West Spring 2018 Bio Prelim P2 MS

1 SECONDARY 4 EXPRESS BIOLOGY PRELIMINARY EXAMINATION, 2018 SUGGESTED MARK SCHEME P2 Section A Answers Marks Remarks 1( a ) [1] (b) 1. Leaves that contain insecticides are eaten by the caterpillars. As these insecticides are not biodegrable/are not broken down, they accumulate in the bodies of caterpillars./ bioaccumulation ; 2. As birds feed on the caterpillars and hawks feed on these birds, the concentration of insecticides increases along the food chain. ; 3. Highest concentration of insecticides will be found in hawks. ; 4. This is known as bioamplication/bioaccumulation ; Reject: indigestible [1] [1] [1] [1] Point 1 is a must Point 2, 3 and 4, any 2 Max 3 marks (c) (i) 1. Initially, the grasshopper population increases as there are less predators feeding on them and they can reproduce more. ; 2. However, their population decreases later dramatically due to the competition for food. ; 3. The flowering plant is the only producer of food in this food web/does not produce enough food for the growing population. ; [1] [1] [1] (c) (ii) 1. Initially, the caterpillar population remains constant because they belong to two different food chains / snakes do not prey on them./have not lost source of food or predator ; 2. However, both grasshoppers and caterpillars feed on the same food source (leaves of flowering plant), an increase in the population of grasshopper provides competition for food with the caterpillars. ; Or No snakes, grasshopper population increases, more food for birds, bird population increases, more caterpillars are eaten [1] [1] www.KiasuExamPaper.com b) 1. Leaves that contain insecticides are eaten by the caterpillars. As these insecticides are not bioddegegegegegegegegegegegegegegegeggggeggegggegggggggegggggegggeggggggeggeggggggegegeggggggeggeggggggggeggggeeegggggggggggggegegggggggggggggggggrarararararrarararaarararararararararararrararararrarrarararrrrrararrrarrarararararrrrarararaarrrrraararaaararrrraarrrarrrarararrrarraaaarrraaaaararaaaaaraaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaraarraaaaablblblblblbbblbbbbbbblblbbblblblbblblblblblblbbblbblblbblbbbbbbblblbbblbbbbbbbbbbbbbbbbbbbbbbbblbbblbbblbbbblbbbbbbbbbbbbbblbbbbbbblbblbblllllblblblbblblllbllllbllbblbblblbbbblbbbbbbbbbbbbbbbbbbbe/e/e/e/e/e/e/e/e/e/e/eee/e/e/e/e/e/e/e/eee/e/e/e/ee/e/e/e/e/e/e/ee/e/e/e/ee/eee/e/e/eee/ee/ee/e/e/e/e/e/e/e/e/ee/e/e/e/ee/ee/e//e/ee/e/e/eee///e/e/e//eee//e///e/e//e/e/////////e///e//e///e/e/e//e////e/eeee/eeeeeeee////araraararaararaaaararararaararararararararaaaararaarararararararrararararaaaarararrararaaaaaaaaaararrarararararaaaaaaarrrararararararararaaaaarararrrrraararrraararaaraaaaaraarraaaaaaaaaraararaaraaraaaaaaraaarrraaaaraaaaeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee not broken down , they accumulate in the bodododododddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddieieieeeeeieeieieieeieieieeieeieieieeieieeieieeeieeeieeieeeieieeeieieeeeeeiieieieiiiiieieiiiieieeie