Question

In each of the following scenarios, a scientist has attempted to support the hypothesis that phosphorus fertilization increases production of chlorophyll by the photosynthetic organisms in freshwater lakes. For each, state whether or not you would accept the conclusions and explain specifically why you would or wouldn't accept them.

a. The scientist fertilizes one lake with phosphorus and takes 12 water samples 1 month later to determine the amount of chlorophyll in the lake. The scientist also takes 12 samples from a control lake of the same size. The average chlorophyll level is much higher in the fertilized samples than in the control samples, so the scientist concludes that phosphorus has a significant effect on production of chlorophyll by photosynthetic organisms.

b- The scientist takes 12 different lakcs and measures their chlorophyll levels in May. The scientist then fertilizes all the lakes with phosphorus and re-measures chlorophyll levels in July. Because the average chlorophyll concentration is much greater in July, the scicntist concludes that phosphorus has a significant effect on
production of chlorophyll by photosynthetic organisms.

c. Because the scientist has a limited budget to buy fertilizer, s/he fertilizes the 6 smallest lakes in the area with phosphorus and measures the change in chlorophyll concentration over time. Because the change in these lakes is significantly greater
than the change in 6 larger control lakes, the scientist concludes that phosphorus has a significant effect on production of chlorophyll by photosynthetic organisms.

Answer 1

a) yes , i am agree with conclusion that addition of phosphorous to freshwater lake increase the chlorophyll content of photosynthetic organism . Here, scientists added phosphorus to one lack and compare it with another same size lake. Difference of chlorophyll content of both lake indicates that addition of phosphorous affect chlorophyll content but it is a preimlinary studies further in depth studies required to ensure that phosphorous increase chlorophyll content.

B) In this study we cant conclude because of lack of controls. In this study , scientists took 12 different lake sample , measure their chlorophyll content in may and then in july after fertilizing lakes with phosphorus. Although increase in chlorophyll content indicate it is an impact of phosphorus but in absence of any control , you can say may be its because of phosphorous or any other factor or may be in these lakes chlorophyll content normally increase from may to july ,so we cant assure that it is occur due to addition of phosphorous.

C) In this study we can' t accept the conclusion because of difference in sample size, comparing smallest lakes to larger control lakes. In any scientific study, we have to compare two things sample and control of exactly of same size and property than only we can say that it is the impact of addition of phosphorous.