Class 12th Biology 2016 Set1 Delhi Board Paper Solution
List the events that reduce the Biological Oxygen Demand (BOD) of a primarty effluent during sewage treatment.
The events that reduce the BOD of a primarty effluent are:
Primary effluent is passed into large aeration tanks where it is mechanically agitated and air is pumped into it. Mechanical agitation of primary effluent leads to growth of aerobic microbes which reduce the BOD.Popular Questions of Class 12th biology
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(a) Adaptations of desert plants and animals
(b) Adaptations of plants to water scarcity
(c) Behavioural adaptations in animals
(d) Importance of light to plants
(e) Effect of temperature or water scarcity and the adaptations of animals. - Q:- With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
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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__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________. - Q:- What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?