TYPE APPROXIMATE AVERAGE LIFE BEFORE
Digestive system lining REPLACEMENT
Lung alveoli 2–9 days
Red blood cell 8 days
Skin cell 120 days
10–30 days

Food provides the carbon-based matter that your body needs. But your
body can’t directly use the substances in food because many human
proteins, carbohydrates, and other molecules are different from the ones
in the foods you eat. Building your body structures requires your cells to
produce versions of carbohydrates, proteins, fats, and other molecules
that the human body can use. The carbohydrate, protein, and fat
molecules in food are broken down in the digestive system into smaller
molecules that your body can use as building blocks. These smaller
molecules enter your bloodstream, where they are transported to all the
tissues and cells in your body.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

How does an organism use the matter in food?

Materials

FOR EACH GROUP OF FOUR STUDENTS

molecular model set containing the following:
18 white "atoms"
8 black "atoms"
8 red "atoms"
1 blue "atom"
34 straight gray "bonds"
set of 13 Matter from Food cards

FOR EACH STUDENT

partially completed Student Sheet 10.1, “Anticipation Guide: Energy and
Matter from Food,” from Activity 10
Student Sheet 16.1, “Forming Molecules for Cells to Function and Grow”

Procedure

Part A: Modeling a Sugar and an Amino Acid

1. Review the molecular model set. As in the previous activity, each
colored sphere represents atoms of one element common in food
molecules, as shown in Table 16.2. A single straight gray connector
represents a single bond. Two curved gray connectors represent a
double bond.

TABLE 16.2: Key to Molecular Model Set

ELEMENT COLOR OF MODEL NUMBER OF
Carbon ATOMS CONNECTIONS PER ATOM
Hydrogen black 4
Nitrogen white 1
Oxygen blue 3
red 2

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MATTER FOR CELLS ACTIVITY 16

2. Work in your group to create two models. One pair will make a model
of a glucose (sugar) molecule, and the other pair will make a model of
a glycine (a kind of amino acid) molecule. Refer to Figure 16.1 as you
create your model.

CH2OH O HH O
C OH
HH C NC C
C
HO OH HH HH OH
C C
H OH

Glucose (a sugar) Glycine (an amino acid)
LabAids SEPUP SGI Cells 3e
LabAids SEPUP SGI Cells 3e Figure: Cells 3e SB 16_02
FMFiIgGyurUiraRed:EPCr1eo6ll.Rs1e3:geTw9S.oB5/M1161o_l0e1cules MyriadPro Reg 9.5/11

3. Discuss this question in your group:
An organism’s diet includes only glucose, but it needs glycine to
make proteins. Can an organism make glycine from glucose?

Record your ideas in your science notebook, and be prepared to share
them with the class.

Part B: Using Matter From Food

You will now focus on how human cells use the carbohydrates and
proteins in food to make carbohydrates and proteins that the human
body can use.

4. Read the Matter from Food cards.
5. With your group, sort the cards into three groups:

• Group I: Background information about the carbon-based

molecules needed for life (6 cards)

• Group II: How cells get the substances they need from food (2 cards)
• Group III: Processes that happen inside the cells (5 cards)

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

FIGURE 16.2

6. With your group, arrange each group of cards into a logical order. As
you decide how to order the cards, be sure to consider the ideas of all
members of your group. If you cannot come to a consensus, record
alternate ideas as well. Record the cards in each group, in order, in
your science notebook.

7. Draw on what you have learned about inputs to the cells and processes
within cells to complete Student Sheet 16.1, “Forming Molecules for
Cells to Function and Grow.” Create a model that shows the movement
and changes of matter for the formation of the carbon-based
molecules needed by cells. Use the information and symbols on the
Group I and Group III cards to help you complete the Student Sheet.
Add a legend or labels and captions to your model as needed.

8. Based on the information on the cards and your model on Student
Sheet 16.1, develop an explanation for how cells produce the molecules
they need to function and grow. Be sure to include:

• the kinds of complex molecules needed by cells to function and grow
• the atoms needed to make these complex molecules
• how cells get the atoms they need to make complex molecules
• what processes the cells use to make complex molecules

9. Read this definition of DNA:
DNA, the molecule that codes for genetic information, is a very
large molecule whose backbone is made of chains that include a
sugar called deoxyribose.

Add to your explanation in Step 8 a description of how you think
cells make the deoxyribose sugar they need and how they use it to
build DNA.

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MATTER FOR CELLS ACTIVITY 16

Build Understanding

1. In what ways are the structures and functions of sugars and amino
acids:
a. similar?
b. different?

2. In what ways are the processes used to build proteins and
carbohydrates and the process of cellular respiration:
a. similar?
b. different?

3. Return to Student Sheet 10.1, “Anticipation Guide: Energy and Matter
from Food,” and complete the “After” column for Statements 6–12.

4. Your digestive system breaks down food molecules into smaller
molecules, including glucose. Use what you have learned in this unit to
list three main things that cells in your body do with glucose and
explain what each thing does for the cells.

5. Issue connection: Based on this activity and Activity 9: Global
Nutrition, explain how it would be possible for a person’s diet to have
sufficient Calories for energy and yet still cause the person to be
undernourished.

KEY SCIENTIFIC TERMS

amino acid
atom
complex carbohydrate
energy
matter
molecule
protein
sugar

B-117



17 Designing Solutions: World Health

according to one estimate by the World Health Organization, a
changing climate is expected to cause approximately 250,000 additional
deaths per year between 2030 and 2050. Approximately 95,000 of these
deaths are predicted to be due to childhood undernutrition, 60,000 due to
malaria, 48,000 due to diarrhea, and 38,000 due to heat exposure in elderly
people. Determining the best ways to address these issues is not an easy
task. As you have learned, social, economic, and environmental factors
vary by country and by region.
Increasingly, experts are adopting an integrated approach that involves
experts from multiple fields—including human, animal, and
environmental health—working together to address human health issues.
How might various individuals or groups have differing points of view
about a common problem? How could these differences be used to develop
an integrated approach to a solution?

FIGURE 17.1: People from different countries can work together to improve global health.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

What solutions can you design for improving global health?

Procedure

Part A: Case Study of an Integrated Approach

1. Read the following case study about an integrated approach to disease
in Bolivia.

CASE STUDY

Disease in Bolivia

In 2012, staff at an animal sanctuary FIGURE 17.2: Howler Monkey
outside of Santa Cruz, Bolivia, discovered Yellow fever is a mosquito-borne virus that
six dead wild howler monkeys nearby.
Since about 60% of infectious diseases infects both humans and non-human primates.
(including rabies and influenza) can be It can result in a hemorrhagic fever that leads to
transmitted between animals and humans, death. Yellow fever transmission can occur if
there was concern that the unknown infected monkeys and any of the mosquito
disease could spread. In the past, this vector species are present. The Ministry of
information may have been used solely to Health immediately instituted a public outreach
prevent and treat disease transmission to
animals and staff within the sanctuary.

But as part of its integrated approach, the
sanctuary reached out to others and sent
specimens from the dead animals to the
University of San Andres’s Institute of
Molecular Biology for analysis. Initial
results suggested that the infection was
caused by a virus transmitted from mosquitoes
or ticks, such as yellow fever. While additional
tests were being conducted, the Bolivian
Ministry of Health was alerted to the situation.
The ministry was concerned about the possible
transmission and outbreak of an infectious
disease among the almost 1.8 million people
living in Santa Cruz.

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DESIGNING SOLUTIONS: WORLD HEALTH ACTIVITY 17

program, a preventive yellow fever vaccination the response to this disease—from its detection
campaign, and mosquito controls. The to the resolution of the outbreak—occurred
university staff soon determined that the within eight days, and no human cases of yellow
monkeys had in fact died of yellow fever. fever appeared. This suggests that increased
awareness and collaboration among partners
Though monkeys infected with yellow fever can improve human health.
had never been previously reported in Bolivia,

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

• Which changing global health pattern—extreme heat, changing

patterns of disease, or climate effects on the food supply—was the
focus of this case study?

• Who were the various stakeholders identified in this case study? Are

there stakeholders who were not identified? If so, who?

• How did the various stakeholders contribute to the solution?
• Could other countries or regions of the world use this integrated

approach to address human health issues? Explain your reasoning.

3. Look over the Venn diagram in Figure 17.3. Diagrams like this can be
used to communicate the elements of an integrated approach to
human health. Discuss with your group how this diagram applies to
the case study and how it relates to the three pillars of sustainability
(economic, social, and environmental).

humans environment

animals

FIGURE 17.3: Integrated Approach Venn Diagram
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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY FIGURE 17.4

Part B: Local Impact of Emerging Global Health Patterns

4. Think about the news headlines you read in Activity 3: Homeostasis
Disrupted.
a. With your class, brainstorm some ways that emerging global
patterns (extreme heat, changing patterns of disease, and climate
effects on the food supply) are affecting your community and how
these global patterns might impact human health.
For example, a community may be experiencing more frequent
heat waves than in the past, which has a number of effects:

• It can affect the environment by causing both water shortages

and an increase in tree death, resulting in less shade and even
higher temperatures.

• It can affect wild animal populations, both the animals that live

in the trees and those that have reduced access to water.

• It can impact people’s recreational opportunities and thus their

social health, as lakes may dry up and parks may provide less shade.

• It can impact human health because higher driveway and

sidewalk temperatures can result in an increase in burns if people
fall or go barefoot outdoors. There can also be an increase in
heat-related illness and death.
b. Work with your classmates to narrow down the list you
brainstormed to one local issue.
c. Brainstorm how an integrated approach might address this issue:

• Who are the possible stakeholders? Remember to think about

local, regional, national, and global levels.

• What solutions might each

stakeholder propose?

• How could you combine these

different solutions into an
integrated approach?

Part C: Design, Evaluate, and Refine a Solution

5. Read and consider the following list of
ways that the emerging global patterns of
extreme heat, changing patterns of
disease, and climate effects on the food
supply are impacting human health:

• Increasing mortality and illness due to

heat waves and other climate-related
events, such as storms, hurricanes,
tornadoes, and flooding

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DESIGNING SOLUTIONS: WORLD HEALTH ACTIVITY 17

• Increasing global rates of noninfectious disease (such as diabetes,

heart disease, and noninfectious respiratory illness such as asthma)
due to changes in lifestyle and climate-related events, such as wildfires

• Emerging infectious diseases (such as COVID-19, Ebola, and H1N1

flu) due to increased interactions between people and the
environment and to increasing globalization

• Increased spread of infectious diseases (such as malaria, Lyme

disease, and rotavirus) due to decreased water quality or to the
spread of disease vectors as a result of the changing climate

• Reduced nutrition due to the decreased quality and quantity of the

food supply

• Increased obesity and illness due to increased available calories and

changes in lifestyle

6. Think about which global health challenge you would like to address.
You will work in your group to propose a solution to improving global
health through an integrated approach. Begin by choosing a challenge
to focus on. Record your chosen area of focus in your science
notebook.

7. Brainstorm four to six possible stakeholders at the local, regional,
national, and/or global levels. Be sure to consider the ways in which
stakeholders could represent humans, environment, and/or animals,
as modeled in Figure 17.3. Record your list of stakeholders in your
science notebook.

8. Decide which group member will represent which stakeholder (or
stakeholders). From the perspective of your stakeholder, design at least
one sustainable solution to your chosen global health challenge.
Record your solution in your science notebook.

Hint: Think about what is most important from your stakeholder’s
perspective. Use your ideas and what you have learned in this course
so far to guide you in designing your stakeholder’s solution.

9. Share your proposed solution with your group. Have your group
members evaluate your solution and provide feedback. Refine your
ideas as needed.

10. Work with your group to develop an integrated approach by
incorporating your various solutions into a master plan for a
community.

11. Present your integrated approach to the class.

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

Build Understanding

1. Imagine presenting your plan to the larger community.
a. What types of data could you collect to monitor the effectiveness of
your plan?
b. What are the trade-offs of your plan, if any?

2. Could the proposed solutions presented in your class be applied in all
countries or regions of the world? Explain why or why not, using
specific examples from your or your classmates’ solutions.

3. Limited funds means that people have to make choices when
addressing global health. Even an integrated approach to human
health can require prioritizing one aspect of a plan over another.
Imagine that you can fund only one aspect of your group’s integrated
approach (or the ideas of only one stakeholder). What (or whose
ideas) would you fund? Support your answer with evidence, and
identify the trade-offs of your decision.

4. Issue connection: Which do you consider to be the most pressing
global health problem: consequences of extreme heat events, changing
patterns of disease, or climate effects on the food supply? Explain your
reasoning.

5. How did the science you learned in this unit give you insight into the
challenges of addressing global health concerns?

KEY SCIENTIFIC TERMS

disease
extreme heat event
infectious
integrated approach
noninfectious
sustainability

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Unit Summary

Human Health and Emerging Global Patterns

Human health is increasingly subject to emerging global patterns,
including extreme heat events, changes in the frequency of disease, and
climate effects on the food supply. While some impacts may be beneficial,
scientists anticipate that there may be greater negative impacts over time.
Experts project that rising temperatures will result in an increase in
extreme weather events, such as heat waves; in changing patterns in the
frequency of infectious and noninfectious disease; and in measurable
impacts on the global supply and quality of food. Increasingly, human
health can be considered a sustainability issue that is affected by the
interaction of environmental, social, and economic factors. Experts are
now recommending an integrated approach that involves stakeholders
from multiple fields—including human, animal, and environmental
health—working together to address human health issues.

Human Health and Homeostasis

The structures of multicellular organisms, including plants and animals,
have several levels of organization. Each level—from cells to tissues,
organs, and organ systems—contributes to the functioning of the
organism. The human body can survive in a range of conditions because
systems at different levels of organization all interact to maintain stability.
The body’s ability to maintain internal conditions within a healthy range is
known as homeostasis. Homeostasis is essential for normal
body functioning and is a result of multiple systems interacting at all levels
of organization: cells, tissues, organs, organ systems, and the whole body.
Body temperature, blood sugar levels, and hydration levels are three
examples of internal conditions that are regulated through homeostasis.
Homeostasis is maintained through feedback mechanisms that can
encourage (through positive feedback) or discourage (through negative
feedback) what is happening inside the body. A negative feedback loop is
one in which the body recognizes a change and brings conditions back to
normal. For example, body temperature, which is regulated through a
negative feedback loop, would rise approximately 1°C per hour if the body

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CELLS SCIENCE & GLOBAL ISSUES: BIOLOGY

did not transfer excess heat to the environment—for example, 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.
Disease—any breakdown in the structure or function of an organism—
disrupts the normal functioning of body systems. Such disruptions of
homeostasis affect all levels of organization, from the whole organism to
the cells. These disruptions can be caused by viruses, bacteria, and other
microbes (as in the case of infectious diseases, such as COVID-19) or by
other factors, including genetics, the environment, and aging (as in the
case of noninfectious diseases, such as diabetes).

Human Health and the Need for Energy and Matter

Photosynthesis and cellular respiration provide most of the energy needed
for life processes. Photosynthesis is the process by which plants use the
energy from sunlight to convert carbon dioxide and water into oxygen and
food for their own energy and matter needs. Other organisms, such as
humans, use plants for energy and matter by either eating plants as food or
by eating other organisms that ultimately depend on plants for food. In this
way, matter and energy are transferred within organisms and from one
organism to another.
Food contains a mixture of substances, including carbohydrates, fats, and
proteins. Molecules of these substances break down into smaller
molecules—sugars, fatty acids, and amino acids—that can be used by
organisms. Humans use these smaller molecules as a source of matter to
build substances needed by the body and to react with oxygen for energy.
Like all organisms, humans use cellular respiration to transfer the energy
stored in food and oxygen into a form usable by the human body. Aerobic
cellular respiration is a chemical process in which the bonds of food
molecules and oxygen molecules are broken and new bonds form to
produce carbon dioxide and water. At the same time, energy is transferred
to form ATP (the main molecule used for storing and carrying energy in
cells), which cells can use for their own energy needs. Cellular respiration
also releases the energy needed to maintain body temperature despite
ongoing energy transfer to the surrounding environment.

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IMPROVING GLOBAL HEALTH SUMMARY

KEY SCIENTIFIC TERMS microbe
micronutrients
accuracy model
aerobic cellular respiration molecule
amino acid negative feedback loop
anaerobic cellular respiration noninfectious
atom nutrition
ATP nutritional sustainability
bond organ
calorie organelle
Calorie photosynthesis
carbohydrate precision
cell product
cellular respiration protein
chemical bond qualitative
chemical energy quantitative
dehydration reactant
disease reliability
energy reproducibility
extreme heat event stored energy
feedback loop structure
function sugar
homeostasis sustainability
hydration system
infectious thermal energy
integrated approach tissue
levels of organization vaccine
macronutrients vector
malnutrition
matter

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GENETICS

FEEDING
THE

WORLD

GENETICS

Unit Issue

after steadily declining for a decade, world hunger is on the
rise, affecting 9.9% of the world’s population (close to 760 million
people!). From 2019 to 2020, the number of undernourished people
grew by as many as 161 million, a crisis driven largely by conflict,
climate change, and the COVID-19 pandemic. This means that more
than one in seven people are hungry or malnourished. The cost of
treating diseases resulting from malnutrition is about US$3.5 trillion
every year. How can we meet the nutritional needs and promote the
economic and social well-being of the world’s people?

For thousands of years, people have selected crops and animals with
desirable traits, such as drought tolerance and disease resistance, and
these crops and animals have been bred to produce offspring with
those traits. This selective breeding has produced modern varieties
of many organisms, such as sweet corn, dairy cows, and domestic
pets. It was not until the mid-19th century that scientists began to
understand that inherited traits are passed from parents to offspring
through genes. Today, scientists continue to learn more about how
genes work and how understanding genetics might help to solve
some of the practical problems we face today—such as increasing
crop productivity, curing diseases, and producing new fuels.

A technique that has been developed more recently is genetic
modification. Scientists have figured out how to manipulate genes
and can now transfer genes from one species into another to give the
target species a specific, desirable trait, such as herbicide resistance.
When a crop plant is modified to be herbicide resistant, farmers can
spray herbicide on their fields to kill weeds without harming their

C-2

herbicide resistant crops. This practice can save farmers time and
money as they control weeds that could cause a decrease in their
crop yields. But what trade-offs might come along with the benefits
of genetic modification?

Examine Figure A. What patterns do you notice in the data? What
questions do you have about these patterns?

20

Number of herbicide resistant 15
weed species in the U.S.
10

5

0
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Year

FIGURE A: Increase in herbicide resistant weed species in the U.S. after the introduction of
herbicide resistant soy plants in 1996.

LabAids SEUPnUPdeSGrsI Gtaennedtiicnsg3ethe benefits and trade-offs of genetic modification is
Figure: Celilms 3peoSBrt0a0n_0t1for making informed decisions about sustainable food
MyriadPropRreogd9u.5c/1t1ion. To better understand this issue, you will analyze and

interpret data about the patterns of inheritance of genes as they are

passed from parent to offspring. You will use models to help you

explain the role of genes in cells and how genes bring about traits,

Maps1 Maps2 andMaps3 you willMaps4 Maps5 generate arguments from evidence about the benefits

and trade-offs of using genetically modified organisms (which are
c60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0 c39 m7 y12 k0

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

sometimes referred to as GMOs). Ultimately, you will provide your

own recommendations about the use of genetically modifiedc0m30y70k0
c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

organisms for sustainable food production.c60m30y100k0 c50m20y75k0 c15m90y90k0 c90m55y40k0
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C-3



1 Superweeds! Where Did They Come From?

Investigative Phenomenon

Farmer Green was harvesting corn in his corn in his fields, Farmer Green had never
fields when he noticed something strange. come across weeds like these. He quickly
Very large weeds were growing between called the herbicide
the rows of corn. He thought this was odd company and learned
since he had applied two different that other farmers in
herbicides at the beginning of the growing nearby counties had
season. Herbicides are chemicals designed also reported these
to kill and prevent the growth of plants, herbicide resistant
such as weeds. Herbicides were first weeds, called
introduced in the 1940s to control weeds in superweeds.
crop fields and thus increase crop yields.
Herbicides usually kill any plant they come
into contact with. To grow crops where
herbicides are being widely applied, the
crops must be genetically modified to resist
the herbicide. Farmer Green’s corn is
genetically modified to be herbicide
resistant so that the corn plants won’t be
affected by the
application of herbicide.

In the past 10 years of
using herbicide resistant

FIGURE 1.1: As superweeds grow among
crops, they can cause damage by shading
out crop plants and by taking up nutrients from the soil.

C-5

GENETICS SCIENCE & GLOBAL ISSUES: BIOLOGY

Investigative Phenomenon

Superweeds are weeds that have acquired so tall that they shaded out the corn
a trait, like herbicide resistance, that makes growing nearby, making the corn shorter
them more difficult to control. The herbicide and have fewer ears. Farmer Green worried
company told Farmer Green that the most that the presence of superweeds would
problematic superweeds are those that are continue to significantly decrease his
resistant to one or more herbicides income in future growing seasons. He
commonly used on large-scale farms like wondered what he could do. His fields
his. The weeds in his corn fields were the were too large to weed by hand. To figure
first to be reported in his county. out how to respond to the problem of
superweeds in his fields, Farmer Green
After harvesting his corn, Farmer Green needed to first figure out how the
noticed that his crop yield was lower than superweeds got there in the first place.
usual. He thought that this may have
happened because the superweeds grew

Guiding Question

What are the different ways that superweeds could have
gotten into Farmer Green’s corn fields?

Materials

FOR EACH GROUP OF FOUR STUDENTS

set of 2 Superweeds cards

Procedure

1. Read the investigative phenomenon. With your group, discuss what
you think might be happening in Farmer Green’s fields, and be
prepared to share your thinking with the class. Be sure to share any
questions you have about the investigative phenomenon.

2. Obtain the Superweeds cards from your teacher, and review the map of
superweed reportings, the timeline of superweed reportings, and the
image of superweeds. Discuss your observations with your group, and
record any new ideas in your science notebook. Be sure to review and
answer the following questions:

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