CLASS– XII
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Section A
1.Flowers
once in 12 years
1
2. (i) 24 (ii) 36
(1/2 each)
3. 25% 1
4.
Analogous organs /same function ,
Convergent evolution (1/2 each)
5.Latex
of poppy plant (Papaver somniferum)
Depressant
and slow down body functions
(1/2 each)
6. Ethidium bromide 1
7. Meristem, It is
free of virus (1/2 each)
8.a.Parasitism b. Commensalism (1/2 each)
9. (i)
Leydig cells - found in interstitial spaces between seminiferous tubules ,
secrete
androgens / testosterone =½ + ½ = 1
(ii)
Sertoli cells -found in between spermatocyteinside seminiferous tubules,
nourish
developing spermatozoa / sperms / germ cells =½+½= 1
10.Saheli
is nonsteroidal ,once a week pill,with high contraceptive value and very less
side
effects.
(1/2 x 4=2)
Or
Be easily
available, effective and reversible with little or no side effects, user
friendly,
not
interfere with the sexual drive of the user or any other. (1/2 x 4=2)
11.Birds-Female is heterogametic and
male is homogametic
ZZ-ZW mechanism
Humans-Female is homogametic and male is
heterogametic
XX-XY mechanism
Egg 1+1=2
12. a)
Salmonella typhi
b)
Streptococcus pneumoniae
c)
Wuchereria bancrofti and Wuchereria malayi
d)
Entamoeba histolytica ½×4=2
13.a.Spirulina
1
b.Methanogens , cellulose (1/2 + 1/2 )
14 Flocs-Masses of bacteria
associated with fungal filaments to form mesh like structures.
These microbes consume the major
parts of the organic matter of the effluent.
This significantly reduce the
BOD. The sewage water is treated till the BOD is reduced.
After the treatment the bacterial flocs
are allowed to sediment. This is called activated sludge. (0.5+ 1+0.5)
15.Streptokinase-bacteria
Streptococcus-clot buster. (1/2 + 1/2 )
Cyclosporin A- Trichoderma polysporum- Immunosuppressant (1/2 + 1/2
)
16. DDT neither excreted nor
metabolized and keeps accumulating in the food chain,
interferes
with Calcium metabolism, decline in bird population / due to thinning
of egg
shell / premature breaking of eggs, bio-magnification. 1+1/2 + 1/2 =2
17.Sporozoites.
Release of toxin haemozoin. (1+1
18. Continuous close inbreeding for
several generations, reduces fertility and productivity
is
called inbreeding depression =½+ ½
Advantages-
produces pure lines / eliminates inferior genes , accumulation of superior
GenesAny
one [1 + 1 = 2marks]
19. Nucleosome
a=DNA
b=H1 histone
c=Octamer of
histone
Non histone
chromosomal Proteins. These are an additional set of Proteins that are required
for packaging of chromatin at higher level. (1/2 each=2)+1
20. Pg 48 Fig 3.6 NCERT (1.5 for labeling+1.5 for function)=3
Or
Pg 48 Fig 3.6 NCERT (2 flow chart + 1for life phases) =3
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