Q23 of 27 Page 1

Large quantities of sewage is generated every day in cities and towns, which is treated in Sewage Treatment Plants (STPs) to make it less polluting. Given below is the flow diagram of one of the stages of STP. Observe the given flow diagram and answer the questions accordingly.


(a) Why primary effluent is passed into large aeration tanks?


(b) What is the scientific term used for the sediment formed? Mention its significance.


(c) Explain the final step resulting in the formation of biogas in the large tank before the treated effluent is released into water bodies.


(a) The primary effluent is passed into large aeration tanks to facilitate the growth of essential aerobic microbes which gets associated with the fungal filaments to form flocs. This takes place due to the constant agitation and the pumping of air which takes place in the aeration tank.

(b) The scientific term used for sediment is Activated Sludge. It acts as an inoculum and some of it is pumped back into the aeration tank.


(c) In the final step, the anaerobic bacteria digest the aerobic bacteria and the fungi (flocs) present in the sludge. During digestion, the bacteria produce a mixture of gases like methane, hydrogen sulphide and carbon dioxide which constitutes the biogas.


More from this chapter

All 27 →
21

When the gene product is required in large amounts, so transformed bacteria with the plasmid inside the bacteria are cultured on a large scale in an industrial fermenter which then synthesizes its protein. This product is extracted from the fermenter for commercial use.

a) Why is the used medium drained out from one side while fresh medium is added from the other?


(b) List any four optimum conditions for achieving the desired product in a bioreactor.


 22


With reference to the above schematic diagram of Spermatogenesis (a) and Oogenesis (b), answer the following questions:


a) About 300 million spermatozoa may be present in a human male ejaculation at one time. Calculate how many spermatocytes will be involved to produce this number of spermatozoa.


b) How many spermatids will be formed?


c) How many chromatids are found during Oogenesis in Primary oocyte and First polar body in a human female?


 24


Observe the diagram of the catalytic converter and answer the questions which follow.


(a) Name any two metals used as catalyst in the catalytic converter.


(b) Name the gases released after passing the exhaust hydrocarbons through the catalytic converter.


(c) Which other poisonous gas is missing in the exhaust pollutant of an automobile in the above diagram?


 25

Certain phenotypes in human population are spread over a gradient and reflect the contribution of more than two genes. What is the term used for the types of inheritance? Describe it with the help of an example in human population.

OR


Summarize the process by which the sequence of DNA bases in Human Genome Project was determined using the method developed by Frederick Sanger. Name a free living non-pathogenic nematode who’s DNA has been sequenced.