Bài giảng Biology - Chapter 1: Exploring Life

Chapter 1Exploring LifeOverview: Biology’s Most Exciting EraBiologyIs the scientific study of lifeThe phenomenon we call lifeDefies a simple, one-sentence definitionFigure 1.1We recognize lifeBy what living things doSome properties of lifeFigure 1.2(c) Response to the  environment(a) Order (d) Regulation (g) Reproduction (f) Growth and  development(b) Evolutionary  adaptation (e) Energy  processing Concept 1.1: Biologists explore life from the microscopic to the global scaleThe study of lifeExtends from the microscope scale of molecules and cells to the global scale of the entire living planetA Hierarchy of Biological OrganizationThe hierarchy of lifeExtends through many levels of biological organizationFrom the biosphere to organismsFigure 1.31 The biosphere From cells to moleculesCell8 Cells6 Organs and organ systems7 Tissues10 Molecules 9 Organelles50 µm10 µm1 µmAtomsFigure 1.3A Closer Look at EcosystemsEach organismInteracts with its environmentBoth organism and environmentAre affected by the interactions between themEcosystem DynamicsThe dynamics of any ecosystem include two major processesCycling of nutrients, in which materials acquired by plants eventually return to the soilThe flow of energy from sunlight to producers to consumersEnergy ConversionActivities of lifeRequire organisms to perform work, which depends on an energy sourceThe exchange of energy between an organism and its surroundingsOften involves the transformation of one form of energy to anotherEnergy flows through an ecosystemUsually entering as sunlight and exiting as heatProducers(plants and other photosyntheticorganisms)Consumers(including animals)SunlightChemical energyHeatHeatEcosystemFigure 1.4A Closer Look at CellsThe cellIs the lowest level of organization that can perform all activities required for life25 µmFigure 1.5The Cell’s Heritable InformationCells contain chromosomes made partly of DNA, the substance of genesWhich program the cells’ production of proteins and transmit information from parents to offspringEgg cellSperm cellNucleicontainingDNAFertilized eggwith DNA fromboth parentsEmbyro’s cells with copies of inherited DNAOffspring with traitsinherited fromboth parentsFigure 1.6The molecular structure of DNAAccounts for it information-rich natureDNACellNucleotideACTATACCGGTATA(b) Single strand of DNA. These geometric shapes and letters are simple symbols for the nucleotides in a  small section of one chain of a DNA molecule.  Genetic information is encoded in specific sequences  of the four types of nucleotides (their names are  abbreviated here as A, T, C, and G). (a) DNA double helix. This model shows  each atom in a segment of DNA.Made  up of two long chains of building  blocks called nucleotides, a DNA  molecule takes the three-dimensional  form of a double helix.Figure 1.7NucleusTwo Main Forms of CellsAll cells share certain characteristicsThey are all enclosed by a membraneThey all use DNA as genetic informationThere are two main forms of cellsEukaryoticProkaryoticEukaryotic cellsAre subdivided by internal membranes into various membrane-enclosed organellesProkaryotic cellsLack the kinds of membrane-enclosed organelles found in eukaryotic cellsEUKARYOTIC CELLMembraneCytoplasmOrganellesNucleus (contains DNA)1 µmPROKARYOTIC CELLDNA (no nucleus)MembraneFigure 1.8Concept 1.2: Biological systems are much more than the sum of their partsA systemIs a combination of components that form a more complex organizationThe Emergent Properties of SystemsDue to increasing complexityNew properties emerge with each step upward in the hierarchy of biological orderThe Power and Limitations of ReductionismReductionismInvolves reducing complex systems to simpler components that are more manageable to studyThe study of DNA structure, an example of reductionismHas led to further study of heredity, such as the Human Genome ProjectFigure 1.9Systems BiologySystems biologySeeks to create models of the dynamic behavior of whole biological systemsWith such modelsScientists will be able to predict how a change in one part of a system will affect the rest of the systemCELLNucleusCytoplasmOuter membrane and cell surfaceFigure 1.10Systems biologyIs now taking hold in the study of life at the cellular and molecular levelsIncludes three key research developments: high-throughput technology, bioinformatics, and interdisciplinary research teamsFeedback Regulation in Biological SystemsA kind of supply-and-demand economyApplies to some of the dynamics of biological systemsIn feedback regulationThe output, or product, of a process regulates that very processIn negative feedbackAn accumulation of an end product slows the process that produces that productBACDEnzyme 1Enzyme 1Enzyme 2Enzyme 3DDDDDDDDDDCBANegative feedbackFigure 1.11In positive feedbackThe end product speeds up productionWWXYZZZZZZZZZZZZZZZZZZZYXEnzyme 4Enzyme 5Enzyme 6Enzyme 4Enzyme 5Enzyme 6PositivefeedbackFigure 1.12Concept 1.3: Biologists explore life across its great diversity of speciesDiversity is a hallmark of lifeFigure 1.13Grouping Species: The Basic IdeaTaxonomyIs the branch of biology that names and classifies species according to a system of broader and broader groupsClassifying lifeSpecies Genus Family Order Class Phylum Kingdom Domain MammaliaUrsusameri-canus(Americanblack bear)UrsusUrsidaeCarnivoraChordataAnimaliaEukaryaFigure 1.14The Three Domains of LifeAt the highest level, life is classified into three domainsBacteriaArchaeaEukaryaDomain Bacteria and domain ArchaeaConsist of prokaryotesDomain Eukarya, the eukaryotesIncludes the various protist kingdoms and the kingdoms Plantae, Fungi, and AnimaliaLife’s three domainsFigure 1.15100 µm0.5 µm4 µmBacteria are the most diverse and widespread prokaryotes and are now divided among multiple kingdoms. Each of the rod-shapedstructures in this photo is a bacterial cell.Protists (multiple kingdoms)are unicellular eukaryotes and their relatively simple multicellular relatives.Pictured here is an assortment of protists inhabiting pond water. Scientists are currently debating how to split the protistsinto several kingdoms that better represent evolution and diversity. Kingdom Plantae consists of multicellula eukaryotes that carry out photosynthesis, the conversion of light energy to food.Many of the prokaryotes known as archaea live in Earth‘s extreme environments, such as salty lakes and boiling hot springs. Domain Archaea includes multiple kingdoms. The photoshows a colony composed of many cells.Kindom Fungi is defined in part by thenutritional mode of its members, suchas this mushroom, which absorb nutrientsafter decomposing organic material.Kindom Animalia consists of multicellular eukaryotes thatingest other organisms.DOMAIN ARCHAEAUnity in the Diversity of LifeAs diverse as life isThere is also evidence of remarkable unityCilia of Paramecium.The cilia of Parameciumpropel the cell throughpond water.Cross section of cilium, as viewedwith an electron microscope15 µm1.0 µm5 µmCilia of windpipe cells. The cells that line the human windpipe are equipped with cilia that help keep the lungs clean by moving a film of debris-trapping mucus upward.Figure 1.16Concept 1.4: Evolution accounts for life’s unity and diversityThe history of lifeIs a saga of a changing Earth billions of years oldFigure 1.17The evolutionary view of lifeCame into sharp focus in 1859 when Charles Darwin published On the Origin of Species by Natural SelectionFigure 1.18The Origin of Species articulated two main pointsDescent with modificationNatural selectionFigure 1.19Natural SelectionDarwin proposed natural selectionAs the mechanism for evolutionary adaptation of populations to their environmentsPopulationof organismsHereditaryvariationsDifferences in reproductive successEvolution of adaptationsin the populationOverproductionand struggle forexistenceFigure 1.20Natural selection is the evolutionary process that occursWhen a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others1 Populations with varied inherited traits2 Elimination of individuals with certain traits.3 Reproduction of survivors.4 Increasing frequency of traits that enhance survival and reproductive success. Figure 1.21The products of natural selectionAre often exquisite adaptations of organisms to the special circumstances of their way of life and their environmentFigure 1.22The Tree of LifeMany related organismsHave very similar anatomical features, adapted for their specific ways of lifeSuch examples of kinshipConnect life’s “unity in diversity” to Darwin’s concept of “descent with modification”Darwin proposed that natural selectionCould enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”Large ground finchSmallgroundfinchGeospizamagnirostrisSeed eaterSharp-beakedground finchCamarhynchuspsitaculaGreenwarbler finchLarge tree finchLarge cactusground finchGround finchesTree finchesInsect eatersBud eaterWarbler finchesCommon ancestor fromSouth American mainland Graywarbler finchCerthideaolivaceaCerthideafuscaGeospizadifficilisCactus flowereaterGeospizascandensSeed eaterGeospizaconirostrisGeospizafortisMediumgroundfinchGeospizafuliginosaMangrovefinchCactospizaheliobatesCactospizapallidaWoodpeckerfinchMediumtree finchCamarhynchuspauperSmall tree finchVegetarianfinchCamarhynchusparvulusPlatyspizacrassirostrisCactusground finchFigure 1.23Each species is on twig of a branching tree of lifeExtending back in time through ancestral species more and more remoteAll of lifeIs connected through its long evolutionary historyConcept 1.5: Biologists use various forms of inquiry to explore lifeAt the heart of science is inquiryA search for information and explanation, often focusing on specific questionsBiology blends two main processes of scientific inquiryDiscovery scienceHypothesis-based scienceDiscovery ScienceDiscovery scienceDescribes natural structures and processes as accurately as possible through careful observation and analysis of dataTypes of DataDataAre recorded observationsCan be quantitative or qualitativeFigure 1.24Induction in Discovery ScienceIn inductive reasoningScientists derive generalizations based on a large number of specific observationsHypothesis-Based ScienceIn science, inquiry that asks specific questionsUsually involves the proposing and testing of hypothetical explanations, or hypothesesThe Role of Hypotheses in InquiryIn science, a hypothesisIs a tentative answer to a well-framed question, an explanation on trialMakes predictions that can be testedWe all use hypotheses in solving everyday problemsObservationsQuestionsHypothesis # 1:Dead batteriesHypothesis # 2:Burnt-out bulbPrediction:Replacing batterieswill fix problemPrediction:Replacing bulbwill fix problemTest prediction Test does not falsify hypothesisTest prediction Test falsifies hypothesisFigure 1.25Deduction: The “Ifthen” Logic of Hypothesis-Based ScienceIn deductive reasoningThe logic flows from the general to the specificIf a hypothesis is correctThen we can expect a particular outcomeA Closer Look at Hypotheses in Scientific InquiryA scientific hypothesis must have two important qualitiesIt must be testableIt must be falsifiableThe Myth of the Scientific MethodThe scientific methodIs an idealized process of inquiryVery few scientific inquiriesAdhere to the “textbook” scientific methodIn mimicryA harmless species resembles a harmful speciesFlower fly(non-stinging)Honeybee (stinging)Figure 1.26A Case Study in Scientific Inquiry: Investigating Mimicry in Snake PopulationsIn this case studyMimicry in king snakes is examinedThe hypothesis predicts that predators in non–coral snake areas will attack king snakes more frequently than will predators that live where coral snakes are presentScarlet king snakeScarlet king snakeKeyRange of scarlet king snakeRange of eastern color snakeEastern coral snakeNorthCarolinaSouthCarolinaFigure 1.27Field Experiments with Artificial SnakesTo test this mimicry hypothesisResearchers made hundreds of artificial snakes, an experimental group resembling king snakes and a control group of plain brown snakes(a) Artificial king snake (b) Brown artificial snake that has been attackedFigure 1.28After a given period of timeThe researchers collected data that fit a key predictionFigure 1.29In areas where coral snakes were present, most attacks were onartificial king snakesKey% of attacks on artificial king snakes % of attacks on brown artificial snakesField site with artificial snakes17%83%NorthCarolinaSouthCarolinaXXXXXXXXXXXXXXIn areas where coral snakeswere absent, most attackswere on artificial king snakes84%16%KeyDesigning Controlled ExperimentsExperiments must be designed to testThe effect of one variable by testing control groups and experimental groups in a way that cancels the effects of unwanted variablesLimitations of ScienceScience cannot address supernatural phenomenaBecause hypotheses must be testable and falsifiable and experimental results must be repeatableTheories in ScienceA scientific theoryIs broad in scopeGenerates new hypothesesIs supported by a large body of evidenceModel Building in ScienceModels of ideas, structures, and processesHelp us understand scientific phenomena and make predictionsTo lungsTo bodyRightartiumRightartiumRightventricleRight ventricleFromlungsFrombodyFigure 1.30The Culture of ScienceScience is a social activityCharacterized by both cooperation and competitionFigure 1.31Science, Technology, and SocietyTechnologyApplies scientific knowledge for some specific purposeFigure 1.32Concept 1.6: A set of themes connects the concepts of biologyUnderlying themesProvide a framework for understanding biologyEleven themes that unify biologyTable 1.1