Table Of ContentLife Science
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Printdate:2009-06-1208:19
CK12psn:08aebdc6f417d7371eb07c346396f42c
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Authors
Jean Brainard, Niamh Gray-Wilson, Jessica Harwood,
Corliss Karasov, Doris Kraus, and Jane Willan.
Supported by CK-12 Foundation
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Contents
1. StudyingLife..................................................................................................................................... 1
2. IntroductiontoLivingOrganisms................................................................................................. 31
3. CellsandTheirStructures............................................................................................................. 55
4. CellFunctions................................................................................................................................. 69
5. Cell Division,Reproduction,and DNA......................................................................................... 89
6. Genetics........................................................................................................................................ 111
7. Evolution....................................................................................................................................... 133
8. Prokaryotes................................................................................................................................... 173
9. ProtistsandFungi........................................................................................................................ 189
10. Plants............................................................................................................................................. 207
11. Introduction to Invertebrates...................................................................................................... 239
12. Other Invertebrates...................................................................................................................... 257
13. Fishes,Amphibians,andReptiles.............................................................................................. 293
14. Birds and Mammals..................................................................................................................... 325
15. BehaviorofAnimals..................................................................................................................... 353
16. Skin, Bones, and Muscles........................................................................................................... 381
17. FoodandtheDigestiveSystem.................................................................................................. 417
18. CardiovascularSystem................................................................................................................ 447
19. Respiratory and Excretory Systems.......................................................................................... 481
20. ControllingtheBody.................................................................................................................... 505
21. DiseasesandtheBody'sDefenses............................................................................................ 545
22. ReproductiveSystemsandLifeStages..................................................................................... 575
23. From Populations to the Biosphere........................................................................................... 607
24. Ecosystem Dynamics.................................................................................................................. 643
25. Environmental Problems............................................................................................................. 663
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1. Studying Life
The Nature of Science
LessonObjectives
• Understandthatscienceisasystembasedonevidence,testing,andreasoning.
• Describewhatthelifesciencesareandsomeofthemanylifesciencespecialties.
• Describethescientificmethodandwhyitisimportant.
• Definethewords"fact,""theory,"and"hypothesis."
• Describesomeofthetoolsoflifescience.
• Knowthatscientistsarerequiredtofollowstrictguidelines.
CheckYourUnderstanding
• Whatdoyouexpecttolearnfromthisclass?
Introduction
• Knowthatscienceisawayofknowingaboutthephysicalworld,basedonobservableevidence,testing,
predictions,andreasoning.
• Inscience,theoriesandknowledgeareconstantlytestedandquestioned.Whennewinformationconflicts
withexistingexplanations,scientistsmodifytheirexplanationstobeconsistentwithallevidence.
• Understand that principles of philosophy and religion usually cannot be tested scientifically, because
theyarenotbasedonobservableevidence.
• Identify what the life sciences are and some of the many specialties and know the difference between
scientifictheoryandfact.Whyismodernscienceproducingmanymoreimprovementsinourlivesthan
itdidahundredyearsago?Isthereanythingthatsciencecannotexplain?Howcanwe“thinklikescien-
tists?”
• Know how to ask questions about the world around you and how to answer those questions based on
yourunderstandingofevidence,testingandreasoning.
• Continuallyquestionandtesttheaccuracyofyourknowledgeandassumptions.
GoalsofScience
Science,religion,mythology,andmagicsharethegoalofknowingaboutandexplainingtheworld,suchas
thephysicalworld,buttheirapproachesarevastlydifferent.Thedifferencebetweenthemistheirapproach
to “knowing.” The vastness of the living, physical world includes all organisms. As humans, some of the
thingswewanttoknowandunderstandarewhatmakesushealthy,whatmakesussick,andhowwecan
protectourselvesfromfloods,famineanddrought.
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Figure1:Escherichiacolibacteria.
(Source:http://en.wikipedia.org/wiki/Image:EscherichiaColi_NIAID.jpg,License:PublicDomain)
Figure2:Amalelion.
(Source:http://en.wikipedia.org/wiki/Image:Lion_waiting_in_Nambia.jpg,License:CreativeCommons
Attribution2.0)
Figure3:AHumpbackwhale.
(Source:http://en.wikipedia.org/wiki/Image:Humpback_stellwagen_edit.jpg,License:GNUFree
Documentation)
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Throughout history, humans have looked for ways to understand and explain the physical world. Try to
imaginewhathumansthoughtaboutthemselvesandtheworldaroundthem1,000yearsago,or5,000years
ago, or more. If you were born then, how would you have explained why the sun moved across the sky,
thendisappeared?Howwouldyouexplainwhyyourbodychangesasyougrow,orbirthanddeath?What
explanationwouldyouhaveforlightening,thunder,andstorms?
Figure4:TheanatomylessonofDr.NicolaesTulp.
(Source:http://en.wikipedia.org/wiki/Image:The_Anatomy_Lesson.jpg,License:PublicDomain)
Figure5:In1847,adoctor,IgnazSemmelweis,demonstratedthatwhenhewashedhishandbeforedeliv-
eringbabiesfewerwomendiedfrominfection.Beforethis,doctorshelduntestedbeliefsaboutthecauses
ofdisease,suchasaperson’sbehavior,ortheairtheybreathed.
(Source:Wikipedia,Artist:RobertA.Thom,License:PublicDomain)
Throughouttime,differentcultureshavecreatedhundredsofdifferentmythsandstoriesandevengodsto
explain what they saw. Ancient Greeks explained that lightening was a show of their god Zeus’ anger.
Scandinaviansclaimedthattheirgodofthunder,Thor,wasresponsiblefortherumblingandboltsoflightning.
Withoutanyformalscience,manycultureshavealsoblameddiseases,suchasepilepsy,onevilspiritsand
otherimaginaryentities.Forexample,thereisevidencethatmanydifferentculturesdrilledholesintheskulls
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ofpatientswhohadseizuresorothermaladies,thinkingthattheywerereleasingevilspirits.
ScienceasaWayofKnowing
Duringyoursandyourparents’lifetimes,advancesinmedicine,technology,andotherfieldshaveprogressed
fasterthananyothertimeinhistory.Thisexplosionofadvancesinourlivesislargelyduetohumanuseof
modern science as a way of understanding. Today’s scientists are trained to base their comprehension of
theworldonevidenceandreasoningratherthanbeliefandassumptions.
Modernscienceis:
• Awayofunderstandingaboutthephysicalworld,basedonobservableevidence,reasoning,andrepeated
testing.
• Abodyofknowledgethatisbasedonobservableevidence,experimentation,reasoning,andrepeated
testing.
Aswelearnmore,newinformationoccasionallyconflictswithourcurrentunderstanding.Whenthishappens
scientific explanations are revised. However, science cannot scrutinize what is good versus what is bad
(morality),becausethesearevalues,ideasthatlackmeasurableevidence.Scienceisnotusedtoexamine
philosophyorsupernaturalentities,suchastheexistenceornonexistenceofagod.However,sciencecan
beusedtoexaminetheeffectsoftheseexperiences.
Themostimportantmessagefromthischapteristhatscienceisnotonlyawayofknowingitisalsoaway
ofthinkingandreasoning.Scientiststrytolookattheworldobjectively-withoutbiasormakingassumptions.
How? Scientists learn to be skeptical, to question the accuracy our ideas. They learn to base their under-
standingofthephysicalworldonevidence,reasoningandrepeatedtestingofideas.
ToThinkLikeaScientist
Tothinklikeascientist,youneedtobeskepticalaboutandquestionyourassumptions,includingwhatoften
seemslikecommonsense.Questioningideascanoftenleadtosurprisingresults.Forexample,ifyouask
people whether it's easier to keep a plastic cutting board clean or a wooden one clean, most people will
thinkthattheplasticboardiseasiertokeepcleanandhasfewergerms.
Figure6:Whichissafer,aplasticorwoodcuttingboard?
Why do most people believe that plastic is safer? Probably because we assume that it is easier to wash
germsoffplasticthanoffwood.Thisassumptionispromotedbythemakersofplasticcuttingboardsandit
sounds reasonable. After all, wood stains and looks unhygienic; plastic cutting boards come out of the
dishwashershinyandcleanlooking.Butisplasticactuallybetter?
Whenscientiststestedthisidea,theanswerturnedouttobeno.Theresearcherstreatedusedcuttingboards
withdifferentkindsofgermsandthenwashedtheboards.Theyfound,muchtotheirsurprise,thatgouged
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