Q16 of 26 Page 1

Given below is a figure of a biogas plant.

(a) Identify A and justify its floating nature.


(b) Identify the products B and C and discuss their significance.



(a) ‘A’ is the floating cover. This cover is placed over the slurry .Which rises whenever microbial activity takes place.


(b) ‘B’ is the biogas. Biogas is a mixture of gases like Methane (CH4), Hydrogen (H), Sulphide and Carbon Dioxide. It is used as a source of gas in various households.


‘C’ is the Slurry. This is removed through another outlet and is used as a fertiliser.


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14

With respect to Messelson and Stahl’s Experiment, answer the following questions:

(a) Identify the method used to distinguish between heavy and light isotopes of nitrogen.


(b) With the help of diagrams, compare the results for the DNA isolated after 20 minutes of experiment with the DNA which was isolated after 40 minutes.


 15

A student was simulating Urey and Millers experiment to prove the origin of life. The set up used by the student is given


(a) Find out the reasons why he could not get desired results. (b) What conclusion was drawn by Urey and Miller through this experiment?


(c) Compare the conclusion drawn with the theory of spontaneous generation.


 17

According to Global Hunger Index 2014 two billion people suffer from hidden hunger. Apply your knowledge of plant breeding techniques to suggest a programme to improve public health. Specify four objectives of the programme. Also mention one example of such a produce.

 18

DNA separated from one cell, when introduced into another cell is able to bestow some of the properties of former to the latter. What is this change called in technical terms? Describe the experimental evidences which led to the discovery of the above phenomenon.