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  • Biology: Life on EarthEighth EditionLecture for Chapter 1An Introduction to Life on EarthCopyright 2008 Pearson Prentice Hall, Inc.Teresa Audesirk Gerald Audesirk Bruce E. Byers

  • Chapter 1 Outline1.1 How Do Scientists Study Life? p. 21.2 Evolution: The Unifying Theory of Biology, p. 91.3 What Are the Characteristics of Living Things? p. 101.4 How Do Scientists Categorize the Diversity of Life? p. 141.5 How Does Knowledge of Biology Illuminate Everyday Life? p. 15

  • Section 1.1 Outline1.1 How Do Scientists Study Life?Life Can Be Studied at Different Levels of OrganizationScientific Principles Underlie All Scientific InquiryThe Scientific Method is the Basis for Scientific InquiryCommunication Is Crucial to ScienceScience is a Human EndeavorScientific Theories Have Been Thoroughly Tested

  • Levels of OrganizationThe living and nonliving world is organized at many levels

  • Levels of OrganizationAll matter is formed of elementsAn atom is the smallest particle of an element retaining the properties of an elementAtoms combine to form moleculesMolecules provide the building blocks for cells, the smallest unit of life

  • Levels of OrganizationSome forms of life consist of single cellsIn multicellular forms cells combine to form tissues Tissues combine to form organs, which can be united as organ systemsMulticellular organisms are composed of multiple organ systems

  • Levels of OrganizationOrganisms of the same type that are capable of interbreeding are called a speciesA group of organisms of the same species living in a given area is a populationInteracting populations make up a community

  • Levels of OrganizationA community and its nonliving environment is an ecosystemThe entire surface of the Earth, including living and nonliving components is the biosphere

  • Scientific PrinciplesBiology is a scientific disciplineAll scientific inquiry is based on a small set of assumptions or principlesNatural causalityUniformity in space and timeSimilar perception

  • Natural CausalityHistorical approaches to studying lifeBelief that some events happen through supernatural forces (e.g. the actions of Greek gods)Belief that all events can be traced to natural causes that we can comprehend (natural causality)Corollary: Evidence gathered from nature has not been deliberately distorted to fool us

  • Natural Laws Apply Everywhere Natural laws are uniform in space and timeThis principle is key understanding biological events (e.g. evolution) that occurred before humans recorded them

  • Natural Laws Apply EverywhereCreationism is contrary to the principle of uniformity-in-time and natural causalityCreationists hold that different species were created one at a time by the direct intervention of a supernatural being, contrary to events we see happening today

  • Similar PerceptionsAssumption that all human beings perceive natural events in fundamentally the same wayCommon perception allows us to accept observations of other humans as reliable

  • Similar PerceptionsCommon perception is usually not found in appreciation of art, poetry, and music, nor between cultures or religious beliefsValue systems are subjectiveScience requires objectively gathered data

  • The Scientific MethodScientific inquiry is a rigorous method for making observationsThe Scientific Method for inquiry follows 4 steps

  • The Scientific MethodObservation of a phenomenonSubsequent development of questionsFormulation of a hypothesisA supposition that explains an observed phenomenon, leading to testable predictions

  • The Scientific MethodTesting through experimentationAdditional controlled observationsDevelopment of a conclusionEvaluation of hypothesis in light of experimental data

  • The Scientific MethodScientific experimentation tests the assertion that a single variable causes a particular observationThe experiment must rule out the influence of other possible variables on the recorded observations

  • The Scientific MethodControls are incorporated into experimentsControls keep untested variables constantScientific method is illustrated by Francesco Redis experiment

  • Application to Everyday ProblemsAssume you are late for an appointment and hurriedly try to start your car Observation: The car wont start

  • Application to Everyday ProblemsHypothesis: the battery is dead

  • Application to Everyday ProblemsExperimental design: Replace your battery with another and restart the car

  • Application to Everyday ProblemsPremature conclusion:The problem was a dead battery because the car starts when replaced with a different one

  • Application to Everyday ProblemsRecognition of inadequate controlsDid you attempt to start the car more than once?Was the battery cable on my original battery loose?

  • Application to Everyday ProblemsEstablishing a controlReinstall your old battery, check for tight cables, now try to start the carIf car still fails to start on old battery, the only variable in this investigation now is the effectiveness of the battery

  • Application to Everyday ProblemsMaking a better conclusion, based on controlled experimentsYour battery was probably dead

  • Limitations of the Scientific MethodCan never be sure all untested variables are controlledConclusions based on the experimental data must remain tentative

  • Limitations of the Scientific MethodResults of experimentation must be communicated thoroughly and accurately to other scientists for repetitionRepetition by other scientists add verification that findings can be used as the basis for further studies

  • Science Is a Human Endeavor Human personality traits are part of real scienceScientists, like other people may be driven by pride, ambition, or fearScientists sometimes make mistakesAccidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances

  • Science Is a Human EndeavorIn the 1920s, bacteriologist Alexander Fleming grew bacteria in cultures One of the bacterial cultures became contaminated with a moldFleming nearly destroyed the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture

  • Science is a Human EndeavorFleming hypothesized that the mold produced an antibacterial substanceFurther tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin

  • Science is a Human EndeavorFleming continued beyond a lucky accident with further scientific investigation to a great discoveryChance favors the prepared mind (Louis Pasteur)

  • Scientific TheoryA scientific theory differs in definition from that of everyday usageMany people use the word theory to mean hypothesis, and educated guess

  • Scientific TheoryA scientific theory is a general explanation for important natural phenomenaIt is extensively and reproducibly testedIt is more like a principle or natural law (e.g. the atomic, gravitational, and cell theories)If compelling evidence arises, a theory may be modified

  • Scientific TheoryNew scientific evidence may prompt radical revision of existing theoryExample: the discovery of prions

  • Scientific TheoryBefore 1980, all known infectious diseases contained DNA or RNAIn 1982, Stanley Prusiner showed that the infectious sheep disease scrapie is caused by a protein (a protein infectious particle or prion)

  • Scientific TheoryPrions have since been shown to cause mad cow disease and diseases in humansThe willingness of scientists to revise accepted belief in light of new data was critical to understanding and expanding the study of prions

  • Science Is Based on ReasoningInductive ReasoningUsed in the development of scientific theoriesA generalization is created from many observationse.g., the cell theory (all living things are made of one or more cells) arises from many observations that all indicate a cellular basis for life

  • Science Is Based on ReasoningDeductive ReasoningGenerating hypotheses based on a well-supported generalization (such as a theory)e.g., based on the cell theory, any newly discovered organism would be expected to be composed of cells

  • 1.2 Evolution: The Unifying Theory of BiologyThree natural processes underlie evolutionMuch of organism variability is inheritedNatural selection preserves survival and reproductive genes

    Section 1.2 Outline

  • Unifying Theory of BiologyAbundant evidence has been found to support evolutionary theory since Darwin and Wallace proposed it in the mid-1800sThose who see evolution as just a theory dont understand the scientific definition of a theory

  • Unifying Theory of BiologyEvolution explains how diverse forms of life originated through changes in their genetic makeup Modern organisms descended with modification from pre-existing life formsNothing in biology makes sense, except in the light of evolution (Theodosius Dobzhansky)

  • Three Natural Processes Underlie EvolutionCharles Darwin and Alfred Russel Wallace formulated the basis of our modern understanding of evolutionEvolution arises as a consequence of three natural processes

  • Three Natural Processes Underlie EvolutionGenetic variation among members of a populationInheritance of those variations by offspring of parents carrying the variationNatural selection of individuals whose survival and enhanced reproduction are due to the favorable variations they carry

  • Genetic VariabilityGenetic variation arises from segments of DNA (genes)Changes in genes (mutation) alter the informational contentMutations arise from