CBSE Class 12 Biology Question Paper 2020 Set 57-3-3

H$moS> Z§.
Code No. 57/3/3
amob Z§. narjmWu H$moS >H$mo CÎma-nwpñVH$m Ho$ _wI-n¥ð
Roll No. >na Adí` {bIo§ &
Candidates must write the Code on the
title page of the answer-book.

ZmoQ> NOTE
(I) H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _o§ _w{ÐV (I) Please check that this question
n¥ð> 15 h¢ & paper contains 15 printed pages.

(II) àíZ-nÌ _| Xm{hZo hmW H$s Amoa {XE JE H$moS (II) Code number given on the right
>Zå~a H$mo N>mÌ CÎma-nwpñVH$m Ho$ _wI-n¥ð> na hand side of the question paper
{bI| & should be written on the title page of
the answer-book by the candidate.
(III) H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _| (III) Please check that this question
>27 àíZ h¢ & paper contains 27 questions.

(IV) H¥$n`m àíZ H$m CÎma {bIZm ewê$ H$aZo go (IV) Please write down the Serial
nhbo, CÎma-nwpñVH$m _| àíZ H$m H«$_m§H$ Number of the question in the
Adí` {bI| & answer-book before attempting it.
(V) Bg àíZ-nÌ H$mo n‹T>Zo Ho$ {bE 15 {_ZQ >H$m (V) 15 minute time has been allotted to
g_` {X`m J`m h¡ & àíZ-nÌ H$m {dVaU read this question paper. The
nydm©• _| 10.15 ~Oo {H$`m OmEJm & question paper will be distributed
10.15 ~Oo go 10.30 ~Oo VH$ N>mÌ Ho$db at 10.15 a.m. From 10.15 a.m. to
10.30 a.m., the students will
àíZ-nÌ H$mo n‹T>|Jo Am¡a Bg Ad{Y Ho$ Xm¡amZ read the question paper only and
do CÎma-nwpñVH$m na H$moB© CÎma Zht {bI|Jo & will not write any answer on the
answer-book during this period.

Ord {dkmZ (g¡ÕmpÝVH$)
BIOLOGY (Theory)
{ZYm©[aV g_` : 3 KÊQ>o A{YH$V_ A§H$ : 70
Time allowed : 3 hours Maximum Marks : 70

.57/3/3 1 P.T.O.

gm_mÝ` {ZX}e :
{ZåZ{b{IV {ZX}em| H$mo ~hþV gmdYmZr go n{‹T>E Am¡a CZH$m g™Vr go nmbZ H$s{OE :
(i) àíZ-nÌ nm±M IÊS>m| _§| {d^m{OV {H$`m J`m h¡  H$, I, J, K Am¡a L> &
(ii) Bg àíZ-nÌ _| 27 àíZ h¢ & g^r àíZ A{Zdm`© h¢ &
(iii) IÊS> H$ _| àíZ g§»`m 1 go 5 VH$ ~hþ{dH$ënr` àíZ h¢, àË`oH$ àíZ 1 A§H$ H$m h¡ &
(iv) IÊS> I _| àíZ g§»`m 6 go 12 VH$ bKw-CÎmar` àH$ma-I Ho$ àíZ h¢, àË`oH$ àíZ 2 A§H$m|
H$m h¡ &
(v) IÊS> J _| àíZ g§»`m 13 go 21 VH$ bKw-CÎmar` àH$ma-II Ho$ àíZ h¢, àË`oH$ àíZ
3 A§H$m| H$m h¡ &
(vi) IÊS> K _| àíZ g§»`m 22 go 24 VH$ bKw-CÎmar` àH$ma-III Ho$ àíZ h¢, àË`oH$ àíZ
3 A§H$m| H$m h¡ &
(vii) IÊS> L> _| àíZ g§»`m 25 go 27 VH$ XrK©-CÎmar` àíZ h¢, àË`oH$ àíZ 5 A§H$m| H$m h¡ &
(viii) CÎma g§{já VWm q~Xþdma hmoZo Mm{hE &
(ix) Bg àíZ-nÌ _| g_J« na H$moB© {dH$ën Zht h¡ & VWm{n EH$-EH$ A§H$ dmbo Xmo àíZm| _|,
Xmo-Xmo A§H$m| dmbo EH$ àíZ _§o, VrZ-VrZ A§H$m| dmbo Xmo àíZm| _§o Am¡a nm±M-nm±M A§H$m|
dmbo VrZm| àíZm| _§o Am§V[aH$ {dH$ën {XE JE h¢ & Eogo àíZm| _| Ho$db EH$ hr {dH$ën H$m
CÎma Xr{OE &
(x) Ohm± Amdí`H$ hmo, dhm± gmµ\$-gwWam, AmZwnm{VH$ VWm g_w{MV Zm_m§{H$V {MÌ ~ZmBE &
(xi) BgHo$ A{V[aº$, Amdí`H$VmZwgma, àË`oH$ IÊS> Am¡a àíZ Ho$ gmW `Wmo{MV {ZX}e {XE JE
h¢ &
IÊS> H$
ZmoQ> : {ZåZ{b{IV àíZm| _| àË`oH$ àíZ _| {XE JE {dH$ënm| go ghr {dH$ën MwZH$a {b{IE :

1. {ñÌ`m| _§o Ho$db gJ^©Vm H$s Ad{Y _§o òm{dV hm°_m}Z h¢ 1

(A) EM.gr.Or. (hCG), EM.nr.Eb. (hPL), àmoOoñQ>oam°Z
(B) [abopŠgZ, EM.gr.Or. (hCG), EM.nr.Eb. (hPL)
(C) EM.gr.Or. (hCG), EM.nr.Eb. (hPL), Am°ŠgrQ>mo{gZ
(D) EM.nr.Eb. (hPL), Wm`am°pŠgZ, EM.gr.Or. (hCG)
.57/3/3 2

General Instructions :
Read the following instructions very carefully and strictly follow them :
(i) Question paper comprises five sections – A, B, C, D and E.
(ii) There are 27 questions in the question paper. All questions are compulsory.
(iii) Section A – Questions no. 1 to 5 are multiple choice questions, carrying
1 mark each.
(iv) Section B – Questions no. 6 to 12 are short-answer questions type-I,
carrying 2 marks each.
(v) Section C – Questions no. 13 to 21 are short-answer questions type-II,
carrying 3 marks each.
(vi) Section D – Questions no. 22 to 24 are short-answer questions type-III,
carrying 3 marks each.
(vii) Section E – Questions no. 25 to 27 are long-answer questions, carrying
5 marks each.
(viii) Answers should be brief and to the point.
(ix) There is no overall choice in the question paper. However, an internal
choice has been provided in two questions of 1 mark, one question of
2 marks, two questions of 3 marks and three questions of 5 marks. Only
one of the choices in such questions have to be attempted.
(x) The diagrams drawn should be neat, proportionate and properly labelled,
wherever necessary.
(xi) In addition to this, separate instructions are given with each section and
question, wherever necessary.

SECTION A

Note : Choose the correct option from the choices given in each of the following
questions :
1. Hormones released in human females only during pregnancy are 1
(A) hCG, hPL, Progesterone
(B) Relaxin, hCG, hPL
(C) hCG, hPL, Oxytocin
(D) hPL, Thyroxine, hCG

.57/3/3 3 P.T.O.

2. gyÌH¥${_ {d{eîQ> OrZm| H$mo V§~mHy$ Ho$ nanmofr nm¡Yo _| Bg g§dmhH$ H$m Cn`moJ H$aHo$ à{dîQ>
H$am`m J`m 1
(A) ßb¡pµÁ_S>
(B) OrdmUw^moOr
(C) pBR 322
(D) EJ«mo~¡ŠQ>r[a`_

3. Q>rH$mH$aU H$m {gÕmÝV Bg A{^bjU (JwU) na AmYm[aV h¡ 1
(A) {d{eîQ>Vm
(B) {d{dYVm
(C) ñ_¥{V
(D) ‘ñd’ Am¡a ‘na’ _§o {d^oX
AWdm
Amo{nAm°BS²>g Bg àH$ma {H«$`m H$aVo h¢ 1
(A) AdgmXH$ ({S>àog|Q²>g)
(B) XX© {ZdmaH$
(C) gwIm^mg XoZo dmbo
(D) CÎmoOH$

4. g§H$Q>mnÞ Om{V`m| Ho$ ~mø ñWmZo (EŠg grQy>) g§ajU H$s {d{Y h¡ 1
(A) Ord_§S>b Ama{jV joÌ (~m`mopñ\$`a [aµOìg©)
(B) amîQ´>r` CÚmZ
(C) {ZåZVmn n[aajU (H«$m`mo{àµOadoeZ)
(D) dÝ`Ord Aä`maU
AWdm
g_Vmn_§S>b _| AmoµOmoZ J¡g H$m gVV {Z_m©U Bg àH$ma hmo ahm h¡ 1
(A) ZdOmV Am°ŠgrOZ na nam~¢JZr {H$aUm| H$s {H«$`m
(B) Am°ŠgrOZ H$s Ob-dmîn Ho$ gmW A{^{H«$`m
(C) AmpÊdH$ Am°ŠgrOZ na nam~¢JZr {H$aUm| H$s {H«$`m
(D) Ob-dmîn na nam~¢JZr {H$aUm| H$s {H«$`m
.57/3/3 4

2. Nematode specific genes were introduced into the tobacco host plant by
using the vector 1
(A) Plasmid
(B) Bacteriophage
(C) pBR 322
(D) Agrobacterium

3. The principle of vaccination is based on the property of 1
(A) Specificity
(B) Diversity
(C) Memory
(D) Discrimination between ‘self ’ and ‘non-self ’
OR
Opioids act as 1
(A) Depressants
(B) Pain killers
(C) Euphoria providers
(D) Stimulants

4. One of the ex situ conservation methods for endangered species is 1
(A) Biosphere reserves
(B) National parks
(C) Cryopreservation
(D) Wildlife sanctuaries
OR
Ozone gas is continuously formed in the stratosphere by 1
(A) Action of UV rays on nascent oxygen
(B) Reaction of oxygen with water vapour
(C) Action of UV rays on molecular oxygen
(D) Action of UV rays on water vapour

.57/3/3 5 P.T.O.

5. {H$gr nm¡Yo H$s nanmofr H$mo{eH$m _| {dOmVr` S>r.EZ.E. IÊS> H$m {ZdoeZ Bg àH$ma àmßV
{H$`m Om gH$Vm h¡ 1
(A) {Ûg§`moOH$ Am`Zm| go g_W© ~ZmH$a
(B) gyú_ A§V:jonU Ho$ Cn`moJ Ûmam
(C) OrZ JZ Ho$ Cn`moJ Ûmam
(D) bmBgmoµOmB_ VWm H$mB{Q>ZoµO H$m Cn`moJ H$aHo$
IÊS> I
6. Y«wdr` àXoe _| hq_J njr (~S>©) Š`m| Zht nmB© OmVr h¢ ? 2
7. ñnmBébmBZm àmoQ>rZm| H$m EH$ CÎm_ òmoV h¡ & Eogo Xmo VarH$m| (Cnm`m|) H$m C„oI H$s{OE
{OZHo$ Ûmam BZ gyú_Ordm| H$m ~‹S>o ñVa (n¡_mZo) na CËnmXZ H$aZm g§^d h¡ & 2
8. ~VmBE, O¡d-Cd©aH$ Š`m h¢ & O¡d-Cd©aH$m| Ho$ {H$Ýht VrZ òmoVm| Ho$ Zm_ {b{IE & 2
9. S>r.EZ.E. AUw na B©H$mo Ama-I (EcoRI) {d{eîQ> ê$n go H¡$go {H«$`m H$aVm h¡ ? ì`m»`m
H$s{OE & 2
10. Cg VH$ZrH$ H$m Zm_ {bIH$a ì`m»`m H$s{OE {OgH$m Cn`moJ Ho$db _mXm nwînYmar nm¡Ym| go
µ\$gb H$s CÞV {H$ñ_| {dH${gV H$aZo _§o {H$`m Om gH$Vm h¡ & 2
AWdm
Anwînr` (nwîn{dhrZ) nmXnm| H$mo H$~ g_W¡bgr VWm C^`qbJml`r H$hm Om gH$Vm h¡; Am¡a
H$~ {df_W¡bgr VWm EH$qbJml`r H$hm Om gH$Vm h¡ ? àË`oH$ H$m EH$-EH$ CXmhaU ^r
Xr{OE &$ 2

11. (a) {H$gr _Zwî` _| ‘XX’ AWdm ‘XY’ Ho$ ~OmE ‘XXY’ qbJ JwUgyÌm| Ho$ hmoZo Ho$ H$maU
H$s ì`m»`m H$s{OE &
(b) Eogo ì`{º$ gm_mÝ` ì`{º$`m| go {OZ Xmo ê$nm| (àH$ma) go {^Þ h¢, CZH$s gyMr ~ZmBE & 2
12. S>rd«rµO Zo {dH$mg H$s {H«$`m{d{Y H$s ì`m»`m H¡$go H$s ? 2

IÊS> J
13. (a) _rW¡ZmoOZ OrdmUw H$m d¡km{ZH$ Zm_ {b{IE & `h OrdmUw gm_mÝ`V: H$hm± nmE OmVo
h¢ ? ~m`moJ¡g CËnmXZ _| BZH$s ^y{_H$m H$s ì`m»`m H$s{OE &
(b) ~m`moJ¡g Ho$ KQ>H$m| Ho$ Zm_ {b{IE & 3

.57/3/3 6

5. Introduction of an alien DNA into a plant host cell is achieved by making
them 1
(A) Competent with bivalent ions
(B) Using microinjections
(C) Using gene gun
(D) Using lysozymes and chitinase

SECTION B

6. Why are humming birds not found in the Polar region ? 2

7. Spirulina is a rich source of proteins. Mention the two ways by which
large scale culturing of these microbes is possible. 2

8. State what are biofertilizers. Name any three sources of biofertilizers. 2

9. How does EcoRI specifically act on DNA molecule ? Explain. 2

10. Name and explain the technique that can be used in developing improved
crop varieties in plants bearing female flowers only. 2
OR
When are the non-flowering plants said to be homothallic and
monoecious; and heterothallic and dioecious ? Give an example of each. 2

11. (a) Explain the cause responsible in a human to have sex
chromosomes as ‘XXY’ instead of ‘XX’ or ‘XY’.
(b) List any two ways such individuals are different from the normal
being. 2

12. How is the mechanism of evolution explained by de Vries ? 2

SECTION C

13. (a) Write the scientific name of methanogen bacteria. Where are these
bacteria generally found ? Explain their role in biogas production.
(b) Name the components of biogas. 3

.57/3/3 7 P.T.O.

14. `Ú{n Amd¥V~r{O`m| Ho$ A{YH$Va nm¡Ym| _| nwîn C^`qbJr hmoVo h¢, naÝVw do ñdnamJU H$mo
hVmoËgm{hV H$aVo h¢ & Bg CÔoí` H$mo àmßV H$aZo hoVw, CZ_§o {dH${gV ~{h:àOZZ H$s {H$Ýht
VrZ `w{º$`m| H$s ì`m»`m H$s{OE & 13=3
15. _mZdm| Ho$ aº$ {dH$ma, hr_mo\$s{b`m VWm W¡bmgr{_`m Ho$ d§emJ{V n¡Q>Z© _| A§Va ñnîQ>
H$s{OE & 3

16. ‘‘H$nmg JmobH$ eb^ H¥${_ H$nmg Ho$ nm¡Ym| H$mo Vrd«Vm go ImVm h¡, naÝVw O~ `h ~rQ>r
H$nmg Ho$ nm¡Ym| H$mo ImVm h¡, Vmo `h H¥${_ _a OmVm h¡ &’’ H$WZ H$s Ý`m`g§JVm {gÕ
H$s{OE & 3
AWdm
(a) _mZdm| _| E.S>r.E. H$s H$_r Ho$ H$maH$ (H$maU) H$m C„oI H$s{OE &
(b) Bg amoJ go J«{gV amo{J`m| Ho$ CnMma _| OrZ {M{H$Ëgm {H$g àH$ma H$s OmVr h¡ ?
(c) Bg amoJ Ho$ ñWmB© CnMma H$s g§^mdZm H$m CëboI H$s{OE & 3
17. (a) JwUgyÌ g§»`m Ho$ g§X^© _|, _mZdm| _§| qbJ {ZYm©aU H$s VwbZm _Yw_ pŠI`m| _| qbJ
{ZYm©aU go H$s{OE &
(b) Cn`w©º$ XmoZm| Ordm| _| `w½_H$ ~ZZo H$s VwbZm H¡$go H$s Om gH$Vr h¡ ? 3
18. AmnH$mo AnZo {dÚmb` Ho$ CÚmZ _| CJo, ~¢JZr \y$bm| dmbo _Q>a Ho$ EH$ nm¡Yo H$m OrZràê$n
kmV H$aZo H$mo H$hm OmVm h¡ & BgH$m g_mYmZ àñVwV H$aZo hoVw AnZm ñnîQ>rH$aU Xr{OE & 3
19. EH$ à{Vajr H$s amgm`{ZH$ àH¥${V H$m CëboI H$s{OE VWm CÝh| CËnÞ H$aZo dmbr
H$mo{eH$mAm| Ho$ àH$ma H$m Zm_ {b{IE & à{Va{j`m| Ho$ AmYma na g{H«$` Am¡a {ZpîH«$`
à{Vajm AZw{H«$`m _| A§Va {b{IE & 3
AWdm
CZ H$mo{eH$mAm| Ho$ Zm_ {b{IE Omo _Zwî`m| _| ‘EM.AmB©.dr.’ g§H«$_U hmoZo Ho$ ~mX
EM.AmB©.dr. \¡$ŠQ>ar H$s Vah H$m`© H$aVr h¢ & BZ g§H«${_V H$mo{eH$mAm| _| hmoZo dmbr
n[aKQ>ZmAm| H$s ì`m»`m H$s{OE & 3
20. ßbmpñQ>H$ An{eîQ> H$s g_ñ`m H$m ~moY hmoZo Ho$ ~mX, ßbmpñQ>H$ H$s ~mo[a`m± ~ZmZo dmbo
~|Jbyê$ Ho$ Ah_X ImZ Zo g_ñ`m H$m Omo hb {ZH$mbm CgH$s ì`m»`m H$s{OE & 3

21. (a) Cg àH«$_ H$m Zm_ {b{IE Omo nmofU MH«$ _| AnaX H$mo _¥Xm ({_Å>r) H$m {hñgm
~ZmVo h¢ &
(b) Bg àH«$_ H$s Xa H$mo {Z`§{ÌV H$aZo Ho$ {bE CÎmaXmB© H$maH$m| H$mo {b{IE &
(c) Cg n[apñW{V H$m C„oI H$s{OE O~ BgH$s Xa AnojmH¥$V Vrd« hmoJr & 3

.57/3/3 8

14. Majority of angiosperms have hermaphrodite flowers, but self-pollination
is discouraged by them. Explain any three outbreeding devices that they
have developed to achieve this. 13=3

15. Differentiate between the pattern of inheritance in humans of the blood
diseases, haemophilia and thalassemia. 3
16. ‘‘Cotton bollworms enjoy feeding on cotton plants, but get killed when
feed on Bt cotton plant.’’ Justify the statement. 3
OR
(a) Mention the cause of ADA deficiency in humans.
(b) How is gene therapy carried out to treat the patients suffering from
this disease ?
(c) State the possibility of a permanent cure of this disease. 3

17. (a) Compare the mechanism of sex determination in humans with that
of honey bees, with respect to chromosome number.
(b) How is the gamete formation comparable in the above two cases ? 3

18. You are asked to find the genotype of a pea plant bearing violet flowers,
growing in your school garden. Give your explanation to get the solution. 3

19. Mention the chemical nature of an antibody and name the type of cells
they are produced by. Write the difference between active and passive
immune responses on the basis of antibodies. 3
OR
Name the cells that act as HIV factory in humans when infected by HIV.
Explain the events that occur in these infected cells. 3

20. Explain the solutions found by Ahmed Khan, a Bengaluru based plastic
sack manufacturer, after realising the problems created by plastic
wastes. 3

21. (a) Name the process that makes the detritus become part of the soil
in the nutrient cycle.
(b) Write the factors responsible for controlling the rate of this
process.
(c) Mention the condition when the rate would be faster. 3

.57/3/3 9 P.T.O.

IÊS> K

22. _mZd A§S>me` H$s AZwàñW-H$mQ> Ho$ ZrMo {XE JE {MÌ H$m AÜ``Z H$aHo$, {ZåZ{b{IV
àíZm| Ho$ CÎma Xr{OE : 3

(a) Cg hm°_m}Z H$m Zm_ {b{IE Omo A  B  C H$s d¥{Õ _§o ghm`H$ h¡ &
(b) A VWm B Ûmam òm{dV hm°_m}Z H$m Zm_ {b{IE &

(c) D Ûmam CËnm{XV hm°_m}Z H$s ^y{_H$m {b{IE &

23. _mZd Ûmam agm`Zm|, nr‹S>H$Zm{e`m| VWm IanVdmaZm{e`m| Ho$ A§YmYw§Y Cn`moJ go h_mao Ob
òmoV àXÿ{fV hmo aho h¢, Omo A§VV: Ordm| H$mo hm{Z nhþ±Mm ahm h¡ & {ZåZ àdmh {MÌ H$m
AÜ``Z H$a, Bg na AmYm[aV àíZm| Ho$ CÎma Xr{OE &

(a) erf© Cn^moº$m _| S>r.S>r.Q>r. H$s gmÝÐVm AË`{YH$ Š`m| h¡ ?
(b) gdm}ƒ ñVa Ho$ Ordm| na Š`m à^md n‹S>oJm ?
(c) ào{jV n[aKQ>Zm H$m Zm_ {b{IE & 3

.57/3/3 10

SECTION D

22. Study the transverse section of human ovary given below and answer the
questions that follow : 3

(a) Name the hormone that helps in the growth of A  B  C.

(b) Name the hormone secreted by A and B.
(c) State the role of the hormone produced by D.

23. Indiscriminate use of chemicals, pesticides and weedicides by humans are
polluting our water bodies, which in turn are harming the living
organisms. Study the flow chart and answer the questions based on it.

(a) Why does the concentration of DDT seem to be considerably high
in the top consumer ?

(b) How would the organisms at the highest level be affected ?

(c) Name the phenomenon observed. 3

.57/3/3 11 P.T.O.

24. Oob d¡ÚwV H$U-g§MbZ (BboŠQ´>mo\$moao{gg) VH$ZrH$ Ûmam S>r.EZ.E. IÊS>m| Ho$ n¥WŠH$aU Ho$
àojUm| H$mo, {ZåZ{b{IV AmaoI Ûmam àX{e©V {H$`m J`m h¡ & AmaoI H$m àojU H$s{OE VWm
{ZåZ{b{IV àíZm| Ho$ CÎma Xr{OE : 3

(a) S>r.EZ.E. IÊS> A  B {Xem _| J{V H$aVo Š`m| {XImB© XoVo h¢ ?
(b) Cg _mÜ`_ H$m Zm_ {b{IE {Og na S>r.EZ.E. IÊS> {dbJ hmoVo h¢ &
(c) n¥WŠH¥$V S>r.EZ.E. IÊS>m| H$mo {H$g àH$ma XoIm Om gH$Vm h¡ Vm{H$ CZH$m VH$ZrH$s
Cn`moJ {H$`m Om gHo$ ?
IÊS> L>
25. (a) nwéfm| _| ewH«$mUw-OZZ àH«$_ H$~ àma§^ hmoVm h¡ ? ewH«$mUw-OZZ àH«$_ H$m dU©Z
H$s{OE &
(b) Bg àH«$_ _| JmoZ¡S>moQ´>m°{nZ H$s ^y{_H$m H$s ì`m»`m H$s{OE & 5
AWdm
EH$ Amd¥V~rOr Ho$ ~rOmÊS> _| Jwé~rOmUwOZZ H$hm± gånÞ hmoVm h¡ ? Bg àH«$_ _§o n[anŠd$
^«yU H$mof ~ZZo VH$ H$s n[aKQ>ZmAm| H$m dU©Z H$s{OE & 5

26. (a) ‘‘n`m©daU{dXm| Ho$ AZwgma, {díd Ho$ CîUH${Q>~§Yr` joÌm| _| O¡d-{d{dYVm A{YH$$
h¡ &’’ Am¡{MË` ~VmBE &
(b) Amdmgr` j{V VWm {dXoer Om{V`m| Ho$ AmH«$_U H$mo O¡d-{d{dYVm H$s j{V H$m
H$maU Š`m| _mZm OmVm h¡ ? àË`oH$ H$s EH$-EH$ CXmhaU H$s ghm`Vm go ì`m»`m
H$s{OE & 5
AWdm
.57/3/3 12

24. Given below is the diagram representing the observations made for
separating DNA fragments by Gel electrophoresis technique. Observe the
illustration and answer the questions that follow : 3

(a) Why are the DNA fragments seen to be moving in the direction
AB?
(b) Write the medium used on which DNA fragments separate.
(c) Mention how the separated DNA fragments can be visualised for
further technical use.

SECTION E

25. (a) When does the process of spermatogenesis begin in human males ?
Describe the process of spermatogenesis.
(b) Explain the role of gonadotropin in this process. 5
OR
Where does megasporogenesis occur in the ovule of an angiosperm ?
Describe the process up to the development of a mature embryo sac. 5

26. (a) According to ecologists, tropical regions in the world account for
greater biological diversity. Justify.
(b) Why are habitat loss and alien species invasion considered as the
causes of biodiversity loss ? Explain with the help of an example of
each. 5
OR

.57/3/3 13 P.T.O.

(a) nm[apñW{VH$ AZwH«$_U Š`m h¡ ?
(b) àmW{_H$ VWm {ÛVr`H$ AZwH«$_U _| A§Va ñnîQ> H$s{OE & àmW{_H$ AZwH«$_U H$s
Anojm {ÛVr`H$ AZwH«$_U Vrd«Va Š`m| hmoVm h¡ ? g_w{MV CXmhaUm| g{hV ì`m»`m
H$s{OE &
(c) _yb AÝdofH$ àOm{V`m± Š`m h¢ ? ewîH$Vma§^r AZwH«$_U VWm Obma§^r AZwH«$_U _|
_yb AÝdofH$ (_ybma§^r) àOm{V`m| Ho$ H«$_e: CXmhaU Xr{OE & 5

27. (a) S>r.EZ.E. Ho$ Cg ñdê$n (àH$ma) H$m Zm_ {b{IE Omo S>r.EZ.E. A§Jw{bN>mnr H$m
AmYma h¡ Am¡a Bg S>r.EZ.E. Ho$ Xmo A{^bjUm| H$m C„oI ^r H$s{OE &
(b) S>r.EZ.E. A§Jw{bN>mnr VH$ZrH$ Ho$ àH«$_ Ho$ {d{^Þ MaUm| H$mo {b{IE VWm BgH$s
Cn`mo{JVm H$m C„oI H$s{OE & 5
AWdm
b¡H$ Amonoam°Z O~ g{H«$`Vm H$s ‘Am°Z (Amaå^)’ AdñWm _| hmoVm h¡, Vmo CgHo$ {d{^Þ
OrZm| H$s ^y{_H$m H$s ì`m»`m H$s{OE & 5

.57/3/3 14

(a) What is an ecological succession ?
(b) Differentiate between primary and secondary succession. Why is
secondary succession faster than primary succession ? Explain
with suitable examples.
(c) What are pioneer species ? Give examples of pioneer species in
Xerarch and Hydrarch successions respectively. 5

27. (a) Name the type of DNA that forms the basis of DNA fingerprinting
and mention two features of this DNA.
(b) Write the steps carried out in the process of DNA fingerprinting
technique, and mention its application. 5
OR
Explain the role of different genes in a lac operon, when in a ‘Switched
On’ state. 5

.57/3/3 15 P.T.O.