Class 12th Biology 2017 Set3 Delhi Board Paper Solution
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Q1 What is Biopiracy ?
Q2 Suggest a method to ensure an anamnestic response in humans....
Q3 State the fate of a pair of autosomes during gamete formatio...
Q4 Our government has intentionally imposed strict conditions f...
Q5 Rearrange the human activities ...
Q6 Plenty of algal bloom is observed in a pond in your locality...
Q7 How do mycorrhizae help the plants to grow better?
Q8 Mention the ploidy of the diffe...
Q9 Describe the structure of a nucleosome.
Q9 Mention the evolutionary significance of the following organ...
Q10 "Growing Spirulina on a large scale is beneficial...
Q11 During a fire in an auditorium ...
Q12 What is inbreeding depression?
Q12 Explain the importance of ‘selection’ during inb...
Q13 p2 + 2pq + q2 = 1
Explain th...
Q14 During a medical investigation,...
Q15 Draw a labelled diagram of the ...
Q16 Parthenocarpy and apomixis have...
Q17 Describe how do ‘flocs’ and ‘activated slu...
Q18 Explain the role(s) of the following in biotechnology.
...
Q18 Explain the role(s) of the following in biotechnology.
...
Q18 Explain the role(s) of the following in biotechnology.
...
Q19 Why do lepidopterans die when they feed on Bt cotton plant? ...
Q20 Show with the help of flow chart only, the life cycle of mal...
Q21 In situ conservation can help endangered / threaten...
Q21 Name and describe any three causes of biodiversity losses.
Q22 Write the steps you would suggest to be undertaken to obtain...
Q23 Public all over India is very m...
Q24 State and explain the ‘law of independent assortment&r...
Q24 How do the observations made during moth collection in pre a...
Q24 Explain the phenomenon that is well-represented by Darwin&rs...
Q25 What is an age pyramid?
Q25 Name three representative kinds of age pyramids for human po...
Q25 Discuss the role of healthy ecosystem services as a prerequi...
Q26 A capsicum flower has 240 ovules in its ovary. But it produc...
Q26 Describe the development of an ...
Q26 Give an example of an angiosperm seed that has a perisperm. ...
Q26 Where in the fallopian tube does ...
Q26 How is polyspermy prevented in humans?
Question 17
Describe how do ‘flocs’ and ‘activated sludge’ help in sewage treatment.
Answer
Flocks are masses of bacteria associated with fungal filaments to form mesh like structure. It helps in aerobic decomposition as well as filament help in traping particles.
Activiated sludges is used as inoculum to produce flocks during secondary treatment. Process for treating sewage and in industrial waste water using air and a biolgical floc composed of bacteria and protozoa.
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