Lesson 2: Digestive System How Food Is Broken Down Level1ConfirmationInquiry

 Grade Level:Thislessonisdesignedfora5thgradescienceclassroom.Science Concept:Thislessonisfocusedonhelpingstudentsunderstandhowfood is broken down as it passes through different organs in the digestivesystem, specifically looking at how snakes and humans digest food. Thislesson expands upon the concepts taught in Lesson 1: Snake DigestiveSystem.Relationship to California Science Content Standards: 2c.Studentsknowthesequentialstepsofdigestionandtherolesofteethandthemouth,esophagus,stomach,small intestine, large intestine,andcoloninthefunctionofthedigestivesystem.Learning Objectives: 

1. Students will illustrate and describe how food is broken down as itpassesthroughasnake’sdigestivesystem.

Evaluation Ideas: 

1. formative: Teacher will evaluate student’s worksheets on the role ofeachdigestiveorganinbreakingdownfood.

2. summative: Students will compose a comic strip that illustrates the

journey through a snake’s digestive system and describes eachdigestiveorgan’sfunction.

Conceptual Background: 

Largeandsmall intestinesareshorterthaninotheranimalsandfoodthatgoesundigested is simpleexpelled. Interestinglysnakes lackabladder.Waste is filtered through the kidneys and isexcretedasawhite, crystallinematerialthatcontainsverylittlewater,helpingtoconservemoisture.

Animals often have digestive systems that are adapted for theparticulartypeoffoodorfeedingbehavioroftheanimal.Asnake’sdigestivesystem consists of the mouth, esophagus, stomach, small intestine, largeintestine, kidneys. As the snake swallows its prey, glands in the snake’smouthsecretedigestive juices. Unlikemammals, thesnake’sesophagushasverylittlemuscle,sothesnakemustrelyonmovementoftheentirebodytotransportthefoodthroughtheesophagustothestomach.Oncethefoodgoes

intothestomach,pressurefromsqueezingmusclesandspecialjuicesstarttobreakdownthefood.Thedigestivejuicesinasnake’sstomachareextremelypowerful and almost all of theprey is digested – even thebones and teeth.Whenthefoodisapulpymass,thestomach’smusclespushitintothesmallintestine.Inthesmallintestine,morejuicescontinuetobreakdownthefoodtoextractnutrients–proteins,carbohydrates, fats,minerals, andvitamins–to be used by the snake’s body. These nutrients are absorbed through thewalls of the small intestine and flow into the snake’s bloodstream,which isthen transferred toallpartsof thesnake’sbody. Sincea snakeconsumes awholeprey,itcansurvivebyeatingonlyonceeverycoupleofweeks.Instead,the snake’s body stores fat from the prey to be broken down as needed.Afterwards, the parts of the food that were not absorbed, i.e. waste, arecollectedinthe large intestine,wherewater isremovedandreturnedtothebody.Kidneysalsofilterwastefromthebloodandreabsorbwaterbackintothe snake’s system. Any food that is still undigested is expelled as waste.Interestingly, snakes do not have a bladder to store waste before it isexpelled,soallthewasteisdisposedthroughthecloaca.

Otherorgansinthedigestivesystemincludetheliver,gallbladder,andpancreas. Theliveristhelargestinternalorganinasnakeandliesbetweentheheartandstomach.Oneoftheliver’smajorfunctionsistoproducebile,adigestiveenzyme.Thebileisstoredinthegallbladder,whichislocatedneartheposteriortipoftheliverandcanbereleasedintothesmallintestinewhenneeded.Thepancreasalsosecretesdigestiveenzymesintothesmallintestineandproduceshormonesthatregulatebloodsugar.Materials: 

1. RoleofDigestiveOrgansWorksheet2. Coloringutensils

Lesson Implementation Plan:ThislessonwillbeimplementedasaLevel1inquiryactivity.Studentswillconfirmhowfoodisbrokendownasitpassesthroughasnake’sdigestivesystem.  Engage–Iwillshowtheclassapictureofasnakeswallowingfoodandask:“Thesnake’sfoodislargerthanitsbody.Whatdoyouthinkhappenstothefood as it travels through the snake’s body?” Students will discuss theirpredictionsinThinkPairShare.

Explore–Iwillsharethatbothhumansandsnakeshavedigestivesystemstohelpbreakdownthefoodthatweeat.Iwillaskstudentstobrainstormhowour bodies break down foods and what food is broken down into (i.e.nutrients,water,waste).Explain–Iwillthendescribethepathoffoodthroughasnake’sdigestivesystemandexplainhowthefoodisbrokendownandabsorbedateachstage.StudentswilltakenotesintheRoleofDigestiveOrgansWorksheetasIdescribetheroleandfunctionofeachdigestiveorgan.

Elaborate–Studentswillplanouttheircomicstripbysketchingaflowchartorcreatingastoryboard.Evaluate–

a. summative – Studentswill compose a comic strip that illustrates thejourney through a snake’s digestive system and describes eachdigestiveorgan’sfunction.

b. formative – Teacherwill evaluate student’sworksheet on the role ofeachdigestiveorganinbreakingdownfood.

Differentiation Plans:   BehavioralforStudentA

If a student is too active, I will allow him to color the snakediagramintheworksheet.

CognitiveforStudentB

Ifastudenthasahardtimekeepingup,Iwillprovidehimwithascaffoldedworksheetthatisapartiallyfilledinwithinformation.

CognitiveforStudentC

If a student is ahead, I will ask him to research a human’sdigestivesystemandcompareandcontrastthetwo.

AffectiveforStudentDIfastudentdoesn’twanttoparticipate,Iwillallowhimtocolorthesnakediagramintheworksheet

LanguageDemandsforStudentsE,F,G

Beginner:Whenexplainingthesnake’sdigestion,providevisualsof the snake’s digestive organs. Use visuals, gestures, andsounds to scaffold phrases such as “break down” or “passthrough.”Intermediate: Provide sentence frames for student to describethepathoffoodasittravelsthroughasnake’sdigestivesystem.“First, the food travels to the __________. Next, the food travelsthrough__________.Then…Afterwards…Finally,thefoodarrivesinthe_________.”Advanced: Use complete sentences to retell teacher’sdescription of the path of food through a snake’s digestivesystem and explanation of how the food is broken down andabsorbedateachstage.

References  Markle,S.(1995).OutsideandInsideSnakes.NewYork:AtheneumBooksforYoungReaders. Wexo,J.B.(1987).Snakes.Mankato:CreativeEducation,Inc.Frisby,H.SnakeAnatomyandPhysiology.RetrievedJuly26,2012,fromhttp://animal.discovery.com/guides/reptiles/snakes/anatomy.html