【正文】 makeyou think criticallyabout thepoints we’ve discussedin class,to state? uh state and defendyour opinion, analyze theissue, speculateabout how thingsmight have turned out , you see,I don’tcare ifyou look updates and that kind of thing. What Iwant isfor you to synthesizeinformationto reflect back on what we’ve 全國免費(fèi)咨詢電話： 4000123267 read and discussed and to form your own ideas,not justrepeat points from the textbook. Does that makesense? Student: Yeah, Ithink looking for mypoint of view. Professor: That’sright. The mid term examshowed methat you know allthe detailsofwho, whereand when. For thistest,I wantto seehow you can put itall togetherto show someoriginalthinking. Student: That’ssounds pretty challenging, especiallytrying to work itinto thistrip. But,yeah, I think I can do it. Professor: I’m sureyou can. Student: Thank you, professor Bronson. Professor: Have a great timein Montreal. Lecture3 Narrator: Listen to apart ofa lecturein a biology class. Professor: 全國免費(fèi)咨詢電話： 4000123267 Ok. Let’s continue our discussion about animalbehavior by talking about decisions that animalsface,plex , even insects,carry out whatlook likevery plex decision making mean no onereally thinks that, say a beegoes through weighing thepros and cons ofpollinating thisflower or that flower. Butthen how do animalssolve plex questions,questionsthat seem to requiredecisionmaking. The answer we’llpropose of courseisthat their behavior islargely a matter ofnatural an example,let’s look at foraging behavior among beavers. Beaverseat plants,mostly they also usetreesand treebranches to construct theirhomesin streamsand lakes. So whenthey do forage forfood and for shelter materials,they have to leavetheir homesand go up on land wheretheir main predators are. So thereare a number ofchoicesthat have to be madeabout foraging. So for example,um? they needto decidewhat kind of treethey should cut down. Sometreeshave highernutritional value than others,and someare betterfor building material, and somearegood forboth? um? aspen f the bark to eat and they alsousethe branches for buildingtheir aspens do double duty. Butash trees,beavers useash treesonly forconstruction. Another decisioniswhen toforage forfood. Should they go out during the daytimewhenit’s hotter outsideand they have to expend moreenergy,or at night whenthe weatheris coolerbut predatorsare moreactive? Ok, but there aretwo moreimportantissues, reallythe mostcentral,the most 全國免費(fèi)咨詢電話： 4000123267 important,Ok? First, let’ssay a beaver could getthe sameamount ofwood from a singlelarge treewhenit haslots ofbranches as itcould get from threesmalltrees. Whichshould it choose? Ifit choosesone largetree, ithas to carry that large pieceof wood back home, and lugging a bigpieceof wood 40 or 50 yards ishard work, takes a lotof courseit’ll have tomake only one tripto get thewood back tothe the otherhand, ifitgoes forthree smalltreesinstead, itwilltakeless energy per treeto getthe wood back homebut it’llhave to makethreetrips back and forth forthe presumably,the moreoftenit wandersfrom home, the moreit’s likely to beexposedto predators. So which isbetter,a singlelarge tree or threesmalltrees? Another criticalissueand it’srelatedto the first,to the sizeissue, ishow farfrom the watershould itgo to get it bewilling to travel a greaterdistancefor a large tree,sinceit’llget somuch wood from it? Beaverscertainlygo farther from the waterto getan aspentreethan foran ash reflects theirrelativevalues. But what about size? Willittravel farther fora larger treethan it willfor a smallertree? Now I wouldhave thought the biggerthe tree,the farther thebeaver would be willing totravel for would makesense, right? Ifyou aregoing totravel far, makethe trip worthit buy bringing back mostwood actually,the oppositeis down only largetreesthat are closeto the water. They willtravel far only to cutdown certain smalltreesthat they can cut down quickly and drag back home , thefarther they go from the water, 全國免費(fèi)咨詢電話： 4000123267 the smallerthe treethey willcut down. They’rewilling to makemoretripsto haul back lesswood, whichcarriesa greater risk ofbeing exposedto predators. So it looks as though beavers arelessinterestedin minimizing theirexposure to predatorsand moreinterestedin saving energy whenforaging for wood, whichmay alsoexplain why beaversforage primarilyduring the evenings. Ok, so whydoes theirbehavior indicate moreofa concern