What Is Biology? - johnbio.wikispaces.com · What Is Biology? Biologists seek answers to questions...

What IsBiology?What IsBiology?

Biologists seek answers to questions aboutliving things. For example, a biologistmight ask how plants, such as sunflowers,convert sunlight into chemical energy thatcan be used by the plants to maintain lifeprocesses. Biologists use many methods toanswer their questions about life. Duringthis course, you will gain an understandingof the questions and answers of biology, andhow the answers are learned.

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UNIT CONTENTSUNIT CONTENTS

Biology: The Study of Life

Unit 1Unit 1

What Is Biology?BIODIGESTBIODIGEST

UNIT PROJECTUNIT PROJECT

Use the Glencoe Science Web site for more project

activities that are connected to this unit.science.glencoe.com

BIOLOGY

http://science.glencoe.com

What You’ll Learn■ You will identify the charac-

teristics of life.■ You will recognize how scien-

tific methods are used tostudy living things.

Why It’s ImportantRecognizing life’s characteristicsand the methods used to studylife provide a basis for under-standing the living world.

2 BIOLOGY: THE STUDY OF LIFE

Biology: The Study of Life1

ChapterChapter

The plants and animals of this forest exhibit allthe characteristics of life.The mushrooms, and theunseen bacteria living in the soil and leaf litterof the forest floor, alsoshare the basic character-istics of life.

Scan the chapter’s section head-ings and make a short list ofexamples of ways you think scientists might work. Forinstance, under data collection,a list might include: computerfiling, taking photos, or takingnotes. Think of how businesses,schools or communities mightbenefit from these experimentsand research.

To find out more about thecharacteristics of living things,visit the Glencoe Science Web site.science.glencoe.com

READING BIOLOGYREADING BIOLOGY

BIOLOGY


Section

The Science of BiologyPeople have always been curious

about living things—how many dif-ferent species there are, where theylive, what they are like, how theyrelate to each other, and how theybehave. These and many other ques-tions about life can be answered. Theconcepts, principles, and theoriesthat allow people to understand thenatural environment form the core ofbiology, the study of life. What willyou, as a young biologist, learn aboutin your study of biology?

A key aspect of biology is simplylearning about the different types ofliving things around you. With all

the facts in biology textbooks, youmight think that biologists haveanswered almost all the questionsabout life. Of course, this is not true.There are undoubtedly many lifeforms yet to be discovered; millionsof life forms haven’t even beennamed yet, let alone studied. Life onEarth includes not only the commonorganisms you notice every day, butalso distinctive life forms that haveunusual behaviors.

When studying the different typesof living things, you’ll ask what, why,and how questions about life. Youmight ask, “Why does this livingthing possess these particular fea-tures? How do these features work?”

1.1 WHAT IS BIOLOGY? 3

How far do monarch butter-flies travel during theirannual migration? Why do

viceroy butterflies look so much likemonarchs? The natural world oftenposes questions like these. Usually,such questions have simple explana-tions, but sometimes the studyof biology reveals startlingsurprises. Whether nature’spuzzles are simple or complex,many can be explained usingthe concepts and principlesof biological science.

SECTION PREVIEW

ObjectivesRecognize some possible benefits fromstudying biology.Summarize the characteristics of livingthings.

Vocabularybiologyorganismorganizationreproductionspeciesgrowthdevelopmentenvironmentstimulusresponsehomeostasisenergyadaptationevolution

1.1 What Is Biology?

OriginWORDWORD

biologyFrom the Greekwords bios, meaning“life,” and logos,meaning “study.”Biology is the studyof life.

Monarch butterfly(above) and Viceroybutterfly (inset)

The answers to such questions leadto the development of general bio-logical principles and rules. Asstrange as some forms of life such asthose shown in Figure 1.1 mayappear to be, there is order in thenatural world.

Biologists study the interactions of life

One of the most general principlesin biology is that living things do notexist in isolation; they are all function-ing parts in the delicate balance ofnature. As you can see in Figure 1.2,


Figure 1.1Few of the creatures you readabout in works of fantasy andfiction are as unusual as someof the organisms that actuallylive on Earth.

Figure 1.2Questions about livingthings can sometimesbe answered only byfinding out about theirinteractions with theirsurroundings.

The seahorse iswell hidden in itsenvironment. Itsbody shape blendsin with the shapesof the seaweeds inwhich it lives.

AA

The spadefoot toad burrowsunderground and encasesitself in a waterproof envelope to prevent waterloss during extended periodsof dry weather.

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Leaves of the insect-eating pitcher plantform a tube lined withdownward-pointinghairs that preventinsects from escaping.Trapped insects fall intoa pool of water anddigestive juices at thebottom of the tube.

CC

Orcas, also known as killer whales, arehighly intelligentmarine mammals thatlive and hunt in socialunits called pods.

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Leaf-cutter ants feed onfungus. They carry bits ofleaves to their nest, thenchew the bits and formthem into moist balls onwhich the fungus grows.

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living things depend upon other livingand nonliving things in a variety ofways and for a variety of reasons.

Biologists Study theDiversity of Life

Many people study biology simplyfor the pleasure of learning about theworld of living things. As you’veseen, the natural world is filled withexamples of living things that can beamusing or amazing, and that chal-lenge one’s thinking. Through yourstudy of biology, you will come toappreciate the great diversity ofspecies on Earth and the way eachspecies fits into the dynamic patternof life on our planet.

Biologists study the interactionsof the environment

Because no species, includinghumans, can exist in isolation, thestudy of biology must include theinvestigation of interactions amongspecies. For example, learning abouta population of wild rabbits wouldrequire finding out what plants theyeat and what animals prey on them.The study of one species alwaysinvolves the study of other specieswith which it interacts.

Human existence, too, is closelyintertwined with the existence ofother organisms living on Earth.Plants and animals supply us withfood and with raw materials likewood, cotton, and oil. Plants alsoreplenish the essential oxygen in theair. The students in Figure 1.3 arestudying organisms that live in a localstream. Activities like this help pro-vide a thorough understanding of liv-ing things and the intricate web ofnature. It is only through suchknowledge that humans can expect tounderstand how to preserve thehealth of our planet.

Biologists study problems and propose solutions

The future of biology holds manyexciting promises. Biological researchcan lead to advances in medical treat-ment and disease prevention inhumans and in other species. It canreveal ways to help preserve speciesthat are in danger of disappearing,and solve other problems, includingthe one described in Figure 1.4. Thestudy of biology will teach you howhumans function and how we fit inwith the rest of the natural world. Itwill also equip you with the knowl-edge you need to help sustain thisplanet’s web of life.


Figure 1.3By understanding theinteractions of livingthings, you will bebetter able to impactthe planet in a posi-tive way.

Figure 1.4Honeybees and manyother insects areimportant to farmersbecause they polli-nate the flowers ofcrop plants, such asfruit trees. In the1990s, populations of many pollinatorsdeclined, raising wor-ries about reducedcrop yields.

Characteristics of Living Things

Most people feel confident thatthey can tell the difference between aliving thing and a nonliving thing, butsometimes it’s not so easy. In identify-ing life, you might ask, “Does it

move? Does it grow? Does it repro-duce?” These are all excellent ques-tions, but consider a flame. A flamecan move, it can grow, and it can pro-duce more flames. Are flames alive?

Biologists have formulated a list ofcharacteristics by which we can rec-ognize living things. Sometimes,nonliving things have one or more oflife’s characteristics, but only whensomething has all of them can it beconsidered living. Anything that pos-sesses all of the characteristics of lifeis known as an organism, like theplants shown in Figure 1.5. All livingthings have an orderly structure, pro-duce offspring, grow and develop,and adjust to changes in the environ-ment. Practice identifying the char-acteristics of life by carrying out theMiniLab on this page.


Predicting Whether Mildew is Alive What is mildew? Is it alive? We see it “growing” on plastic shower curtains or on bathroom grout. Does it show the characteris-tics associated with living things?

Procedure! Copy the data table below.

@ Predict whether or not mildew is alive. Record your prediction in the data table under “First Prediction.”

# Obtain a sample of mildew from your teacher. Examine it for life characteristics. Make a second prediction andrecord it in the data table along with any observed lifecharacteristics. CAUTION: Wash hands thoroughly afterhandling the mildew sample.

$ Following your teacher’s directions, prepare a wet mountof mildew for viewing under the microscope. CAUTION:Use caution when working with a microscope, micro-scope slides, and cover slips.

% Are there any life characteristics visible through the microscope that you could not see before? Make a thirdprediction and include any observed life characteristics.

Analysis 1. Describe any life characteristics you observed.2. Compare your three predictions and explain how your

observations may have changed them. 3. Explain the value of using scientific tools to extend your

powers of observation.

MiniLab 1-1MiniLab 1-1

Prediction Life characteristics

First

Second

Third

none

Data TableFigure 1.5These plants are called Lithops from theGreek lithos, meaning “stone.” Althoughthey don’t appear to be so, Lithops arejust as alive as elephants. Both speciespossess all of the characteristics of life.

Mildew

Observing

Living things are organizedWhen biologists search for signs of

life, one of the first things they lookfor is structure. That’s because theyknow that all living things show anorderly structure, or organization.

The living world is filled withorganisms. All of them, including theearthworm pictured in Figure 1.6,are composed of one or more cells.Each cell contains the genetic mater-ial, or DNA, that provides all theinformation needed to control theorganism’s life processes.

Although living things are verydiverse—there may be five to tenmillion species, perhaps more—theyare unified in having cellular organi-zation. Whether an organism is madeup of one cell or billions of cells, allof its parts function together in anorderly, living system.

Living things make more living things

One of the most obvious of all thecharacteristics of life is reproduction,the production of offspring. The litter of mice in Figure 1.7 is just one example. Organisms don’t live

forever. For life to continue, theymust replace themselves.

Reproduction is not essential forthe survival of an individual organ-ism, but it is essential for the contin-uation of the organism’s species(SPEE sheez). A species is a group oforganisms that can interbreed andproduce fertile offspring in nature. Ifindividuals in a species never repro-duced, it would mean an end to thatspecies’ existence on Earth.


Figure 1.6Like all organisms,earthworms aremade up of cells. Thecells form structuresthat carry out essen-tial functions, such asfeeding or digestion.The interaction ofthese structures andtheir functions resultin a single, orderly,living organism.

Figure 1.7A variety of mecha-nisms for reproduc-tion have evolvedthat ensure the con-tinuation of eachspecies. Some organ-isms, including mice,produce many off-spring in one life-time.

CAREERS IN BIOLOGY

Nature PreserveInterpreter

I f you like people as much as youlove nature, you can combine

your skills and interests in a careeras a nature preserve interpreter.

Skills for the JobInterpreters are also called natu-

ralists, ecologists, and environmentaleducators. They might work for a naturepreserve or a state or national park, where they give talks,conduct tours, offer video presentations, and teach specialprograms. Some interpreters are required to have a degree inbiology, botany, zoology, forestry, environmental science,education, or a related field. They must also be skilled in com-municating with others.

Many interpreters begin as volunteers who have nodegrees, just a love of what they do. Over time, volunteersmay become interns, and eventually be hired. Interpretersoften help restore natural habitats and protect existing ones.Part of their job is to make sure visitors do not harm thesehabitats.

For example, many tidepool organisms find protectionfrom too much sunlight by crawling under rocks. A naturalistcan explain the importance of replacing rocks exactly as theywere found.


Figure 1.8All life begins as a singlecell. As cells multiply, each organism grows anddevelops and begins to take on the characteristicsthat identify it as a memberof a particular species.

Living things change during their lives

An organism’s life begins as a singlecell, and over time, it grows and takeson the characteristics of its species.Growth results in an increase in theamount of living material and theformation of new structures.

All organisms grow, with differentparts of the organism growing at differ-ent rates. Organisms made up of onlyone cell may change little during theirlives, but they do grow. On the otherhand, organisms made up of numerouscells go through many changes duringtheir lifetimes, such as the changes thatwill take place in the young nestlingsshown in Figure 1.8. Think aboutsome of the structural changes yourbody has already undergone since youwere born. All of the changes thattake place during the life of an organ-ism are known as its development.

Living things adjust to their surroundings

Organisms live in a constant inter-face with their surroundings, orenvironment, which includes the air,water, weather, temperature, anyother organisms in the area, and

BIOLOGY For more careers in relatedfields, be sure to check theGlencoe Science Web site.science.glencoe.com


many other factors. For example, thefox in Figure 1.9 feeds on small ani-mals such as rabbits and mice. Thefox responds to the presence of a rab-bit by quietly moving toward it, thenpouncing. Trees adjust to cold, drywinter weather by losing their leaves.Any condition in the environmentthat requires an organism to adjust isa stimulus. A reaction to a stimulusis a response.

The ability to respond to stimuli inthe environment is an importantcharacteristic of living things. It’s oneof the more obvious ones, as well.That’s because many of the structuresand behaviors that you see in organ-isms enable them to adjust to theenvironment. Try the BioLab at theend of this chapter to find out moreabout how organisms respond toenvironmental stimuli.

Regulation of an organism’s inter-nal environment to maintain condi-tions suitable for its survival is calledhomeostasis (hoh mee oh STAY sus).Homeostasis is a characteristic of lifebecause it is a process that occurs in allliving things. In addition to respond-ing to external stimuli, living things

respond to internal changes. Forexample, organisms must make con-stant adjustments to maintain the cor-rect amount of water and minerals intheir cells and the proper internal tem-perature. Without this ability to adjustto internal changes, organisms die.

Living things reproduce themselves,grow and develop, respond to exter-nal stimuli, and maintain homeostasisby using energy. Energy is the abilityto do work. Organisms get theirenergy from food. Plants make theirown food, whereas animals, fungi,and other organisms get their foodfrom plants or from organisms thatconsume plants.

Living things adapt and evolveAny structure, behavior, or inter-

nal process that enables an organismto respond to stimuli and better sur-vive in an environment is called anadaptation (ad ap TAY shun).

Adaptations are inherited from pre-vious generations. There are alwayssome differences in the adaptations ofindividuals within any population of organisms. As the environmentchanges, some adaptations are more


Figure 1.9Living things respond to stimuli and makeadjustments to environmental conditions.

By dropping their leaves in the fall,these trees conserve water and avoidfreezing during winter.

AA

Keen senses ofsmell and hearingenable a fox tofind prey. Furallows foxes andother mammals to regulate bodytemperature.

BB

suited to the new conditions thanothers. Individuals with more suit-able adaptations are more likely tosurvive and reproduce. As a result,individuals with these adaptationsbecome more numerous in the popu-lation. Figure 1.10 shows someexamples of adaptation.

The gradual accumulation of adap-tations over time is evolution (ev uhLEW shun). Clues to the way the pre-sent diversity of life came about maybe understood through the study of

evolution. In later chapters of thisbook, you will study how the theoryof evolution can help answer many ofthe questions people have about liv-ing things.

As you learn more about Earth’sorganisms in this book, reflect on thegeneral characteristics of life. Ratherthan simply memorizing facts aboutorganisms or the vocabulary terms,try to see how these facts and vocab-ulary are related to the characteristicsof living things.


Section AssessmentSection AssessmentUnderstanding Main Ideas1. What are some important reasons for studying

biology?2. Explain the difference between a stimulus and

a response and give an example of each. How do these terms relate to an organism’s internalenvironment?

3. Why is energy required for living things? How do living things obtain energy?

4. How are evolution and reproduction related?

Thinking Critically5. How are energy and homeostasis related in living

organisms?

6. Observing and Inferring Suppose you discoveran unidentified object on your way home fromschool one day. What characteristics would youstudy to determine whether the object is a livingor nonliving thing? For more help, refer toThinking Critically in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

Figure 1.10Living things adapt to their envi-ronments in a variety of ways.

Rotifers are microscopicorganisms that create awater current with theirwheels of cilia. They feedon microscopic food parti-cles brought in with the current.

AA

The desert Octillo has leaves for onlya few days after a good rain. Thisadaptation helps conserve water.

BB

Many nocturnal animals, such as thisowl, possess largeeyes for efficientvision at night.

CC

Magnification:100�

Section

Observing andHypothesizing

Curiosity is often what motivatesbiologists to try to answer simplequestions about everyday observa-tions, such as why earthworms leavetheir burrows after it rains.Earthworms obtain oxygen throughtheir skin, and will drown in water-logged soil. Sometimes, answers toquestions like these also provide bet-ter understanding of general biologi-cal principles and may even lead topractical applications, such as the dis-covery that a certain plant can beused as a medicine. The knowledgeobtained when scientists answer onequestion often generates other ques-tions or proves useful in solvingother problems.

The methods biologists useTo answer questions, different

biologists may use many differentapproaches, yet there are some stepsthat are common to all approaches.The common steps that biologistsand other scientists use to gatherinformation and answer questions arescientific methods.

Scientists often identify problemsto solve—that is, questions to ask andanswer—simply by observing theworld around them. For example, alaboratory scientist who is investigat-ing questions about the reproductionof pea plants may come up with anew question about their develop-ment. Or, a scientist may ask a ques-tion about the feeding habits ofprairie dogs after first observingprairie dog behavior in the field.

1.2 THE METHODS OF BIOLOGY 11

Why do earthworms crawlonto sidewalks after itrains? Why do mosses grow

only in wet, shady areas? Biologistsask questions like these every day.Different approaches may be used toanswer different questions. Scientistswho discovered that earthwormscrawl out of rain-soaked soil to avoiddrowning used different methodsfrom those who learned that mossesrequire water for reproduction. Yet all scientific inquiries share somemethods in common.

SECTION PREVIEW

ObjectivesCompare different sci-entific methods.Differentiate amonghypothesis, theory, andprinciple.

Vocabularyscientific methodshypothesisexperimentcontrolindependent variabledependent variablesafety symboldatatheory

1.2 The Methods of Biology

Mosses are tiny plants thatgrow in dense clumps.

The question of brown tree snakes

Have you ever been told that youhave excellent powers of observation?This is one trait that is required ofbiologists. The story of the browntree snake in Figure 1.11 serves as anexample. During the 1940s, thisspecies of snake was accidentallyintroduced to the island of Guamfrom the Admiralty Islands in thePacific Ocean. In 1965, it wasreported in a local newspaper that thesnake might be considered beneficialto the island because it is a predatorthat feeds on rats, mice, and othersmall rodents. Rodents are often con-sidered pests because they carry dis-ease and contaminate food supplies.

Shortly after reading the newspa-per report, a young biologist walkingthrough the forests of Guam made animportant observation. She notedthat there were no bird songs echoingthrough the forest. Looking into thetrees, she saw a brown tree snakehanging from a branch. After learningthat the bird population of Guam haddeclined rapidly since the introduc-tion of the snake, she hypothesizedthat the snake might be responsible.

A hypothesis (hi PAHTH us sus) is anexplanation for a question or a prob-lem that can be formally tested.Hypothesizing is one of the methodsmost frequently used by scientists. Ascientist who forms a hypothesis mustbe certain that it can be tested. Untilthen, he or she may propose sugges-tions to explain observations.

As you can see from the brown treesnake example, a hypothesis is not arandom guess. Before a scientistmakes a hypothesis, he or she hasdeveloped some idea of what theanswer to a question might bethrough personal observations, exten-sive reading, or previous experiments.

After stating a hypothesis, a scien-tist may continue to make observa-tions and form additional hypothesesto account for the collected data.Eventually, the scientist may test ahypothesis by conducting an experi-ment. The results of the experimentwill help the scientist draw a conclu-sion about whether or not thehypothesis is correct.

ExperimentingPeople do not always use the word

experiment in their daily lives in thesame way scientists use it in theirwork. As an example, you may haveheard someone say that he or she wasgoing to experiment with a cookierecipe. Perhaps the person is planningto substitute raisins for chocolatechips, use margarine instead of butter,add cocoa powder, reduce the amountof sugar, and bake the cookies for alonger time. This is not an experimentin the scientific sense because there isno way to know what effect any one ofthe changes alone has on the resultingcookies. To a scientist, an experimentis a procedure that tests a hypothesisby the process of collecting informa-tion under controlled conditions.


Figure 1.11Brown tree snakes(Boiga irregularis)were introduced toGuam more than 50years ago. Sincethen, their numbershave increased to apopulation of morethan a million andthey have severelyreduced the nativebird population ofthe island.

OriginWORDWORD

hypothesisFrom the Greekwords hypo, meaning“under,” and thesis,meaning a “plac-ing.” A hypothesisis a testable expla-nation of a naturalphenomenon.

What is a controlled experiment? Some experiments involve two

groups: the control group and theexperimental group. The control isthe group in which all conditions arekept the same. The experimentalgroup is the test group, in which allconditions are kept the same exceptfor the single condition being tested.

Suppose you wanted to learn howbacteria affect the growth of differentvarieties of soybean plants. Yourhypothesis might state that the pres-ence of certain bacteria will increasethe growth rate of each plant variety.An experimental setup designed totest this hypothesis is shown inFigure 1.12. Bacteria are present onthe roots of the experimental plants,but not the controls. All other condi-tions—including soil, light, water,and fertilizer—are held constant forboth groups of plants.

Designing an experimentIn a controlled experiment, only

one condition is changed at a time.The condition in an experiment that ischanged is the independent variable,because it is the only variable thataffects the outcome of the experi-ment. In the case of the soybeans, the presence of bacteria is the inde-pendent variable. While changingthe independent variable, the scien-tist observes or measures a secondcondition that results from thechange. This condition is the dependent variable, because anychanges in it depend on changesmade to the independent variable. Inthe soybean experiment, the depen-dent variable is the growth rate of theplants. Controlled experiments aremost often used in laboratory settings.

However, not all experiments arecontrolled. Suppose you were on agroup of islands in the Pacific that isthe only nesting area for a large sea

bird known as a waved albatross,shown in Figure 1.13. Watching thenesting birds, you observe that thefemale leaves the nest when her mateflies back from a foraging trip. Thebirds take turns sitting on the eggsor caring for the chicks, often fortwo weeks at a time. You mighthypothesize that the birds fly in cir-cles around the island, or that theyfly to some distant location. To testone of these hypotheses, you mightattach a satellite transmitter to someof the birds and record their travels.An experiment such as this, which


Figure 1.12This experimenttested the effect ofbacteria on thegrowth of severalvarieties of soybeans.For each experimentthere are three rowsof each variety. Thecenter rows are theexperimental plants.The outer rows arethe controls.

Figure 1.13The waved albatross is alarge bird that nests onlyon Hood Island in theGalapagos Islands. Bytagging the birds withsatellite transmitters, scientists have learnedwhere these birds travel.

Testing for Alcohol Commercials forcertain over-the-counter products maynot tell you that one of the ingre-dients is alcohol. How can youverify whether or not a certainproduct contains alcohol? Oneway is to simply rely on theinformation provided during a commercial. Another way is to experiment and find outfor yourself.

Procedure! Copy the data table.

@ Draw three circles on a glass slide. Label them A, B, and C.CAUTION: Put on safety goggles.

# Add one drop of water to circle A, one drop of alcohol tocircle B, and one drop of alcohol-testing chemical to circlesA, B, and C. CAUTION: Rinse immediately with water iftesting chemical gets on skin or clothing.

$ Wait 2-3 minutes. Note in the data table the color of eachliquid and the presence or absence of alcohol.

% Record the name of the first product to be tested.^ Draw a circle on a clean glass slide. Add one drop of the

product to the circle.& Add a drop of the alcohol-testing chemical to the circle.

Wait 2-3 minutes. Record the color of the liquid.* Repeat steps 5-7 for each product to be tested. CAUTION:

Wash your hands with soap and water immediately afterusing the alcohol testing chemical.

( Complete the last column of the data table. If alcohol is present, the liquid turns green, deep green, or blue. A yellow or orange color means no alcohol is present.

Analysis1. Explain the purpose of using the alcohol-testing chemical

with water, with a known alcohol, and by itself.2. Which products did contain alcohol? No alcohol?

MiniLab 1-2MiniLab 1-2has no control, is the type of biologi-cal investigation most often used infield work.

The experimental design that isselected depends on what otherexperimenters have done and whatinformation the biologist hopes togain. Sometimes, a biologist willdesign a second experiment evenwhile a first one is being conducted,if he or she thinks the new experi-ment will help answer the question.Try your hand at experimenting inthe MiniLab on this page.

Using toolsTo carry out experiments, scientists

need tools that enable them to recordinformation. The growth rate ofplants and the information from satel-lite transmitters placed on albatrossesare examples of important informa-tion gained from experiments.

Biologists use a wide variety oftools to obtain information in anexperiment. Some common toolsinclude beakers, test tubes, hotplates, petri dishes, thermometers,dissecting instruments, balances,metric rulers, and graduated cylin-ders. More complex tools includemicroscopes, centrifuges, radiationdetectors, spectrophotometers, DNAanalyzers, and gas chromatographs.Figure 1.14 shows some of thesemore complex tools.

Maintaining safety Safety is another important factor

that scientists consider when carryingout experiments. Biologists try tominimize hazards to themselves, thepeople working around them, andthe organisms they are studying.

In the experiments in this text-book, you will be alerted to possiblesafety hazards by safety symbols likethose shown in Table 1.1. A safetysymbol is a symbol that warns you


Alcohol presentColor of liquid

Circle A

Circle B

Circle C

Product name

Product name

Data Table

Experimenting

about a danger that may exist fromchemicals, electricity, heat, or proce-dures you will use. Refer to the safetysymbols in Appendix C at the back ofthis book before beginning any labactivity in this text. It is your respon-sibility to maintain the highest safetystandards to protect yourself as wellas your classmates.

Data gatheringTo answer their questions about

scientific problems, scientists seekinformation from their experiments.Information obtained from experi-ments is called data. Sometimes, datafrom experiments are referred to asexperimental results.

Often, data are in numerical form,such as the distance covered in analbatross’s trip or the height that soy-bean plants grow per day. Numericaldata may be measurements of time,temperature, length, mass, area, vol-ume, or other factors. Numericaldata may also be counts, such as thenumber of bees that visit a flower per day or the number of wheat seeds that germinate at different soiltemperatures.

Sometimes data are expressed inverbal form, using words to describeobservations made during an experi-ment. Scientists who first observedthe behavior of pandas in Chinaobtained data by recording whatthese animals do in their naturalhabitat and how they respond totheir environment. Learning thatpandas are solitary animals with largeterritories helped scientists under-stand how to provide better care forthem in zoos and research centers.

Having the data from an experi-ment does not end the scientificprocess. Read the Focus On on thenext page to see how data collectionrelates to other important aspects ofresearch.


Sharp Object Safety This symbol appears when a danger of cuts or punctures caused by the use of sharp objects exists.

Clothing Protection Safety This symbol appears when substances used could stain or burn clothing.

Eye Safety This symbol appears when a danger to the eyes exists. Safety goggles should be worn when this symbol appears.

Chemical Safety This symbol appears when chemicals used can cause burns or are poisonous if absorbed through the skin.

Table 1.1 Safety symbols

Figure 1.14Biologists use manytools in their studies.

The gas chromatographcan measure pesticideresidues in plants orfishes.

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Gel electrophoresiscan be used to produce a DNA fingerprint asshown. ComparingDNA reveals howclosely related twospecies are.

AA

The optical micro-scope makes smalldetails visible.

CC

MAKING HYPOTHESESReptiles are ectotherms—animals with body temperatures influenced

by their external environments. Early in the study of dinosaur fossils,many scientists assumed that because dinosaur skeletons resembled thoseof some modern reptiles, dinosaurs, too, must have been ectotherms. Thisassumption led scientists to conclude that many dinosaurs, being both hugeand ectothermic, were slow-growing, slow-moving, and awkward on land.

Because the most complete dinosaur skeletons occurred in rocks formedat the bottom of bodies of water, scientists hypothesized that dinosaurs

lived in water and that water helped to support their great weight. Whenskeletons of duck-billed dinosaurs, called hadrosaurs, were discovered, thishypothesis gained support. Hadrosaurs had broad, flat ducklike bills,which, scientists suggested, helped them collect and eat water plants.

IGUANODON

What is a scientific theory? Incasual usage, “theory” meansan unproven assumption abouta set of facts. A scientifictheory is an explanation of anatural phenomenon supportedby a large body of scientificevidence obtained from variousinvestigations and observa-tions. The scientific processbegins with observations of thenatural world. These observa-tions lead to hypotheses, datacollection, and experimentation.If weaknesses are observed,hypotheses are rejected ormodified and then tested againand again. When little evidenceremains to cause a hypothesisto be rejected, it may become atheory. Follow the scientific process described here that led to new theories about dinosaurs.

OBSERVINGPeople have been unearthingfossils for hundreds of years.The first person to reconstruct a dinosaur named it Iguanodon,meaning “iguana tooth,”because its bones and teethresembled those of an iguana.By 1842 these extinct animalswere named dinosaurs, meaning“terrible lizards.”

FOCUS ON

FIELD MUSEUM OF NATURAL HISTORY, CHICAGO

ScientificTheories

HADROSAUR

16

FORMING THEORIES Bakker’s hypotheses—supported by data gathered byother paleontologists and by dinosaur bones, growth pat-terns, and behavior—prompted scientists to reexaminetheories about dinosaurs. Were some dinosaurs endothermsand others ectotherms? Did dinosaurs have their ownunique physiology resembling neither reptiles nor mam-mals? Scientific theories about dinosaurs continue toevolve as new fossils are discovered and new tools to studythose fossils are developed.

THINKING CRITICALLYIn the 1960s, paleontologist Robert Bakker (right)hypothesized that dinosaurs were not sluggishectotherms but fast-moving, land-dwellingendotherms—animals like birds and mammals.Bakker observed that many dinosaurs had feet andlegs built for life on land. If hadrosaurs had led asemiaquatic life, Bakker reasoned, their feet wouldhave been webbed with long, thin, widely spaced

toes. But hadrosaurs had short, stubby toes and feet, obviouslysuited for land. In addition to Bakker’s observations, studies of fos-silized stomach contents revealed that hadrosaurs dined on thecones and leaves of cycads (above) and other terrestrial plants.After considering these data carefully, Bakker proposed that manydinosaurs were quick, agile endotherms that roamed Earth’sancient landscape.

COLLECTING DATA To test his hypotheses, Bakker intensified his research ondinosaur skeletons and bone structure. He found reportsfrom the 1950s comparing thousands of cross sections ofdinosaur bones with those of reptiles, birds, and mammals.These reports noted that many dinosaur bones were lessdense than those of modern reptiles and riddled with chan-nels for blood vessels. In short, many dinosaur bones resem-bled those of endotherms not ectotherms. Bakker confirmedhis observations by collecting supporting evidence fromother sources.

1 APPLYING CONCEPTS Robert Bakker’s research led to a differenttheory regarding the physiology of dinosaurs. As new fossils are foundand new tools developed to study them, paleontologists will continue toreplace existing theories with newer ones. What are some reasons fora scientific theory to be changed?

EXPANDING Your View

BREAD PALM, CYCAD FAMILY

ROBERT BAKKER

DINOSAUR BONE SHOWINGCHANNELS FOR BLOOD VESSELSMagnification: 25 x

PALEONTOLOGIST WORKING ON FOSSIL

ROBERT BAKKER WITHBRONTOSAUR FEMUR

Are the claims valid? ”Our product is new and improved.” “Use this mouth wash and your mouth will feel clean all day.” Sound familiar? TV and radio commercials con-stantly tell us how great certain products are. Are these claims always based on facts?

AnalysisListen to or view a

commercial for a product that addresses a medical problem such as heartburn, allergies, or bad breath. If possible, tape the commercial so that you can replay it as often as needed. Record the following information:1. What is the major claim made in the commercial?2. Is the claim based on experimentation?3. What data, if any, are used to support the claim?

Thinking Critically1. In general, was the claim based on scientific methods?

Explain your answer.2. In general, are product claims made in commercials

based on experimental evidence? Explain your answer.

3. Describe a scientific experiment that could be conductedto establish claims made for the product in your commercial.

Problem-Solving Lab 1-1Problem-Solving Lab 1-1 AnalyzingInformation

Thinking about what happened Often, the thinking that goes into

analyzing experimental data takes thegreatest amount of a scientist’s time.After careful review of the results, thescientist must come to a conclusion:Was the hypothesis supported by thedata? Was it not supported? Aremore data needed? Data from anexperiment may be considered con-firmed only if repeating that experi-ment several times yields similarresults. To review how scientificmethods are carried out, read theInside Story.

After analyzing the data, most sci-entists have more questions than theyhad before the experiment. Theycompare their results and conclusionswith the results of other studies byresearching the published literaturefor more information. They alsobegin to think of other experimentsthey might carry out. Are all theclaims you hear on TV commercialsbased on data gathered by the scien-tific method? Find out by conductingthe Problem-Solving Lab here.

Reporting results Results and conclusions of experi-

ments are reported in scientific journals,where they are open to examinationby other scientists. Hundreds of sci-entific journals are published weeklyor monthly. In fact, scientists usuallyspend a large part of their time read-ing journal articles to keep up withnew information as it is reported.The amount of information pub-lished every day in scientific journalsis more than any single scientistcould read. Fortunately, scientistsalso have access to computer data-bases that contain summaries of sci-entific articles, both old and new.

Verifying resultsData and conclusions are shared

with other scientists for an importantreason. After results of an investiga-tion have been published, other sci-entists can try to verify the results byrepeating the experiment. If theyobtain similar results, there is evenmore support for the hypothesis.When a hypothesis is supported bydata from additional experiments, itis considered valid and is generallyaccepted by the scientific community.When a scientist publishes the resultsof his or her investigation, other sci-entists can relate their own work tothe published data.


19

Scientific Methods

Scientific methods are used by scientists to answerquestions and solve problems. The development of

the cell theory, one of the most useful theories in biologi-cal science, illustrates how the methods of science work.In 1665, Robert Hooke first observed cells in cork.

Thinking Critically What is the function of other scien-tists in the scientific process?

Magnification: 30�

Cork cells as drawn by Robert Hooke

INSIDESSTORTORYY

INSIDE

Observing The first step toward scientificdiscovery takes place when a scientist observessomething no one has noticed before. AfterHooke’s discovery, other scientists observedcells in a variety of organisms.

11

Making a hypothesis A hypothesis is a testableanswer to a question. In 1824, René Dutrochethypothesized that cells are the basic unit of life.

22

Collecting data Data can support ordisprove a hypothesis. Over the years,scientists who used microscopes toexamine organisms found that cellsare always present.

33

Forming a theoryA theory is a hypoth-esis that is supportedby a large body ofscientific evidence.By 1839, many scien-tific observationssupported thehypothesis that cellsare fundamental tolife. The hypothesisbecame a theory.

55

Developing new hypotheses A new the-ory may prompt scientists to ask new ques-tions or form additional hypotheses. In 1833,Robert Brown hypothesized that the nucleusis an important control center of the cell.

66

Revising the theory Theories are revised asnew information is gathered. The cell theorygave biologists a start for exploring the basicstructure and function of all life. Importantdiscoveries, including the discovery of DNA,have resulted.

77

Publishing results Results ofan experiment are useful onlyif they are made available toother scientists. Many scientistspublished their observations ofcells in the scientific literature.

44

For example, biologists studyingthe behavior of elephants in Africapublished their observations. Otherscientists, who were studying ele-phant communication, used that datato help determine which of the ele-phants’ behaviors are related to com-munication. Further experimentsshowed that female elephants emitcertain sounds in order to attractmates, and that some of the sounds

produced by bull elephants warnother males away from receptivefemales, as described in Figure 1.15.

Theories and lawsPeople use the word theory in

everyday life very differently fromthe way scientists use this word. Youmay have heard someone say that heor she has a theory that a particularfootball team will win the SuperBowl this year. What the personreally means is that he or she believesone team will play better for somereason. Much more evidence isneeded to support a scientific theory.

In science, a hypothesis that is sup-ported by many separate observationsand experiments, usually over a longperiod of time, becomes a theory. Atheory is an explanation of a naturalphenomenon that is supported by alarge body of scientific evidenceobtained from many different investi-gations and observations. A theoryresults from continual verificationand refinement of a hypothesis.

In addition to theories, scientistsalso recognize certain facts of nature,called laws or principles, that aregenerally known to be true. The factthat a dropped apple falls to Earth isan illustration of the law of gravity.


Figure 1.15Experiments haveshown that male ele-phants communicatewith other malesusing threat posturesand low-frequencyvibrations that warnrival males away.

Section AssessmentSection AssessmentUnderstanding Main Ideas1. Suppose you made the observation that bees

seem to prefer a yellow flower that producesabundant amounts of pollen and nectar over apurple flower that produces less pollen and nec-tar. List two separate hypotheses that you mightmake about bees and flowers.

2. Describe a controlled experiment you could per-form to determine whether ants are moreattracted to butter or to honey.

3. What is the difference between a theory and ahypothesis?

4. Why do experiments usually require a control?

Thinking Critically5. Describe a way that a baker might conduct

a controlled experiment with a cookie recipe.

6. Interpreting Scientific Illustrations Reviewthe Inside Story. What happens when a hypothe-sis is not confirmed? What does the position ofthe word theory indicate about the strength of a scientific theory compared to the strength of ahypothesis? For more help, refer to ThinkingCritically in the Skill Handbook.


Section

Kinds of ResearchYou have learned that scientists use

a variety of methods to test theirhypotheses about the natural world.Scientific research can usually beclassified into one of two main types,quantitative or descriptive.

Quantitative researchBiologists sometimes conduct con-

trolled experiments that result incounts or measurements—that is,numerical data. These kinds ofexperiments occur in quantitative

research. The data are analyzed bycomparing numerical values.

Data obtained in quantitativeresearch may be used to make agraph or table. Graphs and tablescommunicate large amounts of datain a form that is easy to understand.Suppose, for example, that a biologistis studying the effects of climate onfreshwater life. He or she may countthe number of microscopic organ-isms, called Paramecium, that surviveat a given temperature. This study isan example of quantitative research.

1.3 THE NATURE OF BIOLOGY 21

Scientific study includeslearning many knownfacts about the world

around us. Biologists useknown facts to discover newproblems, make hypotheses,design experiments, inter-pret data, and draw conclu-sions. Biology is also anactive process that includesmaking observations andconducting experiments inthe laboratory and in thefield. Science is both a body of facts andideas and a process by which we come tounderstand the natural world.

SECTION PREVIEW

Compare and contrastquantitative anddescriptive research.Explain why scienceand technology cannotsolve all problems.

Vocabularyethicstechnology

1.3 The Nature of Biology

Biologists study thestructure of the humanbrain (top) and observeanimal behavior (inset).

What can be learned from a graph? One way to express information is to present it in the form of a graph. The amount of information available from a graph depends on the nature of the graph itself.

AnalysisStudy the graph at

right. Answer the ques-tions that follow and note the type of information that can and cannot be answered from the graph itself.

Thinking Critically1. Is there ever a year in high school when all students

are enrolled in physical education? Explain your answer.

2. Is there a relationship between the number of studentsenrolled in physical education and their year of highschool? Explain your answer.

3. Can you tell which states in the country have the largestnumber of students enrolled in physical education?

4. Based on the graph, can you explain why so few studentstake physical education in their senior year?

Problem-Solving Lab 1-2Problem-Solving Lab 1-2 Making andUsing Graphs

The data obtained from theParamecium study is presented as agraph in Figure 1.16. You can prac-tice using graphs by carrying out theProblem-Solving Lab on this page.

Measuring in the International System

It is important that scientificresearch be understandable to scien-tists around the world. For example,what if scientists in the United Statesreported quantitative data in inches,feet, yards, ounces, pounds, pints,quarts, and gallons? People in manyother countries would have troubleunderstanding these data because theyare unfamiliar with the English systemof measurement. Instead, scientistsalways report measurements in a formof the metric system called theInternational System of Measurement,commonly known as SI.

One advantage of SI is that thereare only a few basic units, and nearlyall measurements can be expressed inthese units or combinations of them.The greatest advantage is that SI, likethe metric system, is a decimal sys-tem. Measurements can be expressed


Num

ber o

f Par

amec

ia S

urvi

ving

Temperature

Paramecium Survival RatesFigure 1.16This graph shows howmany paramecia surviveas the temperatureincreases.

9

100

80

60

40

20

010Grade

11 12

Perc

ent

Male

Female

U.S. Students Enrolled in Physical Education

Source: Youth Risk Behavior Survey, 1995

Paramecium

Magnification: 65�

in multiples of tens or tenths of abasic unit by applying a standard setof prefixes to the unit. In biology, themetric units you will encounter mostoften are meter (length), gram(mass), liter (volume), second (time),and Celsius degree (temperature).For a thorough review of measure-ment in SI, see Practicing ScientificMethods in the Skill Handbook.

Descriptive research Do you think the behavior of the

animals shown in Figure 1.17 wouldbe easier to explain with numbers orwith written descriptions of what theanimals did? Observational data—that is, written descriptions of whatscientists observe—are often just asimportant in the solution of a scien-tific problem as numerical data.

When biologists use purely obser-vational data, they are carrying outdescriptive research. Descriptiveresearch is useful because some phe-nomena aren’t appropriate for quan-titative research. For example, how aparticular wild animal reacts toevents in its environment cannot eas-ily be illustrated with numbers.Practice your descriptive researchskills in the MiniLab on this page.


Hatching Dinosaurs “Dinosaur eggs” can be found in spe-cially marked packages of oatmeal. You will conduct an investi-gation to determine what causes these pretend eggs to hatch.

Procedure! Copy the data table below.

@ Observe the dinosaur eggs provided and record their characteristics in your table.

# Place an egg in each of two containers.$ Make a hypothesis about the water temperature that will

cause the eggs to hatch.% Pour boiling water into one container and cold water in

the other. Stir for one minute. Record your observations.

Analysis1. Infer whether heat or moisture was more important for

hatching eggs. 2. Design an experiment that would test either heat or mois-

ture as the variable. What kind of quantitative data willyou gather?

3. What will be your control?4. How many trials will you run and how many eggs will you

test? If time permits, conduct your experiment.

MiniLab 1-3MiniLab 1-3 Observing and Inferring

Hot water treatment

Before treatment

Appearanceafter one minute

Cold water treatment

Data Table

Penguins cannot fly.They use their wingsfor swimming in theoceans of the south-ern hemisphere.

AA

Figure 1.17Do you think these ani-mals behave in the sameway in zoos as they doin nature?

Toucans live in the rainforests of South America.

BB

Science and SocietyThe road to scientific discovery

includes making observations, formu-lating hypotheses, performing experi-ments, collecting and analyzing data,drawing conclusions, and reportingresults in scientific journals. No mat-ter what methods scientists choose,their research often provides societywith important information that canbe put to practical use.

Maybe you have heard peopleblame scientists for the existence ofnuclear bombs or controversial drugs.To comprehend the nature of sciencein general, and biology in particular,people must understand that knowl-edge gained through scientificresearch is never inherently good orbad. Notions of good and bad ariseout of human social, ethical, andmoral concerns. Ethics refers to themoral principles and values held byhumans. Scientists might not considerall the possible applications for theproducts of their research when plan-ning their investigations. Society as awhole must take responsibility for theethical use of scientific discoveries.

Can science answer all questions?

Some questions are simply not inthe realm of science. Such questionsmay involve decisions regarding goodversus evil, ugly versus beautiful, orsimilar judgments. There are also sci-entific questions that cannot betested using scientific methods.However, this does not mean thatthese questions are unimportant.

Consider a particular question thatis not testable. Some people assertthat if a black cat crosses your path,as shown in the cartoon in Figure1.18, you will have bad luck. On thesurface, that hypothesis appears to beone that you could test. But what isbad luck, and how long would youhave to wait for the bad luck tooccur? How would you distinguishbetween bad luck caused by the blackcat and bad luck that occurs at ran-dom? Once you examine the ques-tion, you can see there is no way totest it scientifically because you can-not devise a controlled experimentthat would yield valid data.

Can technology solve all problems?

Science attempts to explain howand why things happen. Scientificstudy that is carried out mainly forthe sake of knowledge—with noimmediate interest in applying theresults to daily living—is called purescience.

However, much of pure scienceeventually does have an impact onpeople’s lives. Have you ever thoughtabout what it was like to live in theworld before the development ofwater treatment plants, vaccinations,antibiotics, or high-yielding crops?These and other life-saving develop-ments are indirect results of researchdone by scientists in many differentfields over hundreds of years.

Figure 1.18If bad luck caused byblack cats occurred as reliably and asswiftly in real life asit does in cartoons, it really would be scientifically testable.

OriginWORDWORD

technologyFrom the Greekwords techne, mean-ing an “art or skill,”and logos, meaning“study.” Technologyis the application ofscience in our dailylives.

Other scientists work in researchthat has obvious and immediateapplications. Technology (tek NAHL

uh jee) is the application of scientificresearch to society’s needs and prob-lems. It is concerned with makingimprovements in human life and theworld around us. Technology hashelped increase the production offood, reduced the amount of manuallabor needed to make products andraise crops, and aided in the reduc-tion of wastes and environmentalpollution.

The advance of technology hasbenefited humans in numerous ways,but it has also resulted in some seri-ous problems. For example, irriga-tion technology is often used to boostthe production of food crops. If irri-gation is used over too many years inone area, the soil may becomedepleted of minerals or the evapora-tion of the irrigation water may leavedeposits of mineral salts in the soil.Eventually the soil may become use-less for growing crops, as illustratedin Figure 1.19.

Science and technology will neveranswer all of the questions we ask,nor will they solve all of our prob-lems. However, during your study ofbiology you will have many of your

questions answered and you willexplore many new concepts. As youlearn more about living things,remember that you are a part of theliving world and you can use theprocesses of science to ask andanswer questions about that world.


Section AssessmentSection AssessmentUnderstanding Main Ideas1. Why is it important that scientific experiments be

repeated?2. Compare and contrast quantitative and descrip-

tive research.3. Why is science considered to be a combination of

fact and process?4. Why is technology not the solution to all scien-

tific problems?

Thinking Critically5. Biomedical research has led to the development

of technology that can keep elderly, very illpatients alive. How does the statement “Theresults of research aren’t good or bad; they justare,” apply to such research?

6. Making and Using Graphs Look at the graph in Figure 1.16. Why do you think the high-temperature side of the graph drops offmore sharply than the low-temperature side? For more help, refer to Organizing Informationin the Skill Handbook.


Figure 1.19One example of a possible harmful side effect of technology isthe deterioration of soil caused by irrigation. In the field shownhere, irrigation technology initially appeared to solve the prob-lem of low crop yield, but later caused a different problem—thebuildup of excess mineral salts that prevent crop growth.

Collecting BiologicalData

S eeing different life forms, and even interacting with them, is prettymuch part of a typical day. Petting a dog, swatting at a fly, cutting

the grass, and talking to your friends are common examples. But, haveyou ever asked yourself the question, “What do all of these different lifeforms have in common?” Let’s try to find out.

INTERNETINTERNET

ProblemWhat life characteristics can be

observed in a pill bug?

ObjectivesIn this BioLab, you will:■ Observe whether life characteristics

are present in a pill bug.■ Measure the length of a pill bug.■ Experiment to determine if a pill bug

responds to changes in its environ-ment.

■ Use the Internet to collect and com-pare data from other students.

Materialspill bugs, Armadillidiumwatch or classroom clockcontainer, glass or plasticpencil with dull pointrulercomputer with Internet connection

Safety PrecautionsAlways wear goggles in the lab.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

1. Make copies of the data table andgraph outlines shown here.

2. Obtain a pill bug from yourteacher and place it in a smallcontainer.

3. Observe your pill bug to deter-mine whether or not it has anorderly structure. Record youranswer in the data table.

4. Using millimeters, measure andrecord the length of your pill bugin the data table.

5. Using your data and data fromyour classmates, complete the

PROCEDUREPROCEDURE

Time in secondsTrial

Response to environment

Orderly structure?

Pill bug length in mm

1

2

3

4

5

Total

Average time

Organization and growth and development

Data Table

Sharing Your DataSharing Your Data

Find this BioLab on the Glencoe Science Web

site at science.glencoe.com and post yourdata in the data table provided for thisactivity. Use the additional data from otherstudents on the Internet, analyze the com-bined data, and complete your graphs.

BIOLOGY

graph “Pill Bug Length:Classroom Data.”

6. Go to the Glencoe Science WebSite at the address shown belowto post your data.

7. Gently touch the underside of thepill bug with a dull pencil point. It may be necessary to gently flipthe pill bug over with the pencilto get at its underside. CAUTION: Use care to avoidinjuring the pill bug.

8. Note its response and time, inseconds, how long the animalremains curled up. Record thetime in the data table as Trial 1.

9. Repeat steps 7-8 four more times,recording each trial in the datatable.

10. Calculate the average length oftime your pill bug remains curledup in a ball.

11. Post your data on the GlencoeScience Web Site.

12. Return the pill bug to yourteacher. CAUTION: Wash yourhands with soap and water afterworking with pill bugs.


1. Thinking Critically Explain howyou would define the term“orderly structure.” Explain howthis trait might also pertain tononliving things.

2. Using the Internet Explain howdata from the classroom andInternet graphs support the ideathat pill bugs grow and develop.

3. Interpreting Data What was themost common length of time pillbugs remained curled in responseto being touched?

4. Drawing a Conclusion Explainhow the response to being

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Length in Millimeters1

10987654321

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Num

ber

of P

ill B

ugs

Pill Bug Length: Classroom Data

Length in Millimeters1

100908070605040302010

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Num

ber

of P

ill B

ugs

Pill Bug Length: Internet Data

Response Time in Minutes2

100908070605040302010

4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40

Num

ber

of P

ill B

ugs

Average Pill Bug Response Time: Internet Data

touched is an adaptation.5. Experimenting How might you

design an experiment to deter-mine whether or not pill bugsreproduce?


The term “organic” usually refers to foodsthat are produced without the use of chemi-

cal pesticides, herbicides, or fertilizers. Organicfarmers use nonchemical methods to controlpests and encourage crop growth. Beneficialinsects, such as ladybugs and trichogrammawasps, are brought in to feed on aphids, caterpil-lars, and other damaging insects. Instead ofapplying herbicides, organic farmers pull weedsby hand or by machine. In place of fertilizers,they use composting and crop rotation to enrichthe soil. Organic farming is very labor intensive,so organic foods are usually more expensive thanthose produced by conventional methods.

Different ViewpointsPeople usually buy organic products because

they want to be sure they’re getting nutritiousfood with no chemical residues. But there aredifferences of opinion about how much betterorganic food actually is, and even which foodsshould be called organic.


Organic Food: Is it healthier?The produce section of the supermarket has two bins of leafy lettuce thatlook very much alike. One is labeled “organic” and has a higher price.More and more consumers are willing to pay extra for organically grownfruits, vegetables, meats, and dairy products. What are they paying thatextra money for?

Comparing and Contrasting Propose yourown set of standards for defining organic fruitsand vegetables. Organize a debate in which youand your classmates present arguments to sup-port your proposed standards.

To find out more about the organic food debate, visit

the Glencoe Science Web site.science.glencoe.com

INVESTIGATING THE ISSUEINVESTIGATING THE ISSUE

Is organic food healthier? Agricultural chemicals can leave residues on food and conta-minate drinking water supplies. Since exposureto some chemicals is known to cause healthproblems, including cancer, many consumersthink that organic foods are healthier. Chemicalpest controls kill beneficial organisms as well asunwanted pests, and can adversely affect thehealth of other animals, especially those that feedon insects. Organic pest control methods usuallytarget specific pests and have little effect on beneficial organisms.

Is conventionally grown food healthier?Chemical fertilizers and pesticides make it possible to grow larger crops at lower cost, which makes more food available to more people. Making sure everyone can afford an adequate supply of fruits and vegetables may be more important than the risk of disease posedby agricultural chemicals.

Not everyone agrees about what is organicand what isn’t. Should genetically engineeredplant or animal foods be considered organic?What about herbs or meats preserved by irradiation, or lettuce and tomatoes fertilizedwith sewage sludge?

Produce from anorganic farm

BIOLOGY


Chapter 1 AssessmentChapter 1 Assessment

SUMMARYSUMMARY

Section 1.1

Section 1.2

Section 1.3

Main Ideas■ Biology is the organized study of living things

and their interactions with their natural andphysical environments.

■ All living things have four characteristics incommon: organization, reproduction, growthand development, and the ability to adjust to theenvironment.

Vocabularyadaptation (p. 9)biology (p.3)development (p.8)energy (p.9)environment (p.8)evolution (p.10)growth (p.8)homeostasis (p.9)organism (p.6)organization (p.7)reproduction (p.7)response (p.9)species (p.7)stimulus (p.9)

Main Ideas■ Biologists use controlled experiments to obtain

data that either do or do not support a hypothe-sis. By publishing the results and conclusions of

an experiment, a scientist allows othersto try to verify the results. Repeatedverification over time leads to thedevelopment of a theory.

Vocabularycontrol (p.13)data (p.15)dependent variable

(p.13)experiment (p.12)hypothesis (p.12)independent variable

(p.13)safety symbol (p.14)scientific methods (p.11)theory (p.20)

Main Ideas■ Biologists do their work in laboratories and in

the field. They collect both quantitative anddescriptive data from their experiments andinvestigations.

■ Scientists conduct investigations to increaseknowledge about the natural world. Scientificresults may help solve some problems, but not all.

Vocabularyethics (p.24)technology (p.25)

CHAPTER 1 ASSESSMENT 29

1. For experiments to be considered valid, theresults must be ________.a. verified c. publishedb. inductive d. repeatable

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 2. Reproduction is an important life character-istic because all living things ________.a. replace themselvesb. show structurec. growd. adjust to surroundings

What IsBiology?

The Methodsof Biology

The Nature ofBiology


3. The photograph to the right is an example of which characteristic of life?a. evolutionb. reproductionc. developmentd. response to a

stimulus4. Which of the following is an appropriate sci-

entific question?a. How do paramecia behave when a pond

begins to dry up?b. Which perfume smells the best?c. Which religion is most sound?d. Are llamas less valuable than camels?

5. If data from repeated experiments do notsupport the hypothesis, what is the scientist’snext step?a. Give up.b. Revise the hypothesis.c. Repeat the experiment.d. Overturn the theory.

6. Similar-looking organisms, such as the dogsshown below, that can interbreed and pro-duce fertile offspring are called ________.a. a living system c. organizationb. an adaptation d. a species

7. The environment includes ________.a. air, water, weatherb. response to a stimulusc. adaptationsd. evolution

8. Which of the following terms are mostrelated to each other?a. adaptation—responseb. stimulus—growthc. adaptation—evolutiond. stimulus—evolution

9. Which of the following is not an appropriatequestion for science to consider?a. How many seals can a killer whale con-

sume in a day?b. Which type of orchid flower is most beau-

tiful?c. What birds prefer seeds as a food source?d. When do hoofed mammals in Africa

migrate northward?10. The single factor that is altered in an experi-

ment is the ________.a. controlb. dependent variablec. hypothesisd. independent variable

11. The information gained from an experimentis called ________.

12. The application of scientific research to soci-ety’s needs is ________.

13. A procedure that tests a hypothesis is a(n)________.

14. Processes that scientists use to solve a prob-lem are called ________.

15. An explanation of a natural phenomenonwith a high degree of confidence is a(n)________.

16. The group that is not altered in an experi-ment is the ________.

17. The single change in the manipulated groupin an experiment is a(n) ________ variable.

18. When a horse swats a fly with its tail, the flyis a ________ and the swat of the tail is a________.

30 CHAPTER 1 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Words Are Easy to Learn Make a huge stack of vocabulary flashcards andstudy them. Use your new words in daily conversa-tion. The great thing about learning new words isthe ability to express yourself more specifically.


CHAPTER 1 ASSESSMENT 31

19. The idea that germs are the cause of diseasehas been continuously supported by experi-ments and has, therefore, been elevated tothe status of a ________.

20. The standard group against which others aremeasured in an experiment is a ________.

21. Describe how the human body shows the lifecharacteristic of organization.

22. Explain the relationships among an organism’senvironment, adaptations, and evolution.

23. Comparing and Contrasting Consider thefollowing items: a flame, bubbles blown froma bubble wand, and a balloon released intothe air. List characteristics of each that mightindicate life and those that indicate they arenot alive.

24. Concept Mapping Complete the conceptmap by using the following vocabulary terms:experiment, theory, hypothesis, scientificmethods

THINKING CRITICALLYTHINKING CRITICALLY

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

A team of students measured the number ofseeds that germinated over ten days in acontrol group at 18°C and in an experimen-tal group at 25°C. They graphed their dataas shown below.

Interpreting Data Study the graph andanswer the following questions.1. Which of the following would represent

the hypothesis tested?a. Black seeds are best.b. Seeds germinate faster at warmer

temperatures.c. Fertilization of seeds requires heat.d. Seeds germinate when freezing.

2. When was the first appropriate day toend the experiment?a. day 3 c. day 7b. day 6 d. day 9

3. Which of the following was the inde-pendent variable?a. kind of seeds c. temperatureb. number germinating d. time

4. Which of the following was the depen-dent variable?a. kind of seeds c. temperatureb. number germinating d. time

5. Interpreting Data Describe the germi-nation rate between days 3 and 5 in thecontrol group.

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web site.science.glencoe.com

CD-ROM

Seed

s ger

min

ated

Day

The Effect of Temperature on Germination

50403020100

1 2 3 4 5 6 7 8 9 10

Experimental group

Control group

may begin with an observation,which leads to a(n)

1.

that is tested by a(n)

2.

and, after many repetitions, may result in a(n)

3.

4.


Characteristics of LifeBiologists have formulated a list of character-

istics by which we can recognize living things.

OrganizationAll living things are organized into cells.

Organisms may be composed of one cell or manycells. Cells are like rooms in a building. You canthink of a many-celled organism as a building con-taining many rooms. Groups of rooms in differentareas of the building are used for different pur-poses. These areas are analogous to the tissues,organs, and body systems of plants and animals.

FOCUS ON CAREERSFOCUS ON CAREERS

Thousands of career opportunitiesare available in the biological

sciences. Some of these careers requireonly a high school education. Othersrequire a college degree, or even anadvanced degree. Many careers in biology involve work as a research biologist in the field or in a laboratorysetting.

Other careers also rely on skills orknowledge about biology. Doctors anddentists, nurses and laboratory techni-cians, florists, foresters, and zookeepersall must have a knowledge of biology.Careers related to the biological sci-ences also include food processing,farming, and ranching. Can you thinkof some other careers in which biologyplays an important role?

Biology at Work

32

What Is Biology?Living things abound almost everywhere

on Earth—in deep ocean trenches, atop thehighest mountains, in dry deserts, and in wet tropicalforests. Biology is the study of living organisms and the interac-tions among them. Biologists use a variety of scientific methodsto study the details of life.

For a preview of the what is biology unit, study this BioDigest before you read the chapter.After you have studied the chapter, you can use the BioDigest to review the unit.

BIODIGESTBIODIGEST

If you enjoy work-ing outdoors, acareer in field biol-ogy may be for you.

HomeostasisA stable internal environment is necessary for

life. Organisms maintain this stability throughhomeostasis, which is a process that requires thecontrolled use of energy in cells. Plants obtainenergy by converting light, water, and carbondioxide into food. Other organisms obtain theirenergy indirectly from plants.

Response to a StimulusLiving things respond to changes in their

external environment. Any change, such as a risein temperature or the presence of food, is a stim-ulus.

All livingthings share

certain characteristics.What characteristicstell you these robinsare living organisms?

Growth and DevelopmentWhen living things grow, their cells enlarge

and divide. As organisms age, other changes alsotake place. Development consists of the changesin an organism that take place over time.

ReproductionLiving things reproduce by transmitting their

hereditary information from one generation tothe next.

Scientific MethodsScientists employ a variety of scientific meth-

ods to answer questions and solve problems. Notall investigations will use all methods, and theorder in which they are used will vary.

ObservationCuriosity leads scientists to make observations

that raise questions about natural phenomena.

HypothesisA statement that can be tested and presents

a possible solution to a question is a hypothesis.

ExperimentAfter making a

hypothesis, the next stepis to test it. An experi-ment is a formal methodof testing a hypothesis. Ina controlled experiment,two groups are testedand all conditions exceptone are kept the same forboth groups. The singlecondition that changes isthe independent variable.A condition caused by thechange in the indepen-dent variable is a depen-dent variable.

TheoryWhen a hypothesis

has been confirmed bymany experiments, it may become a theory.Theories explain naturalphenomena.

What Is Biology?

33

BIODIGESTBIODIGEST

Many experiments are con-ducted in the laboratory,where conditions can beeasily controlled.

BIODIGEST ASSESSMENTBIODIGEST ASSESSMENT

Understanding Main Ideas1. The basic unit of organization of living

things is ________.a. an atom c. a cellb. an organism d. an organ

2. Storing energy obtained from food is anexample of ________.a. evolution c. responseb. homeostasis d. growth

3. A hypothesis that is supported many timesbecomes ________.a. an experiment c. a theoryb. a conclusion d. an observation

4. All of the procedures scientists use toanswer questions are ________.a. life characteristics c. researchb. scientific methods d. hypotheses

5. To test a hypothesis, a scientist may________.a. do an experimentb. write a theoryc. do research in a libraryd. make some observations

Thinking Critically1. List the characteristics you would check

to see if a pine tree is a living thing. Givean example that shows how the treeexhibits each characteristic.

2. Compare the characteristics of life with theflames of a fire. How are they similar anddifferent?

3. Why do most experiments have a control?Describe an experiment that does not havea control.

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