CK-12 Biology

2012·106.8 MB·English

by  Jean Brainard

Biology
Jean Brainard, Ph.D. (JBrainard)
Jean Brainard, Ph.D. (JBrainard)
Jean Brainard, Ph.D. (JeanB)
Jean Brainard, Ph.D. (JeanB)
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Contents
1 WhatisBiology? 1
1.1 ScienceandtheNaturalWorld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Biology: TheStudyofLife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2 TheChemistryofLife 24
2.1 MatterandOrganicCompounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2 BiochemicalReactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3 Water,Acids,andBases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3 CellularStructureandFunction 52
3.1 IntroductiontoCells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2 CellStructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.3 CellTransportandHomeostasis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4 PhotosynthesisandCellularRespiration 83
4.1 EnergyforLife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2 Photosynthesis: SugarasFood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.3 PoweringtheCell: CellularRespiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.4 AnaerobicRespiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
4.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5 TheCellCycle,Mitosis,andMeiosis 114
5.1 CellDivisionandtheCellCycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.2 ChromosomesandMitosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.3 ReproductionandMeiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
5.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
6 GregorMendelandGenetics 139
6.1 Mendel’sInvestigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
6.2 MendelianInheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
7 MolecularGenetics: FromDNAtoProteins 159
7.1 DNAandRNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
7.2 ProteinSynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
7.3 Mutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
7.4 RegulationofGeneExpression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
8 HumanGeneticsandBiotechnology 187
8.1 HumanChromosomesandGenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
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8.2 HumanInheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
8.3 Biotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
8.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
9 Life: FromtheFirstOrganismOnward 214
9.1 EarthFormsandLifeBegins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
9.2 TheEvolutionofMulticellularLife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
9.3 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
9.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10 TheTheoryofEvolution 243
10.1 DarwinandtheTheoryofEvolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.2 EvidenceforEvolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
10.3 MicroevolutionandtheGeneticsofPopulations . . . . . . . . . . . . . . . . . . . . . . . . . . 263
10.4 MacroevolutionandtheOriginofSpecies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
10.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
11 ThePrinciplesofEcology 277
11.1 TheScienceofEcology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
11.2 RecyclingMatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
11.3 Biomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
11.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
12 CommunitiesandPopulations 310
12.1 CommunityInteractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
12.2 CharacteristicsofPopulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
12.3 HumanPopulationGrowth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
12.4 TheBiodiversityCrisis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
12.5 NaturalResourcesandClimateChange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
12.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
13 Microorganisms: ProkaryotesandViruses 357
13.1 Prokaryotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
13.2 Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
13.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
14 Eukaryotes: ProtistsandFungi 378
14.1 IntroductiontoProtists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
14.2 TypesofProtists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
14.3 IntroductiontoFungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392
14.4 EcologyofFungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
14.5 Protists,Fungi,andHumanDisease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406
14.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
15 PlantEvolutionandClassification 413
15.1 IntroductiontothePlantKingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414
15.2 FourTypesofModernPlants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
15.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
16 PlantBiology 444
16.1 PlantTissuesandGrowth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445
16.2 PlantOrgans: Roots,Stems,andLeaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
16.3 VariationinPlantLifeCycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
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16.4 PlantAdaptationsandResponses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468
16.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
17 IntroductiontoAnimals 475
17.1 OverviewofAnimals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
17.2 OverviewofInvertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
17.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
18 FromSpongestoInvertebrateChordates 499
18.1 Sponges,Cnidarians,Flatworms,andRoundworms . . . . . . . . . . . . . . . . . . . . . . . . 500
18.2 MollusksandAnnelids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
18.3 ArthropodsandInsects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520
18.4 EchinodermsandInvertebrateChordates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532
18.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
19 FromFishtoBirds 542
19.1 OverviewofVertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543
19.2 Fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
19.3 Amphibians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560
19.4 Reptiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569
19.5 Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577
19.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589
20 MammalsandAnimalBehavior 590
20.1 MammalianTraits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591
20.2 ReproductioninMammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601
20.3 EvolutionandClassificationofMammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
20.4 OverviewofAnimalBehavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
20.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631
21 IntroductiontotheHumanBody: Bones,Muscles,andSkin 632
21.1 OrganizationoftheHumanBody . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633
21.2 TheSkeletalSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639
21.3 TheMuscularSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648
21.4 TheIntegumentarySystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656
21.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 662
22 TheNervousandEndocrineSystems 663
22.1 TheNervousSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664
22.2 TheEndocrineSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684
22.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
23 TheCirculatory,Respiratory,Digestive,andExcretorySystems 694
23.1 TheCirculatorySystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
23.2 TheRespiratorySystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
23.3 TheDigestiveSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713
23.4 TheExcretorySystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729
23.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736
24 TheImmuneSystemandDisease 737
24.1 NonspecificDefenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738
24.2 TheImmuneResponse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744
24.3 ImmuneSystemDiseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754
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24.4 EnvironmentalProblemsandHumanHealth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761
24.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768
25 ReproductionandHumanDevelopment 769
25.1 MaleReproductiveSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
25.2 FemaleReproductiveSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
25.3 FromFertilizationtoOldAge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786
25.4 SexuallyTransmittedInfections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 797
25.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
26 BiologyGlossary 804
26.1 A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 805
26.2 B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809
26.3 C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 811
26.4 D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 815
26.5 E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817
26.6 F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820
26.7 G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822
26.8 H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
26.9 I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827
26.10 J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
26.11 K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830
26.12 L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
26.13 M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833
26.14 N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836
26.15 O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838
26.16 P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839
26.17 Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844
26.18 R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845
26.19 S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 847
26.20 T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851
26.21 U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853
26.22 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854
26.23 W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855
26.24 X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
26.25 Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857
26.26 Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858
Contents
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C 1
HAPTER
What is Biology?
Chapter Outline
1.1 SCIENCE AND THE NATURAL WORLD
1.2 BIOLOGY: THE STUDY OF LIFE
1.3 REFERENCES
Isthispictureacolorfulworkofabstractart,orisitsomethingelse? Imagineshrinkingdowntoatinysize,sosmall
youcouldenterabloodvessel. Thepictureshowswhatyoumightseerushingtowardyou. Doyouknowwhatthe
redobjectsare? Ifyouguessedredbloodcells,youareright. Whatabouttheknobbygreenobjects? Watchoutfor
these! Theyarevirusesthathaveinvadedtheblood. Whenyoureadthisbook,youwilltakeanexcitingjourneyinto
therealmof bloodcells, viruses, andjustabout everythingelsethatisrelatedto life. Youwill learnhowyourown
bodyworks,whatmakeslivingthingsunique,andwhatyouandviruseshaveincommon. Thisfirstchapterexplains
howscientistslearnaboutthenaturalworldandintroducesyoutobiology,thescienceoflife.
Chapter1. WhatisBiology?
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1.1 Science and the Natural World
Lesson Objectives
• Identifythegoalofscience.
• Describehowscientistsstudythenaturalworld.
• Explainhowandwhyscientistsdoexperiments.
• Describetypesofscientificinvestigations.
• Explainwhatascientifictheoryis.
Vocabulary
dependentvariable variableinascientificexperimentthatisaffectedbyanothervariable,calledtheindependent
variable
evidence anytypeofdatathatmaybeusedtotestahypothesis
experiment specialtypeofscientificinvestigationthatisperformedundercontrolledconditions
hypothesis possibleanswertoascientificquestion;mustbefalsifiable
independentvariable variable in a scientific experiment that is manipulated by the researcher to investigate its
affectonanothervariable,calledthedependentvariable
model representationofpartoftherealworld
observation anythingthatisdetectedwiththesenses
prediction statementthattellswhatwillhappenundercertainconditions
science distinctivewayofgainingknowledgeaboutthenaturalworldthattriestoanswerquestionswithevidence
andlogic
scientificinvestigation planforaskingquestionsandtestingpossibleanswers
scientificlaw statementdescribingwhatalwayshappensundercertainconditionsinnature
scientificmethod theprocessofascientificinvestigation
scientifictheory broad explanation that is widely accepted as true because it is supported by a great deal of
evidence
1.1. ScienceandtheNaturalWorld
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Introduction
Did you ever wonder why giraffes have such long necks or how birds learn to sing their special songs? If you ever
asked questions such as these about the natural world, then you were thinking like a scientist. The word science
comes from a Latin word that means “knowledge.” Science is a distinctive way of gaining knowledge about the
naturalworldthatstartswithaquestionandthentriestoanswerthequestionwithevidenceandlogic. Scienceisan
excitingexplorationofallthewhysandhowsthatanycuriouspersonmighthaveabouttheworld. Youcanbepart
of that exploration. Besides your curiosity, all you need is a basic understanding of how scientists think and how
scienceisdone,startingwiththegoalofscience.
The Goal of Science
The goal of science is to understand the natural world. To achieve this goal, scientists make certain assumptions.
Theyassumethat:
• Naturecanbeunderstoodthroughsystematicstudy.
• Scientificideasareopentorevision.
• Soundscientificideaswithstandthetestoftime.
• Sciencecannotprovideanswerstoallquestions.
NatureCanBeUnderstood
Scientiststhinkofnatureasasinglesystemcontrolledbynaturallaws. Bydiscoveringnaturallaws,scientistsstrive
to increase their understanding of the natural world. Laws of nature are expressed as scientific laws. A scientific
lawisastatementthatdescribeswhatalwayshappensundercertainconditionsinnature.
Anexampleofascientificlawisthelawofgravity,whichwasdiscoveredbySirIsaacNewton(seeFigure1.1). The
lawofgravitystatesthatobjectsalwaysfalltowardsEarthbecauseofthepullofgravity. Basedonthislaw,Newton
couldexplainmanynaturalevents. Hecouldexplainnotonlywhyobjectssuchasapplesalwaysfalltotheground,
buthecouldalsoexplainwhythemoonorbitsEarth. IsaacNewtondiscoveredlawsofmotionaswellasthelawof
gravity. Hislawsofmotionallowedhimtoexplainwhyobjectsmoveastheydo.
ScientificIdeasCanChange
Science is more of a process than a set body of knowledge. Scientists are always testing and revising their ideas,
and as new observations are made, existing ideas may be challenged. Ideas may be replaced with new ideas that
better fit the facts, but more often existing ideas are simply revised. For example, when Albert Einstein developed
his theory of relativity, he didn’t throw out Newton’s laws of motion. Instead, he showed that Newton’s laws are a
part of a bigger picture. In this way, scientists gradually build an increasingly accurate and detailed understanding
ofthenaturalworld.
ScientificKnowledgeCanWithstandtheTestofTime
Many scientific ideas have withstood the test of time. For example, about 200 years ago, the scientist John Dalton
proposed atomic theory—the theory that all matter is made of tiny particles called atoms. This theory is still valid
today. Therearemanyotherexamplesofbasicscienceideasthathavebeentestedrepeatedlyandfoundtobetrue.
Youwilllearnaboutmanyofthemasyoustudybiology.
Chapter1. WhatisBiology?