previous 11 of 125 next W. J. Fletcher, of the University of Sydney, Australia,
ID: 100429 • Letter: P
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previous 11 of 125 next W. J. Fletcher, of the University of Sydney, Australia, reasoned that if sea urchins are a imiting biotic factor in a particular ecosystem, then more seaweeds should invade an area from which sea urchins have been removed. To isolate the effect of sea urchins from that of a seaweed-eating mollusc, the limpet, he removed only urchins, only limpets, or both from study areas adjacent to a control ste. m 11 Removing both limpets and urchins or removing only urchins increased seaweed cover dramatically 100 80 Both limpets 80and urchins Fletcher observed a large difference in seaweed growth between areas with and without sea urchins Only uthirs removed Removing both limpets and urchins resulted in the greatest increase in seaweed cover ndicating that both specles have some influence on seaweed distribution. But since remaving only urchins greatly increased seaweed growth whereas removing only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets in limiting seaweed distribution. 60 Almost no seaweed grew in areas where both urchins and limpets were present, or where only limpets were 40 Only limpots romoved Control (both urchins and limpets present) Part A 20 Compared to the control (red line), in which both sea urchins and limpets are present, removing limpets alone (blue line) did not have much effect. This might suggest that impets have litle effect on seaweed distribution. However, seaweed cover increased August 1982 February 1983 August 1983 February 1984 much more when both urchins and limpets were remaved (purple line) than when only urchins were removed (green line). © son Education, Inc. How might you explain this result? espermantal renovals, Eeological Monographs 57 80-100(198T Both limpets and urchins eat seaweed so removing either species has the same effect on seaweed cover Both limpets and urchins eat seaweed, so both species have to be removed in order for seaweed cover to increase only limpets are removed more tme is needed for seaweed cover to increase. nWhen only urchins were removed, limpets increased in abundance and reduced seaweed cover. Submit My Answers Give UpExplanation / Answer
Ans- this may be explained as when only Urchins are removed the limpets are increased in abundance and they reduced the seaweed cover.
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