Questions 9-13 In an a ttigation of interspecies competition, rescarchers grew t
ID: 269374 • Letter: Q
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Questions 9-13 In an a ttigation of interspecies competition, rescarchers grew the unicellular protozoan Parameciam aurel a 5 mL culture and Parameciam caudatum in a separate 5 ml. culture. P, aurelia and P. caudatium were grown competition, researchers grew the unicellular protozoan Paramecium aurelia in together in a third 5 ml, culture. Each day a small sample of each cultur individuals could be estimated, and the remainder of the population was transf The experimental results are represented in the graphs below e was removed so the total number of to fresh growth medium 700 600- 400 2 300 100 1 23456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (days) Figure 1. Population of P. aurelia cultured alone 250 n 200 150 100 E 50 123456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (days)Explanation / Answer
According to the graphs shown, when grown separately, P aurelia reaches stagnant phase after 12 days, while P. caudatum reaches stability after 11 days.
But when grown together, P. aurelia reaches stability after 14 days, while P. caudatum after 8 days shows a slow decline.
12. If allowed to grow for next 25 days, P. caudatum population which has already reached a decline, will be eliminated from the culture very soon. However, P. aurelia will also be eliminated from the culture in next 25 days because of the onset of decline phase in their cells, also the culture will become acidic because of accumulation of dead cells and metabolites. Hence option (C) is the answer.
13. Since we observe that both species reach stationary phase early when cultured together, also we can see that they could not reach their maximum growth when cultured together. Hence option (C) is the answer where the population has a competitive relationship in which each species limits the ability of other to reproduce.
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