Deer: Predation or Starvation

Transcription

1 : Prdation or Starvation National Scinc Contnt Standards: Lif Scinc: s and cosystms Rgulation and Bhavior Scinc in Prsonal and Social Prspctiv s, rsourcs and nvironmnts Unifying Concpts and Procsss Systms, Ordr, and Organization Evidnc, Modls, and Explanation Chang, Constancy and Masurmnt Vocabulary: Prdator Pry Ecosystm Closd Ecosystm Matrials: Postr papr : Prdation or Starvation Workshts (On pr studnt) Two diffrnt colord Sticky nots (on of ach color pr studnt) Introduction: An island population of dr has no prdators and th island is too rmot for huntrs. Is it bttr to lt natur tak its cours with th dr population or should prdators (wolvs) b introducd onto th island? This activity could b don bfor or aftr playing WolfQust. Objctivs: At th nd of this activity, th studnt will: 1. Idntify prdator/pry rlationships and how thy may or may not impact on anothr. 2. Examin th changs that populations undrgo to kp a balanc in th cosystm. 3. Examin changs in populations du to human intrvntion. 4. Crat a graph illustrating population changs in a prdator/pry rlationship. Procdur: Tachr Prp: Copy on worksht pr studnt. Mak thr signs with th ach of th following titls on larg postr papr: ar bttr off with th wolvs ar wors off with th wolvs ar about th sam with th wolvs Lav spac blow th titl for th studnts to add thir opinions. Post ths postrs around th room. 1. Rad th scnario to th studnts prior to handing out th worksht. Ask studnts to hypothsiz how this might or might not work. Hav studnts prdict what may happn to ach of th populations. 2. Now point out th postrs hadings. Ask studnts to plac a sticky not on th postr that has th outcom with which thy agr. 3. Hand out th : Prdation or Starvation workshts. Studnts can ithr work on this alon or with a partnr. This could also b usd as a homwork assignmnt sinc th worksht can b don indpndntly. 4. Aftr studnts hav compltd th analysis qustions, discuss qustions 1 and 2 as a class.

2 Procdur (continud): 5. Again, ask studnts to plac a sticky not this tim using a color diffrnt from th first on on th postr with th hading with which thy agr. 6. As a class, discuss th following things: a) How did your first opinion compar with your scond? b) If you changd your opinion, what causd you to chang it? c) If you didn t chang your opinion, why? 7. Each prspctiv should choos a spoksprson to shar thir idas.

3 : Prdation or Starvation Nam Scnario: In 1997 th dr population of an island forst rsrv about 518 squar kilomtrs in siz was about 2000 animals. Although th island had xcllnt vgtation for fding, th food supply obviously had limits. Thus th forst managmnt prsonnl fard that ovrgrazing might lad to mass starvation. Sinc th ara was too rmot for huntrs, th wildlif srvic dcidd to bring in natural prdators to control th dr population. It was hopd that natural prdation would kp th dr population from bcoming too larg and also incras th dr quality (or halth), as prdators oftn liminat th wakr mmbrs of th hrd. In 1997, tn wolvs wr flown into th island. Th rsults of this program ar shown in th following tabl. Th Chang is th numbr of dr born (dr offspring) minus th numbr of dr that did (prdation and starvation) during that yar. Fill out th last column for ach yar (th first has bn calculatd for you). Yar Wolf Offspring Prdation Starvation Chang , , ,500 1, , , , , , , , , Graph th dr and wolf populations on th graph providd. Us on color to show dr populations and anothr color to show wolf populations. Total and Wolf s by Yar N u m b r of D r Numbr of Numbr of Wolvs

4 Yars Analysis Qustions: Rad and answr th qustions. B sur to us complt sntncs and your good grammar skills! 1. Dscrib what happnd to th dr and wolf populations btwn 1997 and What do you think would hav happnd to th dr on th island had wolvs NOT bn introducd? 3. Most biology txtbooks dscrib that prdators and pry xist in a balanc. This "balanc of natur" hypothsis has bn criticizd by som scintists bcaus it suggsts a rlationship btwn prdators and pry that is good and ncssary. Opponnts of this hypothsis propos th following qustions: Why is dath by prdators mor natural or "right" than dath by starvation? How dos on dtrmin whn an cosystm is in "balanc"? Do prdators rally kill only th old and sick pry? What vidnc is thr for this statmnt?

5 What is your opinion of th balanc of natur hypothsis? Would th dr on th island b bttr off, wors off, or about th sam without th wolvs? Dfnd your position.