Class 12th Biology 2017 Set3 Delhi Board Paper Solution
Describe how do ‘flocs’ and ‘activated sludge’ help in sewage treatment.
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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- Q:-
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
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(i) Fertilisation takes place in _____________.
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