Environmental Science

of the equator, whereas surface currents flow in a coun- Figure 18 ̈ The Pacific, Atlantic,
terclockwise direction south of the equator. Indian, and Arctic Oceans are inter-
connected into a single body of
The second largest ocean on Earth is the water, the world ocean, which covers
Atlantic Ocean. It covers a surface area of 70 percent of Earth’s surface.
81,630,000 km2, which is about half the
area of the Pacific Ocean. Like the Pacific
Ocean, the Atlantic Ocean can be divided
into a north half and a south half based on
the directions of surface current flow north
and south of the equator.

The Indian Ocean covers a surface area of
73,420,000 km2 and is the third-largest ocean on
Earth. It has an average depth of 3,890 m.

The smallest ocean is the Arctic Ocean, which covers
14,350,000 km2. The Arctic Ocean is unique because much of its
surface is covered by floating ice. This ice, which is called pack
ice, forms when either waves or wind drive together frozen sea-
water, known as sea ice, into a large mass.

EARTH SCIENCE CONNECTION

in vent communities can use hydro-
gen sulfide escaping from the vents
as an energy source. Some animals
that live in vent communities con-
sume these bacteria to obtain their
energy. Other animals have bacte-
ria living inside their bodies that
supply them with energy.

CRITICAL THINKING

̈ Over 300 species of organisms have been found in hydrothermal vent 1. Applying Processes Some sci-
communities, including species of tube worms that may grow to a entists have suggested that life
length of 3 m. may have originated in or near
hydrothermal vents because vent
water can reach temperatures as 300 species of organisms—all new to organisms are able to obtain their
high as 400°C. scientists—live near hydrothermal energy from chemicals in the
vents. These organisms include tube absence of sunlight. Does this sug-
The pressure at the ocean bot- worms, giant clams, mussels, shrimp, gestion seem realistic?
tom is tremendous. No sunlight pen- crabs, sea anemones, and octopuses.
etrates these depths, and 2. Making Predictions How
hydrothermal vents spew minerals How is life at hydrothermal might the creatures that live in
into their surroundings. Still, at least vents possible? Bacteria that live hydrothermal vent communities be
of benefit to humankind in the
future?

Section 3 The Hydrosphere and Biosphere 79

Ocean Water The difference between ocean water and fresh water

is that ocean water contains more salts. These salts have dissolved

out of rocks on land and have been carried down rivers

Other 0.7% into the ocean over millions of years. Underwater vol-

Potassium 1.1% canic eruptions also add salts to the ocean.
Most of the salt in the ocean is sodium chlo-

Calcium 1.2% Chlorine 55.0% ride, which is made up of the elements sodium
and chlorine. Figure 19 shows the concentra-

Sulfur 3.7% tion of these and other elements in ocean water.

The salinity of ocean water is the concentra-

Magnesium 7.7% tion of all the dissolved salts it contains. The

Sodium 30.6% average salinity of ocean water is 3.5 percent by
weight. The salinity of ocean water is lower in

places that get a lot of rain or in places where fresh

water flows into the sea. Salinity is higher where

Figure 19 ̈ This pie graph water evaporates rapidly and leaves the salts behind.
shows the percentages by weight Temperature Zones Figure 20 shows the temperature zones of

of dissolved solids found in ocean the ocean. The surface of the ocean is warmed by the sun. In

water. Sodium and chlorine, the two contrast, the depths of the ocean, where sunlight never reaches,
elements that form salt, are the have temperatures only slightly above freezing. Surface waters
most important dissolved solids in are stirred up by waves and currents, so the warm surface zone
ocean water. may be as much as 350 m deep. Below the surface zone is the

thermocline, which is a layer about 300 to 700 m deep where

the temperature falls rapidly with depth. If you have ever gone

swimming in a deep lake in the summer, you have probably

encountered a shallow thermocline. The boundary between the

warm and cold water is the thermocline.

Figure 20 ̈ Water in the ocean can

be divided into three zones based on

temperature.

0

Surface Zone The surface zone is the warm,
top layer of ocean water. Sunlight heats the top
200 100 m of the surface zone. Surface currents mix
the heated water with cooler water below.

Water depth (m) 400

Thermocline Water temperature in this
zone drops faster with increased depth
600 than it does in the other two zones.

800 Deep Zone This bottom layer extends
1,000 from the base of the thermocline to the
bottom of the ocean. The temperature in
this zone averages 2°C.

1,200
0 5 10 15 20 25 30

Water temperature (˚C)

80 Chapter 3 The Dynamic Earth

A Global Temperature Regulator One of the most important MATHPRACTICE
functions of the world ocean is to absorb and store energy from
sunlight. This capacity of the ocean to absorb and store energy The Influence of the
from sunlight regulates temperatures in Earth’s atmosphere. Gulf Stream The tempera-
ture of the British Isles is
The world ocean absorbs over half the solar radiation that moderated by the Gulf Stream.
reaches the planet’s surface. The ocean both absorbs and releases Plymouth, England, and Winnipeg,
heat more slowly than land does. As a consequence, the tempera- Canada, are located at approxi-
ture of the atmosphere changes much more slowly than it would mately 50° north latitude.
if there were no ocean on Earth. If the ocean did not regulate Plymouth, which is located in the
atmospheric and surface temperatures, the temperature would be southwest of England near the
too extreme for life on Earth to exist. Atlantic Ocean, has average low
temperatures of 4°C in December,
Local temperatures in different areas of the planet are also 3°C in January, and 3°C in
regulated by the world ocean. Currents that circulate warm water February. Winnipeg, which is
cause the land areas they flow past to have a more moderate cli- located in the interior of North
mate. For example, the British Isles are warmed by the Gulf America, has average low tempera-
Stream, which moves warm waters from lower latitudes toward tures of –18°C in December,
higher latitudes, as shown in Figure 21. –23°C in January, and –20°C in
February. What is the difference
■✓● Reading Check How does the absorption and release of heat by the in average low temperatures in
degrees Celsius between Plymouth
ocean differ from the absorption and release of heat by land? and Winnipeg?

Figure 21 ̈ In this infrared satellite
image, the Gulf Stream is moving
warm water (shown in red, orange,
and yellow) from lower latitudes
into higher latitudes. The British
Isles are warmed by the waters of
the Gulf Stream.

Section 3 The Hydrosphere and Biosphere 81

QuickLAB Ocean Currents Streamlike movements of water that occur at or
near the surface of the ocean are called surface currents. Surface
Make a currents are wind driven and result from global wind patterns.
Hydrothermal Vent Figure 22 shows the major surface currents of the world ocean.
Surface currents may be warm-water currents or cold-water cur-
Procedure rents. Currents of warm water and currents of cold water do not
1. Fill a large glass container or readily mix with one another. Therefore, a warm-water current
like the Gulf Stream can flow for hundreds of kilometers through
aquarium with very cold water. cold water without mixing and losing its heat.
2. Tie one end of a piece of
Surface currents can influence the climates of land areas they
string around the neck of a flow past. As we have seen, the Gulf Stream moderates the cli-
small bottle. mate in the British Isles. The Scilly Isles in England are as far
3. Fill the small bottle with hot north as Newfoundland in northeast Canada. However, palm
water, and add a few drops of trees grow on the Scilly Isles, where it never freezes, whereas
food coloring. Newfoundland has long winters of frost and snow.
4. Keep the small bottle upright
while you lower it into the glass Deep currents are streamlike movements of water that flow
container until it rests flat on very slowly along the ocean floor. Deep currents form when the
the bottom. cold, dense water from the poles sinks below warmer, less dense
Analysis ocean water and flows toward the equator. The densest and cold-
1. Did the food coloring indicate est ocean water is located off the coast of Antarctica. This cold
that the hot water and cold water sinks to the bottom of the ocean and flows very slowly
water mixed? northward to produce a deep current called the Antarctic Bottom
Water. The Antarctic Bottom Water creeps along the ocean floor
Figure 22 ̈ The oceans’ surface cur- for thousands of kilometers and reaches a northernmost point of
rents circulate in different directions approximately 40° north latitude. It takes several hundred years
in each hemisphere. for water in this deep current to make this trip northward.

82 Chapter 3 The Dynamic Earth

Fresh Water Figure 23 ̈ This photo shows a
network of tributaries flowing into
Most of the water on Earth is salt water in the ocean. A little more a river in the wetlands of southern
than 3 percent of all the water on Earth is fresh water. Most of the Louisiana.
fresh water is locked up in icecaps and glaciers that are so large
they are hard to imagine. For instance, the ice sheet that covers
Antarctica is as large as the United States and is up to 3 km thick.
The rest of Earth’s fresh water is found in lakes, rivers, wetlands,
the soil, rock layers below the surface, and in the atmosphere.

River Systems A river system is a network of streams that drains
an area of land. A river system contains all of the land drained by
a river, including the main river and all its tributaries. As shown
in Figure 23, tributaries are smaller streams or rivers that flow
into larger ones. Some river systems are enormous. For example,
most of the precipitation that falls between the Rocky Mountains
in the west and the Appalachian Mountains in the east eventually
drains into the Mississippi River. The Mississippi River system
covers about 40 percent of the contiguous United States.

Groundwater

Rain and melting snow sink into the ground and run off the land.
Some of this water ends up in streams and rivers, but most of it
trickles down through the ground and collects as groundwater.
Groundwater fulfills the human need for fresh drinking water and
supplies water for many agricultural and industrial uses. But ground-
water accounts for less than 1 percent of all the water on Earth.

Aquifers A rock layer that stores and allows the flow of ground-
water is called an aquifer. The surface of the land where water
enters an aquifer is called a recharge zone. Figure 24 shows the
location of aquifers in the contiguous United States.

Figure 24 ̈ Much of the United
States is underlain by aquifers. The
brown areas are rocks that contain
relatively little stored water.

Section 3 The Hydrosphere and Biosphere 83

www.scilinks.org The Biosphere

Topic: The Biosphere If the Earth were an apple, the biosphere would be its skin. This
Code: HE80162 comparison illustrates how small the layer of the Earth that can
support life is in relation to the size of the planet. The biosphere
Figure 25 ̈ This illustration of the is the narrow layer around Earth’s surface in which life can exist.
biosphere shows the concentration The biosphere is made up of the uppermost part of the geosphere,
of plant life on land and in the most of the hydrosphere, and the lower part of the atmosphere.
ocean. The colors represent differ- The biosphere extends about 12 km into the ocean and about
ent concentrations of plant life in 9 km into the atmosphere.
different regions.
Life exists on Earth because of several important factors. Most
life requires liquid water, moderate temperatures, and a source of
energy. The materials that organisms require must continually be
cycled. Gravity allows a planet to maintain an atmosphere and to
cycle materials. Suitable combinations of the things that organisms
need to survive are found only in the biosphere.

The biosphere is located near Earth’s surface because most of
the sunlight is available near the surface. Plants on land and in
the ocean are shown in Figure 25. Plants need sunlight to pro-
duce their food, and almost every other organism gets its food
from plants and algae. Most of the algae float at the surface of
the ocean. These tiny, free-floating, marine algae are known as
phytoplankton. Except for bacteria that live at hydrothermal
vents, most of the organisms that live deep in the ocean feed on
dead plants and animals that drift down from the surface.

■✓● Reading Check What makes life possible in the biosphere?

84 Chapter 3 The Dynamic Earth

Energy Flow in the Biosphere

When an organism in the biosphere dies, its body is broken down
and the matter in its body becomes available to other organisms.
This matter is continually recycled. Energy, however, must be sup-
plied constantly. The Eden Project, shown in Figure 26, is a closed
system that models this flow of matter and energy.

In a closed system, energy enters and leaves the system, but mat-
ter does not. The Earth is a closed system because the only thing
that enters in significant amounts is energy from the sun, and the
only thing that leaves in significant amounts is heat. Energy from
the sun is used by plants in the biosphere to make their food. When
an animal eats a plant, the energy stored in the plant is transferred
to the animal. The animal, in turn, may be eaten by another animal.
At each stage in the food chain, some of the energy is lost to the
environment as heat, which is eventually lost into space.

In an open system, both matter and energy are exchanged
between a system and the surrounding environment. The Earth
was once an open system. Matter was added to the early Earth as
it was hit by comets and meteorites. Now, however, little matter
reaches the Earth this way.

Figure 26 ̈ The Eden Project is an
attempt to model the biosphere. In
this project, plants from all over the
world live in a closed system. The
Eden Project is housed within a series
of domes that were constructed in an
old clay pit in England.

S E C T I O N 3 Review CRITICAL THINKING
5. Analyzing Processes Read about the ocean’s role
1. Name and describe each of the three major
processes in the water cycle. in regulating temperature under the heading “A
Global Temperature Regulator.” How might Earth’s cli-
2. Describe the properties of ocean water. mate change if the land area on Earth were greater
3. Describe the two types of ocean currents. than the area of the world ocean? READING SKILLS
4. Name two factors that confine living things to the
6. Analyzing Relationships Why is the human body
biosphere. considered an open system?

Section 3 The Hydrosphere and Biosphere 85

3C H A P T E R Highlights

1 The Geosphere Key Terms Main Ideas

2 The Atmosphere geosphere, 63 ̈ The solid part of the Earth that consists of
crust, 64 all rock, and the soils and sediments on Earth’s
3 The Hydrosphere and mantle, 65 surface, is the geosphere.
Biosphere core, 65
lithosphere, 65 ̈ Earth’s interior is divided into layers based
asthenosphere, 65 on composition and structure.
tectonic plate, 66
erosion, 70 ̈ Earth’s surface is broken into pieces called
tectonic plates, which collide, separate, or slip
atmosphere, 71 past one another.
troposphere, 72
stratosphere, 73 ̈ Earthquakes, volcanic eruptions, and
ozone, 73 mountain building are all events that occur
radiation, 74 at the boundaries of tectonic plates.
conduction, 74
convection, 74 ̈ Earth’s surface features are continually
greenhouse altered by the action of water and wind.

effect, 76 ̈ The mixture of gases that surrounds the
Earth is called the atmosphere.
water cycle, 77
evaporation, 77 ̈ The atmosphere is composed almost entirely
condensation, 77 of nitrogen and oxygen.
precipitation, 77
salinity, 80 ̈ Earth’s atmosphere is divided into four layers
fresh water, 83 based on changes in temperature that take
biosphere, 84 place at different altitudes.

̈ Heat is transferred in the atmosphere by
radiation, conduction, and convection.

̈ Some of the gases in Earth’s atmosphere
slow the escape of heat from Earth’s surface in
what is known as the greenhouse effect.

̈ The hydrosphere includes all of the water at
or near Earth’s surface.

̈ Water in the ocean can be divided into three
zones—the surface zone, the thermocline, and
the deep zone—based on temperature.

̈ The ocean absorbs and stores energy
from sunlight, regulating temperatures in the
atmosphere.

̈ Surface currents in the ocean affect the
climate of the land they flow near.

̈ The biosphere is the narrow layer at the sur-
face of the Earth where life can exist.

̈ Earth is a closed system because energy
enters and leaves Earth, but matter does not.

86 Chapter 3 Highlights

3C H A P T E R Review

Using Key Terms 12. Seventy-eight percent of Earth’s atmosphere
is made up of
Use each of the following terms in a separate a. oxygen.
sentence. b. hydrogen.
c. nitrogen.
1. tectonic plate d. carbon dioxide.
2. erosion
3. radiation 13. The ozone layer is located in the
4. ozone a. stratosphere.
5. salinity b. mesosphere.
For each pair of terms, explain how the meanings c. thermosphere.
of the terms differ. d. troposphere.
6. lithosphere and asthenosphere
7. conduction and convection 14. Convection is defined as the
8. crust and mantle a. transfer of energy across space.
9. evaporation and condensation b. direct transfer of energy.
c. trapping of heat near the Earth by gases.
STUDY TIP d. transfer of heat by currents.

The Importance of Nouns Most multiple- 15. Which of the following gases is not a green-
choice questions center around the definitions of house gas?
nouns. When you study, pay attention to the defi- a. water vapor
nitions of nouns that appear to be important in b. nitrogen
the text. These nouns will often be boldfaced key c. methane
terms or italicized secondary terms. d. carbon dioxide

Understanding Key Ideas 16. Liquid water turns into gaseous water vapor
in a process called
10. The thin layer at Earth’s surface where life a. precipitation.
exists is called the b. convection.
a. geosphere. c. evaporation.
b. atmosphere. d. condensation.
c. hydrosphere.
d. biosphere. 17. Currents at the surface of the ocean are
moved mostly by
11. The thin layer of the Earth upon which tec- a. heat.
tonic plates move around is called the b. wind.
a. mantle. c. salinity.
b. asthenosphere. d. the mixing of warm and cold water.
c. lithosphere.
d. outer core. 18. Which of the following statements about the
biosphere is not true?
a. The biosphere is a system closed to matter.
b. Energy enters the biosphere in the form of
sunlight.
c. Nutrients in the biosphere must be contin-
uously recycled.
d. Matter is constantly added to the biosphere.

Chapter 3 Review 87

3C H A P T E R Review

Short Answer Concept Mapping ?
??
19. How do seismic waves give scientists infor-
mation about Earth’s interior? 26. Use the following terms to create a concept
map: geosphere, crust, mantle, core, litho-
20. Explain the effect of gravity on Earth’s sphere, asthenosphere, and tectonic plate.
atmosphere.
Critical Thinking
21. Explain how convection currents transport
heat in the atmosphere. 27. Making Predictions The eruption of Mount
Pinatubo in 1991 reduced global temperature
22. Why does land that is near the ocean change by several tenths of a Celsius degree for sev-
temperature less rapidly than land that is eral years. Write a paragraph predicting what
located farther inland? might happen to Earth’s climate if several
large-scale eruptions took place at the same
23. Why is life on Earth confined to such a nar- time? WRITING SKILLS
row layer near the Earth’s surface?
28. Analyzing Processes Read about the heating
Interpreting Graphics of Earth’s surface and the absorption of
incoming solar radiation under the heading
The map below shows the different amounts of “Heating of the Atmosphere.” How might
chlorophyll in the ocean. Chlorophyll is the pig- the Earth be different if the Earth’s surface
ment that makes plants and algae green. absorbed greater or lesser percentages of
Chlorophyll identifies the presence of marine radiation? READING SKILLS
algae. The red and orange colors on the map
show the highest amounts of chlorophyll, the 29. Analyzing Processes Surface currents are de-
blue and purple colors on the map show the flected by continental landmasses. How might
smallest amounts of chlorophyll. Use the map to the pattern of Earth’s surface currents change
answer questions 24–25. if the Earth had no landmasses? Where on the
world ocean might the majority of warm sur-
24. Is there a greater concentration of marine face currents be located? Where would the
algae at location A or at location B? cold surface currents be located?

25. What conclusion can you reach about condi- Cross-Disciplinary Connection
tions in the parts of the ocean where marine
algae may prefer to live? 30. History Scientists believe that some human
migration between distant landmasses may
have taken place on rafts powered only by the
wind and ocean currents. Look at Figure 22,
which shows the Earth’s surface currents.
Hypothesize potential migratory routes these
early seafarers may have followed.

Portfolio Project

31. Plotting Seismic Activity Most earthquakes
take place near tectonic plate boundaries. Using
the encyclopedia, the Internet, or another
source, find at least 20 locations where major
earthquakes took place during the 20th cen-
tury. Plot these locations on a map of the world
that shows Earth’s tectonic plates. Did the
majority of earthquakes occur at or near tec-
tonic plate boundaries?

88 Chapter 3 Review

Area of oceansMATH SKILLS READING SKILLS
(in millions of km2)
Depth of oceans (m)Use the graph below to answer questions 32–33.Read the passage below, and then answer
32. Analyzing Data Rearrange the oceans in the questions that follow.

order of highest depth-to-area ratio to lowest Researchers at Ohio State University have
depth-to-area ratio. developed a video camera that photographs the
33. Making Calculations On the graph, you are foamy bubbles left when a wave breaks on a
given the average depths of the four oceans. beach. Software analyzes images from the cam-
From these data, calculate the average depth era and uses the movement of the foam to cal-
of the world ocean. culate the speed and direction of currents along
the shore. How do we know that the software
180 4,500 produces an accurate picture of the currents?
To test the software, researchers set up a video
160 Area 4,000 camera on the beach at Duck, North Carolina,
140 Depth 3,500 where dozens of underwater sensors already
measure currents directly. A comparison of the
120 3,000 currents detected by the video camera and by
the sensors showed a close match. The Ohio
100 2,500 State University researchers believe data from
the video camera would be even more accurate
80 2,000 if the camera were directly above the breaking
waves. The researchers’ next step will be to
60 1,500 mount the camera on a blimp suspended over a
beach in Monterey, California.
40 1,000
1. According to the passage, which of the
20 500 following conclusions is true?
a. The video camera uses wave speed to
00 calculate the direction and speed of
Pacific Atlantic Indian Arctic currents.
Ocean Ocean Ocean Ocean b. Underwater sensors are less accurate at
measuring currents than video cameras.
WRITING SKILLS c. Video cameras do not measure cur-
rents directly.
34. Communicating Main Ideas Describe the d. Underwater sensors detect the move-
three important ways in which the movement ment of foam.
of energy takes place in Earth’s atmosphere.
2. What is the importance of foam in mea-
35. Writing Persuasively Write a persuasive suring currents?
essay that explains why the Earth today a. Foam can be measured directly by both
should be regarded as a closed system for video cameras and underwater sensors.
matter rather than an open system. b. The movement of foam can be used to
calculate the direction and speed of a
36. Outlining Topics Write a one-page outline current.
that describes some of the important inter- c. Foam from breaking waves can be
actions that take place in the Earth system. detected by placing a video camera at
any point on a beach.
d. both (b) and (c)

Chapter 3 Review 89

3C H A P T E R Standardized Test Prep

Understanding Concepts Reading Skills

Directions (1–4): For each question, write on a Directions (7–9): Read the passage below. Then
separate sheet of paper the letter of the correct answer the questions.
answer.
A volcano is a mountain built from melted
1 What is the cool, rigid, outermost layer of rock that rises from the Earth’s interior to its
surface. Volcanoes may occur on land or under
the Earth? the sea, where they eventually break the ocean
A. the asthenosphere surface as islands. They are often located near
B. the geosphere tectonic plate boundaries.
C. the lithosphere
D. the mesosphere Volcanic eruptions can be devastating to
local economies, cause great human loss, and
2 The collision of tectonic plates creates what affect global climate for several years. In large
eruptions, clouds of volcanic ash and sulfur-
geologic feature? rich gases may reach the upper atmosphere. In
F. mesosphere addition, ash that falls to the ground can cause
G. inner core buildings to collapse under its weight, bury
H. mountains crops, and damage the engines of vehicles.
I. hydrothermal vents
Major volcanic eruptions, such as the
3 What determines the weather we experience eruption of Mount St. Helens, can change
Earth’s climate for several years.
on Earth?
A. movement of water over land masses 7 Where are most of the Earth’s volcanoes
B. gases trapping heat near Earth’s surface
C. absorption of radiation by the located?
A. within tropical rain forests
thermosphere B. near Mount St. Helens
D. air constantly moving through Earth’s C. near the Antarctic
D. near tectonic plate boundaries
atmosphere
8 What happens during a large volcanic
4 What is the difference between evaporation
eruption?
and condensation? F. The ash causes islands to form.
F. Evaporation is the first stage of the water G. The ash rises from the Earth’s interior.
H. The ash and sulfur-rich gases may reach
cycle; condensation is the last stage.
G. Evaporation is the change from water to the upper atmosphere.
I. The ash falls to the ground and produces
vapor; condensation is the change from
vapor to water. dust storms.
H. Evaporation is the process where water is
heated by the sea; condensation is the 9 Volcanic eruptions can have a global effect
process where water droplets fall from
clouds. on the Earth by
I. Evaporation is the process where water A. changing the Earth’s climate for several
vapor forms droplets; condensation is the
process where water vapor forms clouds. years
B. changing tectonic plates
Directions (5–6): For each question, write a short C. changing local economies
response. D. causing buildings to collapse

5 Differentiate between the three composi-

tional layers of Earth.

6 What is the purpose of the Richter scale?

90 Chapter 3 Standardized Test Prep

Interpreting Graphics

Directions (10–12): For each question below, record the correct answer on
a separate sheet of paper.

0 Which of the following statements is true?

F. The world ocean covers 70% of Earth’s surface.
G. The world ocean is the body of water south of Africa.
H. The world ocean has little effect on Earth’s environment.
I. The world ocean consists of the Atlantic and Pacific Oceans.

The illustration below shows elements in the ocean’s water. Use it to answer
question 11.

Elements in Ocean Water

Other 0.7%

Potassium 1.1% Chlorine 55.0%
Calcium 1.2%

Sulfur 3.7%
Magnesium 7.7%

Sodium 30.6%

q What fraction of ocean salinity is not sodium and chlorine? Test

A. 12.1% If you come upon a
B. 14.6% word you do not know,
C. 12.4% try to identify its pre-
D. 14.4% fix, suffix, or root.
Sometimes knowing
w The Atlantic Ocean covers 81,630,000 km2 of Earth’s surface area even one part of the
word will help you
and the Pacific Ocean covers 165,640,000 km2. How much answer the question.
more surface area is covered by the Pacific Ocean than the Atlantic
Ocean, in millions of km2?
F. 72
G. 84
H. 96
I. 108

Chapter 3 Standardized Test Prep 91

3C H A P T E R Exploration Lab: MODELING

Objectives Beaches

̈ Examine models that show how Almost one-fourth of all of the structures that have been built
the forces generated by wave within 150 m of the U.S. coastline, including the Great Lakes,
action build, shape, and erode will be lost to beach erosion over the next 60 years, according
beaches. to a June 2000 report released by the Federal Emergency
Management Agency (FEMA). The supply of sand for most
̈ USING SCIENTIFIC METHODS beaches has been cut off by dams built on rivers and streams that
would otherwise carry sand to the sea. Waves generated by
Hypothesize ways in which storms also erode beaches. Longshore currents, which are gener-
beaches can be preserved from the ated by waves that break at an angle to a shoreline, transport
erosive forces of wave activity. sediment continuously and change the shape of a shoreline.

Materials You will now observe a series of models. These models will
help you understand how beaches can be both washed away and
metric ruler protected from the effects of waves and longshore currents.
milk cartons, empty, small (2)
pebbles Procedure
plaster of Paris
plastic container (large) or long 1. One day before you begin the investigation, make two plas-
ter blocks. Mix a small amount of water with plaster of Paris
wooden box lined with plastic until the mixture is smooth. Add five or six small rocks to
rocks, small the mixture for added weight. Pour the plaster mixture into
sand, 5 to 10 lb the milk cartons. Let the plaster harden overnight. Carefully
wooden block, large peel the milk cartons away from the plaster.

̈ Step 2 Use a wooden block to 2. Prepare a wooden box lined with plastic or other similar
generate waves at the end of the con- large, shallow container. Make a beach by placing a mixture
tainer opposite the beach. of sand and small pebbles at one end of the container. The
beach should occupy about one-fourth the length of the con-
92 Chapter 3 Exploration Lab tainer. See step 2. In the area in front of the sand, add water
to a depth of 2 to 3 cm. Use the large wooden block to gener-
ate several waves by moving the block up and down in the
water at the end of the container opposite the beach.
Continue this wave action until about half the beach has
moved. Record your observations.

3. Remove the water, and rebuild the beach.
In some places, breakwaters have been built
offshore in an attempt to protect beaches
from washing away. Build a breakwater by
placing two plaster blocks across the mid-
dle of the container. Using the metric ruler,
leave a 4 cm space between the blocks. See
step 3. Use a wooden block to generate
waves. Describe the results.

4. Drain the water, and make a new beach
along one side of the container for about
half its length. See step 4. Using the wooden
block, generate a series of waves from the
same end of the container as the end of the
beach. Record your observations.

5. Rebuild the beach along the same side of the container. A ̈ Step 3 Build a breakwater by plac-
jetty or dike can be built out into the ocean to intercept and ing two plastic blocks across the mid-
break up a longshore current. Make a jetty by placing one of dle of the container.
the small plaster blocks in the sand. See step 5. As you did in
the previous steps, use the wooden block to generate waves. ̈ Step 4 Make a beach lengthwise
Describe the results. along one side of the container. The
length of the beach should equal
6. Remove the wet sand, and put it in a container. Dispose of one-half the length of the container.
the water. (Note: Follow your teacher’s instructions for dis-
posal of the sand and water. Never pour water containing
sand into a sink.)

Analysis

1. Describing Events In step 2 of the procedure, what hap-
pened to the beach when water was first poured into the
container? What happened to the particles of fine sand?
Predict what would happen to the beach if it had no source
of additional sand.

2. Analyzing Results In step 3 of the procedure, did the break-
water help protect the beach from washing away?

3. Describing Events What happened to the beach that you
made in step 4 of the procedure? What happened to the
shape of the waves along the beach?

4. Analyzing Results What effect did the jetty have on the
beach that you made in step 5 of the procedure?

Conclusions

5. Drawing Conclusions What can be done to preserve a beach
area from being washed away as a result of wave action and
longshore currents?

6. Drawing Conclusions What can be done to preserve a
beach area that has been changed as a result of excessive
use by people?

Extension

1. Building Models Make a beach that would be in danger of
being washed away by a longshore current. Based on what
you have learned, build a model in which the beach would
be preserved by a breakwater or jetties. Explain how your
model illustrates ways in which longshore currents can be
intercepted and broken up.

̈ Step 5 Place one of the small plas-
ter blocks in the sand to make a jetty.

Chapter 3 Exploration Lab 93

EARTH SCIENCE CONNECTION

EARTHQUAKE HAZARD MAP OF THE CONTIGUOUS UNITED STATES

MAP SKILLS

Use the earthquake-hazard map of the contiguous 4. Inferring Relationships Most earthquakes take
United States to answer the questions below. place near tectonic plate boundaries. Based on the
hazard levels, where do you think a boundary
1. Using a Key Which area of the contiguous United between two tectonic plates is located in the
States has a very high earthquake-hazard level? United States?

2. Using a Key Determine which areas of the con- 5. Forming a Hypothesis The New Madrid earth-
tiguous United States have very low earthquake- quake zone passes through southeastern Missouri
hazard levels. and western Tennessee and has experienced some
of the most widely felt earthquakes in U.S. history.
3. Analyzing Relationships In which areas of the Yet this earthquake zone lies far from any tectonic
contiguous United States would scientists most likely plate boundary. Propose a hypothesis that would
set up earthquake-sensing devices? explain these earthquakes.

94 Chapter 3 Maps in Action

EARTH SCIENCE CONNECTION

TRACKING OCEAN CURRENTS WITH TOY DUCKS

Scientists usually study ocean cur- 29,000 plastic toys. Ten months and plastic packages. Did the pack-
rents by releasing labeled drift later, the toys—blue turtles, yellow ages make them sink when they were
bottles from various points and ducks, red beavers, and green first released? To find the answer, sci-
recording where they are found. frogs—began washing up near entists obtained some of the pack-
However, only about 2 percent of Sitka, Alaska. In the following aged toys from the manufacturer in
drift bottles are recovered, so this years, toys began to be found far- China and dropped them in buckets
type of research takes a long time. ther north, in the Bering Sea. The of sea water. The glue in the packag-
A large toy spill is helping scien- map below shows where the con- ing dissolved within a day and
tists track surface currents in the tainers went overboard and where released the toys. So it was obvious
Pacific Ocean. the toys were found. that the toys had floated most of the
way to where they were found.
Toys Ahoy! The Data in the Deep Blue Sea
Experiments showed how fast
In 1993, thousands of bathtub toys Obviously, the toys had traveled east the toys moved under the influence
were found on Alaskan beaches. from where they were spilled. But of wind without any current. The
When oceanographers heard about what did this reveal about the cur- toys had floated past a weather sta-
this, they placed advertisements in rents in the North Pacific? The tion where many drift bottles had
newspapers up and down the answer is not as obvious as it might been released and also past the place
Alaskan coast asking people who seem. First, floating objects are where 61,000 shoes had fallen off a
found the toys to call them. They moved by wind as well as by cur- ship in 1990. About two percent of
discovered that in 1992 a container rents. The floating toys stuck up the shoes were recovered in Alaska.
ship that was traveling northwest of about 4 cm above the water, which Comparing data from the toys and
Hawaii ran into a storm. Several may have caused them to be moved the shoes with other data from as
containers were washed overboard by the wind as well as by currents. far back as 1946, the researchers
and burst open. One of these held The toys started out in cardboard concluded that the current across
the northeast Pacific Ocean changes
̈ This map is a computer simulation that shows the possible trajectory of the little from year to year. But the data
toys and their estimated locations on certain dates as they floated across the showed that in 1990 and 1992 the
Pacific Ocean from the point of the spill to recovery points in Alaska. current was unusually far north.

Data that help us understand
ocean currents and many other natu-
ral processes come not just from sci-
entific experiments. Data sometimes
come from the most unusual sources.

What Do You Think?

Take a look at Figure 22. If the
toys continue to be carried by
surface currents, where might
they be found in the future?
How might the height of the
toys above the water’s surface
have influenced the speed at
which they traveled?

Chapter 3 Society and the Environment 95

ECOLOGY

96

2U N I T

CHAPTER 4

The Organization
of Life

CHAPTER 5

How Ecosystems Work

CHAPTER 6

Biomes

CHAPTER 7

Aquatic Ecosystems

This Australian plant called the
fork-leafed sundew gets the nutri-
ents that it needs to survive by
dissolving insects that get stuck
on its sticky tips.

97

The Organization of Life 4C H A P T E R

1 Ecosystems: Everything

Is Connected

2 Evolution

3 The Diversity of Living

Things

PRE-READING ACTIVITY

Layered
Book
Before you
read this
chapter, create the FoldNote
entitled “Layered Book”
described in the Reading and
Study Skills section of the
Appendix. Label the tabs of
the layered book with
“Ecosystem,” “Population,”
“Community,” and
“Habitat.” As you read the
chapter, write information
you learn about each
category
under
the
appro-
priate
flap.

A coral reef is an ecosystem that
contains a wide variety of species.
How many different species can you
find in this photograph?

98 Chapter 4 The Organization of Life

SECTION 1

Ecosystems: Everything Is Connected

You may have heard the concept that in nature everything is Objectives
connected. What does this mean? Consider the following example.
In 1995, scientists interested in controlling gypsy moths, which ̈ Distinguish between the biotic and
kill oak trees, performed an experiment. The scientists removed abiotic factors in an ecosystem.
most mice, which eat young gypsy moths, from selected plots of
oak forest. The number of gypsy moth eggs and young increased ̈ Describe how a population differs
dramatically. The scientists then added acorns to the plots. Mice from a species.
eat acorns. The number of mice soon increased, and the number
of gypsy moths declined as the mice ate them as well. ̈ Explain how habitats are impor-
tant for organisms.
This result showed that large acorn crops can suppress gypsy
moth outbreaks. Interestingly, the acorns also attracted deer, Key Terms
which carry parasitic insects called ticks. Young ticks soon
infested the mice. Wild mice carry the organism that causes Lyme ecosystem
disease. Ticks can pick up the organism when they bite mice. biotic factor
Then the ticks can bite and infect humans. This example shows abiotic factor
that in nature, things that we would never think are connected— organism
mice, acorns, ticks, and a human disease—can be linked to each species
other in a complex web. population
community
habitat

Defining an Ecosystem

The mice, moths, oak trees, deer, and ticks in the previous example
are all part of the same ecosystem. An ecosystem (EE koh SIS tuhm)
is all of the organisms living in an area together with their physical
environment. An oak forest is an ecosystem. The coral reef on
the opposite page is an ecosystem. Even a vacant lot, as shown
in Figure 1, is an ecosystem.

www.scilinks.org

Topic: Ecosystems
Code: HE80466

Figure 1 ̈ This vacant lot is actually
a small ecosystem. It includes various
organisms, including plants and
insects, as well as soil, air, and sunlight.

Section 1 Ecosystems: Everything Is Connected 99

Figure 2 ̈ Like all ecosystems, this
coastal region in France contains
certain basic components. What
components can you identify?

Geofact Ecosystems Are Connected People often think of ecosystems as
isolated from each other, but ecosystems do not have clear
The Living Soil Soil, which is part boundaries. Things move from one ecosystem into another. Soil
of nearly all ecosystems on land, is washes from a mountain into a lake, birds migrate from Michigan
formed in part by living organisms, to Mexico, and pollen blows from a forest into a field.
which break down dead leaves and
organisms. Small, plantlike organ- The Components of an Ecosystem
isms even help break down rocks!
In order to survive, ecosystems need certain basic components.
Figure 3 ̈ This caribou is a biotic These are energy, mineral nutrients, carbon dioxide, water, oxy-
factor in a cold, northern ecosystem gen, and living organisms. As shown in Figure 2, plants and soil
in Denali National Park, Alaska. are two of the most obvious components of most land ecosys-
tems. The energy in most ecosystems comes from the sun.

To appreciate how all of the things in an ecosystem are con-
nected, think about how a car works. The engine alone is made
up of hundreds of parts that all work together. If even one part
breaks, the car might not run. Likewise, if one part of an ecosys-
tem is destroyed or changes, the entire system may be affected.

Biotic and Abiotic Factors An ecosystem is made up of both
living and nonliving things. Biotic factors are the living and once
living parts of an ecosystem, including all of the plants and animals.
Biotic factors include dead organisms, dead parts of organisms,
such as leaves, and the organisms’ waste products. Abiotic (ay bie
AHT ik) factors are the nonliving parts of the ecosystem. Abiotic
factors include air, water, rocks, sand, light, and temperature.
Figure 3 shows several biotic and abiotic factors in an Alaskan
ecosystem.

Scientists organize living things into levels. Figure 4 shows
how an ecosystem fits into the organization of living things.

■✓● Reading Check What is the difference between a biotic factor and

an abiotic factor? (See the Appendix for answers to Reading Checks.)

100 Chapter 4 The Organization of Life

Organisms An organism is an individual living thing. You are an Figure 4 ̈ An individual organism is
organism, as is an ant crawling across the floor, an ivy plant on part of a population, a community,
the windowsill, and a bacterium in your intestines. an ecosystem, and the biosphere.

A species is a group of organisms that can mate to produce Figure 5 ̈ Two of the populations
fertile offspring. All humans, for example, are members of the shown here are a population of purple-
species Homo sapiens, while all black widow spiders are mem- flowered musk thistle (left) and a herd
bers of the species Latrodectus mactans. Every organism is a of bison (right).
member of a species.

Populations Members of a species may not all live in the same
place. Field mice in Maine and field mice in Florida will never
interact even though they are members of the same species. An
organism lives as part of a population. A population is all the
members of the same species that live in the same place at the
same time. For example, all the field mice in a corn field make
up one population of field mice.

An important characteristic of a population is that its members
usually breed with one another rather than with members of
other populations. The bison in Figure 5 (right) will usually
mate with another member of the same herd,
just as the wildflowers (left) will usually be
pollinated by other flowers in the same field.

Section 1 Ecosystems: Everything Is Connected 101

Figure 6 ̈ Salamanders, such as this Communities Every population is part of a community, a group
red-backed salamander, live in habi- of various species that live in the same place and interact with
tats that are moist and shaded. each other. A community is different from an ecosystem because a
community is made up only of biotic components. A pond commu-
S E C T I O N 1 Review nity, for example, includes all of the populations of plants, fish,
and insects that live in and around the pond. All of the living
things in an ecosystem belong to one or more communities.

Communities differ in the types and numbers of species they
have. A land community is often characterized by the types of
plants that are dominant. These plants determine the other organ-
isms that can live in this community. For example, the dominant
plant in a Colorado forest might be its ponderosa pine trees. This
pine community will have animals, such as squirrels, that live in
and feed on these trees.

Habitat

The squirrels mentioned above live in a
pine forest. All organisms live in particular
places. The place an organism lives is called
its habitat. A howler monkey’s habitat is
the rain forest and a cactus’s habitat is a
desert. The salamander shown in Figure 6 is
in its natural habitat, the damp forest floor.

Every habitat has specific biotic and abi-
otic factors that the organisms living there
need to survive. A coral reef contains sea
water, coral, sunlight, and a wide variety of
other organisms. If any of these factors
change, then the habitat changes.

Organisms tend to be very well suited to
their natural habitats. Indeed, animals and
plants cannot usually survive for long peri-
ods of time away from their natural habitats. For example, a fish
that lives in the crevices of a coral reef will die if the coral reef is
destroyed.

■✓● Reading Check Why is an organism’s habitat important for that

organism? (See the Appendix for answers to Reading Checks.)

1. List the abiotic and biotic factors you see in the CRITICAL THINKING
northern ecosystem in Figure 3. 5. Analyzing Relationships Write your own defini-

2. Describe a population not mentioned in this section. tion of the term community, using the terms biotic
factors and abiotic factors. WRITING SKILLS
3. Describe which factors of an ecosystem are not part
of a community. 6. Understanding Concepts Why might a scientist
say that an animal is becoming rare because of
4. Explain the difference between a population and a habitat destruction?
species.

102 Chapter 4 The Organization of Life

SECTION 2

Evolution

Organisms tend to be well suited to where they live and what they Objectives
do. Figure 7 shows a chameleon (kuh MEEL ee uhn) capturing an
insect. Insects are not easy to catch, so how does the chameleon do ̈ Explain the process of evolution by
it? Chameleons can change the color and pattern of their skin, and natural selection.
then blend into their backgrounds. Their eyes are raised on little,
mobile turrets that enable the lizards to look around without mov- ̈ Explain the concept of adaptation.
ing. An insect is unlikely to notice such an animal sitting motionless ̈ Describe the steps by which a
on a branch. When the insect moves within range, the chameleon
shoots out an amazingly long tongue to grab the insect. population of insects becomes
resistant to a pesticide.
Evolution by Natural Selection
Key Terms
In 1859, English naturalist Charles Darwin observed that organ-
isms in a population differ slightly from each other in form, natural selection
function, and behavior. Some of these differences are hereditary evolution
(huh RED i TER ee)—that is, passed from parent to offspring. adaptation
Darwin proposed that the environment exerts a strong influence artificial selection
over which individuals survive to produce offspring. Some indi- resistance
viduals, because of certain traits, are more likely to survive and
reproduce than other individuals. Darwin used the term natural Connection to Geology
selection to describe the survival and reproduction of organisms
with particular traits. Darwin and Fossils In the
1800s, fossil hunting was a popu-
Darwin proposed that over many generations natural selection lar hobby. The many fossils that
causes the characteristics of populations to change. A change in people found started arguments
the genetic characteristics of a population from one generation to about where fossils come from.
the next is known as evolution. Darwin’s theory of evolution pro-
posed that fossils are the remains
■✓● Reading Check How is natural selection related to the process of of extinct species from which
modern species evolved. When his
evolution? book on the theory of evolution
was first published in 1859, it
became an immediate bestseller.

www.scilinks.org

Topic: Evolution
Code: HE80546

Figure 7 ̈ A chameleon catches an
unsuspecting insect that has strayed
within range of the lizard’s long, fast-
moving tongue.

Section 2 Evolution 103

Table 1 ̄ Nature Selects Darwin thought that nature selects for certain
Premises traits, such as sharper claws or lighter feathers, because organisms
with these traits are more likely to survive and reproduce. For
example, lions that have the trait of sharper claws can kill their
prey more easily than lions with duller claws. Thus, lions with
sharper claws are more likely to survive and reproduce. Over time,
the lion population includes a greater and greater proportion of
lions with sharper claws. As the populations of a given species
change, so does the species. Table 1 summarizes the premises of
Darwin’s theory of evolution by natural selection. Darwin proposed
his theory after drawing a conclusion based on these premises.

Evolution by Natural Selection

Conclusion

1. Individuals in a population vary in each generation. Based on these four premises, individuals
with genetic traits that make them more
2. Some of these variations are genetic, or inherited. likely to grow up and reproduce in the
existing environment will become more
3. More individuals are produced than live to grow up and common in the population from one
reproduce. generation to the next.

4. Individuals with some genes are more likely to survive
and reproduce than individuals with other genes.

Darwin’s Finches

Before Charles Darwin formulated but different species have differently ̈ Notice the beaks in the two
his theory of evolution, he sailed specialized bills adapted to eating species of Darwin’s finches. What
around the coast of South America. different types of food. Some species do you think these finches eat?
The plants and animals he saw had a have large, parrotlike bills adapted to
great effect on his thinking about cracking big seeds, some species Princeton University biologists
how modern organisms had origi- have slim bills that are used to sip Peter and Rosemary Grant have
nated. He was surprised by the nectar from flowers, and some spent 25 years studying Darwin’s
organisms he saw on islands because species have even become insect finches on Daphne Major, one of
they were often unusual species eaters. Darwin speculated that all the Galápagos Islands. Here, one
found nowhere else. the Galápagos finches had evolved
from a single species of seed-eating
He was particularly impressed finch that found its way to the
by the organisms in the Galápagos islands from the South American
Islands, an isolated group of volcanic mainland. Populations of the finches
islands in the Pacific Ocean west of became established on the various
Ecuador. The islands contain 13 islands, and the finches that survived
unique species of birds, which have were those able to eat what they
become known as Darwin’s finches. found on their island.
All the species look generally similar,

104 Chapter 4 The Organization of Life

Figure 8 shows an example of evolution in which a population of Figure 8 ̈ These steps show
deer become isolated in a cold area. Many die, but some have genes the evolution of thicker fur in a
for thicker, warmer fur. These deer are more likely to survive, and population of deer.
their young with thick fur are also more likely to survive to repro-
duce. The deer’s thick fur is an adaptation, an inherited trait that
increases an organism’s chance of survival and reproduction in a
certain environment.

In the cold mountain climate, deer with
thicker fur are more likely to survive.

These deer live in a warm climate.
Some have thicker fur than others.

Some deer become As years pass, each
separated from the generation has a
rest of the group. greater proportion
of deer with thick fur.
After many generations,
most deer have thick fur.

species, the medium ground finch, eat became scarce. Only finches food source. Second, shifts in rain-
has a short, stubby beak and eats that had large beaks survived. Large fall determine which plants live and
seeds as well as a few insects. The beaks allowed them to eat larger die, further limiting the finches’
ground finches have few predators. seeds from the larger plants that food sources.
The Grants found that the main fac- had survived the drought.
tor that determined whether a finch The islands are strongly influ-
lived or died was how much food The finches that survived the enced by El Niño and La Niña
was available. During a long drought passed their genes for weather patterns. These weather
drought in 1977, many plants died large beaks to their offspring. Two patterns produce alternating peri-
and the small seeds that the finches years later, the Grants found that ods of very wet and very dry
the beaks of medium ground weather in a relatively short time.
finches on Daphne Major were The plants vary, depending on the
nearly 4 percent larger, on aver- weather pattern, exerting different
age, than they had been before selective pressures on the animals
the drought. The Grants had that depend on the plants for food.
observed evolution occurring in
birds over a short period of time, CRITICAL THINKING
something that had seldom been
seen before. 1. Analyzing Relationships
Could the finches that evolved
Two factors make the Galápagos bigger beaks in this study evolve
Islands well suited for researching smaller beaks some day?
evolution. First, there are few plant
species in the community, so the
finches have little choice in their

Section 2 Evolution 105

Figure 9 ̈ This Hawaiian honey- Coevolution Organisms evolve adaptations to other organisms
creeper is using its curved beak to sip and to their physical environment. The process of two species
nectar from a lobelia flower. evolving in response to long-term interactions with each other
is called coevolution (koh EV uh LOO shuhn). One possible
MATHPRACTICE example is shown in Figure 9. The honeycreeper’s beak is
long and curved, which lets it reach the nectar at the base
Plumper Pumpkins of the long, curved flower. The flower has evolved struc-
Each year a farmer saves tures that cause the bird to get pollen on its head as it sips
and plants only the seeds from the nectar. When the bird moves to another flower, some of
his largest pumpkins. Suppose that the pollen rubs off. In this way, the bird helps lobelia plants
he starts with pumpkins that average reproduce. The honeycreeper’s adaptation for obtaining more
5 kg and each year grows pumpkins
that are 3 percent more massive, on nectar is a long, curved beak. The plant has two adaptations for
average, than those he grew the year greater pollination. One is sweet nectar, which attracts the birds.
before. What will be the average The other is a flower structure that forces pollen onto a bird’s head
mass of his pumpkins after 10 years? when the bird sips the nectar.

Evolution by Artificial Selection

Many populations of plants and animals do not live in the wild
but are cared for by humans. People control how these organisms
reproduce and therefore how they evolve. The two species in
Figure 10 are closely related. Over thousands of years, humans
bred the ancestors of today’s wolves to produce the variety of
dog breeds. The selective breeding of organisms by humans for
specific characteristics is called artificial selection.

The fruits, grains, and vegetables we eat were also produced
by artificial selection. By selecting for traits such as size and
sweetness, farmers directed the evolution of crop plants. As a
result, crops produce fruits, grains, and roots that are larger,
sweeter, and easier to harvest than their wild relatives. Native
Americans cultivated the ancestor of today’s corn from a grasslike
plant in the mountains of Mexico. Modern corn is very different
from the wild plant that was its ancestor.

■✓● Reading Check How is artificial selection different from natural

selection?

Figure 10 ̈ As a result of artificial
selection, the Chihuahua on the right
looks very different from its wolf
ancestor on the left.

106 Chapter 4 The Organization of Life

Insect pests are sprayed with When the same insecticide is used
an insecticide. Only a few again, more insects survive because
resistant insects survive. more of them are resistant.

The survivors
pass the trait for
insecticide resistance
to their offspring.

Evolution of Resistance Figure 11 ̈ The evolution of resist-
ance to a pesticide starts when the
Sometimes humans cause populations of organisms to evolve pesticide is sprayed on the corn.
unwanted adaptations. You may have heard about insect pests Most of the insects are killed, but a
that are resistant to pesticides and about bacteria that are resist- few resistant ones survive. After each
ant to antibiotics. What is resistance, and what does it have to spraying, the insect population con-
do with evolution? tains a larger proportion of resistant
organisms.
Resistance is the ability of one or more organisms to tolerate
a particular chemical designed to kill it. An organism may be FIELD ACTIVITY
resistant to a chemical when it contains a gene that allows it to
break the chemical down into harmless substances. By trying to Artificial Selection Look around
control pests and bacteria with chemicals, humans promote the your school grounds and the area
evolution of resistant populations. around your home for possible
examples of artificial selection.
Pesticide Resistance Consider the evolution of pesticide Observe and report on any exam-
resistance among corn pests, as shown in Figure 11. A pesticide ples you can find.
is sprayed on corn to kill grasshoppers. Most of the grasshop-
pers die, but a few survive. The survivors happen to have a ver- Dogs are one example of artifi-
sion of a gene that protects them from the pesticide. The cial selection mentioned in this
surviving insects pass on the gene to their offspring. Each time chapter, but you will probably
the corn is sprayed, insects that are resistant to the pesticide find many more plant examples.
will have a greater chance of survival and reproduction. As a Record your observations in
result, the insect population will evolve to include more and your EcoLog.
more resistant members.

S E C T I O N 2 Review

1. Explain what an adaptation is, and provide three CRITICAL THINKING
examples.
5. Understanding Concepts Read the description of
2. Explain the process of evolution by natural selection. evolution by natural selection in this section and
describe the role that the environment plays in the
3. Describe one way in which artificial selection can theory. READING SKILLS
benefit humans.
6. Identifying Relationships A population of rabbits
4. Explain how a population of insects could become evolves thicker fur in response to a colder climate. Is
resistant to a pesticide. this an example of coevolution? Explain your answer.

Section 2 Evolution 107

SECTION 3

The Diversity of Living Things

Objectives Life on Earth is incredibly diverse. Take a walk in a park, and
you will see trees, birds, insects, and maybe fish in a stream. All
̈ Name the six kingdoms of organ- of these organisms are living, but they are all very different from
isms and identify two characteris- one another.
tics of each.
Most scientists classify organisms into six kingdoms, as
̈ Explain the importance of bacteria described in Table 2, based on different characteristics. Members
and fungi in the environment. of the six kingdoms get their food in different ways and are made
up of different types of cells, the smallest unit of biological
̈ Describe the importance of pro- organization. The cells of animals, plants, fungi, and protists con-
tists in the ocean environment. tain a nucleus (NOO klee uhs), which consists of a membrane
that surrounds a cell’s genetic material. Bacteria, fungi, and
̈ Describe how angiosperms and plants all have cell walls, structures that surround their cells and
animals depend on each other. provide them with support.

̈ Explain why insects are such suc-
cessful animals.

Key Terms

Archaebacteria Archaebacteria and Eubacteria
Eubacteria
fungus Organisms in the kingdoms Archaebacteria and Eubacteria share
protist a lot of features, even though they are not closely related. They
gymnosperm are microscopic, single-celled organisms that usually have cell
angiosperm walls and reproduce by dividing in half. Unlike all other organ-
invertebrate isms, members of Archaebacteria and Eubacteria lack nuclei.
vertebrate Archaebacteria are often found in extreme places, such as hot
springs. Eubacteria are very common and can be found in soil
Table 2 ̄ and animal bodies. Many types of eubacteria are commonly
referred to as bacteria.

The Kingdoms of Life

Kingdom Characteristics Examples

Archaebacteria single celled; lack cell nuclei; reproduce methanogens (live in swamps and
by dividing in half; often found in harsh produce methane gas) and extreme
environments thermophiles (live in hot springs)

Eubacteria single celled; lack cell nuclei; reproduce proteobacteria (common in soils and in
by dividing in half; incredibly common animal intestines) and cyanobacteria (also
called blue-green algae)

Fungi absorb their food through their body sur- yeasts, mushrooms, molds, mildews,
face; have cell walls; most live on land and rusts

Protists most single celled but some have many diatoms, dinoflagellates (red tide), amoebas,
cells; most live in water trypanosomes, paramecia, and Euglena

Plants many cells; make their own food by ferns, mosses, trees, herbs, and grasses
photosynthesis; have cell walls

Animals many cells; no cell walls; ingest their corals, sponges, worms, insects, fish,
food; live on land and in water reptiles, birds, and mammals

108 Chapter 4 The Organization of Life

Bacteria and the Environment Bacteria play many Figure 12 ̈ The long, orange
important roles in the environment. Some kinds of bac- objects in the image above are E. coli
teria break down the remains and wastes of other organ- bacteria as they appear under a
isms and return nutrients to the soil. Others recycle microscope.
mineral nutrients, such as nitrogen and phosphorous.
For example, certain kinds of bacteria play a very Spider Map
important role by converting nitrogen in the air into a Create the
form that plants can use. Nitrogen is important because Graphic Organizer entitled
it is a main component of proteins and genetic material. “Spider Map” described in the
Appendix. Label the circle
Bacteria also allow many organisms, including humans, “Kingdoms.” Create a leg for each
to extract certain nutrients from their food. The bacteria kingdom. Then, fill in
in Figure 12 are Escherichia coli, or E. coli, a bacterium the map with details
found in the intestines of humans and other animals. about the organisms
Here, E. coli helps digest food and release vitamins that in each kingdom.
humans need. A different form of E. coli can cause
severe food poisoning.

Fungi

A fungus (plural, fungi) is an organism whose cells have nuclei
and cell walls. A mushroom is the reproductive structure of a fun-
gus. The rest of the fungus is an underground network of fibers.
These fibers absorb food from decaying organisms in the soil.

Fungi get their food by releasing chemicals that help break
down organic matter, and then absorbing the nutrients. The
bodies of most fungi are a huge network of threads that grow
through the soil, dead wood, or other material on which the
fungi are feeding. Like bacteria, fungi play an important role in
the environment by breaking down the bodies and body parts
of dead organisms.

Like bacteria, some fungi cause diseases, such as athlete’s
foot. Other fungi add flavor to food. The fungus in blue cheese,
shown in Figure 13, gives the cheese its strong flavor. And fungi
called yeasts produce the gas that makes bread rise.

■✓● Reading Check Name one way that bacteria and fungi are similar

and one way that they are different.

Figure 13 ̈ A mushroom (left) is the
reproductive structure of a fungus
that lives in the soil. The cheese
(above) gets its taste and its blue
color from a fungus.

Section 3 109

Figure 14 ̈ Kelp (left) are huge Protists
protists with many cells that live
attached to the ocean floor. The Most people have some idea what bacteria and fungi are, but few
microscopic diatoms (right) are could define a protist. Protists are a diverse group of one-celled
protists that live in the plankton. organisms and their many-celled relatives. Some, such as amoebas,
are animallike. Others, such as the kelp in Figure 14, are plantlike.
Connection to Biology
Still others are more like fungi. Most protists are one-celled
Cell Size Every cell must microscopic organisms. This group includes amoebas and
exchange substances with its diatoms (DIE uh TAHMS). Diatoms, shown in Figure 14,
environment across its surface. float on the ocean surface. The most infamous protist is
The larger the cell, the smaller its Plasmodium, the one-celled organism that causes the dis-
surface is compared with its vol- ease malaria. From an environmental standpoint, the
ume. So the larger the cell, the most important protists are probably algae. Algae are
more slowly substances move plantlike protists that can make their own food using the
from outside the cell to its sun’s energy. Green pond “scum” and seaweed are exam-
interior. This relationship limits
most cells to microscopic sizes. ples of algae. Algae range in size from the giant kelp to the
one-celled phytoplankton, which are the initial source of food in
most ocean and freshwater ecosystems.

Plants

Plants are many-celled organisms that have cell walls and that
make their own food using the sun’s energy. Most plants live on
land, where the resources a plant needs are separated between the
air and the soil. Sunlight, oxygen, and carbon dioxide are in the
air, and minerals and water are in the soil. Plants have roots that
access water and nutrients in the soil and leaves that collect light
and gases in the air. Leaves and roots are connected by vascular
tissue, a system of tubes that carries water and food. Vascular tis-
sue has thick cell walls, so a wheat plant or a tree is like a build-
ing supported by its plumbing.

Lower Plants The first land plants had no vascular tissue, and
they also had swimming sperm. As a result, these early plants
could not grow very large and had to live in damp places. Their
descendants alive today are small plants such as mosses. Ferns
and club mosses were the first vascular plants. Some of the first
ferns were as large as small trees. Tree ferns still live in the trop-
ics and in New Zealand today. Some examples of lower plants
are shown in Figure 15.

Figure 15 ̈ Lower plants, such as
these mosses and ferns, live in damp
places because they need water to
reproduce.

110 Chapter 4

Gymnosperms Pine trees and other evergreens with needle-like Figure 16 ̈ This gymnosperm has
leaves are gymnosperms (JIM noh SPUHRMZ). Gymnosperms are male and female reproductive struc-
woody plants that produce seeds, but their seeds are not enclosed tures called cones.
in fruits. Gymnosperms such as pine trees are also called conifers
because their seeds are inside cones, as shown in Figure 16. QuickLAB

Gymnosperms have several adaptations that allow them to live Pollen and
in drier conditions than lower plants can. Gymnosperms produce Flower Diversity
pollen, which protects and moves sperm between plants. These
plants also produce seeds, which protect developing plants from Procedure
drying out. And a conifer’s needle-like leaves lose little water. 1. Use a cotton swab to collect
Much of our lumber and paper comes from gymnosperms.
pollen from a common flower-
Angiosperms Most land plants today are angiosperms (AN jee ing plant.
oh SPUHRMZ), flowering plants that produce seeds in fruit. All of 2. Tap the cotton swab on a
the plants in Figure 17 are angiosperms. The flower is the repro- microscope slide and cover the
ductive structure of the plant. Some angiosperms, such as grasses, slide with a cover slip.
have small flowers that produce pollen that is carried by the 3. Examine the slide under a
wind. Other angiosperms have large flowers that attract insects microscope, and draw the
or birds to carry their pollen to other plants. Many flowering pollen grains in your EcoLog.
plants depend on animals to disperse their seeds and carry their 4. Repeat this exercise with a
pollen. For example, a bird that eats a fruit will drop the seeds grass plant in bloom.
elsewhere, where they may grow into new plants. Analysis
1. Based on the structure of the
Most land animals could not survive without flowering flower and the pollen grains,
plants. Most of the food we eat, such as wheat, rice, beans, explain which plant is pollinated
oranges, and lettuce, comes from flowering plants. Building mate- by insects and which is polli-
rials and fibers, such as oak and cotton, also come from flower- nated by wind.
ing plants.

■✓● Reading Check How do angiosperms depend on animals, and how

do animals depend on angiosperms?

Figure 17 ̈ This meadow contains a
wide array of angiosperms, including
grasses, trees, and wildflowers.

Section 3 The Diversity of Living Things 111

MATHPRACTICE Animals

Insect Survival Most Animals cannot make their own food like plants can. They have
invertebrates produce large to take in food from their environment. In addition, animal cells
numbers of offspring. Most of have no cell walls, so animals’ bodies are soft and flexible. Some
these offspring die before reaching animals have evolved hard skeletons against which their muscles
adulthood. Suppose an insect lays can pull to move their bodies. As a result, animals are much more
80 eggs on a plant. If 70 percent mobile than plants and all animals move around in their environ-
of the eggs hatch and 80 percent ments during at least one stage in their lives.
of those that hatch die before
reaching adulthood, how many Invertebrates Animals that lack backbones are invertebrates
insects will reach adulthood? (in VUHR tuh brits). Many invertebrates live attached to hard
surfaces in the ocean and filter their food out of the water. These
www.scilinks.org organisms move around only when they are larvae (juveniles). At
this early stage of life, they are part of the ocean’s floating plank-
Topic: Invertebrates ton. Filter feeders include corals, various worms, and mollusks
Code: HE80812 such as clams and oysters. Figure 18 shows a variety of inverte-
brates. Other invertebrates, including squid in the ocean and
Figure 18 ̈ Examples of inverte- insects on land, move around actively in search of food.
brates include the banana slug (left),
the leaf-footed bug (middle), and More insects exist on Earth than any other type of animal.
the cuttlefish (right). Insects have a waterproof external skeleton that keeps them from
losing water in dry environments. Insects move quickly and they
reproduce quickly. Also, most insects can fly. Their small size
allows them to live on little food and to hide from enemies in
small spaces, such as a seed or in the hair of a mammal.

Many insects and plants have evolved together and depend on
each other to survive. Insects carry pollen from male parts of flowers
to female parts of flowers to fertilize a plant’s egg, which develops
into a fruit. Without insect pollinators, we would not have toma-
toes, cucumbers, apples, and many other crops. Insects also eat
other insects that we consider to be pests. But, humans and insects
are often enemies. Bloodsucking insects transmit human diseases,
such as malaria, sleeping sickness, and West Nile virus. Insects
probably do more damage indirectly, however, by eating our crops.

112 Chapter 4

Vertebrates Animals that have backbones are called vertebrates. Figure 19 ̈ Examples of vertebrates
Members of three vertebrate groups are shown in Figure 19. The include the toco toucan (left), the
first vertebrates were fish, but today most vertebrates live on land. blue-spotted stingray (middle), and
Amphibians, which include toads, frogs, and salamanders, are the snow leopard (right).
partially aquatic. Nearly all amphibians must return to water to
lay their eggs. Ecofact

The first vertebrates to complete their entire life cycle on land Conserving Water Arthropods
were the reptiles, which today include turtles, lizards, snakes, and and vertebrates are the only two
crocodiles. These animals have an almost waterproof egg, which groups of animals that have adap-
allows the egg to hatch on land, away from predators in the water. tations that prevent dehydration so
effectively that some of them can
Birds are warm-blooded vertebrates with feathers. Bird eggs move about freely on land on a
have hard shells. Adult birds keep their eggs and young warm until dry, sunny day.
they develop insulating layers of fat and feathers. Mammals are
warm-blooded vertebrates that have fur and feed their young milk.
The ability to maintain a high body temperature allows birds and
mammals to live in cold areas, where other animals cannot survive.

S E C T I O N 3 Review

1. Describe how animals and angiosperms depend on CRITICAL THINKING
each other. Write a short paragraph to explain your 5. Analyzing Relationships Explain how the large
answer. WRITING SKILLS
number and wide distribution of angiosperm species
2. Describe the importance of protists in the ocean. is related to the success of insects.
6. Understanding Concepts Write a short paragraph
3. Name the six kingdoms of life, and give two charac- that compares the reproductive structures of gym-
teristics of each. nosperms and angiosperms. WRITING SKILLS

4. Explain the importance of bacteria and fungi in the Section 3 The Diversity of Living Things 113
environment.

4C H A P T E R Highlights

1 Ecosystems: Everything Is Key Terms Main Ideas
Connected
ecosystem, 99 ̈ Ecosystems are composed of many intercon-
biotic factor, 100 nected parts that often interact in complex ways.
abiotic factor, 100
organism, 101 ̈ An ecosystem is all the different organisms
species, 101 living in an area as well as the physical
population, 101 environment.
community, 102
habitat, 102 ̈ Organisms live as populations of one species
in communities with other species. Each species
has its own habitat, or type of place that it lives.

2 Evolution natural selection, 103 ̈ The naturalist Charles Darwin used the term
evolution, 103 natural selection to describe the survival and
adaptation, 105 reproduction of organisms with particular
artificial selection, traits.

106 ̈ Darwin proposed that natural selection is
resistance, 107 responsible for evolution—a change in the
genetic characteristics of a population from
one generation to the next.

̈ By selecting which domesticated animals and
plants breed, humans cause evolution by artifi-
cial selection.

̈ We have unintentionally selected for pests
that are resistant to pesticides and for bacteria
that are resistant to antibiotics.

3 The Diversity of Living Things archaebacteria, 108 ̈ Organisms can be divided into six kingdoms,
eubacteria, 108 which are distinguished by the types of cells
fungus, 109 they possess and how they obtain their food.
protist, 110
gymnosperm, 111 ̈ Bacteria and fungi play the important envi-
angiosperm, 111 ronmental roles of breaking down dead organ-
invertebrate, 112 isms and recycling nutrients.
vertebrate, 113
̈ Gymnosperms, which include the conifers,
are the earliest plants with seeds. Angiosperms
are flowering plants.

̈ Insects, invertebrates that are the most suc-
cessful animals on Earth, affect humans in both
positive and negative ways.

̈ Vertebrates, or animals with backbones,
include fish, amphibians, reptiles, birds, and
mammals.

114 Chapter 4 Highlights

4C H A P T E R Review

Using Key Terms 12. Which of the following components of an
ecosystem are not abiotic factors?
Use each of the following terms in a separate a. wind
sentence. b. small rocks
c. sunlight
1. adaptation d. tree branches
2. invertebrate
3. abiotic factor 13. Some snakes produce a powerful poison that
4. habitat paralyzes their prey. This poison is an exam-
5. species ple of
For each pair of terms, explain how the meanings a. resistance.
of the terms differ. b. an adaptation.
6. community and population c. a reptile.
7. evolution and natural selection d. an abiotic factor.
8. gymnosperm and angiosperm
9. bacteria and protists 14. Angiosperms called roses come in a variety
of shapes and colors as a result of
STUDY TIP a. natural selection.
b. coevolution.
Make an Outline After reading each section, c. different ecosystems.
summarize the main ideas into a short outline, d. artificial selection.
leaving space between each entry. Then write
the key terms under the subsection in which 15. Single-celled organisms that live in swamps
they are introduced, followed by a short defini- and produce methane gas are
tion for each. a. protists.
b. archaebacteria.
Understanding Key Ideas c. fungi.
d. eubacteria.
10. Which of the following pairs of organisms
belong to the same population? 16. Which of the following statements about
a. a dog and a cat protists is not true?
b. a marigold and a geranium a. Most of them live in water.
c. a human mother and her child b. Some of them cause diseases in humans.
d. a spider and a cockroach c. They contain genetic material.
d. Their cells have no nucleus.
11. Which of these phrases does not describe
part of the process of evolution by natural 17. Which of the following statements about
selection? plants is not true?
a. the environment contains limited resources a. They make their food from oxygen and
b. organisms produce more offspring than water through photosynthesis.
will survive to reproduce b. Land plants have cell walls that help hold
c. communities include populations of several their stems upright.
species c. They have adaptations that help prevent
d. organisms in a population differ in their water loss.
traits d. Plants absorb nutrients through their roots.

Chapter 4 Review 115

4C H A P T E R Review

Short Answer Concept Mapping ?
??
18. List the five components that an ecosystem
must contain to survive indefinitely. 25. Use the following terms to create a concept
map: ecosystem, abiotic factor, biotic factor,
19. What is the difference between biotic and population, species, community, and habitat.
abiotic factors in an ecosystem?
Critical Thinking
20. What is the difference between adaptation
and evolution? 26. Analyzing Ideas Can a person evolve? Read
the description of evolution in this chapter
21. Describe the three steps by which a population and explain why or why not. READING SKILLS
of insects becomes resistant to a pesticide.
27. Making Inferences A scientist applies a
22. List the six kingdoms of organisms and the strong fungicide, a chemical that kills fungi,
characteristics of each kingdom. to an area of forest soil every week during
October and November. How might this
Interpreting Graphics area look different from the surrounding
ground at the end of the experiment?
Below is a graph that shows the number of
aphids on a rose bush during one summer. The 28. Drawing Conclusions In what building in
roses were sprayed with a pesticide three times, your community do you think bacteria are
as shown. Use the graph to answer questions 23 evolving resistance to antibiotics most rap-
and 24. idly? Explain your answer.

23. What evidence is there that the pesticide 29. Evaluating Assumptions Many people
killed aphids? assume that the human population is no
longer evolving. Do you think these people
24. Aphids have a generation time of about 10 are right? Explain your answer.
days. Is there any evidence that the aphids
evolved resistance to the pesticide during the Cross-Disciplinary Connection
summer? Explain your answer.
30. Geography Find out how the isolation of
Aphid Population Changes Over populations on islands has affected their
Multiple Pesticide Sprayings evolution. Research a well-known example,
such as the animals and plants of Madagascar,
600 the Galápagos Islands, or the Hawaiian
Islands. Write a short report on your find-
Spraying 1 ings. WRITING SKILLS

500

Aphid population 400 Spraying 3 Portfolio Project

Spraying 2 31. Study an Ecosystem Observe an ecosystem
near you, such as a pond or a field. Identify
300 biotic and abiotic factors and as many popu-
lations of organisms as you can. Do not try
200 to identify the organisms precisely. Just list
them, for example, as spiders, ants, grass,
100 not as a specific type. Make a poster show-
ing the different populations. Put the organ-
0 June July August isms into columns to show which of the
kingdoms they belong to.
May

116 Chapter 4 Review

MATH SKILLS READING SKILLS

Use the graph below to answer questions 32–33. Read the passage below, and then answer
the questions that follow.
32. Analyzing Data The graph below shows the
mass of different types of organisms found in Some Central American acacia trees, called
a meadow. How much greater is the mass of ant acacias, have a mutually beneficial rela-
the plants than that of the animals? tionship with ants that live on them. The trees
have several structures that benefit the ants.
33. Analyzing Data What is the ratio of the mass The trees have hollow thorns in which the
of the bacteria to the mass of the fungi? ants live, glands that produce sugary nectar,
and swollen leaf tips, which the ants remove
Mass of Organisms in a Meadow and feed to their larvae.

5,000 The ants reduce the damage that other
organisms do to the tree. They remove dust,
4,000 fungus spores, and spider webs. They destroy
seedlings of other plants that sprout under the
Kilograms 3,000 tree, so that the tree can obtain water and
nutrients without competition from other
2,000 plants. The ants sting animals that try to eat
the tree.
1,000
Proof that the ants are valuable to the aca-
0 cia tree comes from studies in which the ants
Bacteria Plants Fungi Animals Protists are removed. Fungi invade the tree, it is eaten
by herbivores, and it grows more slowly.
WRITING SKILLS When ants are removed from the tree, it usu-
ally dies in a few months.
34. Communicating Main Ideas Why is evolu-
tion considered to be such an important idea 1. According to the passage, which of the
in biology? following statements is not true?
a. Ants and ant acacias have evolved a
35. Outlining Topics Outline the essential relationship beneficial to both of them.
steps in the evolution of pesticide resistance b. The ants prevent fungi from growing
in insects. on the acacia.
c. The tree would benefit from not
having ants.
d. The ants benefit from living on
the tree.

2. What is the advantage to an acacia of
not having other plants grow nearby?
a. Ants cannot crawl onto the acacia
from the other plants.
b. The acacia keeps more ants for itself.
c. This reduces competition for water
and nutrients.
d. This reduces competition for fungi.

Chapter 4 Review 117

4C H A P T E R Standardized Test Prep

Understanding Concepts 6 Describe one of the important roles of

Directions (1–4): For each question, write on a bacteria.
separate sheet of paper the letter of the correct
answer. Reading Skills

1 What is the term for the area where Directions (7–9): Read the passage below. Then
answer the questions.
organisms live together with their physical
environment? Ecosystems are composed of many intercon-
A. biome nected parts that often interact in complex
B. biosphere ways. People often think of ecosystems as iso-
C. ecosystem lated from each other, but ecosystems do not
D. population have clear boundaries. Things move from one
ecosystem into another.
2 Which of the following describes the theory
Ecosystems are made up of both living and
of natural selection? nonliving things. Biotic factors are the living
F. Organisms with desired traits are selected and once-living parts of an ecosystem,
including all the plants and animals. Biotic
for reproduction. factors include dead organisms, dead parts of
G. Heredity determines which organisms organisms, such as leaves, and the organisms’
waste products. The biotic parts of an ecosys-
will survive in their environment. tem interact with the abiotic factors, the non-
H. Traits are developed in organisms in living parts of the ecosystem. There are
different levels in the ecological organization,
response to interaction with other from the individual organism to the biosphere.
organisms.
I. Organisms with strong survival traits 7 What is one example of an abiotic factor?
are more likely to pass on the traits in
reproduction. A. armadillo
B. carnation
3 What inherited trait increases an organism’s C. robin
D. rock
chance of survival and reproduction in a
certain environment? 8 Why would it be incorrect to describe
A. adaptation
B. characteristic ecosystems as being isolated from each
C. evolution other?
D. natural selection F. All ecosystems have different species.
G. Things can move from one ecosystem
4 What are the six kingdoms of life?
into another because ecosystems do not
F. Archaebacteria, Eubacteria, Fungi, have clear boundaries.
Protists, Plants, Animals H. Ecosystems have biotic and abiotic
factors.
G. Eubacteria, Fungi, Protists, Plants, Land I. Both ecosystems and communities have
Animals, Marine Animals biotic and abiotic factors.

H. Archaebacteria, Fungi, Plantlike Protists, 9 State the kinds of biotic factors that would
Animal-like Protists, Plants, Animals
be found in an ocean ecosystem.
I. Bacteria, Fungi, Protists, Flowering
Plants, Non-flowering Plants, Animals

Directions (5–6): For each question, write a short
response.

5 Everything in nature is connected. Use the

concept of interdependence to analyze how
an ecosystem works.

118 Chapter 4 Standardized Test Prep

Interpreting Graphics

Directions (10–12): For each question below, record the correct answer on
a separate sheet of paper.
The map below shows changes in forest cover in Costa Rica over 40 years.
Use this map to answer questions 10 through 12.

Forest Cover in Costa Rica

0 Approximately what percentage of Costa Rica was covered by forest

in 1947?
A. 25%
B. 33%
C. 50%
D. 75%

q What conclusion can be drawn about the forest cover of Costa Rica?

F. Most of the remaining forests are near cities.
G. The remaining forests are concentrated along the western coast.
H. Costa Rica lost more than half of its forest cover in less than

50 years.
I. Deforestation has accounted for little change in Costa Rica’s

environment.

w What can be inferred about organisms adapted to living in trees in Test

Costa Rica? Allow a few minutes
A. Organisms that are adapted for living in trees will continue to at the end of the test-
taking period to check
thrive across the country. for mistakes made in
B. Organisms that are adapted for living in trees will be eliminated marking answers.

from the country’s environment.
C. Organisms that are adapted for living in trees will continue to

thrive in areas that used to have forest.
D. Organisms that are adapted for living in trees will thrive in forested

areas but struggle in areas that no longer have trees.

Chapter 4 Standardized Test Prep 119

4C H A P T E R Inquiry Lab: DESIGN YOUR OWN

Objectives How Do Brine Shrimp Select a Habitat?

̈ USING SCIENTIFIC METHODS Observe Different organisms are adapted for life in different habitats. For
the behavior of brine shrimp. example, brine shrimp are small crustaceans that live in saltwater
lakes. Organisms select habitats that provide the conditions, such
̈ USING SCIENTIFIC METHODS Identify a as a specific temperature range and amount of light, to which
variable, and design an experiment they are best adapted. In this investigation, you will explore habi-
to test the effect of the variable on tat selection by brine shrimp and determine which environmental
habitat selection by brine shrimp. conditions they prefer.

Materials Procedure

aluminum foil Establish a Control Group
brine shrimp culture
corks sized to fit tubing 1. To make a test chamber and to establish a control group,
Detain™ or methyl cellulose divide a piece of plastic tubing into four sections by making
fluorescent lamp or grow light a mark at 10 cm, 20 cm, and 30 cm from one end. Label the
funnel sections "1", "2", "3", and "4".
graduated cylinder or beaker
hot-water bag 2. Place a cork in one end of the tubing. Then transfer 50 mL
ice bag of brine shrimp culture to the tubing. Place a cork in the
metric ruler other end of the tubing. Set the tube aside, and let the brine
Petri dish shrimp move about the tube for 30 min.
pipet
plastic tubing, 40cm ҂ 1cm, 3. After 30 min, divide the tubing into four sections by placing
a screw clamp at each mark on the tubing. While someone in
clear, flexible your group holds the corks firmly in place, tighten the mid-
screen, pieces dle clamp at 20 cm and then tighten the other two clamps.
screw clamps
tape 4. Remove the cork from the end of section 1 and pour the con-
test-tube rack tents of section 1 into a test tube labeled "1." Repeat this
test tubes with stoppers step for the other sections by loosening the screw clamps and
pouring the contents of each section into their corresponding
test tubes.

5. To get an accurate count for the number of brine shrimp in
each test tube, place a stopper on test tube 1, and invert the
tube gently to distribute the shrimp. Use a pipet to transfer a 1
mL sample of the culture to a Petri dish. Add a few drops of
Detain™ to the sample so that the brine shrimp move slower.
Count and record the number of brine shrimp in the Petri dish.

̈ Making a Test Chamber Use a
screw clamp to divide one section of
tubing from another.

120 Chapter 4 Inquiry Lab

6. Empty the Petri dish, and take two more 1 mL samples of ̈ Brine Shrimp These crustaceans
brine shrimp from test tube 1. Calculate the average of the have specific habitat preferences.
three samples recorded for test tube 1.

7. Repeat steps 5 and 6 for each of the remaining test tubes to
count the number of brine shrimp in each section of tubing.

Ask a Question

8. Write a question you would like to explore about brine
shrimp habitat selection. For example, you can explore
how temperature or light affects brine shrimp. To
explore the question, design an experiment that uses the
materials listed for this lab.

9. Write a procedure and a list of safety precautions for
your group’s experiment. Have your teacher approve your
procedure and precautions before you begin the experiment.

10. Set up and conduct your group’s experiment.

Analysis

1. Constructing Graphs Make a bar graph of your data. Plot
the environmental variable on the x-axis and the number of
brine shrimp on the y-axis.

2. Evaluating Results How did the brine shrimp react to
changes in the environment?

3. Evaluating Methods Why did you have to have a control in
your experiment?

4. Evaluating Methods Why did you record the average of
three samples to count the number of brine shrimp in each
test tube in steps 6 and 7?

Conclusions

5. Drawing Conclusions What can you conclude from your
results about the types of habitat that brine shrimp prefer?

Extension

1. Formulating Hypotheses Now that you have observed
brine shrimp, write a hypothesis about how brine shrimp
select a habitat that could be explored with another
experiment, other than the one you performed in this lab.
Formulate a prediction based on your hypothesis.

2. Evaluating Hypotheses Conduct an experiment to test your
prediction. Write a short explanation of your results. Did
your results support your prediction? Explain your answer.

Chapter 4 Inquiry Lab 121

BUTTERFLY ECOLOGIST them travel an amazing 3,200 km Keeping Warm
before reaching central Mexico.
Imagine millions of butterflies Alfonso’s research showed that when
swirling through the air like autumn Wintering Habitat at Risk the temperature falls below freezing,
leaves, clinging in tightly packed as it often does in the mountains
masses to tree trunks and branches, Unfortunately, the habitat that the where the monarchs winter, under-
and covering low-lying forest veg- monarchs travel long distances to story vegetation can mean the differ-
etation like a luxurious, moving reach is increasingly threatened by ence between life and death for some
carpet. According to Alfonso illegal logging and other human monarchs. These conditions are life
Alonso-Mejía, this is quite a sight activities. Logging reduced the size threatening to the monarchs because
to see. of the wintering region by approxi- low temperatures (–1°C to 4°C, or
mately 90 percent over a 30-year 30°F to 40°F) limit their movement.
Every winter Alfonso climbs up period, from about 1970 to 2000. In fact, the butterflies are not even
to the few remote sites in central Mexico has set aside five of the able to fly at such low temperatures.
Mexico where about 150 million known butterfly sites as sanctuar- They can only crawl. At even colder
monarch butterflies spend the winter. ies, but even these are endangered temperatures (–7°C to –1°C, or 20°F
He is researching the monarchs by people who cut down fir trees to 30°F), monarchs resting on the
because he wants to help preserve for fuel or money. forest floor may freeze to death. But
their habitat and the butterflies if the forest has understory vege-
themselves. His work helped him Alfonso’s work is helping tation, the monarchs can slowly
earn a Ph.D. in ecology from the Mexican conservationists better climb the vegetation until they are at
University of Florida. understand and protect monarch least 10 cm above the ground, where
butterflies. Especially important is it is warmer. This tiny difference in
Monarchs are famous for their Alfonso’s discovery that the mon- elevation can provide a microclimate
long-distance migration. The butter- archs depend on bushlike vegeta- that is warm enough to ensure the
flies that eventually find their way tion, called understory vegetation, monarchs’ survival.
to Mexico come from as far away that grows beneath the fir trees.
as the northeastern United States
and southern Canada. Some of

̈ Butterfly Man Alfonso exam-
ines a monarch as part of
his efforts to under-
stand its ecology.

122 Chapter 4 Making a Difference

̈ Monarch Sanctuaries Monarch
butterflies spend the winter at
forested sites just above Mexico City.

The importance of understory ̈ A Sea of Orange At their over- What Do You Think?
vegetation was not known before wintering sites in Mexico, millions of
Alfonso did his research. Now, monarchs cover trees and bushes in a As a migrating species, mon-
thanks to Alfonso’s work, Mexican fluttering carpet of orange and black. archs spend part of their lives
conservationists will better protect in the United States and part
the understory vegetation. And the Monitoring and Assessment of in Mexico. Should the U.S.
Mexican government has passed a Biodiversity (MAB) program. and Mexico cooperate in their
new decree that protects monarchs efforts to understand and
in areas the butterflies are known Information... manage the monarch? Should
to use. nations set up panels to man-
If you are interested in learning age other migrating species,
The Need for Conservation more about monarchs, including such as many songbirds?
their spectacular migration, visit
Although the monarchs continue the Website for Monarch Watch.
to enjoy the forests where they Monarch Watch is an organization
overwinter, those forests are still based at the University of Kansas
threatened. There is little forest left that is dedicated to educating peo-
in this area, and the need for ple about the monarch and pro-
wood increases each year. Alfonso moting its conservation.
hopes his efforts will help protect
the monarch both now and in the
future.

Now that he has completed his
Ph.D., Alfonso is devoting himself
to preserving monarchs and other
organisms. He works as director for
conservation and development for
the Smithsonian Institutions

Chapter 4 Making a Difference 123

How Ecosystems Work 5C H A P T E R

1 Energy Flow in Ecosystems
2 The Cycling of Materials
3 How Ecosystems Change

PRE-READING ACTIVITY

Double-
Door Fold
Before you
read this chap-
ter, create the FoldNote
entitled “Double-Door Fold”
described in the Reading and
Study Skills section of the
Appendix. Write “Energy
flow in ecosystems” on one
flap of the double door and
“Movement of materials in
ecosystems” on the other
flap. As you read the chapter,
compare the two topics,
and write characteristics of
each on the inside of the
appropri-
ate flap.

This green frog gets the energy it
needs to survive by eating other
organisms, such as dragonflies.

124 Chapter 5 How Ecosystems Work

SECTION 1

Energy Flow in Ecosystems

Just as a car cannot run without fuel, an organism cannot survive Objectives
without a constant supply of energy. Where does an organism’s
energy come from? The answer to this question depends on the ̈ Describe how energy is transferred
organism, but the ultimate source of energy for almost all organ- from the sun to producers and
isms is the sun. then to consumers.

Life Depends on the Sun ̈ Describe one way in which con-
sumers depend on producers.
Energy from the sun enters an ecosystem when a plant uses sunlight
to make sugar molecules in a process called photosynthesis. ̈ List two types of consumers.
During photosynthesis, plants, algae, and some bacteria capture ̈ Explain how energy transfer in a
solar energy. Solar energy drives a series of chemical reactions
that require carbon dioxide and water, as shown in Figure 1. The food web is more complex than
result of photosynthesis is the production of sugar molecules known energy transfer in a food chain.
as carbohydrates. Carbohydrates are energy-rich molecules that ̈ Explain why an energy pyramid is
organisms use to carry out daily activities. As organisms consume a representation of trophic levels.
food and use energy from carbohydrates, the energy travels from
one organism to another. Plants, such as the sunflowers in Figure 2, Key Terms
produce carbohydrates in their leaves. When an animal eats a plant,
some energy is transferred from the plant to the animal. Organisms photosynthesis
use this energy to move, grow, and reproduce. producer
consumer
decomposer
cellular respiration
food chain
food web
trophic level

Figure 1 ̈ During photosynthesis,
plants use carbon dioxide, water, and
solar energy to make carbohydrates
and oxygen.

Figure 2 ̈ The cells in the leaves of
these sunflowers contain a green
chemical called chlorophyll. Chloro-
phyll helps plants trap energy from
the sun to produce energy-rich
carbohydrates.

Energy Flow in Ecosystems 125

Figure 3 ̈ Transfer of Energy From Producers to Consumers When a rabbit eats a clover plant,
Almost all organisms depend on the the rabbit gets energy from the carbohydrates the clover plant made
sun for energy. Plants like the clover through photosynthesis. If a coyote eats the rabbit, some of the
shown above get energy from the energy is transferred from the rabbit to the coyote. In Figure 3, the
sun. Animals like the rabbit and clover is the producer. A producer is an organism that makes its
coyote get their energy by eating own food. Producers are also called autotrophs, or self-feeders. The
other organisms. rabbit and the coyote are consumers, organisms that get their energy
by eating other organisms. Consumers are also called heterotrophs,
Figure 4 ̈ The tube worms (above) or other-feeders. In Figure 3, the clover, rabbit, and coyote get their
depend on bacteria that live inside energy from the sun. Some producers get energy directly from the
them to survive. The bacteria (right) sun by absorbing it through their leaves. Consumers get energy indi-
use energy from hydrogen sulfide to rectly from the sun by eating producers or other consumers.
make their own food.
An Exception to the Rule: Deep-Ocean Ecosystems The bottom
of the ocean off the coast of Ecuador is teeming with life. Scientists
found large communities of worms, clams, crabs, mussels, and bar-

nacles living near thermal vents in the ocean floor.
These deep-ocean communities exist in total
darkness, where photosynthesis cannot occur.
So where do these organisms get their
energy? Bacteria, such as those pictured in
Figure 4, live in some of these organisms and
use hydrogen sulfide to make their own food.
Hydrogen sulfide is present in the hot water
that escapes from the cracks in the ocean floor.

Therefore, the bacteria are producers. The bacteria
are eaten by the other underwater organisms and thus
support a thriving ecosystem.

■✓● Reading Check How do producers and consumers get energy from

the sun? (See the Appendix for answers to Reading Checks.)

126 Chapter 5 How Ecosystems Work

What Eats What MATHPRACTICE

Table 1 below classifies organisms by the source of their energy. A Meal Fit for a Grizzly
Consumers that eat only producers are called herbivores, or plant Bear Grizzly bears are
eaters. Rabbits are herbivores and so are cows, sheep, deer, grass- omnivores that can eat up to
hoppers, and many other animals. Consumers, such as lions and 15 percent of their body weight
hawks, that eat only other consumers are called carnivores, or per day when eating salmon and
flesh eaters. You already know that humans are consumers, but up to 33 percent of their body
what kind of consumers are we? Because most humans eat both weight when eating fruits and
plants and animals, we are called omnivores, or eaters of all. other vegetation. How many
Bears, pigs, and cockroaches are other examples of omnivores. pounds of salmon can a 200 lb
Some consumers get their food by breaking down dead organisms grizzly bear eat in one day? How
and are called decomposers. Bacteria and fungi are examples of many pounds of fruits and other
decomposers. The decomposers allow the nutrients in the rotting vegetation can the same bear eat
material to return to the soil, water, and air. in one day?

Table 1 ̄

What Eats What in an Ecosystem

Energy source Examples

Producer makes its own food grasses, ferns, cactuses,
Consumer through photosynthesis flowering plants, trees,
or chemical sources algae, and some bacteria

gets energy by eating mice, starfish, elephants,
producers or other turtles, humans, and ants
consumers

Types of Consumers in an Ecosystem

Energy source Examples

Herbivore producers cows, sheep, deer, and Figure 5 ̈ Bears, such as the grizzly
Carnivore other consumers grasshoppers bear below, are omnivores. Grizzly
bears eat other consumers, such as
lions, hawks, snakes, salmon, but they also eat various
spiders, sharks, alligators, plants.
and whales
Omnivore both producers
and consumers bears, pigs, gorillas, rats,
raccoons, cockroaches,
Decomposer breaks down dead some insects, and
organisms in an humans
ecosystem and returns
nutrients to the soil, fungi and bacteria
water, and air

Section 1 Energy Flow in Ecosystems 127

Connection to Chemistry Cellular Respiration: Burning the Fuel

Chemical Equations Chemical So far, you have learned how organisms get energy. But how do
reactions are represented by they use the energy they get? To understand the process, use
chemical equations. A chemical yourself as an example. Suppose you have just eaten a large meal.
equation is a shorthand descrip- The food you ate contains a lot of energy. Your body gets the
tion of a chemical reaction using energy out of the food by using the oxygen you breathe to break
chemical formulas and symbols. down the food. By breaking down the food, your body obtains
The starting materials in a reaction the energy stored in the food.
are called reactants, and the sub-
stances formed from a reaction The process of breaking down food to yield energy is called
are called products. The number of cellular respiration, which occurs inside the cells of most organ-
atoms of each element in the reac- isms. This process is different from respiration, which is another
tants equals the number of atoms name for breathing. During cellular respiration, cells absorb oxy-
of those elements in the products gen and use it to release energy from food. As you can see in
to make a balanced equation. Figure 6, the chemical equation for cellular respiration is essen-
tially the reverse of the equation for photosynthesis. During cellu-
Figure 6 ̈ Through cellular respira- lar respiration, sugar and oxygen combine to yield carbon
tion, cells use glucose and oxygen dioxide, water, and, most importantly, energy.
to produce carbon dioxide, water,
and energy.

DDT in an Aquatic Food Chain

In the 1950s and 1960s, something on a fish, the bird accumulates more concentrations in fatty tissues of
strange was happening in the estu- DDT in its fatty tissues. In some estu- organisms were magnified almost 10
aries near Long Island Sound, near aries on Long Island Sound, DDT million times from the bottom to the
New York and Connecticut. Birds of
prey, such as ospreys and eagles, ̈ A high concentration of DDT decreases the thickness and the strength of
that fed on fish in the estuaries had eggshells of many birds of prey.
high concentrations of the pesticide
DDT in their bodies. But when the
water in the estuaries was tested, it
had low concentrations of DDT.

What accounted for the high
levels of DDT in the birds? Poisons
that dissolve in fat, such as DDT, can
become more concentrated as they
move up a food chain in a process
called biological magnification. When
the pesticide enters the water, algae
and bacteria take in the poison.
When fish eat the algae and bacteria,
the poison dissolves into the fat of
the fish rather than diffusing back
into the water. Each time a bird feeds

128 Chapter 5 How Ecosystems Work