Transcript of "Eoy2012 hscs-3 na-paper 2-answer key to summary qn"
1190 Paper 2 Summary Question 21Secondary Three (Normal Academic) End of Year Examinations at Hai Sing Catholic SchoolWild salmon are decreasing at an alarming rate. Using your own words as far as possible, write asummary of the factors that contribute to this unfortunate situation.USE ONLY THE MATERIAL FROM PARAGRAPHS 4 TO 6.Your summary, which must be in continuous writing (not note form), must not be longer than 80words (not counting the words given to help you begin).Begin your summary as follows:Threatened by pollution, acid rain, shrinking ocean habitats and …4 Wild Atlantic salmon populations remain small to this day. The list of suspects in the continuing decline is long, including degradation of rivers, acid rain, shrinking ocean habitat and  netting of juvenile salmon by herring and mackerel trawlers. But the single threat that most concerns many conservationists today is  fish farming. From its cottage-industry beginnings in Norway in the late sixties, Atlantic salmon farming has exploded into a two-billion-dollar-a-year business that produces 2.6 billion pounds of fish. Unlike wild Atlantic salmon, caged salmon swim ceaselessly in circles, their fins5 worn from rubbing into other fish and nylon nets. The only outlet for their strength is to skitter on their tails in short bursts across densely packed pens. Crammed into cages in one spot, fed chemicals, and defecating in a shallow estuary, the fish soon become infected with lice that graze on their flesh. What is worse is that this infection spreads quickly to wild salmon and sea trout nearby, killing them. What really causes scientists to lose sleep, however, is the  continuing escape6 of massive numbers of farmed salmon. From the earliest years of aquaculture, salmon have escaped whenever seals chewed through pens in search of an easy meal, storms demolished cages, or fish were spilled during handling resulting in  interbreeding between wild and farmed salmon. This brings about the concern of a hybrid fish,  poorly adapted to life in the wild which will one day spread across the Atlantic. Studies have also found that  farmed salmon do not reproduce in the wild nearly as well as native salmon – a phenomenon that, over time could depress populations. In addition,  individual strains of wild salmon which have evolved over thousands of years to help them adapt to unique conditions in each of 2,600 Atlantic rivers could be lost in the interbreeding. A genetically homogenous salmon, descended from aquaculture fish, could be ill suited to life in many rivers and could also leave the species less able to cope with threats such as disease and climate change. 1 PagePrepared by Yeo Yam Hwee for Secondary Three Normal Academic Students Page 1
1190 Paper 2 Summary Question 21Secondary Three (Normal Academic) End of Year Examinations at Hai Sing Catholic SchoolSUMMARY POINTS:1 …Trawl-netting of juvenile salmon.2 Big scale commercialised fish farming3 Infection of farmed salmon spreads quickly to wild salmon.4 massive numbers of farmed salmon escape continually.5 Interbreeding occurs between wild and farmed salmon.6 Farmed salmon are poorly adapted to life in the wild.7 farmed salmon do not reproduce in the wild nearly as well as native salmon8 Individual strains of wild Altantic salmon could be lost in the interbreeding.9 Genetically homogenous salmon could be ill suited to life in many rivers.10 Such salmon are less able to cope wth threats such as disease and climate change. 2 PagePrepared by Yeo Yam Hwee for Secondary Three Normal Academic Students Page 2