Antibiotics produced by microbes are regarded as one of the most significant discoveries of the twentieth century. Antibiotics are the chemical substances which are produced by some microbes and can kill or retard the growth of other (diseasecausing) microbes.
(a) Name the scientist who discovered the first antibiotic and the organism he was working on.
(b) Name the first antibiotic and its source organism.
(c) Name the scientists who established the potential of the above as an effective antibiotic.

Large quantities of sewage is generated everyday in cities and towns, which is treated in Sewage Treatment Plants (STPs) to make it less polluted. 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 is the primary effluent passed into large aeration tanks?
(b) Write the technical term used for the sediment formed. Mention its significance.
(c) Explain the final step that results in the formation of biogas in the large tank before the treated effluent is released into water bodies.

The diagram above is that of a typical biogas plant. Explain the sequence of events occurring in a biogas plant. Identify a, b and c.

In agriculture, there is a method of controlling pests that relies on natural predation rather than on chemicals. An organic farmer believes that the more biodiversity a landscape has, the more sustainable it is.
(a) Mention two disadvantages of using chemical methods to control pests.
(b) Give an example of a bacterium and a fungus that are used as biocontrol agents.
(c) An organic farmer does not eradicate the 'pests'. Give two reasons.

Read the following and answer any four questions from (i) to (v) given below:
Discovery of penicillin by Alexander Fleming in 1928 marked the beginning of the remarkable era in medical field. Penicillin was the first antibiotic extracted from Penicillium notatum. Antibiotics are used to treat bacterial diseases. These can be broad spectrum which can kill diverse group of disease causing bacteria and narrow spectrum which is effective only against one group of pathogenic strain. Antibiotics can act as bactericides or bacteriostatic. Bactericidal antibiotics kill bacteria by - disruption of cell wall synthesis (e.g., penicillin, cephalosporin, etc.), inhibition of 50S ribosome function (e.g., erythromycin), inhibition of 30S ribosome function (e.g., streptomycin, neomycin), inhibition of amino acid-tRNA binding to ribosome (e.g., tetracyline), etc. Bacteriostatic antibiotics do not kill the bacteria rather they restrict the growth of bacteria. Penicillin belongs to B-Iactum group of antibiotics and it inhibits bacterial cell wall synthesis by binding and inactivating protein. It inhibits transpeptidation of reaction and blocks cross-linking of the cell wall. It is used to treat tonsilitis, sore throat, gonorrhoea, rheumatic fever and some pneumonia types.
(i) The first antibiotic was extracted from a

(ii) Which of the following kills bacteria by interfering 50S ribosome function?

(iii) \(\beta \)-Iactum group of antibiotics kill the bacterial pathogen by

(iv) Penicillin is not used to treat

(v) Assertion :Cephalosporins act by disruption of bacterial cell wall synthesis mechanism.
Reason: Cephalosporins are bacteriostatic antibiotics.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.