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Q What is biology in the 21st century? Biology has always been the study of life, but our knowledge of living things and our use of technology to study them is always changing. For example, this enlarged image of a yellow fever mosquito was made with a scanning electron . Why bother with a mosquito? Because even in the 21st century, mosquitoes can carry viruses for which we have no defense.

READING Toolbox This reading tool can help you learn the material in the following pages.

USING LANGUAGE Your Turn Hypothesis or Theory? In everyday language, there Use what you have learned in this paragraph to answer is little difference between a hypothesis and a theory. But the following questions. in science, the meanings of these words are more distinct. 1. What is the difference between a hypothesis and A hypothesis is a specific, testable prediction for a limited a theory? set of conditions. A theory is a general explanation for a 2. Propose a testable hypothesis to explain why the broad range of data. A theory can include hypotheses chicken crossed the road. that have been tested, and it can also be used to gener- ate new hypotheses. The strongest scientific theories explain the broadest range of data and incorporate many well-tested hypotheses.

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Unit 1:Introducing Biology act as storage tanks for other antsinthecolony. and wa F science biology species biosphere VOCABULARY contributions ofscientists describe thehistory and ofbiology environment; 3F research onsociety andthe 3D subsection (b)(2)ofthissection; has limitations, asspecifiedin of igure 1.1

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on Earth. Thereon are Earth. tiny such as honeypot the ant in are massive animals such as blue the which whale, is largest the living include tiny mosses and giant redwood trees on which moss can grow. There but come also inahuge they variety of shapes and sizes. , for example, in Antarctica. Not only are living things found just about anywhere on Earth, darknessin the and floors of ocean inthousands-of-years-old deepest the ice It to believe, but of mightare difficult pools life. full be those also Life is found In Yellowstone National Park, there are of pools hot water as acidic as vinegar. MAIN IDEA MAIN IDEAS C

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Biologists studylife inall itsforms. size of agrape. can store much so for food other ants that it swells to the other living things are found indifferent areas of the atmosphere. ofdifferent types And plants, animals, and and freshwater environments, as well as portions of the oftypes forests. The biosphere includes also saltwater environments such grasslands, as deserts, and different of biosphere.part the The biosphere includes land sphere is connected, however distantly, other with every Earth make up the Earth livingAll things are and places the they all found on The Biosphere

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duce. duce. to them repro- plants allows and the interaction pollinates other plants. This from plant to pollen from one plant, the on behind plant left is flies bee the bee’s to the pollen sticks food, the as pollen to use body. collects bee Then, as a plant. When the and bee the from aflower, both benefits interaction that an and their environments. their and organisms other relate with interact and live on that diverseThe organisms Earth biodiversity. biological diversity, called is area or agiven of in organisms variety The Biodiversity extinct in1944,butextinct ateam of scientists reported it seeing inArkansas in2004. again. For example, woodpecker ivory-billed was the thought to have become year.every Occasionally, however, thought aspecies is found extinct to be some scientists estimate that over die out, 50,000species or become extinct, many exist. actually species insect discovered. of half Over known the are species but insects, no one knows how identified, but biologists estimate that tens of millions of remain species to be produce offspring. fertile About 2million different living have species been science: life science, earth science, life andscience: science, earth physical science. grounds and different of fields interest. is one Biology of three basic areas of or verified tested.be People contribute who to come science from back- all conditions inorder to discover and facts formulate laws or principles that can

teristics. and ability the to make and tools use were considered human strictly charac- sticks and other tools to hunt and insects other organisms, intelligence high mans and our world. For example, until chimpanzees to were use observed their interactions with definition of of definition consistent food supply for manydifferentspecies. provide areas alarger,those more areas, warm in survive can plants, especially things, moreBecause living year. the temperature during changes have that large areas in than peratures tem- consistently in warm survive equator. able are to things More living poles to the from Earth’s increases MAIN IDEA MAIN Eve The s The

Describe biodiversity in terms of species. Biology ry year,ry biologists discover more In than species. 10,000new contrast, re are different several ways term species the tudy of living things sheds light new on our understanding of hu- Science

Biodiversity generally generally Biodiversity species , or life science, is the scientific study of living things and their their and things of study living or science, scientific life the is is knowledge the obtained natural by observing events and is agroup of organisms that are closely related and can 2A ­ env ironment. FIGURE biosphere = everywhere life exists VISUAL VOCAB 1.2 of life iscalled Across the shows a bee collecting pollen shows collecting abee can be defined. One defined. can be biosphere, biodiversity. the equator. greater closer to Biodiversity is thevariety F collects pollen. the f ­organisms, suchasthisbeeand study of igure 1.2 Biodiversity GO ONLINE terms andconcepts. help you summarizevocabulary Use atwo-column to chart T Chapter inthe21stCentury 1:Biology emo ocp meaning term orconcept aking lowering plant from whichit READING READING

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Unit 1:Introducing Biology Egyptian Egyptian processes andmaterials. Ancient requires precise understanding of many impro a ship ofanatomy andgeometry. ­Vitruvian Man,sho in Europe. Da Vinci’s drawing, ofscientific learning including , were ofa part study ofmanyare F F F them. and studiedthelivingthings around indica igure 1.5 igure 1.4 igure 1.3 ­ proces te that early humansobserved ved mummification over ­centuries. s ofpreserving bodies, ­civilizations studiedand

Prehistoric cave paintings ’s Mummification, as ofscience, ws arelation- Vitruvian Man, Vitruvian close studies of anatomy the of animals both and humans. The drawing ItalianEarly period, time inthis artist and scientist Leonardo Vinci da began and and science of beginning Revolution the Scientific the (1450s–1700). continued to grow inother of parts world, the such as India and China. are marked by little development, scientific though knowledge scientific progress of science. The of European (500s-1450sCE) history and philosophy, but changes inpolitics and governance the influenced also ancient Greek and Roman are societies known for milestones their inscience Scientists of any era are limited by demands the and of rules society. The Revolution Scientific The evidence in science. in evidence credited with developing asystem of and logic adependence on empirical withoutthose such blood, as mollusks and arthropods. is also divided animals up into with red such those blood, as wolves and rabbits, and Greek philosopher Aristotle and dates Aristotle’s back to 330BCE. system fourthe humours were thought to cause most illnesses. humours or black fluids:blood, bile, and phlegm, yellow bile. Imbalances in the ,the such production milk as high and taste or yield incrops. high were using geneticsfor to select characteristics that were most valuable in as Even earlymals as 8500BCE. without knowing it, early these humans Evidence shows that some human populations began conceptscal such as anatomy, of use medicinal herbs, and . ings, and papyri show how early humans began to understand basic biologi- interested carv- art, and asOther food. used animals inthe observed they sci history. haveHumans living studied throughout things school of . He taught that were living all bodies made up of four science. Around Greek 400BCE, royalty, nobility, and wealthy, the as shown in irrigation. Ancient civilizations Egyptian practiced tions developed agriculturaltechniques, such as crop society. Asian civilizations . herbal South American used civiliza- about natural processes and knowledge this used to address of needs the Many ancient civilizations studied biology. Just as we do now, learned they Civilizations Ancient in Science the , or other tools scientific and techniques. Early records, such as The study of living things began long before invention the of computers, Fifte The f Greek civilization made significant contributions to development the of life

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(cr) ©Musée Pasteur de Dole Apply advances throughout are inbiology discussed also book. the chapter inthe theory Cell and . important Other concepts are collectively known theory. as cell the You read more will about summarizing basic properties the theory of living organisms. basic These , Matthias and Schleiden, Rudolph Virchow, proposed a living things. As aresult of and this other studies, three scientists, German come from equipment shown in living matter. Experiments by in1859,using broth inthe ­spo edge and built upon or replaced old knowledge. with greater and precision. accuracy Such explorations to knowl- led new programs, and allowed for the exchange of universities ideas, developed robust science brought about significant advances inscience. Travel and communication The Industrial Revolution, which last began inthe of half 18th the Revolution Industrial fromScience to the Today ofdiscovery cells and . inventionthe of microscope the around of start the 1600sallowed the for the RevolutionScientific were made possible by technologies. new For example, advancesthe and inbiology other areas of that during science the occurred and philosophy.observation insides whereas of Greeks the descriptions their bodies, based only on external his descriptionsso of anatomy were on repeated based explorations of the observations by ancient the Greeks. Vesalius of practiced corpses, mid-1500s.the Vesalius challenged anatomical concepts made from limited today. , aFlemish physician, published of abook anatomy in tion of systematic and observation documentation that methods are inuse still understanding of anatomy and movement. His includes legacy introduc- the 2. 3. 1. R 1.1

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Unit 1:Introducing Biology from insects. (LM;magnification 700 these leaf hairsthat protect aleaf Figure 2.1 system DNA cell organism VOCABULARY in specia occur amongsystems...; 10 10A describe theinteractions that of diversity inandamongspecies; adaptation andto thedevelopment relationship ofnatural selection to 7E synthesis ofnew molecules; transport ofmolecules, and homeostasis, energy conversions, cellular processes, including the maintenance ofhomeostasis of internal feedback mechanismsin whole system; 11Adescribe therole levels to each other andto the biological systems andrelate the the levels oforganization in

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1.2 Cells can work together 10 4B, 7E, 10A, C , 11A , suchas C anal Unifying ThemesofBiology yze 3 ) fields ofbiology. All organisms share certain characteristics. these themes,orconcepts, can helpyou to connect thedifferent areas ofbiology. time, even intopics that mightseem to becompletely unrelated. Understanding biology, you see will something similar. That is,some concepts come uptimeafter computer desktop. Inboth cases, that themeshows upover andover again. In the musicat ofyour thestart favorite show orthecolors TV and organization ofa What doyou thinkaboutwhenyou hear theterm theme?Maybe you thinkabout Connect to Your World Ke

y of functions the of life, just as you do. Larger organisms day that you every see forms of life Asingle-celled, or on unicellular, Earth. organism out carries all of life. In microscopic, fact, organisms single-celled are most the common An An Cells nonliving. show They some, but not of all, characteristics the of living things. Forperfect. example, into fall amiddlerange viruses living between and categories of living and nonliving are constructed by humans, and are they not characteristics,certain but an definition actual of life is not simple. Why? The MAI MAI C

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is any individual living organisms thing. All share on Earth Unifying themesconnect c Need for energy plete organism. information. Together, cells make you specialized acom- digestive juices, and your brain cells interpret sensory muscle cells contract and relax, your stomach cells secrete source of chemical energy. Some organisms, such as plants, chemicals from environment their to make own their ferrets to ferns, chemical use energy. Some organisms use change or to do work. living All things, from to bacteria out lifecarry processes. is ability the Energy to cause a have functions, as shown specialized in isms. Different of types cells inamulticellular organism are made of many cells and are multicellular called organ- 10c

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(cr) ©David Fleetham/Bluegreen All levels oflife have systems ofrelated parts. Summarize

car’s characteristics come from arrangement the and interaction of its parts. group of related that parts interact to form awhole. any Like other system, a valves, arteries, and veins form asystem inyour circulatory system. body—the way that so to has cell do its the energy work. Moving up alevel, muscle, heart muscleheart cell, for example, chemicals and processes interact inaprecise to cells that only seen with can amicroscope, be to biosphere. the In just one to reproduce. to development allows organisms to mature and gain ability the cals—DNA and ribonucleic acid (RNA). The process of isms, from to people, bacteria are by carried same the chemi- instructions the cases, for growth and development of organ- combining genetic the information from two parents. In both way do you have aworking car. Acar is asystem. A of thatOnly all parts when the make up acar are put together correct inthe you have acomplete of set caryou parts, might not have afunctioning car. aboutThink separate the of parts acar—tires, engine, seats, and on. so Even if isms, such as gold-specs the jawfish in that is identical to cell. original the Many multicellular organ- div eating other organisms. In organisms, all is important energy for chemicals that later used can be as asource of energy. Animals obtain by energy and absorb from some bacteria, energy sunlightalgae, and store some of it in KLEE-ihk), orKLEE-ihk), deoxyribonucleic (dee- called acid mation that determines inherited characteristics is amolecule In organisms, all genetic the material that contains infor- the reproduce, pass genetic their they material to offspring. their to produce individuals, new or reproduce. When organisms Reproduction anddevelopment that you know as mushrooms. ample, plants grow toward light. light need Some fungi to form structures the shade your organisms eyes. Other respond also to changes inlight. For ex- behavior might change. also You might put on sunglasses or raise your hand to One of your body’s responses is to contract pupils the of your eyes. Your respond to light you when leave adimly lit room and go into bright sunlight. stimuli,called to which organisms must respond. about Think how you Light, temperature,survive. and touch are just afew of physical the factors, Response to environment or of all chemical the processes that build up or break down materials. MAI ides into cells have new two cells. Both genetic information Sys Single-celled organisms can reproduce one when cell N ID tems inbiology, exist on scales all from that molecules cannot seen, be

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in hismouth. unhatched eggs by holding them ma gies differ amongspecies.The Figure 2.2 le gold-specs jawfish protects Chapter inthe21stCentury 1:Biology

Reproductive strate-

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Figure 2.4 Figure 2.3 protection inreturn. eel’s mouthandgets food and Theshrimpcleansbenefit. the system inwhichboth organisms the cle magnifications: beetle 20 rough surfaces. (colored SEMs; to easily walk onboth smooth and pads onitstarsi (right)that allow it (belo Unit 1:Introducing Biol w) has specialized prongs and aner shrimpare ofa parts

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cals and then cause the chemicals to react with eachother. to with react chemicals the cause then and cals chemi- proteinsThese to have to only certain them attach allow shapes that are protein that molecules make chemical processes possible inliving things. a tube that chemicals to allows pass specific into and out of acell. extends through membrane, the or outer layer, of acell. It has astructure like differentvery structures and functions. Achannel is aprotein that molecule example, membrane channels and enzymes are proteins, both but have they your help teeth you eat, but different of have types teeth different functions. Thenteeth. you probably chew it mostly with your grinding molars. of All For example, you when eat, you probably bite into with your food sharp front What something inan does organism is directly related to its shape or form. perform that Structure function. and are function related also inliving things. isfunction directly related to its structure. No other of part car the can structure For function. of acargives aspecific part part the example, a tire’s aboutThink acar again. In acar, different have parts different structures. The MAI Str N ucture and are function related at level the of chemicals incells. For ID E A

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how interactions. chemicals brain inthe social affect across different system levels. For example, some scientists study an ecosystem. However, more and more biologists are working behavior inbirds might on focus predator–prey relationships in chemical interactions that place take inacell. Aperson studying example, aperson studying DNA might specific on focus very as an individual tree. or aforest. area, But small such an avery ecosystem be can also might about think alarge region, suchacoral reef, as adesert, physical environment. When you hear term ecosystem, the n see in n see 4 Two organisms that interact asystem, be can as you also Oft b , 10 , ecosystem f en, different biologists study different systems. For igure 2.3. C On alarger you scale, are of apart abio- is acommunity of organisms and their

to carry oxygen.to Their carry structure allows smaller, disk shaped, and are specialized are different. very are They much messages cells to other blood cells. Red long extensions that allow to them send mation from have other also cells. They have many branches that receive infor- in your brain process information. They structures. Forspecialized example, cells different functions that on depend their Diff erent of have types cells also you you

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(cr) ©Andrew Syred/Photo Researchers, Inc.; (b) ©Fritz Polking/Peter Arnold, Inc. in diverse environments. to homeostasis survive maintain must Organisms Summarize Infer

and feel thirsty you when water? need Why(98.6°F)? do you shiver you when are cold, sweat you when are hot, ture is below but freezing, have still astable temperature body around 37°C get cold, too and move they into shadeget warm. too ifthey may put on ajacket. Reptiles sit on awarm rock insunlight ifthey regulate temperature their through behavior. If you feel cold, you body. temperaturebody above rises normal, different responses your cool shiver, and vessels blood near your skin’s constrict. surface If your return your temperature to normal. Your muscles cause you to temperaturebody drops below normal, systems inyour to act body computer the speed, set the tells up. car the to speed Similarly, ifyour computer the speed, set tells car the to slow down. If car the slows below thatsend information to acomputer. If to car the go begins faster than the controlA cruise system has sensors that monitor car’s the and then speed how acar’s control cruise keeps acar moving at aconstant speed. set tends to return that system to its state. original For example, about think feedback. In negative feedback, achange inasystem causes aresponse that homeostasis are often life threatening. sugar, acidity, and other conditions must controlled. be Breakdowns in within best function alimited range of conditions. Temperature, blood internal conditions inan organism. Homeostasis is important cells because

in conditions inside organisms usually stay quite stable. How polar the bear does Temperature and other environmental conditions are always changing, but the is impossiblewall for you. in The beetle surfaces. Walking on such asurface as iceis more and up walking a difficult, example, your foot structure allows you easily on to walk rough, fairly level out your body. Of course, abrain cannot cell place the take of cell. ared blood tothem fit through vessels smallest even the blood to deliver oxygen through- function thanfunction your foot has, but for are both walking. specialized for on walking rough surfaces.The beetle’s tarsus has adifferent structure and have sharp prongs that can grip smooth surfaces,as or well as pads vertical soft MAI Figure 2.5

Beh Hom Str Homeostasis Do you think heart muscle has the same structure as arm muscle? muscle? arm as structure same the has muscle heart youDo think 10 N ucture and are function related also on level the of organism. the For C ID avior involved is also inhomeostasis. For example, animals eostasis is usually maintained through aprocess negative called

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t is homeostasis, and why is it important? important? it why is and homeostasis, t is (hoh 4B, 10A, 11A 10A, 4B, -mee-oh-STAY-sihs) is maintenance the of constant Figure 2.4 is different. Its tarsi, or feet, 4B E xpl ain. magnification 450 retain itsbodyheat. (SEM; adaptation that helps thebear climates. Itshollow hairisone maintain homeo Figure 2.5 Chapter inthe21stCentury 1:Biology

The polar bear can 3 stasis invery cold )

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Unit 1:Introducing Biol (right), look like ofplants. parts insects, suchasthethornbug that look like insects, andsome some or Figure 2.6 the Evolution unit. are described inmore detail in , andadaptation The processes ofevolution, Evolutio CO NNE chids (left) have flowers CT TO

Through evolution, n ogy E volution explains the unity and diversity and oflife.volution explains unity the

see andsee eat it. This adaptation allows thorn the bug and to survive reproduce. thorn bug’s appearance is an adaptation that makes predators less likely to orchidthe can pollinate flower, the helping orchid the to reproduce. The likelooks lures an insect to other it. that insects The insects are attracted to adapted inways that make resemble them other organisms. The orchid that ual organismsual and on is passed to future generations is an environment.particular An inherited trait that gives an advantage to individ- and survive reproducespecies more successfully than other individuals ina natural agenetic, selection, or inherited, trait helps some individuals of a One way evolution is through occurs natural of selection . In Adaptation E and genetic comparisons of shows species, that evolution is continuing today. biosphere.the range Awide of evidence, scientific including the record concept of evolution observations links from levels of all biology, from cells to a change genetic inthe makeup of asubgroup, or population, of The aspecies. evolve to point the at are which they different species. adaptations indifferent environments. The two populations may continue to adaptation. Two different populations of same might the species have different time, makeup the of apopulation changes more because individuals have the

MAI volution Con N ID sider orchid the and thorn the bug in is change the inliving things over time. More specifically, evolution is E A

7 e f igure 2.6. igure 2.6. Both organisms have have organisms Both adaptation. Over Over

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In different environments, however, you would find other orchid and insect species that have different adaptations. Adaptation in evolution is different from the common meaning of adapta- tion. For example, if you say that you are adapting to a new classroom or to a new town, you are not talking about evolution. Instead, you are talking about consciously getting used to something new. Evolutionary adaptations are changes in a species that occur over many generations due to environmental pressures, not through choices made by organisms. Evolution is simply a long-term response to the environment. The process does not necessarily lead to more complex organisms, and it does not have any special end point. Evolution continues today, and it will continue as long as life exists on Earth. Unity and Diversity Evolution is a unifying theme of biology because it accounts for both the diversity and the similarities, or the unity, of life. As you study biology, you will see time after time that organisms are related to one another. When you read about cells and , you will see that all organisms have similar cell structures and chemical processes. These shared characteristics result from a common evolutionary descent. Humans and bacteria have much more in common than you may think. Both human and bacterial genetics are based on the same molecules—DNA and RNA. Both human and bacterial cells rely upon the same sources of energy, and they have similar cell structures. Both human and bacterial cells have membranes made mostly of fats that protect the inside of the cell from the environment outside the cell. Now think about the vast number of different types of organisms. All of the species alive now are the result of billions of years of evolution and adaptation to the environment. How? Natural selection of genetic traits can lead to the evolution of a new species. In the end, this genetic diversity is responsible for the diversity of life on Earth. Analyze How does evolution lead to both the diversity and the unity of life? 7E

Self-check Online HMDScience.com 1.2 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. Describe a . 4. Analyze How are structure and Cells 10c function related to adaptation? 7. Do you think homeostasis is 2. Why is homeostasis essential for 7e necessary at the level of a living things? 4b 5. Apply How is the process of natural single cell? Explain. 4b, 10A, 10c 3. What is the relationship between selection involved in evolution? adaptation and natural selection? 7e 7e 6. Apply Describe the relationship between cells and organisms. 10C

Chapter 1: Biology in the 21st Century 13 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 14 D A T A ANALYSIS

1:

Introducing Biology numerical measurements. Notice that thequalitative data are descriptions. The quantitative data are objective, Quantitative data examples Qualitative data examples Some ofherobservations are qualitative data, andsome are quantitative data. them every day for amonth.Sherecords detailed observations abouttheirbehaviors. and activities ofdolphins.Sheidentifiesdifferent dolphinswithinthegroup andobserves Suppose that amarinebiologist observes thebehavior Model distance, concentration, time,orfrequency. measurements such asmass, volume, temperature, nomattersame whomeasures them.They include measurements. The data are objective—they are the Quantitative data quality ofanobservation, suchascolor, odor, ortexture. words ofwhat isbeingobserved. They are based onsome Qualitative data data andquantitative data. Scientists collect two different typesofdata: qualitative Quantitative and Qualitative

the photograph ofthejackals shown to theright. take photographs oftheirinteractions to studylater. Examine in Africa. You observe their behaviors and interactions and Suppose that you are a studying jackals in their natural Practice • • • • • •

The sonar frequenc Dolphins eat theequiv There are ninedolphinsinthispod. Dolphins have smoo Dolphins inapodengag Dolphin colors range from gray to white. 2. 1.

could beobtained from thephotograph ofthejackals. Analyze could beobtained from thephotograph ofthejackals. Analyze

Identify Data Types

Give three e Give three e Qualita

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©Michael Nichols/National Geographic Image Collection theory constant variable dependent variable independent experiment hypothesis data observation VOCABULARY from various sources... scientific information extracted 3Bcommunicatetesting...; andapply and experimental andobservational empirical evidence, logical reasoning, scientific explanations by using analyze, evaluate, andcritique theories; 3Ainall fields ofscience, s developed; 2D science andnew technologies are tosubject change asnew areas of explanations, butthey may be well-established andhighly-reliable hypotheses, scientific theoriesare independent researchers. Unlike of beingtested by multiple physical phenomena and are capable theories are based onnatural and evidence...; 2Cknow scientific supported by observational capable ofbeingsupported ornot testable statements that mustbe hypotheses are tentative and limitations...; 2Bknow that science andunderstand that ithas cientific hypotheses andscientific F on observations. other ar igure 2Aknow thedefinitionof 3.1 eas ofscience, depends 1.3

Biology, like distinguish between 3A, 3B 2A, 2B, 2C, 2D, Scientific ThinkingandProcesses gat Like all science, biology aprocess is ofinquiry. questions that you have abouttheworld? observation andexperimentation. How doyour daily observations helpanswer like all scientists, askquestionsabouttheworld andtryto findanswers through disease? How isresearch inalaboratory similar to research inarain forest? Biologists, What doesthestudyoffungushave incommon withthestudyofhumanheart Your to World Connect K ey

and thinking. logical on same the principles. on iscuriosity, based thinking Scientific skepticism, There is no by one scientists, used all method is butbased inquiry scientific all is ahumanScience process to understand of world trying the around us. • • • MAIN IDEA MAIN MAIN IDEAS MAIN

hering evidence. hering C

oncept conclusions that are supported by evidence. Log ­con Skep them. Curi Scientists communica A theoryexplains awiderange ofobservations. Biologists use experiments to test hypotheses. Like all science, isaprocess biology ofinquiry. clusions. ical thinking is the use of is use the thinking reasoningical through information to make osity is what drives scientists to ask questions about world the around ticism is the use of toticism is use thinking the question critical results and

Science is a way of thinking, questioning, and and questioning, thinking, of way a is Science 2A, 2B, 3A 2B, 2A, the gorilla in the phenomena. The written descriptions and drawings of construct testable explanations and predictions of natural research and investigation. Such to is used evidence directly through that is evidence evidence is observed as basis the forevidence knowledge. scientific Empirical long-standing Scientists ideas. on depend empirical that may evidence scientific support or even overturn science. honest exchange of data is extremely important in share findings their with each other. The open and To improve our understanding of world, the scientists empirical from evidence investigation afield of gorillas. te information inmanydifferent ways.

One o FIGURE 3.1 FIGURE f the mostf the important points of is science are examples of observations and Chapter inthe21stCentury 1:Biology

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CONNECT TO Observations, Data, and Hypotheses data analysis All scientific inquiry begins with careful and systematic observations. Of Biology relies on the analysis of course, observation includes using our senses to study the world, but it may scientific data. Use the Data also involve other tools. For example, scientists use computers to collect Analysis activities in each chapter measurements or to examine past research results. Empirical evidence is in this book to build your data analysis skills. gathered through observation. Observations are often recorded as data that can be analyzed. Scientists collect two general types of data: qualitative data and quantitative data. ­Qualitative data are descriptions of a phenomenon that can include sights, sounds, and smells. This type of data is often useful to report what happens but not how it happens. In contrast, quantitative data are characteristics that can be measured or counted, such as mass, volume, and temperature. ­Anything that is expressed as a number is quantitative data that can be used T’ ing! A maz to explore how something happens. Video Inquiry Scientists use observations, data, and scientific literature to form a hypo­ HMDScience.com thesis. A hypothesis (plural, hypotheses) is a proposed answer for a scientific GO ONLINE question. A hypothesis must be specific and testable. You probably form and Poison Frogs test many hypotheses every day, even though you may not be aware of it. Suppose you oversleep, for example. You needed to get up at 7 a.m., but when you wake up you observe that it is 8 a.m. What happened? Did the alarm not go off? Was it set for the wrong time? Did it go off, but you slept through it? You just made three hypotheses to explain why you overslept—the alarm did not go off, the alarm was set for the wrong time, or the alarm went off, but you did not hear it. Hypotheses, Results, and Conclusions A hypothesis leads to testable predictions of what would happen if the hypothesis is valid. How could you use scientific thinking to test a hypothesis about oversleeping? If you slept late because the alarm was set for the wrong time, you could check the alarm to find out the time for which it was set. Suppose you check, and the alarm was actually set for 7 p.m. In this case, your hypothesis would be supported by your data. For scientists, just one test of a hypothesis is usually not enough. Most of the time, it is only by repeating tests that scientists can be more certain that their results are not mistaken or due to chance. Why? Biological systems are highly variable. By repeating tests, scientists take this variability into account and try to decrease its effects on the experi- mental results. After scientists collect data, they use statistics to math- ematically analyze whether a hypothesis is supported. Analyzed data are the results of the experiment. There are two possible outcomes or results.

• Nonsignificant The data show no effect, or an effect so small that the Figure 3.2 In this experiment, a scientist studies how chemicals results could have happened by chance. are detected in the mouth and • Statistically significant The data show an effect that is likely not due to nose to produce taste. chance. When data do not support a hypothesis, the hypothesis is rejected. But these data are still useful because they often lead to new hypotheses. ©Colin Cuthbert/Photo Inc. Researchers,

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FIGURE 3.3 Scientific Thinking Science is a cycle. The steps are shown in a certain order, but the cycle does not begin or end at any one point, and the steps may take place in various orders.

Observing Scientists make obser- vations and examine prior research.

Evaluating results Scientists eval- Forming hypotheses Scientists uate the data and conclusions ask questions and try to explain presented by other scientists. observations.

Analyzing data Scientists Testing hypotheses Scientists analyze their data to draw collect data that they use to conclusions about their research. support or reject a hypothesis.

Synthesize Where in the cycle would retesting a hypothesis fit? Explain.

Experimental methods and results are evaluated by other scientists in a process called peer review. Only after this review process is complete are research results accepted. Whether the results support an existing theory or disagree with earlier research, they are often used as a starting point for new questions. In FIGURE 3.3, you see the cycle of observing, forming hypotheses, testing hypo­ theses, analyzing data, and evaluating results that keeps scientific inquiry going. Synthesize Why is there no one correct process of scientific investigation? 3A

MAIN IDEA 2B Biologists use experiments to test hypotheses. Observational studies help biologists describe and explain something in the world. But in observational studies, scientists try not to interfere with what Biology HMDScience.com happens. They try to simply observe a phenomenon. One example involves GO ONLINE the endangered white stork. The number of white storks had decreased sharply by 1950, even becoming extinct in some countries. To help protect the Experimental Design storks, biologists studied the migration patterns of the birds. Observational studies can tell a biologist about changes in migration path and distance. They told scientists where the storks were breeding and how many eggs they would lay. Because of these efforts, stork populations have rebounded by 20% worldwide. Observational studies can provide much information and answer many questions. But there is one question that observations cannot answer: What causes any changes that might be observed? The only way to answer that question is through an experiment.

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Scientific experiments allow scientists to test hypotheses and find out how something happens. In experiments. scientists study factors called indepen-

HMDScience.com dent variables and dependent variables to find cause-and-effect relationships. The independent variable in an GO ONLINE VISUAL VOCAB experiment is a condition that is The Scientific Process manipulated, or changed, by a scien- The independent variable is a condition that is manipulated, or tist. The effects of manipulating an changed, by a scientist. independent variable are measured by independent variable changes in dependent variables. affects Dependent variables are observed and measured during an experiment; dependent variable they are the experimental data. Dependent variables are observed Changes in dependent variables and measured during an experiment; depend upon the manipulation of the they are the experimental data. independent variable. Suppose a scientist is testing medications to treat high blood pressure. The independent variable is the dose of medication. The dependent variable is blood pressure, R E A D I N G TOOLB ox as shown in FIGURE 3.4. Ideally, only one independent variable should be tested in an experiment. vocabulary In common usage, the term Thus, all of the other conditions have to stay the same. The conditions that do constant means “unchanging.” not change during an experiment are called constants. To study the effects of In experimental research, a an independent variable, a scientist uses a control group or control condition. constant is a condition or Subjects in a control group are treated exactly like experimental subjects factor that is controlled so that it does not change. except for the independent variable being studied. The independent variable is manipulated in experimental groups or experimental conditions. Constants in the blood pressure medication experiment include how often the medication is given and how the medication is taken. To control the BI_CTXESE026100_32A experiment, these factors must remain the same, or be held constant. For final example, the medication could be tested with 0, 25, 50, or 100 milligram 8-6-12 doses, twice a day, taken by swallowing a pill. By changing only one variable at LKell a time—the amount of medication—a scientist can be more confident that the results are due to that variable. Infer How do experiments show cause-and-effect relationships?

FIGURE 3.4 Comparing Variables y-axis This graph compares the effects of the same dosage of two different medications on blood pressure. The medication B independent variable (dosage) stayed the same for each type of Blood pressure medication tested.

Dependent variable medication A

x-axis Dose of medication (100 mg) Independent variable

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(inset) ©Dr. E. Walker/Photo Researchers, Inc.; (t) ©David McCarthy/Photo Researchers, Inc. A theory explains awide rangeA theory ofobservations. Compare

phenomena, may testable never be or scientific. orwith new better technology. phenomena, Other such as supernatural Some phenomena that are not testable scientifically now may become testable cannot or verified replicated be cannot count inquiry. inscientific as evidence example, observations must testable be and verifiable. that Observations limitations to kinds the of questions thatcan answer. inquiry scientific For and, inhumans, classic both and variant Creutzfeldt–Jakob disease. early pointed evidence 1980swhen to prions as cause the of mad cow disease prions Thebetween link disease. was and not disease even suggested until the and prions. Viruses and prions are not living organisms, but do cause they example, expanded due has been to discoveries the germ the theory of viruses acceptedstill today. However, has changed germ the theory over time. For isms, such of This which is is basis asthe of disease, bacteria. germ the theory researchscientific suggested that were diseases caused by microscopic organ- supernatural causes or to imbalances of body’s the humours, or fluids.Then cause of Until disease. were mid-1800s, the illnesses thought related to be to ments and observations refine and expand knowledge. scientific about living the world is gathered. is an Science ongoing process. New experi- must always to theories willing and revise be conclusions evidence as new observations and experimentalresults can replace older theories. Scientists futed, and are they always subject to change. New theories that better explain . hypotheses Scientific and theories may supported be or re- never proved. Eventually, may broadly be atheory accepted by scientific the providing any explanations. change form, but it cannot created be or destroyed. Alaw without describes verse. For example, law the of conservation of states energy that may energy lawa scientific relationships defines that uni- inthe are everywhere valid provide explanations of phenomena. In contrast to hypotheses and theories, large amount of data, and it explains how populations can evolve. For example, natural is theory. ascientific selection It is supported by a testedbeen over variety awide of conditions are incorporated into theories. question. Hypotheses about natural and physical phenomena that have thatof ahypothesis evidence. Recall is aproposed answer to ascientific of observations and experimentalresults that is supported by range awide is very different.theory is very A word theory means aguess or ahunch. In science, meaning the of word the Theused. word theory has different meanings. In conversation, everyday the The meaning of aword may change depending on context the inwhich it is MAIN IDEA MAIN Scie One e The Hypo

ories are not easily accepted inscience, and by definition are they ntific inquiry is importantntific inquiry to understanding nature, but there are Distinguish between a hypothesis, a theory, and a law. and atheory, ahypothesis, between Distinguish theses proposetheses answers to questions. scientific theories Scientific xample of how understanding scientific can change involves the

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sium. implications at ascience sympo- pres F F safety. patterns andadvise viewers about marize andpredict future weather may use aDoppler image to sum- In atelevision report, forecasters 2003, are modelsofweather data. this oneofHurricane Cl Unit #:Introducing Biol igure igure 3. 2. 1. R 1.3

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online biology 21 HMDScience.com DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B

1.4 Biologists’ Tools and Technology

2F, 3E Key Concept Technology continually changes the way biologists work. VOCABULARY MAIN IDEAS measurement Observations include making measurements. accuracy Technology contributes to the progress of science. precision Complex systems are modeled on computers. microscope The tools of give rise to new biological studies. gene molecular genetics Connect to Your World Can you imagine life without cars, computers, or cell phones? Technology changes 2F collect and organize the way we live and work. Technology also plays a major part in the rapid increase of qualitative and quantitative data and make measurements with accuracy biological knowledge. In the early days of biology, scientists were limited to making and precision using tools... and measurements and observations with simple tools. Today, technology allows biolo- 3E evaluate models according to their limitations in representing gists to view tiny structures within cells and activity within a human brain. Technol- biological objects or events ogy even allows biologists to study and change genes. What will technology allow next?

MAIN IDEA 2f Observations include making measurements. A wildlife biologist records a description of the alligator mating rituals she observes in her field journal. A pharmaceutical researcher uses probes and computers to measure and calculate the pH of stomach acids. Though very different, these situations are both examples of observation and the use of tools in scientific investigations. Tools serve a variety of purposes. Some tools, such as and hot plates, allow scientists to set up experiments. Tools such as microscopes and hand lenses are used to enhance senses. Rulers, balances, and timing devices enable the gathering of quantitative data. Com- puter software is a tool that enables scientists to analyze and report data.

FIGURE 4.1 Accuracy and Precision high precision, low accuracy high accuracy, low precision high precision, high accuracy

Measurements can be precise, accurate, both, or neither.

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© HMH science. Technology contributes to progress the of ob E xplain

the true value of true the quantity the measured. have inavacuum. to be to studyused living organisms specimens the being studied because However, electron microscopes, light unlike microscopes, cannot be to directly study used canThey even be individual protein molecules. clearly specimens as much magnify as size. 1,000,000timesactual their show can also they much things. smaller Electron microscopes can cells, but to see produce used they be much highermagnifications so electrons instead of light microscopes These objects. to can magnify images of Light as cells as bacteria. small living to or see used specimens, and preserved provide they clear are often stained with chemicals to make details stand out. specimens upnify to about size, 1500timesactual their and samples that you might on use, are same the based still A Microscopes first inalong line of technologies that changed study the of biology. living things at existed. never alevelknew they Thus, microscope the was the microscopethe was invented. Scientists suddenly had ability the to study Until late the 1600s,no one about knew cells or organisms. single-celled Then Quantitative data are gathered through shoes tosses in surement. Accuracy and precision are demonstrated by results the of horse- clearer images. Today’s light microscopes, such as one the in 1800s,mostthe microscopes had combinations of lenses that provided microscopes but objects magnified did not produce clear images. By organisms—were not even imaginable before microscopes. The first most basic concepts of biology—such that as fact the cells make up all racy and precision.racy measurement. The quality of measurements by accu- their described can be International the called System of Units, or SI, is language the for scientific all dimensions of something using astandard unit. system, metric The modern and closeto each other, results the are precise both and accurate. results are accurate. When horseshoes the are centered around post goal the are centered around are even ifthey post, goal the not near each other, the arethey not results the near post, goal the are precise. When horseshoes the MAI solete. microscope Ele N

Describe why newer technology may not make older technology technology older make may not whytechnology newer Describe ctron microscopes, beams of first developed 1930s,use inthe ID E A

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small to beseen withthenaked eye. to studyc Figure 4.2 Chapter inthe21stCentury 1:Biology ells whichareells generally too

Biologists use microscopes

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QUICKLAB observing 2f Life Under a Microscope Using a microscope properly is an important skill for many biologists. In this lab, you will review microscope skills by examining a drop of water from the surface of a local pond.

Problem What types of organisms can be found in pond water? Materials Procedure • 1 drop pond water 1. Make a wet mount slide. Place a drop of pond water in the center • eyedropper of a microscope slide, and carefully put a cover slip over the water. • microscope slide Learn how to make a wet mount by reading the Lab Handbook. • cover slip 2. View the pond water sample under low power on the microscope. • microscope Use the coarse focus knob to bring the sample into focus. Draw and label any organisms that you see in the sample. 3. View the slide under high power. Use the fine focus knob to bring portions of the sample into focus. Draw and label any organisms, including details of their structures, that you see in the sample. Analyze and Conclude 1. Connect Describe how organisms in the sample exhibit the characteristics of living things. 2. Compare and Contrast Make a table to compare and contrast the characteristics of organisms in the sample of pond water.

There are two main types of electron microscopes. • A scanning (SEM) scans the surface of a specimen with a beam of electrons. Usually, the specimen’s surface is coated with a very thin layer of a metal that deflects the electrons. A computer forms a Biology three-dimensional image from measurements of the deflected electrons. HMDScience.com • A transmission electron microscope (TEM) transmits electrons through a GO ONLINE thin slice of a specimen. The TEM makes a two-dimensional image similar Cells Through Different to that of a light microscope, but a TEM has a much higher magnification. Microscopes SEM and TEM images are artificially colorized with computers so that tiny details, such as the leaf pores, or stoma, shown in figure 4.3, are easier to see. FIGURE 4.3 Comparing Micrographs Scanning Electron Transmission Electron Light Micrograph (LM) Micrograph (sem) Micrograph (tem)

stoma stoma

stoma

A light micrograph shows a two-dimen- An SEM shows a three-dimensional A TEM shows a two-dimensional image sional image of a specimen. This light image of a specimen’s surface. (colored of a thin slice of a specimen. (colored micrograph shows the actual color of SEM; magnification 15003) TEM; magnification 50003) the specimen. (LM; magnification 20003) (tr) ©HMH; (bl) ©ISM/Phototake; (bc), (r) ©Dr. Jeremy Burgess/Photo Researchers, Inc. Jeremy Burgess/Photo Researchers, (r) ©Dr. (tr) ©HMH; (bl) ©ISM/Phototake; (bc),

24 Unit 1: Introducing Biology CorrectionKey=B DO NOT EDIT--Changes mustbemadethrough “File info”

(l) ©Photo Researchers, Inc.; (r) ©Susan Leavines/Photo Researchers, Inc. cer Infer in detail Figure 4.4 the brainthe are aperson is active doing while task. aparticular example, atechnique MRI(fMRI)can functional show called which areas of connected to acomputer, data the and calculated can be analyzed instantly. constant readings of data such as temperature and pH.When probeware is databoth and collection analysis. Probeware are measuring tools that can take representations. Theof use probeware inconjunction with computers allows rately calculate, analyze, and display data incharts, graphs, and other visual to generateused reports. Spreadsheet software to quickly is used and accu- have become invaluable to practice the of biology. Word processing software is improved, computers, computer software, and hardware, such as probeware, expensive and large so that one computer an entire filled room. As technology The first digital, electronic computers were invented were 1940s.They inthe Computers and in together to give acomplete of of view all tissues the inthat area, as you can see cross-section image of of apart body. the of Aseries MRIimages put can be nance imaging astrong MRIuses (MRI)is used. to magnetic field produce a such as ligaments, cartilage, or brain. the foruseful looking at skeleton the but for not useful examining so tissues soft muscle, but are by absorbed bones and Thus, teeth. x-ray images are very image is formed by x-rays, which pass through tissues, soft such as skinand dentists have probably x-ray taken images of you times. An x-ray several Imaging is technology not limited to microscopes. For example, doctors or Imaging Medical tain lake? F

To ima IGURE H ow might probeware be used by a biologist studying the decline of fish in a in fish of decline the studying by abiologist used be probeware ow might . AnMRIofthehumanknee(right)shows both soft anddense tissues indetail.

4.4. An x-ray ofthehumanknee(left) shows dense tissues, suchasbone, ge tissues, soft another magnetic reso- imaging called technology Advances have intechnology for to uses led new MRI.For 2f P rob eware electron micrograph. TEM stands for transmission micrograph, andtheabbreviation SEM stands for scanning electron micrograph, theabbreviation abbreviation LMstands for light a micrograph the inthisbook, microscopes. Whenever you see micrographs, orimages from Biologists use several typesof I Chapter inthe21stCentury 1:Biology magi CO NNE n g CT TO

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MAIN IDEA 2f, 3e Complex systems are modeled on computers. Normal heartbeat Computer-based technology has greatly expanded biological research. As computers have become faster and more powerful, biologists have found ways to use them to model living systems that cannot be studied directly. A com- puter model simulates the interactions among many different variables to provide scientists with a general idea of how a biological system may work. Computers can model complex systems within organisms. For example, computer models are used to study how medicines might affect the body or, as you can see in FIGURE 4.5, the effects of a heart attack. Scientists have even used computer models to find out how water molecules travel into and out of cells. Heart attack The scientists made a computer program that took into account more than 50,000 virtual atoms in a virtual cell. The computer model showed that water molecules must spin around in the middle of a channel, or a passage into the cell, to fit through the channel. Water molecules had a specific fit that other molecules could not match. Computer models can also help biologists study complex systems on a much larger scale. , which is the study of how diseases spread, depends on computer models. For example, the computer model in FIGURE 4.6 can predict how fast and how far a disease might spread through a herd of Figure 4.5 This computer- cattle. A model can calculate the number of cattle who might get sick and generated model shows that heart activity (red) is tightly regulated suggest where the disease could be spread to humans through eating contami- during a normal heartbeat. During nated meat or other sources. This study cannot be done with real cattle and a heart attack, heart activity is people. Computer models are used when actual experiments are not safe, widespread and disorganized. ethical, or practical. However, all models have limitations, and they are not able to replicate exactly all aspects of the system they are showing. Conclude What are some reasons why biologists use computer models? 3e

FIGURE 4.6 Computer Simulation Simulator File Edit Tools Zoom Help Computer simulations can help Interface Information Procedures epidemiologists to predict the spread of disease and to Edit 3D develop a response plan. Start Simulation Stop Simulation

Set Up Simulation

uninfected animal(s) 500

infected animal(s) 1

incubation (days) 7

chance of immunity (%) 10

chance of death (%) 25

Reset Spread of Disease Within a Herd

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(t) ©David Parker/Photo Researchers, Inc.; (r) ©Kevin Curtis/Photo Researchers, Inc. rise to new biological studies. toolsThe give genetics ofmolecular Connect 3. 2. 1. Re

1.4 from molecular genetics. plants and animals, even replacement of faulty genes. advances These come parents transgenic were foods, school—genetically modified inhigh has to led many technologies that were unimaginable your when genetic information. understanding Our of DNA the molecule children are school? inhigh biologist could computer use databases to search for similar molecules. gist identifies that amolecule prevents growth the of cancerous tumors. The patterns,find similarities, and differences inbiological data. Suppose abiolo- By searching computer databases, aprocess data mining, called abiologist can within and across species. another. changing genes, to implanting genes from one into species gone from learning how geneticworks, the code to life has happened ingenetics. In just 40years, we have perhaps greatest the leap forward inour knowledge of Genomics F Computer-based technologies, such shown as those in sequences, or genomes, of humans and other organisms have found. been quickly DNA find sequences. Through of use the computers, entire the DNA genetics with computer technology. For example, computers are to used , , and many other areas of biology. DNA on amolecular level. Molecular genetics to study is used evolution, MAI

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1.5 Biology and Your Future

2A, 3D Key Concept Understanding biology can help you make informed decisions. VOCABULARY MAIN IDEAS biotechnology Your health and the health of the environment depend on your knowledge of biology. transgenic Biotechnology offers great promise but also raises many issues. Biology presents many unanswered questions.

2A know the definition of Connect to Your World science and understand that it has Should brain imaging technology be used to tell if someone is lying? Is an endangered limitations, as specified in subsection (b)(2) of this section and moth’s habitat more important than a new highway? Would you vote for or against 3D evaluate the impact of scientific the pursuit of stem cell research? An informed answer to any of these questions research on society and the environment requires an understanding of biology and scientific thinking. And although science alone cannot answer these questions, gathering evidence and analyzing data can help every decision maker.

MAIN IDEA 3D Your health and the health of the environment depend on your knowledge of biology. Decisions are based on opinions, emotions, education, experiences, values, and logic. Many of your decisions, now and in the future, at both personal and societal levels, involve biology. Your knowledge of biology can help you make informed decisions about issues involving endangered species, biotechnology, medical research, and pollution control, to name a few. How will your deci- sions affect the future of yourself and others? Biology and Your Health R E ADI N G TO OLB ox What you eat and drink is directly related to your health. But you may not think twice about the possibility of contaminated food or water, or a lack of TAKING NOTES in your diet. Not long ago, diseases caused by deficiencies Use a mind map to take notes were still fairly common. The first vitamins were identified less than 100 years about the importance of studying biology. ago, but today the vitamins found in foods are printed on labels.

personal health Even today we still face food-related causes of illness. For example, you lifestyle choices might hear about an outbreak of food poisoning, and mad cow disease was only recognized in the late 1980s. Of perhaps greater concern to you are food Importance of allergies. Many people suffer from severe, even life-threatening, allergies to biology foods such as peanuts and shellfish. Beyond questions about the sources of food are questions and concerns about what people eat and how much they eat. For example, scientists estimate that more than 60% of adults in the United States are overweight or obese. The health consequences of obesity include increased risks of diabetes, stroke, heart disease, breast cancer, colon cancer, and other health problems. Biology can help you to better understand all of these health-related issues.

28 Unit 1: Introducing Biology CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info”

(t) ©Courtesy of Brookhaven National Laboratory; (b) ©Frans lanting/Minden Pictures Connect radiation, or of some type infection. could have caused by been factors such as achemical water, inthe ultraviolet question by testing hypotheses. several studied They deformities the whether and missing eyes. What caused deformities? the Scientists investigated that Manythem. of frogs the had deformities, including missing legs, legs, extra students stopped to at look frogs, the and what saw they shocked through awetland and frogs for collecting aschoolproject. The In 1995,some middleschoolstudents from Minnesota were walking World the Biology and You Around you in can see just lungs; the affect it change can also a person’s , body as using and alcohol, drugs, tobacco? Cigarette illegal smoke not does sunscreen? What are of benefits the exercise? What are of effects the of lifestyle choices that your affect Why health. is it important to use ch to high blood pressure.to blood high brain and can mood, affect lower levels inthe could contribute could you make an informed decision related to any of questions? these ent chemical that Without used? could be an understanding of biology, how there any of evidence human problems health area? inthe Is there adiffer- considered.be What is economic the impact on of area? the factory the Is instance like political, this, legal, economic, and biological concerns have to able or In to closed ban chemical? fined? the be Should any factory the increased number of parasite infections. ­How has answered some questions about cause the of legdeformities. the parasites, trematodes, called and predation by dragonfly nymphs. Science suggest that frog the deformities were due to acombination of infection by arisk to otherpose species? infrogs.ties Might that parasite present be also inMinnesota? If so, did it area? In other regions of United the States, parasites caused similar deformi- chemical water, inthe might arisk to people chemical the living pose inthe couldthem other area. affect inthe species If deformities the were caused by a interest?scientific The frogs are of apart an ecosystem, whatever so affected conclusions from many different sources. of scientists. It is up to to everyone make decisions on and evidence based natural use, but decisions about future the are not hands inthe pollution, biodiversity, habitat preservation, land conservation, and Biologists and other scientists research environmental issues such as emical, and cellular, for example—can help you make any number Why w An understanding of on biology many different levels—genetic, The Sup At fir 3D ever, scientists now that think achemical may connected to be the

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knowledge of , genetic principles, and functions even the of genes. of biotechnology are debated. Understanding and benefits these risks requires herbicide resistance, plants? to wild Around world, the and benefits the risks plantsif genetically modified spread undesirable genes, such for as those known. Is it saferesistance? to insect eat with genetically foods modified What However, long-term the crops of effects genetically modified are not fully Insect-resistant crops could reduce or for end need the chemical pesticides. changed to increase nutrients the and yield of plants the and to resist insects. you foods, are modified cally hearing about transgenic organisms. cows can make human antibodies and proteins. When you hear about geneti- can make human to treat people with diabetes. Transgenic sheep and algae, as shown in of problems, modern such as search the for alternative sources energy using found at Biotechnology scenes. crime has great potential to help solve avariety from prison DNAwhen testing has shown that their DNA did not match DNA other For fields. example, people wrongly convicted of crimeshave freed been biotechnology inmedicine, is used , forensic science, and many centuries, such of as use the microorganisms to make bread and cheese. Today, and techniques. In some fact, forms of biotechnology have around been for processes. Biotechnology includes broad avery range of products, processes, ogy come questionsogy about its uses. MAI Gen Gen N ID etic screening also raises ethical concerns. screening raisesetic ethical also For example, should who etically modified foods have foods modified manyetically potential Crop benefits. plants are E A

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considered a disorder? Of greater concern is the possibility that people might Web use genetic screening to choose the characteristics of their children. Is it ethical to allow people to choose to have only brown-eyed male children who HMDScience.com would be at least 6 feet (ft) tall? GO ONLINE Bioethics Predict How might genetically modified crops affect biodiversity?

MAIN IDEA 2A Biology presents many unanswered questions. The structure of DNA was described in 1953. By 2003, the entire human DNA sequence was known. Since 1953, our biological knowledge has exploded. But even today there are more questions than answers. Can cancer be prevented or cured? How do viruses mutate? How are memories stored in the brain? One of the most interesting questions is whether life exists on planets other than Earth. Extreme environments on Earth are home to living things like the methane worms in FIGURE 5.4. Thus, it is logical to suspect that other planets may also support life. But even if life exists elsewhere in the universe, it may be completely different from life on Earth. How might biological theories change to take into account the characteristics of those organisms? A large number of questions in biology are not just unanswered—they are Figure 5.4 Methane hydrate ice unasked. Before the microscope was developed, no one investigated anything worms live in frozen methane gas microscopic. Before the middle of the 20th century, biologists did not know at the bottom of the Gulf of Mex- ico. Because some organisms can for sure what the genetic material in organisms was made of. As technology live in such extreme environments, and biology advance, who knows what will be discovered in the next 20 years? some scientists hypothesize that life exists, or once existed, on the Evaluate Do you think technology can help answer all biological questions? Explain planet Mars. (SEM; magnification 203) your views. 2A ©Charles Fisher, The Pennsylvania State University ©Charles Fisher, Self-check Online HMDScience.com 1.5 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. Give three examples of ways in 4. Synthesize Scientists disagree on ecology which biology can help inform whether genetically modified foods 6. What effects might geneti- everyday decisions. 3D are safe to eat. What type of scien- cally modified plants and 2. What are some of the potential tific evidence would be needed to animals have on an ecosys- benefits and potential risks of show that a genetically modified tem if they breed with wild biotechnology? 3D food is unsafe? 3D plants and animals? 3D 3. What are some of the unanswered 5. Connect How might your study of questions in biology? 2A biology help inform you about your lifestyle choices? 3D

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CHAPTER G N I D A E R

Think abouttherel basic building block ofall organisms?” Answer: thecell organism, cell, thequestioncould be“What isthe uses thesecond term astheanswer. For theterms below. Thenwrite aquestionaboutthefirstterm that Write

the two terms ineach ofthefollowing pairs. Describe onesimilarity andonedifference between Compare andContrast R 1.2 1.1 vo Chapter 8. 6. 4. 2. 5. 3. 1 7. 1. eviewing

DNA, gene DNA, observ evolution, a accur hypothesis, theory homeostasis? these definitions related to themeaning oftheword word that means “stoppage,” or“standstill.” How are means “same.” Thesuffix-stasis comes from aGreek The prefix homeo biosphere, ec contain theprefix bio-? rel The prefix bio-means “life.” How doesthismeaning ate to thedefinitionsofterms inthechapter that science biology species biodiversit biosphere ecosystem system DNA metabolism cel organism Y our acy, precision l Review ation, data X O B L O O T O wn Questions c V daptation abu y ocabulary osystem ationship between each word pair lary - comes from aGreek word that Word Word latin and greek O rig ins 1.3

theory constant dependent variable independent variable experiment hypothesis dat observation adaptation evolution homeostasis a R

18. 10. 16. 14. 12. 15. 19. 13. 17. 11. 9. eviewing Review Games•ConceptMapSectionSelf-Checks online Go

benefits andrisks. Describe anexample ofbiotechnology, includingits hea How can anunderstanding play ofbiology arole inyour micro Briefly describe why thedevelopment ofthe sens Explain thedifference between tools that enhance and ascientific theory? What isthedifference between ascientific hypothesis dev Explain how scientists use observations anddata to homeost How doesnegative feedback act to maintain rel Give anexample ofhow structure are and function things on Ear Briefly describe thebasiccharacteristics that all living likel Explain whydomestication ofplants andanimals was organisms? of organisms withboth theirenvironments andother tha Why isitimportant ated inanorganism. lth? inthehealth ofyour environment? elop ahypothesis. y oneofthefirst areas ofbiology. es andtools that are used for measurements. scope was inbiology. important HMDScience.com Interact 2F asis inlivingthings?

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IDEAS genic t biology studiestheinteractionst biology 3D Chapter inthe21stCentury 1:Biology 2B 10C 2C, 2D 11A 10A 2F, 3F 3F 3D

33 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A

Critical Thinking 20. Synthesize In 1973, the insecticide called DDT was Analyzing Data Identify Data Types banned in the United States due to scientific research Use the information below to answer the next three showing it was toxic to fish and that it may have questions. ­affected birds. There is little scientific evidence that DDT is directly harmful to humans. How could banning DDT Suppose a team of scientists is studying the migration be beneficial to human health and society? 3D of animal species in Africa. One of the scientists takes the photograph below. 21. Apply A student is trying to predict the effects on wildlife of a proposed construction project in an undeveloped area nearby. Describe how the student can evaluate scientific information extracted from news reports, marketing materials, and online resources. 3B

22. Evaluate Discuss the impact of scientific research on society and the environment. Consider the benefits and risks of scientific research and the challenges that unanswered questions leave for biologists and other scientists to wrestle with. 3D 23. Evaluate Suppose a scientist is investigating plant growth. During the experiment, both the type of light and the type of plant are manipulated. The scientist concludes that the results are caused only by changes 27. Apply Give three examples each of quantitative and in the light. Is this an appropriate conclusion? Why or qualitative data that could be collected during this why not? 3A research. 24. Justify Why is science limited to studying phenomena 28. Identify What are four tools that the team of scientists that are scientifically testable? Give two examples of likely used while conducting, analyzing, and communi- questions that are outside the realm of science. cating their work? Explain your answer. 2A 29. Evaluate Suppose the scientists wanted to change the Interpreting Visuals number of species present in this study. What are some Use the diagram below to answer the next two limitations and advantages of using a computer model questions. to simulate the change?

OBSERVING Making Connections

EVALUATING RESULTS FORMING HYPOTHESES 30. Defend Much of the work and ideas of early scientists, such as ’s four humours and Aristotle’s classification system for animals, were shown to be incorrect and have been discarded or replaced. Why, ANALYZING DATA TESTING HYPOTHESES then, are early Greeks credited as the fathers or inven- tors of science? 3F 31. Analyze The yellow fever mosquito shown on 25. Apply Observing is shown at only one point during the the Chapter Opener is just one type of mosquito that cycle. At what other points during the cycle is observing can pass disease-causing viruses to people. Mosquitoes necessary? Explain. 2B can also carry other diseases such as malaria, Dengue 26. Distinguish Where in the process are scientists most fever, and West Nile virus. And even if mosquitoes do likely to make inferences and predict trends from data? not carry dangerous viruses, they are certainly pests. On 2G the other hand, mosquitoes are a source of food for many types of animals. Suppose you developed a way to rid Earth of mosquitoes. Do you think it should be used? Why or why not? 3A ©Martin Harvey/Foto Natura/Minden Pictures

34 Unit 1: Introducing Biology Biology End-of-Course Exam Practice

Record your answers on a separate piece of paper. 2E, 10A MULTIPLE CHOICE 4 A student is provided with a sample of pond water that contains a variety of single-celled 7E organisms. How might the student determine if 1 Finch species in the Galapagos Islands have any of the organisms in the sample are in the a wide variety of beak shapes. The theory of process of reproducing? natural selection suggests that these differences A Examine the pond water with a hand lens to arose because — determine if the water in the sample is moving. A changes occurred over a short period of time B Examine a sample of the pond water with a B finches with certain beak shapes survived in compound microscope to determine if any of greater numbers the cells are dividing into two cells. C conscious decisions allowed certain finches to C Observe a drop of pond water with a survive compound microscope, return the drop back to the larger sample, and then repeat the D individual finches adapted to their process every hour for three hours to see if the environment population size changes. D Examine the pond water with a compound 11A microscope to determine whether the single- 2 celled organisms it contains are moving. ?? 2E, 2G, 11B is controlled by maintains 5 Students hypothesized that water pollution affects the growth of fish. In an experiment, they added the same amount of food to ponds polluted by feedback mechanisms systems fertilizers and industrial waste. They measured fish growth and found that most fish grow slowly in each of these environments. Why is their Which of the following best completes this conclusion not reliable? concept map? A They did not have a control. A biodiversity B They did not have a clear hypothesis. B homeostasis C They only tested one independent variable. C evolution D They did not have a dependent variable. D adaptation THINK THROUGH THE QUESTION 3E When scientists study how one thing affects another, 3 Based on their limitations, which of the following the investigation generally has a control, a testable models is the best representation of how the hypothesis, one manipulated (independent) variable, human skeletal and muscular systems work and one measured (dependent) variable. Are these together to produce motion? components present in the student’s experiment? A a detailed illustration in a textbook B a skeleton made up of human bones that can be manually manipulated C a computer simulation of the skeletal and muscular systems in motion D a human running on a treadmill

Chapter 1: Biology in the 21st Century 35