Biology: Exploring Life Chapter - Pearson Education
C h a p t e rBiology: Exploring Life1Red pandas (Ailurus fulgens), such as the one on the cover of this textbook and the onepictured to the right, have a characteristic kitten-like face and grow to be about the size of alarge house cat. These captivating creatures are well adapted for life in the mountainous forestsof Asia. Their cinnamon red and white coat camouflages themwith the red mosses and white lichens of their environment,Who are a red panda’swhile their dark underbelly helps hide them from predatorsclosest relatives?looking up from below. Their long bushy tail helps thembalance in the trees and, when wrapped around their bodies, provides warmth during the winter.And a bony projection in their wrist helps them grasp one of their favorite foods, bamboo.You might think of the much larger, black and white pandas when you think about b ambooeaters. Giant pandas live in similar regions in Asia. Are they closely related to red pandas?Scientists once thought so but have since reclassified red pandas into their own family. Later inthe chapter we’ll explore how scientists have traced the family tree of red pandas.Despite their distinct lineages, the red panda and the giant panda do have something incommon—they are both at risk of going extinct in the wild. Scientists don’t have an accuratecount of the red panda’s numbers or know exactly where they live. The most recent countsestimate there are about 10,000 red pandas left in the world, a number that is likely tofall below 9,000 over the next 30 years. Finding and counting these shy, solitary animalsin their remote habitats is difficult—just one example of the challenges and adventuresencountered in biology, the scientific study of life.We will begin this chapter by defining biology. Next we’ll consider the nature and process ofscience. And we’ll end the chapter with an exploration of five unifying themes that you will findwoven throughout your study of biology.Big IdeasBiology: The ScientificStudy of Life (1.1–1.3)Life can be defined by a group ofproperties common to all livingorganisms and ischaracterized byboth a hugediversity oforganismsand ahierarchy oforganization.TAYL6012 09 C01 PRF.indd 40The Process of Science (1.4–1.8)Science is based on verifiable evidence.In studying nature, scientists makeobservations, form hypotheses, and testpredictions.11/11/16 1:25 PM
Five Unifying Themes inBiology (1.9–1.14)Themes that run through all of biologyare evolution, information, structureand function, energyand matter, andinteractions.1TAYL6012 09 C01 PRF.indd 111/11/16 1:25 PM
Biology: The Scientific Study of Life1.1 What is life?new cells is the basis for all reproduction and for the growthand repair of multicellular organisms. A cell may be part of acomplex plant or animal, or it may be an organism in its ownright. Indeed, single-celled bacteria and other unicellularorganisms far outnumber multicellular organisms on Earth.Figure 1.1 also illustrates that the living world is wondrouslyvaried. In the next module we see how biologists attempt toorganize the remarkable diversity of life.?How would you define life?Life can be characterized by its properties and processes, such as thosedepicted in Figure 1.1.Defining biology as the scientific study of life raises the obvious question: What is life? Even a small child realizes that anant or a plant is alive, whereas a rock or a car is not. But the phenomenon we call life defies a one-sentence definition. We recognize life mainly by what living things do. Figure 1.1 exploressome of the properties and processes we associate with life.All organisms, from ants to plants to people, are composedof cells—the structural and functional units of life. The phenomenon we call life emerges at the level of a cell: A cell canregulate its internal environment, take in and use energy, andrespond to its environment. The ability of cells to give rise toReproduction: Organismsreproduce their own kind.Order: Life is characterizedby highly orderedstructures.Response to the environment:All organisms respond toenvironmental stimuli. ThisVenus flytrap rapidly closedits trap in response to a flylanding on it.Regulation: Organisms have regulatory mechanisms thatmaintain a beneficial internal environment. “Sunbathing”raises this lizard's body temperature on cold mornings.Growth and development: Inheritedinformation encoded in DNA controlsthe pattern of growth and developmentof all organisms.Energy processing:Organisms take inenergy and use it topower all their activities.Evolutionary adaptation: Adaptations, such as thisred panda’s warmth-providing tail, evolve overcountless generations as individuals with heritabletraits that are best suited to their environments havegreater reproductive success.Figure 1.1 Some properties of life2Chapter 1TAYL6012 09 C01 PRF.indd 2 Biology: Exploring Life11/11/16 1:25 PM
LM 3403Colorized SEM 7,5003Diversity is a hallmark of life. One way in whichDomain BacteriaDomain Archaeabiologists make sense of the vast array of organismsexisting now and over the long history of life onEarth is to organize life’s diversity into groups. Eachunique form of life is called a species and is givena two-part, italicized, scientific name. The nameidentifies the genus and the particular species within that genus. For instance, the name for our speciesis Homo sapiens, meaning “wise man.” Biologistshave so far identified and named about 1.8 millionspecies. Estimates of the total number of speciesrange from 10 million to more than 100 million.BacteriaArchaeaThere seems to be a human tendency to groupthings, such as snakes or butterflies, althoughDomain Eukaryawe recognize that each group includes many different species. And we often cluster groups intobroader categories, such as reptiles (which includesnakes) and insects (which include butterflies).Taxonomy, the branch of biology that names andclassifies species, arranges species into a hierarchyof broader and broader groups, from genus, family,order, class, and phylum, to kingdom. A goal ofthis classification system is to reflect the evolutionary history and relationships of organisms.Historically, biologists divided all of life intofive kingdoms. But new methods for assessingevolutionary relationships, such as comparisonsProtists (multiple kingdoms)Kingdom Plantaeof DNA sequences, have led to an ongoing reevaluation of the number and boundaries of kingdoms.Although the debate continues on such divisions,there is consensus among biologists that lifecan be organized into three higher levels calleddomains. Figure 1.2 shows representatives ofdomains Bacteria, Archaea, and Eukarya.Domains Bacteria and Archaea both c onsistof microscopic organisms with relatively simplecells. You are probably most familiar with bacteria,a very diverse and widespread group. Many members of domain Archaea live in Earth’s extremeenvironments, such as salty lakes and boiling hotKingdom FungiKingdom Animaliasprings. Each rod-shaped or round structure inthe photos of bacteria and archaea in Figure 1.2 isFigure 1.2 The three domains of lifea single cell. These photos were made with anKingdom Fungi, represented by the mushrooms in Figure 1.2,electron microscope, and the number along theis a diverse group whose members mostly decompose organicside indicates the magnification of the image.wastes and absorb the nutrients into their cells.All the organisms with more complex cells are calledAnimals, which are grouped in Kingdom Animalia, obtaineukaryotes and are grouped in domain Eukarya. Protistsfood by eating other organisms. The butterfly in Figure 1.2 isare a diverse collection of mostly single-celled organisms.drinking nectar from a thistle flower.Figure 1.2 shows an assortment of protists in a drop of pondAnother way in which biologists make sense of the diverwater. Biologists continue to assess how to group the protistssity and complexity of life is to organize it into a hierarchy ofto reflect their evolutionary relationships.structural levels, extending from the microscopic level of cellsThe three remaining groups within Eukarya are distinto the global scale of the entire Earth. In the next module weguished partly by their modes of nutrition. Kingdom Plantaetake a visual journey through these levels.consists of plants, which produce their own food by photosynthesis. The plant pictured in Figure 1.2 is a tropical brome? To which of the three domains of life do we belong?liad, a plant native to the Americas.Colorized SEM 10,00031.2 Biologists arrange the diversity of life into three domainsEukaryaBiology: The Scientific Study of LifeTAYL6012 09 C01 PRF.indd 3311/11/16 1:25 PM
Visualizingthe Concept1.3 In life’s hierarchy of organization, new propertiesemerge at each levelto birth—is divided into threetrimesters1. Biosphere:All life on Earth and theplaces where life exists.Biologists study life across a very broad range of scales,from the molecules in a cell to the entire living planet. Theydivide this vast scope of biology into a series of structuralFloridaThese placesinclude most regions of land,bodies of water, and the loweratmosphere.In this aerial view ofa mangrove ecosystem, you see aforest of mangrove trees huggingthe shoreline.12. Ecosystem:All the organisms in aparticular area, as well asthe physical componentswith which life interacts,such as soil, water,and light.An emergent property of anecosystem is the cycling of matterbetween organisms and the soil,water, and air.3. Community:All the organismsin an ecosystem.In this community,we find mangrove trees and eel grass,crabs and barnacles, alligators and snakes, ahuge diversity of insects, birds, and fish, andcountless microorganisms.4. Population:All the individuals of aparticular species livingin a community.Schoolmaster snappersswim together among themangrove roots.4Chapter 1TAYL6012 09 C01 PRF.indd 4 Biology: Exploring Life11/11/16 1:25 PM
levels. Follow the arrows to take a visual tour down throughthis organizational hierarchy, using a mangrove swamp inFlorida as an example.Biologists often focus their study of the natural world onone or a few of these levels, exploring individual componentsand interactions between those components, as well asconnections to other levels. Indeed, if we reverse the arrowsand move upward through this figure from molecules to thebiosphere, we find that novel properties arise at each higherlevel, properties that were not present at the preceding level.Such emergent properties result from the specific arrangement and interactions of component parts. For example,the arrangement and connections of nerve cells enablesnervous signals to travel from a fish's brain to its tail. Andmovement is an emergent property arising from the interactions and interconnections of a fish's nervous, muscular, andskeletal systems.A fish's nervous systemconsists of its brain, spinal cord,and nerves.5. Organism:An individual living thing.An organ,such as the brain, iscomposed of severaldifferent tissues.6. Organs and organ systems:Body parts that perform a specificfunction. Several organs maycooperate in an organ system.Storing and transmittinghereditary information areproperties that emerge from thearrangement of atoms in amolecule of DNA.7. Tissue:A group of similarcells performing aspecific function.The nucleus is an organellethat encloses a cell's DNA, itsgenetic instructions.Nucleus8. Cell:DNANerve cellThe fundamentalstructural andfunctional unit of life.Atom9. Organelle:10. Molecule:A chemical structureconsisting of twoor more units calledatoms.A membrane-enclosedfunctional structurein a cell.?The property of lifeemerges at the level ofthe cell.Which of these levels of biological organization includes all of theothers in the list: cell, molecule, organ, tissue?OrganBiology: The Scientific Study of LifeTAYL6012 09 C01 PRF.indd 5511/11/16 1:25 PM
The Process of Science1.4 What is science?6Chapter 1TAYL6012 09 C01 PRF.indd 6Observation:Flashlight doesn’t work.Question:Why doesn’t theflashlight work?Hypothesis #1:Batteries are dead.Hypothesis #2:Bulb is burned out.Prediction:Replacing batterieswill fix problem.Prediction:Replacing bulbwill fix problem.Test of prediction:Replace batteries.Test of prediction:Replace bulb.Results:Flashlight doesn’t work.Hypothesis is contradicted.Results:Flashlight works.Hypothesis is supported.Figure 1.4 An everyday example of forming and testing hypothesesHow is science different from other ways of describingand explaining nature, such as philosophy or religion? Thoseendeavors also seek to make sense of the world around us, andthey often play an important role in society. But the scientificview of the world is based on hypothesis testing and verifiableevidence. Indeed, one of the distinguishing characteristics ofscience is the willingness to follow the evidence—and to correct itself when new evidence is found.To help you better understand what science is, we includea Scientific Thinking module in each chapter. These modulesencompass several broad activities that scientists engage in:observing nature; forming hypotheses and testing themusing various research methods; analyzing data; using toolsand technologies to build scientific knowledge; communicating the results of scientific research; and evaluating the implications of such studies for society as a whole.?What is the main requirement for a scientific hypothesis?It must generate predictions that can be tested by experiments or gatheringfurther observations.Science is a way of knowing—an approach to understandingthe natural world. It stems from our curiosity about ourselvesand the world around us. At the heart of science is inquiry, asearch for information and explanations of natural phenomena.Biology, like other sciences, begins with careful observation.In gathering information, biologists often use tools such asmicroscopes to extend their senses and precision instrumentsto facilitate careful measurement. Recorded observationsare called data—the evidence on which scientific inquiry isbased. Some data are qualitative, often in the form of recordeddescriptions. For example, Jane Goodall spent decades recording her observations of chimpanzee behavior during fieldresearch in Tanzania (see Module 35.22). She also recorded volumes of quantitative data, such as the frequency and durationof specific behaviors. Quantitative data are generally numericalmeasurements, which may be organized into tables and graphsand analyzed with a type of mathematics called statistics.Observations often prompt us to ask questions and then seekanswers by forming and testing hypotheses. A hypothesis isa proposed explanation for a set of observations, and it leads topredictions that can be tested by making additional observations or by performing experiments. An experiment is a scientific test, often carried out under controlled conditions.We all use hypotheses and predictions in solving everyday problems. Let’s say you are preparing for a big storm thatis approaching your area and find that your flashlight isn’tworking. That your flashlight isn’t working is an observation,and the question is obvious: Why doesn’t it work? Figure 1.4presents two hypotheses, each of which leads to predictionsyou can test. Predictions are the results we should expect if thehypothesis is correct, and they often take an “if Á then” form.For example, if the dead-battery hypothesis is correct, thenreplacing the batteries with new ones will fix the problem.An important point about scientific inquiry is that we cannever prove that a hypothesis is true. As shown in Figure 1.4,the burned-out bulb hypothesis is the more likely explanation in our hypothetical scenario. But perhaps the old bulbwas simply loose and the new bulb was inserted correctly. Wecould test this hypothesis by carefully reinstalling the original bulb. If the flashlight doesn’t work, the burned-out bulbhypothesis is supported by another line of evidence. Testinga hypothesis in various ways provides additional support andincreases our confidence in the hypothesis. Indeed, multiplerounds of hypothesis testing may lead to a scientific consensus—the shared conclusion of many scientists that a particularhypothesis explains the known data well and stands up toexperimental testing.How is a theory different from a hypothesis? A scientifictheory is much broader in scope and is supported by a largeand usually growing body of evidence. For example, the the ory of evolution by natural selection explains a great diversityof observations, is supported by a vast quantity of evidence,and has not been contradicted by any scientific data. Biology: Exploring Life11/11/16 1:25 PM
1.5 Hypotheses can be tested using controlled experimentsMany animals match their environment: toadsthe color of dead leaves, green cabbage wormson green leaves, or white snowy owls in theirarctic habitat. From these observations, onemight hypothesize that such color patterns haveevolved as adaptations that protect animals frompredation. Can scientists test this hypothesis?Beach population Beach mice livingon sparsely vegetated sand dunesControlled Experiments In an experimentaltest of a hypothesis, a researcher often manipulates one component in a system and observesthe effects of this change. Variables are factorsthat vary in an experiment. The factor that ismanipulated by the researchers is called the independent variable. The measure used tojudge the outcome of the experiment is calledthe dependent variable. This variable dependson, or is affected by, the manipulated variable.A controlled experiment is one in which anFigure 1.5experimental group is compared with a controlgroup. These groups ideally differ only in the one variable theexperiment is designed to test.Let’s consider an example of a controlled experimentinvolving two populations of mice that belong to the samespecies (Peromyscus polionotus) but live in different environments. The beach mouse lives along the Florida seashore; theinland mouse lives on darker soil farther inland. As you can seein Figure 1.5, there is a striking match between mouse coloration and habitat. In 2010, biologist Hopi Hoekstra of HarvardUniversity and a group of her students headed to Florida totest the camouflage hypothesis. They predicted that if camouflage coloration protects mice from predators, then mice thatmatched their environment would be preyed on less frequentlythan mice with coloration that did not match their habitat.This experiment is an example of a field study, one notdone in a laboratory but out in nature, using the natural habitat of the mice and their predators. The researchers built 250plastic models of mice and painted them to resemble eitherbeach or inland mice. Equal numbers of models were placedrandomly in both habitats. The models resembling the nativemice in each habitat were the control group. The mice withthe non-native coloration were the experimental group. Signsof predation were recorded for three days.As you can see by the results in Table 1.5, the noncamouflaged models had a much higher percentage of predationInland population Members of thesame species living about 30 km inlandBeach mouse and inland mouse with their native habitatattacks in both habitats. The data thus support the camouflage hypothesis: Coloration that matches the environmentprotects animals from predation.Testing Hypotheses in Humans Controlled experimentsinvolving humans, such as tests of new medications, are calledclinical trials or clinical studies. Subjects are usually randomlyassigned to control and experimental groups. The controlgroup participants are often given a placebo, a treatment(such as a sugar pill) that doesn’t contain the substance beingstudied. In a double-blind trial, neither the researchers northe subjects know who is in which group. Clinical trials mustbe cut short if preliminary results show that the treatment iseither significantly harmful or significantly beneficial to theparticipants, because
things, such as snakes or butterflies, although we recognize that each group includes many dif-ferent species. And we often cluster groups into broader categories, such as reptiles (which include snakes) and insects (which include butterflies). Taxonomy, the branch of biology that names and clas
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Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .
TO KILL A MOCKINGBIRD. Contents Dedication Epigraph Part One Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Part Two Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18. Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26
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DEDICATION PART ONE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 PART TWO Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 .
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