oceanssediments, forming beaches. section 4 life in the oceans main idea the oceans are home to many...

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OceansOceans affect all livingthings—even those far from the shore.

SECTION 1Ocean WaterMain Idea The composition of ocean water has remained nearlyconstant for hundreds ofmillions of years.

SECTION 2Ocean Currents and ClimateMain Idea Ocean currentsmove water and distributeheat from place to place and can influence climate.

SECTION 3WavesMain Idea Waves carryenergy that can erode shorelines and deposit sediments, forming beaches.

SECTION 4Life in the OceansMain Idea The oceans are home to many differ-ent kinds of organisms.

Ocean LifeThere are eight species of sea turtles, the majority of which arefound in tropical waters. Sea turtles feed on a range of organismsfrom seaweed to sponges to jellyfish. Sea turtles return to land to laytheir eggs, migrating up to 2,200 km to beaches to make their nests.

Write three questions that you would ask a scientist studyingocean life.Science Journal

Jeff Hunter/Getty Images

373373

Oceans Make the followingFoldable to help you identifythe major topics about oceans.

Collect 2 sheets ofpaper and layerthem about 2.5 cmapart vertically. Keepthe edges level.

Fold up the bottomedges of the paperto form 4 equal tabs.

Fold the papers andcrease well to holdthe tabs in place.Staple along thefold. Label the tabsas shown.

Find Main Ideas As you read the chapter, writeinformation about the main ideas of each topicon the appropriate tab.

STEP 3

STEP 2

STEP 1

Why are oceans salty?Ocean water tastes different from the waterin most lakes. Its salty taste comes from saltsthat are dissolved in the water. In the labbelow, you will experiment to find out howsome of those salts end up dissolved in oceanwater.

1. Mix five spoonfuls of dry sand with onespoonful of salt in a pie pan.

2. Bend a small section of the edge of the piepan down so it is level with the bottom ofthe pan.

3. Hold the edge of the pie pan over a smallbowl and sprinkle water on the salt andsand mixture. Don’t wash the sand andsalt out of the pie pan. Let the water filterthrough the mixture. Allow the water tocollect in the bowl.

4. Place the bowl in sunlight or under a hotlamp and let the water evaporate.Observe what remains.

5. Think Critically Describe in your ScienceJournal which material the water dis-solved as it filtered through the salt andsand. Infer where some of the salt in theoceans comes from.

Start-Up Activities

Preview this chapter’s contentand activities at red.msscience.com

Life

Waves

Currents

Ocean Water

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374 A CHAPTER 13 Oceans

Apply It! As you read thischapter, make a chart of the main ideas.Next to each main idea, list at least three supporting details.

Learn It! The best way for you to remember information isto write it down, or take notes. Good note-taking is useful for studyingand research. When you are taking notes, it is helpful to• phrase the information in your own words;• restate ideas in short, memorable phrases;• stay focused on main ideas and only the most important supporting

details.

Practice It! Make note-taking easier by using a chart to help youorganize information clearly. Write the main ideas in the left column. Thenwrite at least three supporting details in the right column. Read the textfrom Section 1 of this chapter under the heading Water Temperature andPressure, page 378. Then take notes using a chart, such as the one below.

Main Idea Supporting Details

1.2.3.4.5.

1.2.3.4.5.

374 B

Before You Read Statement After You ReadA or D A or D

1 Oceans cover almost three-fourths of Earth’s surface.

2 Salinity is a measure of the amount of solids, orsalts, dissolved in seawater.

3 Ocean currents on the western coasts of continents are usually warm.

4 All ocean currents are driven by wind.

5 An upwelling is a current in the ocean thatbrings deep, cold water to the surface.

6 Wavelength is the vertical distance between thecrest and the trough of a wave.

7 Longshore currents run perpendicular to shore.

8 A tide is a giant wave that can be thousands ofkilometers long.

9 Tiny marine organisms that float in ocean currents are called plankton.

10 Coral reefs generally form in temperate andpolar regions in water no deeper than 30 m.

Print out a worksheetof this page at red.msscience.com

Read one or two paragraphs

first and take notes after you

read. You are likely to take

down too much information

if you take notes as you read.Use this to focus on the main ideas as you read the chapter.

Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper.

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

After you read the chapter, look back to this page to see if you’ve

changed your mind about any of the statements.

• If any of your answers changed, explain why.

• Change any false statements into true statements.

• Use your revised statements as a study guide.


374 CHAPTER 13 Oceans

Importance of Oceans Have you looked at a globe and noticed that oceans cover

almost three-fourths of the planet’s surface? A better name forEarth might be “The Water Planet.”You might live far away froman ocean, or maybe you’ve never seen the ocean. But oceansaffect all living things—even those far from the shore.

Oceans provide a place for many organisms to live. Oceanstransport seeds and animals and allow materials to be shippedacross the world. Oceans also furnish people with resourcesincluding food, medicines, and salt. Some examples of resourcesfrom the ocean are shown in Figure 1. The water for most ofEarth’s rain and snow comes from the evaporation of oceanwater. In addition, 70 percent of the oxygen on Earth is given offby ocean organisms.

Ocean Water

Figure 1 Oceans provide many resources.

■ State the importance of Earth’soceans.

■ Discuss the origin of the oceans.■ Describe the composition of

seawater.■ Explain how temperature and

pressure vary with depth.

Oceans affect all people’s lives,even those who don’t live near an ocean.

Review Vocabularyatmosphere: Earth’s air; forms aprotective layer around the planetand is divided into five layers

New Vocabulary

• salinity

• photosynthesis

• thermocline

Fish and other creatures providemany people with food.

Salt is obtained byevaporating seawater.

Sea sponges are used in medicines for treating asthma and cancer.

(l)Laurie Evans/Stone/Getty Images, (c)Michele Westmorland/Danita Delimont Agent, (r)Kevin Schafer/Peter Arnold, Inc.

SECTION 1 Ocean Water 375

Formation of Oceans When Earth was still a young

planet, many active volcanoes existed,as shown in Figure 2. As they erupted,lava, ash, and gases were released fromdeep within Earth. The gases enteredEarth’s atmosphere. One of these gaseswas water vapor. Scientists hypothesizethat about 4 billion years ago, watervapor began accumulating in theatmosphere. Over millions of years, thewater vapor cooled enough to condense and form clouds. Thentorrential rains began to fall from the clouds. Over time, moreand more water accumulated in the lowest parts of Earth’s sur-face, as you can see in Figure 2. Eventually, much of the land wascovered by water that formed oceans. Evidence indicates thatEarth’s oceans formed more than 3 billion years ago.

Composition of Ocean Water If you taste seawater, you’ll know immediately that it tastes

different from water you normally drink. As a matter of fact, youreally can’t drink seawater. Dissolved substances cause the saltytaste. Rivers and groundwater dissolve elements such as calcium,magnesium, and sodium from rocks and carry them to theocean, as you saw in the Launch Lab. Erupting volcanoes addelements such as bromide and chlorine to ocean water.

Figure 2 Oceans could haveformed from water vapor that wasreleased by volcanoes into Earth’satmosphere.

When the water vapor cooledenough to form clouds and rain,water collected in low areas andformed oceans.

Water

96.5%

Magnesium

3.7%

Calcium 1.2%

Potassium 1.1%

Other 0.7%

Sulfate

7.7%Dissolved solids

3.5%

Chloride

55%

Sodium

30.6%

Composition of Ocean Water

Ocean water

Ions


Salinity The two most abundant elements in the dissolvedsalts in seawater are sodium and chlorine. If seawater evapo-rates, the sodium and chloride ions combine to form a saltcalled halite. You use this salt to season food. Halite, as wellas other salts and substances, give ocean water its uniquetaste.

Salinity (say LIH nuh tee) is a measure of the amount ofsolids, or salts, dissolved in seawater. It is measured in gramsof dissolved solids per kilogram of water. One kilogram ofocean water usually contains about 35 g of dissolved solids,or 3.5 percent. Figure 3 shows the most abundant salts inocean water.

What is salinity?

The proportions and amount of dissolved salts in seawaterremain in equilibrium. This means that the composition of theoceans is in balance. Despite the fact that rivers, volcanoes, andthe atmosphere constantly add substances to the ocean, itscomposition has remained nearly constant for hundreds ofmillions of years. Biological processes and chemical reactionsremove many of the substances, such as calcium, from oceanwater. For example, many organisms, such as oysters and clams,use calcium to make their shells. Other marine animals use cal-cium to make bones. Calcium also can be removed from oceanwater through chemical reactions, forming sediment on theocean floor.

Figure 3 Every kilogram ofocean water contains about 35 gof dissolved solids. Sodium andchloride make up nearly 86 percentof this mass. This circle graphshows the most abundantdissolved solids.

SECTION 1 Ocean Water 377

Dissolved Gases Although all of the gases in Earth’s atmo-sphere dissolve in seawater, three of the most important are oxy-gen, carbon dioxide, and nitrogen.

The greatest concentration of dissolved oxygen is near thesurface of the ocean. There, oxygen enters seawater directly fromthe atmosphere. Also, organisms like the kelp in Figure 4 pro-duce oxygen by photosynthesis—a process in which organismsuse sunlight, water, and carbon dioxide to make food and oxy-gen. Because sunlight is necessary for photosynthesis, organismsthat carry on photosynthesis are found only in the upper 200 mof the ocean, where sunlight reaches. Below 200 m, the level ofdissolved oxygen drops rapidly. Here, many animals use oxygenfor respiration and it is not replenished. However, more dis-solved oxygen exists in very deep water than in water just below200 m. This cold, deep water originates at the surface in polarregions and moves along the ocean floor to other regions.

How does oxygen get into seawater?

A large quantity of carbon dioxide is absorbed directly intoseawater from the atmosphere. Carbon dioxide reacts withwater molecules to form a weak acid called carbonic acid.Carbonic acid helps control the acidity of the oceans. In addi-tion, during respiration, organisms use oxygen and give off car-bon dioxide, adding more carbon dioxide to the oceans.

Nitrogen is the most abundant dissolved gas in the oceans.Some types of bacteria combine nitrogen with oxygen to formnitrates. These nitrates are important nutrients for plants.Nitrogen is also one of the important building blocks of plantand animal tissue.

Figure 4 Kelp growing in shal-low water use sunlight to photo-synthesize. During photosynthesis,oxygen is given off and dissolves inthe water.Describe How does carbon dioxideenter seawater?

Carbon dioxide � Water Sunlight

Food � Oxygen

Topic: Dissolved GasesVisit for Weblinks to information aboutdissolved gases in the ocean.

Activity Make a profile of howthe concentration of a dissolvedgas such as oxygen or carbon diox-ide changes with water depth.Present the results on a poster toshare with your class.

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F. Stuart Westmorland/Danita Delimont Agent


Self Check1. List at least four reasons why oceans are important

to you.

2. Explain the relationship between volcanic activity andthe origin of Earth’s oceans.

3. Describe how and why temperature and pressure varywith ocean depth.

4. Think Critically Why are the compositions of riverwater and ocean water not the same?

SummaryImportance of Oceans

• Oceans cover almost three-fourths of Earth’ssurface. A variety of organisms live in the ocean.

Formation of Oceans

• Scientists hypothesize that oceans formed aswater from torrential rains filled Earth’s basins.

Composition of Ocean Water

• Ocean water contains both dissolved salts anddissolved gases.

Water Temperature and Pressure

• The warmest water is at the ocean surface. Asdepth increases, water temperature decreases.

• As water depth increases, pressure increases.

5. Recognize Cause and Effect How does animal respiration affect the amount of dissolved oxygen in deeper water?

Water Temperature and PressureOceans have three temperature layers—the surface layer,

the thermocline layer, and the deep-water layer, shown in Figure 5. The surface layer is warm because it receives solar energy. The warmest surface water is near the equatorwhere the Sun’s rays strike Earth at a direct angle. Water near the poles is cooler because the Sun’s rays strike Earth at alower angle.

The thermocline often begins at a depth of about 200 m, butthis varies. In this layer, temperature drops quickly with increas-ing depth. This occurs because solar energy cannot penetratethis deep. Below the thermocline lies the deep-water layer, whichcontains extremely cold water.

Pressure, or force per unit area, also varieswith depth. At sea level, the pressure of the

atmosphere pushing down on the ocean surface is referred to as1 atmosphere (atm) of pressure. An atmosphere is the pressureexerted on a surface at sea level by the column of air above it. Asyou go below the ocean’s surface, the pressure increases becauseof the force of the water molecules pushing down. The pressureincreases by about 1 atm for each 10-m increase in depth.

For example, at a depth of 20 m, a scuba diver would experi-ence a pressure of 3 atm (1 atm of air � 2 atm of water). Diversmust carry tanks that supply their lungs with air at the same pres-sure as the water around them. If they didn’t, the water pressurewould keep their lungs from inflating when they tried to inhale.

Water Temperature and Depth

600

400

800

1,000

1,200

200

0

Average water temperature (�C)

Dep

th (i

n m

eter

s)

0 5 10 15 20 25

1,400

1,600

Surfacelayer

Thermocline

Deep-waterlayer


Figure 5 The depth of the ther-mocline varies with location. In the location shown on this graph, thethermocline layer begins at 300 m. Determine How deep does the thermocline extend?

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Many people in the world do not have enoughfreshwater to drink. What if you could removefreshwater from the oceans and leave the saltbehind? That’s called desalination.

Real-World QuestionHow does desalination produce freshwater?

Goals■ Observe how freshwater can be made from

salt water.■ Recognize that water can be separated

from salt by the process of evaporation.

Materials large spoon large bowltable salt plastic wrapwater tape250-mL beakers (2) large marble

Safety Precautions

Wear your safety goggles and apron through-out the experiment.

Procedure1. Mix a spoonful of salt into a beaker of water.

2. Pour a thin layer of salt water in the bowl.

3. Place the clean beaker in the center ofthe bowl.

4. Cover the bowl loosely with plastic wrap sothe wrap sags slightly in the center. Do notlet the plastic wrap touch the beaker.

5. Tape the plastic wrap to the bowl to hold itin place.

6. Place the marble on the plastic wrap overthe center of the beaker.

7. Leave the bowl in sunlight until water col-lects in the beaker. You might have to tapthe marble on the plastic wrap lightly to getthe water to drop into the beaker.

8. After some water has collected in thebeaker, remove the plastic wrap. Let thewater in the beaker and the bowl evaporate.

9. After the water has evaporated, rub the bottom of the beaker and the bottom of thebowl with your finger. Notice what you feel.

Conclude and Apply1. Describe what you found remaining in

the bowl and in the beaker after all thewater had evaporated.

2. Explain what kind of water collected in thebeaker—salt water or freshwater? How doyou know?

DesalinStion

Make a poster that illustrates how you would make water that you could drink if you were stranded on a deserted island inthe middle of the ocean. For more help,refer to the Science Skill Handbook.

LAB 379Mark Burnett

Ja

pan Current Gulf Stream

Peru Curren

t

California Current

Trade Winds

Westerlies

Wes

terli

es

Trade W

inds

Trade Winds

Westerlies

Wes

terli

es

Trade W

inds

Trade Winds

Westerlies

Trade W

inds

Wes

terli

es

Trade Winds

Westerlies

Wes

terli

es

Trade W

inds

Trade Winds

Westerlies

Wes

terli

es

Trade W

inds

Surface Currents Ocean water never stands still. Currents move the water

from place to place constantly. Ocean currents are like rivers thatmove within the ocean. They exist both at the ocean’s surfaceand in deeper water. Major surface currents and winds areshown in Figure 6.

Causes of Surface Currents Powered by wind, surfacecurrents usually move only the upper few hundred meters of sea-water. When the global winds blow on the ocean’s surface, they canset ocean water in motion. Because of Earth’s rotation, the oceancurrents that result do not move in straight lines. Earth’s rotationcauses surface ocean currents in the northern hemisphere to curveto the right and surface ocean currents in the southern hemisphereto curve to the left. You can see this in Figure 6. This turning ofocean currents is an example of the Coriolis effect.

Ocean Currentsand Climate

■ State how wind and Earth’s rota-tion influence surface currents.

■ Explain how ocean currentsaffect weather and climate.

■ Describe the causes and effectsof density currents.

■ Explain how upwelling occurs.

Ocean currents affect weatherand climate.

Review Vocabularycurrent: a fluid moving continu-ously in a certain direction

New Vocabulary

• surface current • upwelling

• density current

Figure 6 Earth’s global winds create surfacecurrents in the oceans.Observe Which way do currents rotate in thenorthern hemisphere?

SECTION 2 Ocean Currents and Climate 381

The Gulf Stream Much of what is known about surface cur-rents comes from records kept by early sailors. Sailing shipsdepended on certain surface currents to carry them west andothers to carry them east. One of the most important currentsfor sailing east across the North Atlantic Ocean is the GulfStream. This 100-km wide current was discovered in the 1500sby Ponce de Leon and his pilot Anton de Alaminos. In 1770,Benjamin Franklin published a map of the Gulf Stream drawnby Captain Timothy Folger, a Nantucket whaler.

The Gulf Stream, shown in Figure 7, flows from Floridanortheastward toward North Carolina. There it curves towardthe east and becomes slower and broader. Because the GulfStream originates near the equator, it is a warm current.Look back at Figure 6. Notice that currents on eastern coasts ofcontinents, like the Gulf Stream, are usually warm, while cur-rents on western coasts of continents are usually cold. Surfacecurrents like the Gulf Stream distribute heat from equatorialregions to other areas. This can influence the climate of regionsnear these currents.

What kind of current is the Gulf Stream?

Figure 7 In this satellite image,the warm water of the Gulf Streamappears red and orange.

Topic: Surface CurrentsVisit for Weblinks to information about the GulfStream and other surface currents.

Activity Investigate what typeof ongoing research is taking placeon other surface currents such asthe California Current or the PeruCurrent. Present your results tothe class.

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TSADO/GSFC/Tom Stack & Assoc.



Climate As an example of how surface currents affect climate,locate Iceland on the map in Figure 8. Based on its location andits name, you might expect it to have a cold climate. However,the Gulf Stream flows past Iceland. The current’s warm waterheats the surrounding air and keeps Iceland’s climate mild andits harbors ice free year-round, as shown in Figure 8.

Cold Surface Currents The currents on the westerncoasts of continents carry colder water back toward the equator.In Figure 6, find the California Current off the west coast ofNorth America and the Peru Current along the west coast ofSouth America. They are examples of cold surface currents. TheCalifornia Current affects the climate of coastal cities. For exam-ple, San Francisco has cool summers and many foggy daysbecause of the California Current.

Density CurrentsIn water at a depth of more than a few hundred meters,

winds have no effect. Instead, currents develop because of differ-ences in the density of the water. A density current forms whenmore dense seawater sinks beneath less dense seawater. Seawaterbecomes more dense when it gets colder or becomes more salty.

A density current exists in the Mediterranean Sea. In this sea,lots of water evaporates from the surface, leaving salts behind.Therefore, the remaining water is high in salinity. This moredense water sinks and moves out into the less dense water of theAtlantic Ocean. At the surface, less dense water from the Atlanticflows into the Mediterranean Sea.

ATLANTIC OCEANUNITEDSTATES

CANADA

GREENLAND

ICELAND

Arctic Circle

Gulf Stream

Figure 8 The warm water ofthe Gulf Stream helps moderateIceland’s climate. Describe how the CaliforniaCurrent affects the climate ofcoastal cities.

The harbor at Reykjavik (RAY kyuhvihk), Iceland’s capital, remainsfree of ice all year long.

Seawater Density The for-mula for determining den-sity is mass/volume. Whensalinity increases, does itaffect mass or volume?When temperatureincreases, does it affectmass or volume?

Tibor Bognar/The Stock Market/CORBIS

SECTION 2 Ocean Currents and Climate 383

PACIFICOCEAN

INDIANOCEAN

ATLANTICOCEAN

Deep

Water

North

Atlantic

North

Atlantic

Antarctic Circumpolar Current

Surface CurrentsDeep Currents

Figure 9 Like a giant conveyor belt,cold, salty water sinks in the northernAtlantic Ocean and flows southward,while warm surface water flows north-ward from the equator to replace it.

Modeling a DensityCurrentProcedure1. Fill a paper cup three-

fourths full with water. 2. Add two spoonfuls of salt

and three drops of foodcoloring to the water. Stirwith a spoon to dissolvethe salt.

3. Push one thumbtack intothe cup 1 cm from thebottom of the cup andanother 3 cm from thebottom.

4. Carefully place the cup intoa clear-plastic box and fillthe box with water untilthe water level in the boxis about 0.5 cm above thetop tack.

5. Remove both tacks at thesame time and record inyour Science Journal whatyou observe.

Analysis1. Infer what is happening at

the two holes in the cup. 2. Make a sketch to describe

the current’s direction. 3. Explain what causes the

density current to form.

Cold and Salty Water An important density current thataffects many regions of Earth’s oceans begins north of Iceland.In the winter months, the water at the surface starts to freeze.When water freezes, dissolved salts are left behind in theunfrozen water. Therefore, this unfrozen water is very densebecause it is cold and salty. It sinks and slowly flows along theocean floor toward the southern Atlantic Ocean, as shown inblue in Figure 9. There it spreads into the Indian and PacificOceans. As the water is sinking near Iceland, warm surface waterof the Gulf Stream, shown in red, moves northward from theequator to replace it. The Gulf Stream water warms the conti-nents that border the North Atlantic.

Density Currents and Climate Change Suppose densitycurrents near Iceland stopped forming. Some scientists hypoth-esize that this has happened in Earth’s past and could happenagain. Increasing carbon dioxide concentrations in Earth’satmosphere could trap more of the Sun’s heat, raising Earth’stemperature. If Earth’s temperature rose enough, ice couldn’teasily form near the polar regions. Freshwater from melting gla-ciers on land also could reduce the salinity of the ocean water.The density currents would weaken or stop. Scientists hypothe-size that if dense water stopped flowing along the ocean bottomtoward the southern Atlantic Ocean, warm water would nolonger flow northward on the surface to replace the missingwater. All of Earth could experience drastic climate shifts,including changing rainfall patterns and temperatures.


Self Check1. Explain how winds create surface currents.

2. Describe how the rotation of Earth modifies ocean cur-rents in the northern hemisphere.

3. Summarize what causes the density current in theMediterranean Sea.

4. Think Critically Why is the surface water cooler nearSan Diego, California, compared to that off the coast ofCharleston, South Carolina?

SummarySurface Currents

• As global winds blow along the ocean’s sur-face, they can set surface water in motion.Due to the Coriolis effect, ocean surface cur-rents do not move in straight lines.

• Surface currents can influence local climate.

Density Currents

• Density currents form when more dense sea-water sinks beneath less dense seawater.

Upwelling

• Upwelling brings deep, cold water to theocean surface. The concentration of nutrientsin upwelled water is high.

5. Compare and contrast density currents and upwellingin the ocean.

UpwellingAn upwelling is a current in the

ocean that brings deep, cold water to theocean surface. This occurs along somecoasts where winds cause surface waterto move away from the land. Windblowing parallel to the coast carrieswater away from the land because of theCoriolis effect. Figure 10 shows upwellingas it occurs off the coast of Peru. Noticethat when surface water is pushed awayfrom the coast, deep water rises to thesurface to take its place. This cold, deepwater continually replaces the surfacewater that is pushed away from the

coast. The cold water contains high concentrations of nutrientsproduced when dead organisms decayed at depth. This concen-tration of nutrients causes tiny marine organisms to flourishand fish to be attracted to areas of upwelling. Upwelling alsoaffects the climate of coastal areas. Upwelling contributes to SanFrancisco’s cool summers and famous fogs.

El Niño During an El Niño (el NEEN yoh) event, the windsblowing water from the coast of Peru slacken, the eastern Pacificis warmed, and upwelling is reduced or stops. Without nutrientsprovided by upwelling, fish and other organisms cannot findfood. Thus, the rich fishing grounds off of Peru are disrupted.

Surface winds

Surface water

Cold water

Figure 10 Winds push wateraway from shore along the SouthAmerican coastline. This creates anupwelling of cold water.

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Waves Caused by Wind Have you ever wanted to surf? By catching a high, curled

wave, you can ride all the way to the beach. A wave in water is arhythmic movement that carries energy through the water.Waves that surfers ride could have originated halfway around theworld. Whenever wind blows across a body of water, frictionpushes the water along with the wind. If the wind speed is greatenough, the water begins piling up, forming a wave. Three thingsaffect the height of a wave: the speed of the wind, the length oftime the wind blows, and the distance over which the windblows. A fast wind that blows over a long distance for a long timecreates huge waves. Once a wave forms, it can travel a great dis-tance. But when winds stop blowing, waves stop forming.

Parts of a Wave Each wave has a crest, its highest point, anda trough, its lowest point. Wave height is the vertical distancebetween the crest and trough. The wavelength is the horizontaldistance between the crests or troughs of two successive waves.Figure 11 shows the parts of a wave.

In the open ocean, most waves have heights of 2 m to 5 m.Ocean waves rarely reach heights of more than 15 m. However,storm winds can produce waves more than 30 m high—tallerthan a six-story building—that can capsize even large ships.

Waves

■ Describe how wind can formocean waves.

■ Explain the movement of watermolecules in a wave.

■ Describe how the Moon and Suncause Earth’s tides.

■ List the forces that cause shore-line erosion.

Wave erosion affects life in coastalregions.

Review Vocabularysediments: loose materials, suchas rock fragments, mineral grains,and the remains of once-livingplants and animals, that aremoved by wind, water, ice, orgravity

New Vocabulary

• wave

• tide

Figure 11 Every wave has acrest, trough, wavelength, andwave height.

CrestWavelength

Wave height

Trough

SECTION 3 Waves 385


Wave Motion When you observe an ocean wave, it looks asthough the water is moving forward. But unless the wave isbreaking onto shore, the water does not move forward. Eachmolecule of water stays in about the same place in a passingwave. If you want to demonstrate how molecules move in awave, tie a ribbon to the middle of a rope. Then hold one end ofthe rope and have someone else hold the other end. Wiggle therope until a wave starts moving toward the other person. Noticethat the wave travels through the rope to the other person, butthe ribbon moves only in small circles, not forward.

Breakers As a wave approaches a shore, it changes shape.Friction with the ocean floor slows the water at the bottom ofthe wave. Notice in Figure 12 that as the bottom of the waveslows, the crest and trough come closer together and the waveheight increases. Because the top of the wave is not slowed byfriction, it moves faster than the bottom. Eventually, the wavetop overtakes the bottom, and the wave collapses. Water tumblesover on itself. This collapsing wave is called a breaker. Breakersmake the best waves for surfers to ride. After a wave breaks ontoshore, gravity pulls the water back into the sea.

What causes breakers to form?

Along smooth, gently sloping coasts, waves deposit erodedsediments on shore, forming beaches. Beaches extend inland asfar as the tides and waves are able to deposit sediments.

Waves usually approach a shore at slight angles. This createsa longshore current of water, which runs parallel to the shore.As a result, beach sediments are moved sideways. Longshorecurrents carry many metric tons of loose sediment from onebeach to another.

Figure 12 As a wave moves by,individual molecules of watermove around in circles. As a waveapproaches shore, wavelengthdecreases and wave heightincreases. Eventually the bottom ofthe wave cannot support the top,and the wave falls over on itself, creating a breaker.

BreakerWave length decreases

SwellsBeach

Wave height increases

Wave direction

Sloping bottom

Modeling Water Particle MovementProcedure1. Fill a large bowl with

water and place a pennyon the bottom in the cen-ter of the bowl.

2. Float a small piece oftoothpick in the bowldirectly above the penny.

3. Gently dip a spoon intothe water to make smallwaves.

Analysis1. Compare and contrast the

movement of the wavesand the toothpick.

2. Compare the movement ofthe toothpick with themovement of water parti-cles in a wave.

Tides Throughout a day, the water level at the ocean’s edge

changes. This rise and fall in sea level is called a tide. A tide is agiant wave that can be thousands of kilometers long but only 1 m to 2 m high in the open ocean. As the crest of this wavereaches shore, sea level rises to form high tide. Later in the day,the trough of the wave reaches shore and sea level drops. This islow tide. The difference between sea level at high tide and lowtide is the tidal range. The tidal range in some coastal areas canbe as much as 20 m.

Causes of Tides Tides are not created by wind. They are createdby the gravitational attraction of Earth and the Moon and of Earthand the Sun. The Moon and Earth are relatively close together inspace, so the Moon’s gravity exerts a strong pull on Earth. Thisgravity pulls harder on particles closer to the Moon than on parti-cles farther from the Moon, causing two bulges of water to form.One bulge forms directly under the Moon and one on the oppositeside of Earth. As Earth rotates, these bulges move to follow theMoon on its daily passage. The crests of these bulges are high tides.Between these bulges are troughs that create low tides.

The Sun’s gravity also affects the tides. When the Moon,Earth, and Sun line up together, the high tides are higher and thelow tides are lower than normal, creating spring tides. When theSun, Earth, and Moon form a right angle, high tides are lowerand low tides are higher than normal, creating neap tides.Figure 13 illustrates this effect.

and Neaptides occur whenthe Sun, Moon,and Earth form aright angle.

Figure 13 As the Moon andEarth revolve around a commoncenter of mass, a bulge of waterforms on the side of Earth closestto the Moon and on the side oppo-site the Moon.

SECTION 3 Waves 387

Topic: Tidal RangesVisit for Weblinks to information about tidalranges around the world.

Activity Select a coastal locationand find one month’s worth oftidal data for that area. Graph thedata. Calculate the tidal range forthat month.

red.msscience.com

and Springtides occur whenthe Sun, Moon, andEarth are aligned.



Self Check1. Summarize how wind creates waves. What factors

determine the size of waves?

2. Describe how a water molecule moves in a wave. Whatcauses a wave to break?

3. Explain what causes tides. How do spring tides andneap tides differ?

4. Think Critically If a storm arrives at a beach duringhigh tide, why is erosion especially damaging?

SummaryWaves Caused by Wind

• Waves form as wind blows across a body ofwater.

• Although it appears as though water is mov-ing forward in a wave, each molecule of waterstays in approximately the same place as awave passes.

Tides

• Tides are the rise and fall in sea level that canbe measured along the shore.

Wave Erosion

• Waves can cause erosion to occur along rockycoasts as well as sandy shores. Longshore cur-rents also can erode beaches.

Wave Erosion Waves can erode many meters of land in a single season.

They wear away rock at the base of rocky shorelines, as shown in Figure 14. Then overhanging rocks fall into the water, leaving asteep cliff. Houses built on ocean cliffs can be damaged ordestroyed by the erosion below. At Tillamook Rock, Oregon,storm waves hurled a 61-kg rock high into the air. The rockcrashed through the roof of a building 30 m above the water.

Beach Erosion Sandy shorelines also can be eroded by waves.Large storms and hurricanes can produce waves that move muchof the sand from the beach and can destroy large parts of somenearshore islands. Longshore currents also can erode beaches.This happens most often when people build structures calledgroins that extend out into the water. Although groins may pro-tect beaches in some places, they often cause erosion elsewhere.

Figure 14 In a single day about14,000 waves will crash onto thisrocky shore.

5. Recognize Cause and Effect The city of Snydervillekeeps pumping sand onto its beach, but the sand keeps disappearing. Explain where it is going.

red.msscience.com/self_check_quizGary Vestal/Stone/Getty Images


SECTION 4 Life in the Oceans 389

Types of Ocean LifeOrganisms live in many different areas of the ocean. Where an

organism lives and how it moves from place to place determineswhether it is classified as plankton, nekton, or a bottom dweller.

Plankton Tiny marine organisms that float in ocean currentsare called plankton. Most plankton are one-celled organ-isms, such as the diatoms (DI uh tahmz) pictured in Figure 15. Some plankton can swim, but most drift with cur-rents. You would need a microscope to see most of these organ-isms. Examples of animal plankton include eggs of oceananimals, very young fish, larval jellyfish and crabs, and tinyadults of some organisms. Figure 15 shows a tiny jellyfish about2 cm in diameter and the eggs of corals being released into thewater where they will float.

Life in the Oceans

■ Describe the characteristics ofplankton, nekton, and bottom-dwelling organisms.

■ Distinguish among producers,consumers, and decomposers.

■ Discuss how energy and nutri-ents are cycled in the oceans.

■ Explain how organisms in theoceans interact in food chains.

Marine organisms provide peoplewith much of the food they needto survive.

Review Vocabularynutrients: substances neededby organisms to carry out lifeprocesses

New Vocabulary

• plankton • chemosynthesis

• nekton • consumer

• ecosystem • decomposer

• producer • food chain

The eggs of corals become plankton whenthey are released into the water column.

Figure 15 Plankton,such as this jellyfish,float in the upperlayers of the ocean.

Diatoms, shown above, areone-celled organisms thatundergo photosynthesis.

(tl)Norbert Wu/DRK Photo, (bl)Fred Bavendam/Minden Pictures, (br)Darlyne Murawski/National Geographic Image Collection


Nekton Animals that can actively swim, rather than drift inthe currents, are called nekton. Fish, whales, shrimp, turtles, andsquid are nekton. Swimming allows these animals to searchmore areas for food. Some nekton, such as herring, come to thesurface to feed on plankton, but others remain in deeper water.

Some of the nekton that live in the dark abyss of the deepestparts of the ocean have organs that produce light, which attractslive food. Shown in Figure 16, an anglerfish dangles a luminouslure over its head. When small animals like shrimp bite at thelure, the anglerfish swallows them whole.

Bottom Dwellers Some organisms live on the ocean bottom.They can burrow in sediments, walk or swim on the bottom, orbe attached to the seafloor.

Bottom-dwelling animals include anemones, crabs, corals,snails, starfish, and some fish. Many of these animals, such as seacucumbers, eat the partially decomposed matter that sinks tothe ocean floor. Some, such as the sea star in Figure 17, prey onother bottom dwellers. Others that are attached to the bottom,such as sponges, filter food particles from the water. Still others,such as anemones, corals, and the sea fans shown in Figure 17,are found in coral reefs. They capture organisms that swim by.

Figure 16 Swimming animals,such as this anglerfish (left), arenekton.List two other examples of nektonin the ocean.

Figure 17 Bottom dwellersvary greatly. Many sea stars feedon other bottom dwellers such asclams. Sea fans, shown in thephoto on the right, live attachedto the bottom and cannot movefrom place to place.

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Ocean Ecosystems The oceans are home to many different kinds of organisms.

No matter where organisms live, they are part of an ecosystem.An ecosystem is a community of organisms and the nonlivingfactors that affect them, such as sunlight, water, nutrients, sedi-ment, and gases. Every ecosystem has producer, consumer, anddecomposer organisms.

Producers Producer organisms, such as those shown in Figure 18, form the base of all ecosystems. Producers are organ-isms that can make their own food. Producers near the ocean’ssurface contain chlorophyll. This allows them to make food andoxygen during photosynthesis.

In deep water, where sunlight does not penetrate, producersthat use chlorophyll can’t survive. In this part of the ocean, pro-ducers make food by a process called chemosynthesis. Chemomeans “chemical.” This process often takes place along mid-ocean ridges where hot water circulates through the crust.Bacteria produce food using dissolved sulfur compounds thatescape from hot rock. The bacteria then are eaten by organismssuch as crabs and tube worms.

Consumers and Decomposers Consumer and decom-poser organisms depend upon producers for survival. Organismsthat eat, or consume, producers are called consumers.Consumers get their energy from the food stored in the produc-ers’ cells. Some also eat other consumers to get energy. Whenproducers and consumers die, decomposers digest them.Decomposers, such as bacteria, break down tissue and releasenutrients and carbon dioxide back into the ecosystem.

What is a consumer?

Magnification: 100�

Economics and Fish Manycoastal areas of the worlddepend on harvesting fishto keep the local economyhealthy. Certain areas ofthe world such as the coastof Peru, the Gulf of Alaskaand the Bering Sea, and theGrand Banks on the eastcoast of Canada, are wellknown for their fisheries.Events such as El Niño orthe overharvesting of fishcan greatly affect a fishingseason.

Figure 18 Producers can belarge like the sea grass shown onthe left. Sometimes they are assmall as the microscopic algaeshown on the right.Infer what all producers have incommon.

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Food Chains Throughout the oceans, energy is transferredfrom producers to consumers and decomposers throughfood chains. In Figure 19, notice that algae (producers) areeaten by krill that are, in turn, eaten by Adélie penguins. Leopardseals eat the penguins, and killer whales eat the leopard seals. Ateach stage in the food chain, energy obtained from one organ-ism is used by other organisms to move, grow, repair cells,reproduce, and eliminate wastes. Energy not used in these lifeprocesses is transferred along the food chain.

All ecosystems have many complex feeding relationships.Most organisms depend on more than one species for food.Notice in Figure 19 that krill eat more than algae and in turn areeaten by animals other than Adélie penguins. In the AntarcticOcean, as in all ecosystems, food chains are interconnected toform highly complex systems called food webs.

Are fish that contain mercury safe to eat?

When mercury, once used in pesticides, is addedto oceans or bodies of freshwater, bacteria change itto methyl mercury, which is a more toxic formof mercury. Fish then absorb the methyl mercuryfrom the water as it flows over their gills or as theyfeed on aquatic organisms. Larger fish feed on thesmaller fish, and humans often eat larger fish. Thetable on the right lists the methyl mercury rangesfor a variety of fish.

Identifying the Problem The average methyl mercury present in each fish

is given in the chart in parts per million (ppm). Thedetection limit is 0.10 ppm. Any values less than0.10 ppm are shown as ND (not detected). TheFDA’s (Food and Drug Administration) safe limitfor human consumption is 1 ppm. Which species offish could put you in danger of mercury poisoningif you eat them?

Solving the Problem 1. Which of the fish listed do not contain any methyl mercury? Explain.2. The FDA limit of 1 ppm is 10 times lower than levels found in fish that have caused

illness. The FDA recommends eating shark or swordfish no more than once a week.Does this appear consistent with the information given in the data table? Explain.Which fish could you safely eat as often as you wanted?

Topic: Food WebsVisit for Weblinks to information about oceanfood chains and food webs.

Activity Find an example of anocean food chain or food web.Display the information you findon a poster.

red.msscience.com

Methyl Mercury Contentin Domestic Fish

Species Range Average

(ppm) (ppm)

Catfish ND–0.16 ND

Cod ND–0.17 0.13

Crab ND–0.27 0.13

Flounder ND ND

Halibut 0.12–0.63 0.24

Salmon ND ND

Tuna (canned) ND–0.34 0.20

Tuna (fresh) ND–0.76 0.38

Swordfish 0.36–1.68 0.88

Shark 0.30–3.52 0.84


NGS TITLE

Figure 19

VISUALIZING FOOD CHAINS IN A FOOD WEB


Other consumers, such as the killerwhale and the leopard seal, eat severaldifferent types of organisms to gainthe energy they need.

C

A food web represents a network of interconnected food chains. It showshow energy moves through an ecosystem—from producers to consumersand eventually to decomposers.This diagram shows a food web in the

Antarctic Ocean. Arrows indicate the direction in which energy is transferredfrom one organism to another.

Killer whale

Algae

Cod

Small animals and other organisms

Leopard seal

Weddell sealCrabeater seal

Krill

Adelie penguin

Squid

Decomposers feed on wastesand dead organisms and returnnutrients to the ecosystem in theprocess. In this way, decomposersare a vital link in the food web.

D

All food chains beginwith a producer—in thiscase, photosynthetic algaethat drift through polar seas.

A

Some consumers get energy fromone primary source. For example,crabeater seals, despite their name, dine almost exclusively on krill.

B

Bacteria

(Killer whale)Pieter Folkens, (Crabeater seal)G.L. Kooyman/Animals Animals, (Leopard seal)Peter Johnson/CORBIS, (Weddell seal)Galen Rowell/CORBIS, (Adelie penguin)Rick & Nora Bowers/Visuals Unlimited, (cod)British AntarcticSurvey, (squid)Jeffrey L. Rotman/CORBIS, (krill)Flip Nicklin, (copepod plankton)Douglas P. Wilson/Frank Lane Picture Agency/CORBIS, (algae)Deneb Karentz, (bacteria)Professor N. Russell/Science Photo Library/Photo Researchers


Ocean NutrientsNearly everything in an ecosystem is recycled. When

organisms respire, carbon dioxide is released back into theecosystem. When organisms excrete wastes or die and decom-pose, nutrients are recycled. All organisms need certain kindsof nutrients in order to survive. For example, plants need

nitrogen and phosphorus.Figure 20 shows how nitrogencycles through the ocean.

Carbon also is recycled.You learned earlier in thischapter that oceans absorbcarbon dioxide from theatmosphere. You also learnedthat producers use carbondioxide to make food and tobuild their tissues. Carbonthen can be transferred toconsumers when producersare eaten. When organismsdie and sink to the bottom,some carbon is incorporatedinto marine sediment. Overtime, carbon is exchangedslowly between rocks, oceans,the atmosphere, and organ-isms, as seen in Figure 21.

Nitrogen

Nitrogen

Bacteria change nitrogen gas into nitrates. Algae and plants use

nitrates for growth. Bacteria decompose dead organisms to produce nitrates and nitrogen gas.

Animals get nitrogen by eating other organisms.

Lightning changes nitrogen in the atmosphere to nitrates.

Carbondioxide

CarbondioxideCarbon

dioxide

Carbon

Carbon

Consumers

Algae and producers

Carbondioxide

Carbon

Figure 20 Nitrogen cycles fromnitrogen gas in the atmosphere tonitrogen compounds and backagain.

Figure 21 Carbon cyclesthrough the ocean and betweenthe ocean and the atmosphere.


Self Check1. List the characteristics of plankton, nekton, and

bottom-dwelling organisms.

2. List the characteristics of producers, consumers, anddecomposers.

3. Explain how carbon is cycled through the oceans. Howis nitrogen cycled?

4. Think Critically Why must every ecosystem includeproducers as well as other organisms?

SummaryTypes of Ocean Life

• Marine organisms can be classified based onwhere they live and how they move from placeto place: plankton, nekton, or bottom dweller.

Ocean Ecosystems

• Ocean ecosystems contain producers, con-sumers, and decomposers.

• Energy in an ecosystem is transferred througha food chain or a food web.

Ocean Nutrients

• Nutrients are passed from producers to con-sumers when producers are eaten. Whenorganisms die, decomposers release thesenutrients back into the ecosystem.

5. Form Hypotheses Write a hypothesis about how anincrease in the amounts of ocean nutrients mightaffect producers. How would the increase in nutrients affect consumers?

Coral Reefs and Nutrient Recycling Coral reefs areecosystems that need clear, warm, sunlit water. Each coral ani-mal builds a hard calcium carbonate capsule around itself.Inside the animals’ cells live algae that provide the animals withnutrients and give them color. As corals build one on top ofanother, a reef develops. Other bottom-dwelling organisms andnekton begin living on and around the reef. Nearly 25 percent ofall marine species and 20 percent of all known marine fish liveon coral reefs. Coral reefs generally form in tropical regions inwater no deeper than 30 m.

A healthy reef maintains a delicate balance of producers,consumers, and decomposers. Energy, nutrients, and gases arecycled among organisms in complex food webs in a coral reef.Look at Figure 22 to see one example of how materials arecycled through a coral reef.

Figure 22 Parrot fish are effi-cient recycling organisms. Theyturn coral into fine sand as theygraze on the algae in the coral.

red.msscience.com/self_check_quizMike Severns/Stone/Getty Images


Model and InventModel and Invent


Real-World QuestionThe water in the Gulf of Mexico is subject to the same forces as waterin the open ocean. Daily high and low tides affect the water level, andwaves are involved in shoreline erosion. How can you simulate oceanwaves and represent tidal changes in water level? How will the tidesaffect the amount of erosion in various areas? How can you modelocean waves and tides in the classroom? Can you simulate wavesand tides along the edge of an ocean using a basin of water in theclassroom?

Make a Model1. Determine how you are going to create a model of the edge of

the ocean. Draw a picture of what your model will look like.

2. Decide how you will create waves and tides in your model. Whatcan you use to move the water? How can you simulate tides bychanging the height of the water level?

3. Predict where in your model erosion may occur and where it maynot. How might you be able to see where erosion will occur?

Check the Model Plans1. Compare your model plans with those of other students in the

class. Discuss why each of you chose the design you did.

2. Make sure that your teacher approves your model plans before youconstruct your model.

Goals■ Construct a model of

the edge of the ocean.■ Demonstrate how

you can simulate wavesand tides in yourmodel.

■ Predict how erosionmight occur in yourmodel.

Possible Materialslarge basinwaterboardssand*gravelbricksrocksplastic bottlesfan (battery-operated)*Alternate materials

Safety Precautions

Waves and Tides

Betsy R. Strasser/Visuals Unlimited

Test Your Model1. Construct your model based on your design plans.

2. Create waves in your model and observe what happens. Record your observa-tions in your Science Journal.

3. Change the tide by changing the water level and repeat step 2.

Analyze Your Data1. Describe what you observed when you created waves and tides in your ocean

model.

2. Were you able to see any evidence of erosion in your model? If so, in what areasof your model was erosion present and where was it absent? If not, wherewould you expect to see erosion over a longer period of time? Explain.

Conclude and Apply1. Did the waves you created always look the same or did they seem to vary in

wave height or wavelength? Explain.

2. Did you see anything that looked like breakers as the waves hit the shore?

3. In what ways was your model similar to and different from the edge of a realocean?

4. What features were you able to simulate and what features were missingfrom your model?

LAB 397

Discuss with your family or students inother classes how ocean waves and tidesaffect erosion along the edge of oceans. For more help, refer to the Science SkillHandbook.

KS Studios

Find Out About ItVisit red.msscience.com/science_stats to find the surface area of the three largest oceans.

Make a graph showing the relative sizes of these oceans.


. . . The deepest place inthe ocean is the Marianas Trench,located east of the Philippines. Thedeepest part of the Marianas Trenchis the Challenger Deep, which extends11,033 m down. That’s deep enoughto hold Mount Everest and the world’sfive tallest buildings stacked on top ofone another.

Ocean FactsDid You Know...

. . . At more than 2,000km long, the Great BarrierReef in the Coral Sea is thelargest organic structure onEarth and can be seen clearlyfrom space.

Great Barrier Reef

MarianasTrench

Averageocean depth

MountEverest

Averageland height

Sea level

109876543210

–1–2–3–4–5–6–7–8–9

–10–11

Dep

th/H

eigh

t (1,

000s

of m

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Height and Depth Comparisonof Land and Ocean

Use the graph tofind out about how much deeper the Marianas Trenchis than Mount Everest is high.

NASA/Science Source/Photo Researchers


eat other organisms return nutrientsmake food

Types of Ocean Organisms

Copy and complete the following concept map about types of ocean organisms.

CHAPTER STUDY GUIDE 399

Ocean Water

1. Oceans provide much of the oxygen and foodfor Earth’s organisms. Oceans interact withthe atmosphere to create weather and climate.

2. Scientists think early oceans formed whenwater, from the vapor of erupting volcanoes,condensed and filled low-lying areas.

3. Seawater is a combination of water, dis-solved solids, and dissolved gases.

4. Ocean temperatures vary with latitude anddepth. Water pressure is created by gravitypulling down water molecules.

Ocean Currents andClimate

1. Winds blowing across oceans producesurface currents. Earth’s rotation deflectssurface currents.

2. Ocean surface currents can be warm or cold,and affect the climates of coastal regions.

3. Density currents develop because watermasses have different temperatures anddifferent salinity levels.

Waves

1. Winds cause water to pile up, formingwaves.

2. Tides are created by the gravitationalattraction of Earth and the Moon andof Earth and the Sun.

Life in the Oceans

1. Plankton drift in ocean currents, and nek-ton actively swim. Some organisms live onthe seafloor.

2. In an ecosystem, producers, consumers, anddecomposers interact with each other andtheir surroundings.

3. Nutrients are cycled in the oceans.

makeup a

red.msscience.com/interactive_tutor(l)Tom & Therisa Stack/Tom Stack & Assoc., (r)W. Wayne Lockwood/CORBIS


Fill in the blanks with the correct vocabularywords.

1. __________ float in the upper layers ofoceans.

2. Organisms that get their energy from eatingother organisms are __________.

3. __________ are caused by wind blowingacross oceans.

4. __________ are caused by differences in theocean water’s salinity.

5. The layer of ocean water where thetemperature drops quickly with depthis the __________.

Choose the word or phrase that best answers thequestion.

6. Which of the following is a measure of dis-solved solids in seawater?A) density C) thermoclineB) nekton D) salinity

7. Which of these organisms is an example ofa bottom dweller?A) sea star C) sharkB) seal D) diatom

8. Which of these organisms is a producer?A) sea star C) sealB) coral D) algae

9. Which of the following terms is the highpoint of a wave?A) wavelength C) troughB) crest D) wave height

10. Which of the following terms is the lowpoint of a wave?A) wavelength C) troughB) crest D) wave height

Use the figure below to answer question 11.

11. Which type of tide forms when the Sun,the Moon, and Earth are aligned as shown?A) high tide C) spring tideB) low tide D) neap tide

12. Which substance is found in the mostcommon ocean salt?A) calciumB) chlorineC) carbonD) cobalt

13. Which of these gases is produced duringphotosynthesis?A) oxygenB) carbon dioxideC) nitrogenD) water vapor

14. Which of these terms describes the dailyrhythmic rise and fall of sea level?A) surface currentB) tideC) density currentD) upwelling

Sun

EarthMoon

400 CHAPTER REVIEW

chemosynthesis p. 391consumer p. 391decomposer p. 391density current p. 382ecosystem p. 391food chain p. 392nekton p. 390photosynthesis p. 377

plankton p. 389producer p. 391salinity p. 376surface current p. 380thermocline p. 378tide p. 387upwelling p. 384wave p. 385

red.msscience.com/vocabulary_puzzlemaker


CHAPTER REVIEW 401

15. Explain why a boat tied to a dock bobs upand down in the water.

16. Describe why the water at a beach in south-ern California is much colder than thewater at a beach in South Carolina.

17. Infer How would other ocean life in anarea be affected if an oil spill killed muchof the plankton in that area?

18. Discuss reasons why more marine creatureslive in shallow water near shore than inany other region of the oceans.

19. Interpret Scientific Illustrations Use Figure 20to describe how nitrogen is cycled fromthe atmosphere to marine organisms.

20. Compare and contrast the way that consumersand decomposers get their energy.

Use the illustration below to answer question 21.

21. Interpret Scientific Illustrations Infer whatwill happen to sea urchins and kelp ifsea otters decline in number.

22. Draw Conclusions Place the organisms inthe proper sequence in a food chain:krill, killer whale, algae, cod, leopard seal.

23. Letter Write to the National WildlifeFederation about coral bleaching. Askwhat is being done to protect coral reefs.

24. Pamphlet Research beach nourishment,jetties, and other ways that people havetried to reduce beach erosion. Createa pamphlet of your findings and passit out to your classmates.

25. Pressure The pressure at sea level is 1 atmos-phere. If the pressure increases by 1 atmospherefor every 10 m in depth, what is the pressure at200 m?

Use the figure below to answer question 26.

26. The Thermocline How much of a temperaturechange is there between the beginning of thethermocline and 1,200 m?

27. The Area of Oceans The Indian Ocean’s total areais 73.6 million km2. The Arctic Ocean’s total areais 14.1 million km2. How many times larger is theIndian Ocean than the Arctic Ocean?

Water Temperature and Depth

600

400

800

1,000

1,200

200

0

Average water temperature (�C)

Dep

th (i

n m

eter

s)

0 5 10 15 20 25

1,400

1,600

Surfacelayer

Thermocline

Deep-waterlayer

red.msscience.com/chapter_review

Bull sharksPeople

Sheepsheadfish

Sea otters

Abalone

Kelp

Sea urchins

Spiny lobsters


Record your answers on the answer sheet providedby your teacher or on a separate sheet of paper.

Use the table below to answer questions 1 and 2.

Ms. Mangan’s class is studying differentorganisms. Here is a table of some of theorganisms they have been studying.

1. The producers are different from the con-sumers because only the producers areable toA. swim in deep water.B. make their own food.C. contribute to the marine food web.D. digest the nutrients in other organisms.

2. What would happen to consumers if allproducers perished? A. Consumers would also die.B. Consumers would begin making their

own food.C. Consumers would decompose organic

matter.D. Consumers would move to a new

environment.

3. The layer of water in which temperaturedrops quickly with increasing depth is the A. surface layer.B. thermocline layer.C. deep-water layer.D. bottom layer.

4. Organisms that break down tissue andrelease nutrients and carbon dioxide backinto the ecosystem are calledA. producers. C. decomposers.B. consumers. D. photosynthetic.

Use the diagram below to answer questions 5 and 6.

5. What process is shown in the figure? A. downwellingB. density currentsC. El NiñoD. upwelling

6. Wind blowing parallel to the coast carrieswater away from land because ofA. the Coriolis effect.B. the gravitational pull of the Moon on

Earth.C. the gravitational pull of the Sun on

Earth.D. the speed of the wind.

Surface winds

Surface water

Cold water

402 STANDARDIZED TEST PRACTICE

Never skip a question. If you are unsure of an answer, markyour best guess on your answer sheet and mark the question inyour test booklet to remind you to come back to it at the end ofthe test.

Marine Organisms

Producers Consumers

Seaweed Krill

Kelp Squid

Algae Seal

STANDARDIZED TEST PRACTICE 403

Record your answers on the answer sheerprovided by your teacher or on a sheet of paper.

7. Ten percent of the total available energyis stored by a consumer at each level ofthe food chain. If 3,424 energy units arepassed on to a salmon feeding on zoo-plankton, how many energy units will thesalmon store?

8. The average depth of the ocean is 3,730 m.The Marianas Trench is 11,033 m deep. Howmany times deeper is the Marianas Trenchthan the average depth of the ocean? Roundyour answer to the nearest whole number.

9. Why aren’t all ocean surface currents thesame temperature?

Use the figure below to answer questions 10 and 11.

10. Some coastlines experience semidiurnaltides, or two high tides and two low tidesin approximately a 24-hour period. Othercoastlines experience diurnal tides, orone high tide and one low tide in approx-imately a 24-hour period. Which type oftide is shown in the graph above?

11. What is the tidal range during the period oftime tidal data was recorded for the graph?

Record your answer on a sheet of paper.

12. Explain why temperatures could decreasein some regions of Earth if global warm-ing occurred.

13. Why are some organisms considered to beplankton in one stage of their life but nek-ton in another stage of their life?

Use the graph below to answer questions 14–17.

14. Describe what happens to the levelsof oxygen concentration as water depthincreases.

15. Why is oxygen concentration at itshighest near the surface of the water?What accounts for the decrease in oxygenconcentration between about 200 m and500 m?

16. Explain why the concentration of oxygenincreases between 500 m and 2,000 m.

17. Infer how the levels of carbon dioxideconcentration would vary with depth.What biological processes affect theconcentration of carbon dioxide?

Oxygen Concentration and Water Depth

1,500

1,000

2,000

500

0

Concentration of dissolved oxygen(parts per million by weight)

Dep

th (m

)

1.5 3.0 4.5 6.0 7.5

O2

Tidal Data, Cape Cod, MA

1

2

0

�1

�2

3

4

Time (h)

Tid

al h

eig

ht

(m)

0 6 12 18 24 30 36 42 48

High tide

Low tide

red.msscience.com/standardized_test


oceanssediments, forming beaches. section 4 life in the oceans main idea the oceans are home to many...

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