XII biology CBSE BOARD QS WITH KEY (CHAPTER WISE

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KENDRIYA VIDYALAYA CRPF AVADI CHENNAI-65
BIOLOGY CBSE BOARD QUESTIONS
2009-2012
COMPILED BY:
Mrs. SATHYABAMA PARTHIPAN
PGT BIOLOGY
KENDRIYA VIDYALAYA CRPF AVADI CHENNAI-65
BIOLOGY CBSE BOARD QUESTIONS. 2009-2012
Chap 2SEXUAL REPRODUCTION IN FLOWERING PLANTS
How do the pollen grains of vallisneria protect themselves?
Have mucilaginous covering ( to prevent it from getting wet)
2
State one advantage and one disadvantage of cleiostogamy.
Advantage – self pollination assured/seed production assured
Disadvantage – least variations/ leading to inbreeding depression.
3
Why banana is considered a good example of parthenocarphy?
Formation of fruit without fertilization/ no formation of seeds
4
Why banana is considered a good example of parthenocarphy?
Formation of fruit without fertilization/no formation of seeds.
5
Differentiate between perisperm and endosperm giving one example each.
Perisperm – persistant nucleus =1/2,diploid=1/2,eg., black pepper/beet=1/2
Endosperm – nutritive tissue for embryo = ½,triploid = ½, ex: maize/rice =1/2
6
Explain the function of each of the following
a) coleorhizae – protects the radical of monocot embryo = 1
b) b) germ pores – allow germination of pollen grains/formation of pollen tubes
=1
7 a) Why is fertilization in angiosperm referred to as double fertilization? mention the
ploidy of the cell involved.
b)draw a neatly labeled sketch of L.S of an endospermous monocot seed.
a)fertilization of haploid egg cell by one haploid male gamete to form diploid
zygote is called syngamy 1/2x3=11/2
fertilization of two (diploid) polar nuclei by the other haploid male gamete to
form triploid primary endosperm nucleus is called triple fusion =1/2x3=1 ½
1
8
9
Any four labels including endosperm =2
Name the type of flower which favours cross pollination.
Chasmogamous.
Why is bagging of the emasculated flower essential during hybridization
experiments?
1
2
1
1
3
2
5
1
1
10
11
To prevent the entry of unwanted pollen// in order to have desired cross pollination
Fertilization is essential for production of seed, but in some angiosperms seeds
develop without fertilization.
i)
Give an example of angiosperm that produces seeds without
fertilization.name the process.
ii)
Explain two ways by which seeds develop without fertilization.
ans: i)members of Asteraceae/grasses/citrus/mango, apomixes = ½+1/2
ii)two ways-in some species the diploid egg cell is formed without reduction
division and develops into embryo without fertilization = 1
b) more often, as in many citrus and mango varieties some of the nucellar cells
surrounding the embryo sac start dividing, protrude into the embryo sac and develop
into the embryos.
a) Trace the development of embryo after syngamy in a dicot plant.
b) Endosperm development precedes embryo development. Explain
c) Draw a diagram of a mature dicot embryo and label cotyledons, plumule,
radical and hypocotyls in it.
explanation of the figure / above diagram can be considered//
the zygotes divides unequally to form two cells namely embryo cell and
suspensor cell, the smaller cell divides repeatedly to produce a row of 4-8
cells,
the terminal cell divides to produce a cluster of cells called the globular
embryo/ proembryo and the remaining cells constitute the suspensor,
a few cells of the proembryo nearest of the suspensor develop into
hypocotyls and radical while other cells give rise to epicotl plumule and
cotyledons = 1/2x4
b) provides nourishment to the developing embryo=1
3
5
c)
hypocotyl
12
1/2x4=2
Give reasons why:
i) most zygotes in angiosperms divide only after certain amount of endosperm is
formed.
ii)groundnut seeds are exalbuminous and castor seeds are albuminous
iii)micropyle remains as a small pore in the seed cat of a seed
iv) integuments of an ovule harden and the water content is highly redused, as the
seed matures.
v)apple and cashew are not called true fruits.
Ans:i)to obtain from the endosperm for the developing embryo=1
ii)ground nut- endosperm completely consumed =1/2
castor – endosperm persists =1/2
iii)for the entry of water/oxygen,for germination=1/2=1/2=1
iv) protect the embryo/keep the seed viable,until favourable conditions return for
germination=1/2=1/2=1
v)ovary is not taking part in fruit formation/thalamus contributes to fruit
formation=1
1x5=5 marks
or
a)draw a labeled diagram of L.S of an embryo of grass(any six labels)
5
b)give reason for each of the following:i) anthers of angiosperm flowers are described as
dithecus.
ii)hybrid seeds have to be produced year after year.
i)
each bilobed anther has two theca
ii)
progeny show segregation,do not maintain hybrid characters=1/2=1/2=1
13
How does the pollen mother cell develop into a mature pollen grain? Illustrate the
stages with labeled diagrams.
PMC/Microspore mother cell undergoes meiosis, to form microspore tetrad by the
process called microsporogenesis, each microspore develops into pollen grain, each
pollen grain undergoes unequal mitotic division, and produces two cells – vegetative
cell and generative cell 1/2x5=2 ½
14
a) trace the development of megaspore mother cell up to the formation of a
5
1/2x5=2 1/2
5
mature embryo-sac in flowering plant
b) draw a labeled diagram of the structure of mature dicot embryo
ans:MMCmegaspore mother cell undergoes meiosis to form four
megaspores,one of the megaspore is functional while other three degenerate,
the nucleus of functional megaspores divides thrice mitotically, to form 8
nucleate stage of the embryo sac followed by the formation of cell walls,
cells are arranged as one egg cell and two synergids at micropylar end, 3
antipodals at chalazal end and two polar nuclei at the centre =1/2x6
b
15
16
17
Pea flowers produce assured seed sets. Give a reason.
Pea flower is a cleistogamous flower/do not open=1
a) Mention any four strategies adopted b flowering plants to prevent self
pollination.
b) why is geitonogamy also referred to as genetical autogamy?
Ans: a)pollen release and stigma receptivity are at different times=1/2
Anther and stigma are placed at different positions=1/2
Self incompatibility/prevents pollen from fertilizing the ovule of the same
plant=1/2
Production of unisexual flowers=1/2
b)pollen grains come from the same plant=1
Describe the post-zygotic events leading to implantation and placenta formation in
humans. Mention any two functions of placenta.
Ans: maize seed/castor seed/onion seed (any one figure)
1
3
5
b)better adaptive strategies for dispersal to new habitats
they have food reserves for the seedling or embryo
the seed coat provides protection to the embryo
generate genetic variation
remain viable for a considerable period of time.(any two) =1x2
1
2
3
4
5
CHAP-3 HUMAN REPRODUCTION
Give reasons for the following
a) The human testes are located outside the abdominal cavity?
b)some organisms like honey-bees are called parthenogenetic animals
a) to maintain the temperature (2-2.5c) lower the normal body temperature essential
for spermatogenesis
1
b) they/drone/males develop from unfertilized eggs.
1
Where are the leydig cells present?what is their role in reproduction?
Ans: between / outside the seminiferous tubules// interstitium of the testes=1
Role – stimulates and secretion of androgens =1
a) When and how does placenta develop in human female?
b) How is the placenta connected to the embryo?
c) Placenta acts as an endocrine gland. explain.
Ans: a) after implantation of the embryo placenta develop in the human female, the
chorionic villi, and uterine tissue, become interdigitated with each other and jointly
form a structural and functional unit between developing embryo(foetus) and
maternal body called placenta=1/2x4=2
b)through the umbilical cord=1
c)placenta acts as an endocrine tissue and produces several hormones like
human chorionicgonadotropin (hCG) human placental lactogen(hPL) /
estrogen/placental progestogens/
any two=1/2+1/2=1
in the maternal blood increased level of these hormones is essential for
supporting the foetal growth/metabolic changes in mother and maintenance
of pregnancy (any two effects) =1/2+1/2
Name the embryonic stage that gets implanted in the uterine wall of a human female.
Blastocyst/blastula
Set 1 diagram
The following is the illustration of ovarian events ‘a’ to ‘I’in a human female
2
1
5
1
5
a) Identify the figure that illustrates corpus luteum and name the pituitary
hormone that influences its formation.
b) Specify the endocrine function of corpus luteum. How does it influence the
uterus? Why is it essential?
c) What is the difference between “d” and “e”?
d) Draw a neat labeled sketch of graffian follicle.
a)’g’-1/2 lutenising harmone LH-1/2
b)produces the harmone progesterone,causes proliferation of the
endometriumwhich gets highly vacularised,it is essential for the implantation of
the fertilized ovum and to maintain the same during the pregnancy.-1/2x3
c)”d” is the developing tertiary follicle-1/2
“e” is the graafian follicle-1/2
6
How is the entry of only one sperm and not many ensured into an ovum during
fertilization in humans?
On the sperm head
1
7
Draw a labeled diagram of the reproductive system in a human female.
Ans:
3
8
9
10
Where is acrosome present in human? Write its function.
On the sperm head-1/2, Has enzymes to dissolve the follicles of ovum / facilitate
1the entry of sperm nucleus for fertilization/ help the sperm enter into the
cytoplasm of the ovum. 1
a) Where do the signals for parturition originate from the humans?
b) Why is it important to feed the newborn babies on colostrums?
Ans: a) from the fully developed foetus/placenta/foetal ejection reflex
b) contains IgA antibodies to (passively) immunize the baby
a) Draw a diagrammatic labeled sectional view of a seminiferous tubule of a
human.
b) Describe in sequence the process of spermatogenesis in humans.
Ans:
b)at puberty spermatogonia undergo mitosis to form primary spermatocytes,each
undergoes first meiotic division to form two secondary spermatocytes, each
completes second meiotic division to form two spermatids, spermatid undergoes
spermiogenesis to form spermatozoa =1/2x4=2
// labeled schematic representation may be considered in lieu of explanation.
1
2
5
11
12
13
14
1
2
3
1
2
What stimulates pituitary to release the hormone responsible for parturition? Name
the hormone.
Ans:signal from the developed foetus and placenta induces mild uterine
contractions/foetal ejection reflex =1/2
Oxytocin =1/2
Differentiate between major structural changes in human ovary during the follicular
and luteal phase of the menstrual cycle.
Ans: follicular phase: primary follicle matures to form graffian follicle=1
luteal phase: the ruptured graafian follicle changes into corpus luteum.=1
Describe the post zygotic events leading to implantation and placenta formation in
humans mention any two functions of placenta.
Ans:zygote moves through oviduct and cleavage begins,forms blastomeres,at 8-16
cell stage embryo is called morula,mitosis continues and embryo moves to uterus,
blastomeres form outer layer called trophoblast, the rest of the cells form mass of
cells, at blastocyst stage embryo gets implanted, trophoblast puts forth chorionic villi
which finall along with uterine tissue forms placenta=1/2x8
Functions of placenta:
Supplies oxygen and nutrients to the embryo
Removes co2 and excretory waste
Endocrinal function producing human chorionic gonadotropins / human placental
lactogen/estrogen/progestogens
(Any two)=1/2x2
Explain the functions of umbilical cord.
Transports nutrients and respiratory gases and metabolic wastes to and from mother
and foetus =1 mark
Chap 4
REPRODUCTIVE HEALTH
Why do some women use “saheli” pills?
Once a week pill/with very few side effects/high contraceptive value/prevents
pregnancy. any two 1=1
Describe the lactational amenorrhea method of birth control.
Ans:during intense lactation/breast feeding=1
No menstrual cycle.no ovulation =1
Explain the zygote intra fallopian transfer technique (ZIFT). How is intra uterine
transfer technique IUT different from it?
ZIFT – when the zygote at 8 celled stage is transferred to the fallopian tube =1
IUT – when the zygote at 8 celled stage is implanted in the uterus =1
Chap 5 PRINCIPLES OF INHERITANCE AND VARIATION
Name the respective pattern of inheritance when F1 phenotype
a) doesn’t resemble either of the two parents and is in between the two
b)resembles only one of the two parents
ans: a) incomplete dominance
b) dominace
1
a) Explain the phenomena of multiple allelism and codominance taking ABO blood
group as an example.
One gene I has three alleles IA IB and i. hence multiple allelism. We inherit any two
3
2
5
1
2
2
2
1
3
4
of them. When the genotype is IAIB, the individual has AB blood group since both
IA and IB equally influence the formation of antigen A and B codominance.
b) What is the phenotype of the following?
(i) IA i
(ii) i i
Ans:a)A blood group
c)O blood group
A garden pea plant produced axial white flowers. Another of the same species
1
produced terminal violet flowers. Identify the dominant traits.
Ans: axial, violet flowers.
a) Explain a monohybrid cross taking the seed coat colour as a trait in Pisum sativum 5
. Work out the cross upto F2 generation.
b) State the laws of inheritance that can be derived from such a cross.
c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?
Ans: monohybrid cross
YY
Yellow
yy
green
Yy
Yellow
F2 selfing
Y
y
Y
YY
yellow
Yy
yellow
F1 =1/2
y
Yy
yellow
yy
green
Phenotypic ratio =3:1
Genotypic ratio = 1:2:1
Law of dominance
In a contrasting pair of factors one member of the pair dominates the other.
Law of segregation
Factors or allele of a pair segregate from each other such that agamete receives
only one of the two factors.
c) phenotypic ratio of F2 in monohybrid cross is 3:1 whereas in a dihybrid cross the
phenotypic ratio is 9:3:3:1.
5
1. Describe the pattern of mechanism of inheritance of ABO blood group in
human.
(OR)
(a) Why is haemophilia generally observed in human males? Explain the
condition under which a human female can be haemophilic?
5
6
(b) A pregnant human female was advised to undergo MTP. It was diagnosed by
her doctor that the foetus she is carrying has developed from a zygote formed by an
XX- egg fertilized by Y-carrying sperm. Why was she advised to undergo MTP?
Ans: Human blood group is determined by glycoprotein/antigen A, and
glycoprotein/ antigen B. = 1
The alleles are IA, IB and i– Hence referred to as multiple allelism.= 1
IAIA, IA i - A group
IBIB, IB i - B group
IA IB
- AB group
ii
- O group = 1
In the case of A, B and O – Law of dominance is the pattern of inheritance as IA/ IB
dominant over i. = 1
In AB group both the alleles IA and IB express- it is the case of Co-dominance. = 1
[1+1+1+1+1 = 5marks]
(OR)
Ans: (a) Haemophilia is caused due to the recessive, gene on X chromosome. =½+½
Y has no allele for this/if a male is XhY then he is haemophilic/if a male inherits Xh
from the mother he is haemophilic(with a genotype XhY) = 1
If female inherits XhXh, one from the carrier mother and other from a haemophilic
father(then she can be haemophilic)= 1
(b) Embryo has (trisomy of sex chromosome) XXY/Klinefelter’s syndrome. =1
Advised MTP since the child will have the following problem:
Male with feminine traits/ like gynaecomastia/ underdeveloped tetes/sterile. = 1
[1+1+1+1+1 = 5marks]
1. A relevant portion of b-chain of haemoglobin of a normal human is given
below:
2
The codon for the sixth amino acid is GAG. The sixth codon GAG mutates to GAA
as a result of mutation ‘A’ and into GUG as a result of mutation ‘B’. Haemoglobin
structure did not change as a result of mutation ‘A’ where as haemoglobin changed
because of mutation ‘B’ leading to sickle shaped RBCs. Explain giving reason how
mutation ‘B’ could change the haemoglobin structure and not mutation ‘A’.
Ans: GAA also codes for glutamic acid and hence no change in RBC. = 1
GUG codes for Valine and so the sickle shaped RBCs. = 1
[1+1= 2 marks]
7
a) A true breeding homozygous pea plant with green pods and axial flowers as
dominant characters is crossed with a recessive homozygous pea plant with yellow
pods and terminal flowers. Work out the cross upto F2 generation giving the
phenotypic ratio of F1 and F2 generation respectively.
(b) State the Mendelian principle which can be derived from such a cross and not
5
from monohybrid cross.
Ans: (a) Parent: GGAA
Green axial
Gamete:
F1 -
ggaa = ½
yellow terminal
GA
ga
GgAa
GgAa (hybrid) green axial = ½
Selfing
F2: [½+½+½+½+½=2½marks]
GA
Ga
gA
ga
GA
GGAA
Green
axial
GGAa
GgAA
Green axial Green
axial
GgAa
Green axial
Ga
GGAa
GGaa
Green
terminal
Ggaa
Green
terminal
Green
axial
GgAa
Green
axial
gA
GgAA
Green
axial
GgAa
ggAA
Green axial yellow
axial
ggAa
yellow
axial
ga
GgAa
Ggaa
Green
terminal
Ggaa
Yellow
terminal
Green
axial
ggAa
yellow
axial
Phenotypes: green : green : yellow : yellow
axial terminal axial terminal
Phenotypes: 9 : 3
: 3
:
1
ratio
(b) Law of independent assortment, when two pairs of traits are combined in a
hybrid segregation of one pair of character is independent of the other pair of
character.= 1
[½+½+2½+1=5marks]
8
Explain the mechanism of sex determination in insects like Drosophila and
grasshopper.
Ans: In Drosophila sex is determined by the type of sperm, with X or with Y;
fertilizing the ovum with X. In grasshopper sex is determined by the type of
sperm, with X or without sex chromosomes, fertilizing the ovum with egg. [½ *
6= 3marks]
3
9
1. (a) State the law of independent assortment.
(b) using punnett square demonstrate the law of independent assortment in a
dihybrid cross involving two heterozygous parents.
Ans: (a) When two pairs of traits are combined in a hybrid segregation of one pair of
character is independent of the other pair of character. = 1
(b) Parent
5
10
Both parental type and recombinant types are observed to show that genes for the
colour and genes for the shape of seeds segregate independently during gametes
formation. =1
[1+3+1= 5marks]
Write the genotype of
i) An individual who is carrier of sickle cell anemia gene but apparently
unaffected
ii) An individual affected with the disease.
Ans: i) HbA HbS = ½
ii) HbS HbS = ½
1
11
12
[½+½ = 1mark
Explain the health determination mechanism in humans. How is it different in birds?
Ans: Human: Females produces all gametes with X chromosomes. If the egg fuses
with a sperm with X chromosome a daughter is born. If the egg fuses with the sperm
with a Y chromosome a son is born.
[½*3 = 1½ marks]
Birds: male produces all gametes with Z chromosomes. If the sperm fuses with egg
with Z chromosome a male is born. If the sperm fuses with egg with W chromosome
a female is born.
[½*3 = 1½ marks]
[1½+1½= 3marks]
Recently a girl baby has been reported to suffer from haemophilia. How is it
possible? Explain with the help of a cross.
Ans:
XhY
Father is haemophilic
=1
13
3
3
XXh
mother is a carrier
=1
XhXh
Possibility of the daughter being haemophilic. =1
[1+1+1 = 3marks]
A particular garden pea plant produces only violet flowers.
a) Is it homozygous dominant for the trait or heterozygous?
b) How would you ensure its genotype? explain with the help of crosses.
Ans: a) it could be homozygous dominant , heterozygous dominant =1/2+1/2=1
b) by test cross = ½
if parent homozygous:
if the parent heterozygous
VV x
vv =1/2
Vv
x
vv
=½
(violet) (white)
(violet)
(white)
5
Gamete
V
v
Vv =1/2
(All violet)
100%
14
15
=1/2
V
v
Vv
(violet)
50%
=1/2
v
vv
(white)
50%
=1/2
=1/2
(1/2x10=5)
A human being suffering from Down’s syndrome shows trisomy 21st chromosome.
Mention the cost of this chromosomal abnormality.
Ans: Failure of segregation of chromatids during cell division/ presence of extra
21st chromosome. = 1mark
(a) You are given tall pea plants with yellow seeds whose genotypes are unknown.
1
5
How would you find the genotype of these plants? Explain with the help of crosses.
(b) Identify a, b and c in the table given below:
S.No. Pattern of Inheritance
1.
Co dominance
2.
b
3.
Incomplete dominance
Ans: (a) Test cross =½
Cross I
Monohybrid F1, phenotypic
expression
a
The progeny resembles only one of
the parent
c
TTYY
X
ttyy
TY
=
ty
TtYy (tall yellow) =
Cross II
TtYy
1
X
TtYy
TY
Ty
tY
TtYy
Ttyy
ttYy
:
1
:
ty
ttyy
ty
+
1 : 1
(b) a = Equal expression for both
b = Dominance
c = Intermediate = *3
16
1
=
[3
+1
= 5marks]
6
MOLECULAR BASIS OF INHERITANCE
Mention the contribution of genetic maps in human project?
Ans: Sequence of gene, DNA finger printing, tracing human history, and
chromosomal location for disease associated sequence. (Any one)
1
2
3
4
5
6
= 1mark
1. Write the full form of VNTR. How is VNTR different from ‘Probe’?
Ans: VNTR: Variable Number of Tandem Repeats. =1 mark
Probe- is labeled/radio active (single stranded hybridized DNA fragments).
= 1 mark
1. (i) Name the enzyme that catalyses the transcription of hnRNA.
(ii) Why does the hnRNA need to undergo change? List the changes hnRNA
undergoes and where in the cell such changes take place.
Ans: (i) RNA polymerase II = 1mark
(ii) Has (non functional) introns. = ½
(Methyl guanosine tri-phosphate is added to 5’ end) capping, tailing
(Poly A tail at 3’ end added), splicing (introns are removed and exons are joined). =
½*3 [1+2= 3mark]
2. i) Name the scientist who called t-RNA an adapter.
(ii) Draw a clover leaf structure of t-RNA showing the following:
(a) Tyrosine attached to its amino acid site.
(b) Anticodon for this amino acid in its correct site
(iii) What does the actual structure of t-RNA look like?
Ans: (i) Francis Crick. = 1
(ii)
(iii) tRNA looks like inverted L. = 1 [1+1+1 = 3marks]
3. Answer the following based on meselson and stahl’s experiment:
(a) Write the name of chemical substance used as a source of nitrogen in the
exp. by them.
(b) Why did the scientists synthesise the light and the heavy DNA molecule
in the organism used in the exp.
(c) How did the scientist make it possible to distinguish the heavy DNA
molecule from the light DNA molecule? Explain.
(d) Write the conclusion the scientist arrived at after completing the exp.
Ans:
(a) NH4Cl = 1
(b) To check whether DNA replication was semi-conservative. = ½
(c) Distinguish them by centrifugation in the cesium chloride density
gradient. = ½
(d) DNA replicated semi conservatively. = 1
[1+1+1=3marks]
4. (a) State the arrangement of different genes that in bacteria is referred to as
2
3
3
3
5
‘operon’.
(b) Draw a schematic labeled illustration of lac operon in a switched on
state.
(c) Describe the role of lactose in lac operon.
Ans: (a) polycistronic structural gene/ three structural genes adjacent to, an
operator, a promoter, and a regulator. = 1 ½
(b)
=3
(c) Lactose is the inducer that inactivates repressor, this allows RNA
polymerase access to the promoter, to initiate transcription of the
natural gene or switch the fan also there.
=1
7
1. Name the enzyme involved in the continuous replication of DNA strand.
Mention the polarity of template strand.
Ans: (DNA dependent) DNA polymerase. 3’ -> 5’ = 1mark
1
8
1. In a series of experiment with Streptococcus and mice F. Griffith concluded
that R- strain bacteria had been transformed. Explain.
Ans: S strain bacteria when injected – mice die; R- mice live; heat killed S –
mice live; heat killed S + live R – mice die; recovered living S from dead mice;
R strain bacteria have been transformed to S strain by the genetic material of
heat killed S strain.
3
9
1. How did Alfred Hershey and Martha Chase arrive at the conclusion that
DNA is the genetic material?
Ans:
5
10
11
= 5marks
1. When and at what end the ‘tailing’ of hnRNA does takes place?
Ans: during conversion of hnRNA into functional mRNA, at 3’ end. = 1marks
1. Explain the dual function of AUG codon. Give the sequence of bases it is
transcribed from and its anticodon.
Ans: Codes for Methonine and is an initiation codon. = 1mark
The sequence of bases from which it is transcribed is TAC. = ½
Its anticodon is UAC. = ½
[1 + ½ + ½ = 2marks]
12
1
2
2
(a ) Name the molecule ‘X’ synthesized by ‘i’ gene. How does this molecule
get inactivated?
(b) Which one of the structural genes codes for β-galactosidase?
(c) When will the transcription of this gene stop?
Ans: (a) Repressor = ½
Lactose (inducer) binds with the repressor molecule. = ½
(b) Z gene. = ½
(c) When all the lactose molecule are consumed/ repressor becomes free to
bind with the operator. = ½
[½+½+½+½ = 2marks]
13
14
15
3
(a) What is the diagram representing?
(b) Name the parts a, b and c.
(c) In the eukaryotes the DNA molecules are organized within the nucleus.
Ans: (a) Nuclesome. = ½
(b) a- histone octamer = ½ ; b- DNA = ½; c- H1 histone. = ½
(c)In a bacteria DNA is nucleoid, is organized in large loops held by
proteins. = 1mark
[½ + ½ + ½ + ½ + 1 = 3marks]
1. What is the satellite genome? Explain their role in DNA fingerprinting.
Ans: DNA sequences which are repeated many times, show a high dergree of
polymorphism and form a bulk of DNA in a genome, called satellite DNA. = 1½
marks
DNA from every tissue from an individual shows the same degree of
polymorphism and is heritable, hence very useful in DNA fingerprinting. 1½
marks
[1½ + 1½ = 3marks]
5. a) Draw a schematic diagram of the structure of a transcription unit and
show the following in it:
(i)
Direction in which the transcription occurs
(ii)
Polarity of the two strands involved
(iii)
Template strand
(iv)
Terminator gene
(b) Mention the function of promoter gene in transcription.
1. (Ans: (a)
3
3
16
17
2marks
(b) Promoter – provides binding site for RNA polymerase/ initiates transcription. =1
marks.
[2+1 = 3marks]
1. (a) In human genome which one of the chromosomes has the most genes and 3
which one has the fewest?
(b) Scientists have identified about 1.4 million single nucleotides
polymorphism in human genome. How is the information of their existence
going to help the scientist?
Ans: (a) Chromosome 1 has most genes and Y has fewest. =1 mark
(b) This information promises to revolutionize the processes of finding chromosomal
locations for disease associated sequence. = 1marks
c) Tracing human history. = 1marks
[1 +1+1 = 3marks]
(a) How did Griffith explain the transformation of R strain (non - virulent) bacteria
5
into S strain (virulent)?
(b) Explain how Macleod, McCarty and Avery determined the biochemical
nature of the molecule responsible for transforming R strain bacteria into S
strain bacteria.
Ans: (a)
= 2marks
(b) They discovered that protein digesting enzymes and RNA digesting enzymes did
not affect transformation so the transforming substance was not a protein or RNA. =
1
Digestion with DNases did inhibit transformation. = 1
They conclude that DNA is the hereditary material/ by purifying the biochemical
using enzymes like proteases, RNases and DNases. = 1
[2+1+1+1= 5marks]
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19
20
21
Study the given portion of double stranded polynucleotide chain carefully. Identify
a, b, c and the 5’ end of the chain.
2
Ans: a = hydrogen bond = ½
b = Adenine/ Thymine = ½
d = 5’ = ½
c = deoxyribose sugar = ½
[½ + ½ + ½ + ½ + ½ = 2marks]
List the salient features of DNA double helix structures.
3
Ans: DNA helix made up of two polynucleotide chains, each constituted by
sugar phosphate bases, the chains are antiparellel in polarity (5’-----.> 3’ and
3’ ….> 5’), the bases are linked with H bonds, adenine pairs with thymine
with two H bonds while guanine pairs with cytosine with three H bonds,
coiling of the chain are in right handed fashion, pitch of the helix is 3.4 nm
and there are 10bps per turn, the plane of one base pair stacks over the other
in a double helix. ( any six) 1/2x6 = 3
How are the structural genes activated in the lac operon in E.coli?
3
Lactose acts as the inducer , binds with repressor protein, frees operator
gene, RNA polymerase freely moves over the structural genes, transcribing
Lac mRNA, which in turn produces the enzyme responsible for digestion of
lactose.= 1/2x6=3
Describe Frederick Griffiths experiment on Streptococcus pneumonia.
5
Discuss the conclusion he arrived at.
Griffith observed two types of streptococcus pneumonia- smooth shiny
colony called Stype virulent with capsule, the other R type rough colony, non
virulent ½+1/2=1
Experiment:
Live S type-- injected into mice- mice died= ½
Live R type-- injected into mice- no infection= ½
Heat killed type- injected into mice - no infection=1/2
Heat killed + live R type- injected into mice- mice died= ½
Griffith concluded that the genetic material of heat killed S type could
transform R type into virulent S type =1/2
He concluded that R strain bacteria had been transformed by the heat killed
S-strain bacteria=1
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2
3
4
(5 marks)
7 EVOLUTION
1. Name the common ancestor of the great apes and man?
(1 mark )
Ans: Dryopithecus/Ramapithecus
1. Branching descent and natural selection are the two key concepts of Darwinian
Theory of
Evolution. Explain each concept with the help of suitable
examples.
Ans: Branching descent
Different species descending from the common ancestor-get adapted in
different habitats = ½ e.g. Darwin’s finches- varieties of finches arose from grain
eaters/ Australian marsupials- evolved
Natural selection:
A process in which heritable Variations enable better survival of a apices to
reproduce in large number=1/2
e.g. White moth surviving before the industrial revolution and black moth surviving
after industrial revolution/Long necked giraffe survived/DDT resistant mosquito
survive(Any suitable example ) = ½+ 1/2 = 1.
1. (a)
How does the Hardy Weinberg’s expression (P2 +2pq+q2 = 1 )
explain that genetic equilibrium is maintained in the population?
(b)
List any two factors that can disturb the genetic equilibrium.
Ans.(a)
Gene frequencies in a population are stable, constant from generation,
until some change in frequency happens, due to some factor= ½ x ¼
(b)
Gene migration/ gene flow/gene drift/mutation/genetic
recombination/natural selection (Any two) = ½ x 2
According to Hardy- Weinberg’s principle the allele frequency of a population
remains constant. How do you interpret the change of frequency of alleles in a
population?
Ans : It indicates gene migration/ gene flow/gene drift/mutation/genetic
recombination/natural selection leading to evolution
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1
2
2
3
(a) Write your observation on the variations seen in the Darwin’s finches shown
above.
(b) How did Darwin explain the existence of different varieties of finches on
Galapagos Islands?
Ans: (a) From the original seed eating features, many other forms with altered
beaks arose, enabling them to become insectivorous and vegetarian finches= ½ x 3
(b) The process of evolution of different species in a given geographical area
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2
3
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starting from one point, and literally radiating to other areas of geography(habitats),
is called adaptive radiation= ½ x3
State the significance of coelacanth in evolution.
Ancestor of ambhibians
=1
Comment on the similarity between the wings of a cockroach and the wing of a
bird. What do you infer from the above, with reference to evolution?
Similar in function/ analogous organs = ½ convergent evolution = 1/2
How does industrial melanism supports Darwin’s theory of natural selection?
Explain.
Before industrial revolution the environment was unpolluted the lichens on the barks
of trees – pale white winged moths could easily camouflage, while the dark winged
were spotted out by the birds for food – hence they could not survive. After
industrial revolution the lichens became dark. This favoured the dark winged moths
while the white winged were picked by birds the population of the former increases (
naturally selected) =1/2x6=3
CHAP 8
HUMAN HEALTH AND DISEASE
List the two types of immunity a human baby is born with. Explain the difference
between the two types.
Ans: Innate immunity and Acquired/ Passive immunity. =1
Innate immunity: Non-specific type of defense, providing barriers to the entry of
antigens. = ½
Acquired immunity: specific type of defense, foetus receiving the antibodies from
the mother through the placenta. = ½
[1+½+½= 2marks]
(a) Name the causative agent of typhoid in human.
(b) Name the test administered to confirm the disease.
(c) How does the pathogen gain the entry into the human body? Write the diagnostic
symptoms and mention the body organ that gets affected in severe cases.
Ans: (a) Salmonella typhi = ½
(b) Widal test = ½
(c) Through contaminated food and water =½
Sustained high fever (300C to 400C), weakness, stomach pain, constipation,
headache, loss of appetite. (any two) = ½+½
Intestine gets affected in severe cases. =½
[½+½½+1+½ = 3marks]
Why is tobacco smoking associated with rise in blood pressure and emphysema?
Explain.
Ans: tobacco has nicotine that stimulates the release of adrenaline/non
adrenaline to raise blood pressure. = 1
Smoking tobacco releases CO which reduces the concentration of haem bound
oxygen. This causes emphysema. = 1
[1+1= 2marks]
Study the diagram showing replication of HIV in humans and answer the following
question:
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1
3
2
3
2
3
5
(i) Write the chemical nature of the coat ‘A’
(ii) Name the enzyme ‘B’ acting on ‘X’ to produce molecular ‘C’.
(iii) Mention the name of the host cell ‘D’ the HIV attacks first when it
enters into the human body.
(iv) Name the two different cells the new viruses ‘E’ subsequently attacks.
Ans: (i) Protein = ½
(ii) ‘B’ –Reverse transcriptase = ½
‘C’ – viral DNA = ½
(iii) D – macrophage = ½
(iv) Macrophage, helper T lymphocyte = ½+½
[½+1+½+1= 3marks]
Define the term ‘health’. Mention any two ways of maintaining it.
(OR)
Why does a doctor administer tetanus antitoxin and not a tetanus vaccine to a child
injured in a roadside accident with a bleeding wound? Explain.
Ans: State of complete physical, mental and social well being. =1
Balance diet, personal hygiene, regular exercise. = ½+½
[1+½+½ = 2marks]
(OR)
Tetanus is a deadly disease requiring a quick immune response, so preformed
antibodies are injected directly. [1+1 = 2marks]
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7
8
9
10
11
12
13
Name the opioid drug and its source plant. How does the drug affect the human
body?
Ans: Heroin (smack)/ morphine = ½
Poppy plant/Papaver somniferum. = ½
Binds with opioid receptor in CNS/ gastro intestinal tract, and slows down the
system/ depressant. =½+½
[½+½+1= 2marks]
Mention the name of the casual organism, symptoms and the mode of transmission
of the disease Amoebiasis.
Ans: Entamoeba histolytica =1
Constipation/abdominal pain/cramps/mucous stool/stool with blood clot. (Any two)
=½+½
Houseflies’ carrier from faeces to person via food products/ contaminated water.
=1[1+1+1= 3marks]
1. Name the type of cells the AIDS virus enters into after getting in the human
body.
Ans: macrophage/ Helper-T-cells. = 1mark]
A boy of 10years had chicken pox. He is not expected to have the same disease for
the rest of his life. Mention how is it possible.
Ans: Antibodies produced during the first infection; result in the memory of the
first encounter to protest the body in future.
[½+½ = 1mark
(a)Name the lymphoid organ in human where all the blood cells are produced.
(b) Where do the lymphocytes produced by the lymphoid organ mentioned
above migrate and how do they affect immunity?
Ans: (a) Bone marrow. =1
(b) Secondary lymphoid organ/spleen/lymph nodes/tonsils/ Payer’s patches of
small intestine/appendix. =½
They trap the microbes/they activate the lymphocytes/they trap the antigens. =½
[1+½+½ = 2marks]
List the specific symptoms of typhoid. Name its causative agent.
Ans: Sustained high fever(300C to 400C), weakness, stomach pain, constipation,
headache, loss of appetite.(any three)= 1½
Causative agent: salmonella typhi = ½
[1½+½ = 2marks]
(a) Why do the symptoms of malaria not appear immediately after the entry of
sporozoites into the human body when bitten by female Anopheles? Explain.
(b) Give the scientific name of the malaria parasite that causes malignant
malaria in human.
Ans: (a) The symptoms of fever appear only when RBCs burst, releasing
haemozoin (along with the multiple no. of the parasite), but prior to this the
parasite has to complete an asexual cycle in liver cells, no symptoms appears in the
infected person between the period the parasite enters the body till RBCs release
haemozoin. =½*4
(b) Plasmodium falciparum =1
[2+1 = 3marks]
Name the type of cells the AIDS virus first enters into after getting inside the human
body. Explain the sequence of events that the virus undergoes within these cells to
increase their progeny.
Ans: Macrophage/ Helper-T-cells, the virus enters the macrophages where RNs
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3
1
1
2
2
3
2
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21
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genome of the virus replicates to form viral DNA, with the help of the enzyme
reverse transcriptase, this viral DNA gets incorporated into host cell’s DNA and
directs the infected cells to provide virus particles. [½*4 = 2marks]
What type of virus causes AIDS? Name its genome material.
Ans: Retrovirus, RNA [½+½ = 1mark]
Name on plant and the addictive drug extracted from the latex. How does this drug
affect the human body?
Ans: Poppy/ Papaver somniferum = ½
Opioids/smacks/heroin/morphine/diacetylmorphine = ½
It is a depressant. = 1
[½+½+1 = 2marks]
a) Write the scientific names of the two species of filarial worms causing filariasis.
(b) How do they affect the body of infected person?
(c) How does the disease spread?
Ans: (a) Wuchereria bancrofti, Wuchereria malayi = ½+½
(b) Inflammation of the lymphatic vessels of the lower limbs/ inflammation of
the genital organs/gross deformities of the lower limbs/deformities of the genital
organs. (Any two) =½+½
(c) Through the bite of female (Culex) mosquito. 1 [1+1+1 = 3marks]
State two different roles of spleen in the human body.
Spleen stores lymphocytes, it filters microbes, acts as a reservoir to store
erythrocytes( any two) ½=1/2=1
Name the group of viruses responsible for causing AIDS in humans. why are these
viruses named so?
a) List any two ways of transmission of HIV infection in humans, other than
sexual contact.
a)retrovirus,( have RNA genome) have reverse transcriptase// carry on
RNA…>DNA ….>RNA =1/2+1/2=1
b)infected blood transfusions, sharing syringes/ needles, children born to
HIV mothers.(any two) = 1/2+1/2=1
Name any two organisms that are responsible for ringworm in humans. mention
two diagnosticsymptoms.name the specific parts of the human body where these
organisms thrive and explain why.
Microsporum/ trichophyton/ epidermophyton = ½
Dry/ scaly lesions on skin/nails/scalp/intence itching (any two) =1/2
Body- groin/ between toes,thrive better in heat/ moisture/perspiration = ½+1/2=1
Trace the life cycle of malarial parasite in the human body when bitten by an
infected female anopheles .
Sporozoites of plasmodium gets into human blood through the bite of female
anopheles mosquito, sporozoites reproduce asexually in liver cells, then they get into
red blood cells, there they reproduce asexually and infect more blood cells, after a
while they change into gametocytes, wait to be picked up by the mosquitoes =
1/2x6=3
Name the plant source of ganja. How does it affect the body of the abuser?
Cannabis sativa/hemp plant =1
Damages cardiovascular system =1
Name the two special types of lymphocytes in humans. How do they differ in their
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3
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2
2
3
2
2
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2
3
4
5
roles in immune response?
B lymphocytes and T lymphocytes =1
B-cells produce pathogen specific antibodies/humoral immune response =1/2
T cells helps the B-cells to produce antibodies responsible for immediate immunity
=1/2
Name the bacterium that causes typhoid. Mention two diagnostic symptoms. How is
the disease transmitted to others?
Salmonella typhi =1/2
Constipation, stomach pain, headache, weakness, loss of appetite, high fever (any
two) = ½+1/2=1the disease is transmitted through contaminated food/water
What is metastasis? Is it fatal? Why?
Cells sloughed off from tumours reach distant sites through blood, and wherever
they get lodged in the body they start a new tumor there,this property is called
metastasis =1/2+1/2,
It is fatal because it causes malignant tumours/cancer =1
CHAP 9 STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION
Write the name of the following
a) The most common species of bees suitable for apiculture.
b) An improved breed of chicken.
a)Apis indica/ Apis mellifera/ Apis dorsata=1/2
b)leghorn/Rhode island red/ Minorca =1/2
What is the programme called that is involved in improving success rate of
production of desired hybrid and herd size of cattle?
b) Explain the method used for carrying this programme for cows.
Ans: multiple ovulation embryo transfer method/MOET =1/2
B) High milk yielding cow administered with FSH …..> 6-8 eggs produced-
inseminated artificially -- fertilized eggs recovered nonsurgically at 32cell stage - transferred to surrogate mother for further growth = 1/2x5=2 1/2
State the use of biodiversity in modern agriculture.
Ans: A source of hybrid, GM plants, biopesticides, organic farming, biofertilisers.
(Any two) = 1 mark
Describe the technology that has successfully increased the herd size of cattle in a
short time to meet the increasing demand of growing human population.
Ans: Multiple ovulation embryo transfer technology (MOET). = ½
Cow is administered with FSH, to induce follicular maturation and super ovulation,
to produce 6 to 8 eggs, mated or artificially inseminated, fertilized eggs recovered
non-surgically, transferred to surrogate mother. = 2½
[½+2½ = 3 marks]
Scientist has succeeded in recovering healthy sugar plants from a diseased one.
(a)
Name the part of the plant used as explants by the scientist.
(b)
Describe the procedure the scientists followed to recover the healthy
plants.
(c)
Name this technology used for crop improvement.
Ans: (a) Meristem (apical, axillary) = ½
(b)Explant/ Virus free meristem is growing in nutrient medium, under
aseptic condition; tissue proliferates to form undifferentiated mass or callus,
transferred to a medium containing auxins and cytokinins. = 2 marks
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2
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3
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3
3
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5
(c) Tissue culture or micro propagation. = ½
[½+2+½ = 3marks]
(a) Mention the property that enables the explants to regenerate into a new plant.
(b) A banana herb is virus infected. Describe the method that will help in
obtaining healthy banana plants from this diseased plant.
Ans: (a) Totipotency. = 1
(b) Extract the disease free meristem, in vitro culture to get virus free plants. 1+1
[1+1+1 = 3 marks]
Mention the strategy used to increase homozygosity in cattle for desired traits.
Ans: Inbreeding. = 1 mark
MOET programme has helped in increasing the herd size of the desired verity of
cattle. List the steps involved in conducting the programme.
Ans: - Cow is administered hormone like FSH, super ovulation. = ½+½
Mated with selected bull or artificially inseminated. =½
Fertilized eggs are recovered and transferred to surrogate mother. = ½
[½+½+½+½ = 2marks]
State the importance of biofortification.
Ans: Breeding of crops for improvement of nutritional quality. = ½
Higher levels of proteins/vitamins/minerals/healthier fats. (Any one) = ½ [½+½ = 1
10-MICROBES IN HUMAN WELFARE
1-Which one of the following is the baker’s yeast used in fermentation?
1.
SaccharumBarberi
2.
Saccharomyces Cerevisiae
3
Sonalika
Ans:-2. Saccharomyces Cerevisiae
Many members of the genus Glomus form mycorrhiza.
a) What are called mycorrhizae?
Ans:-a) Fungal associations with roots of higher plants.
b) What are the other benefits shown by the plants having such association other
than increase in plant growth and development?
Ans:-b)Resistance to root borne pathogens ,tolerance to salinity and drought
Name the genus to which baculo viruses belong. Describe their role in the
integrated pest management program?
Nucleopolyhedrovirus =1
They control only species specific pest, do not affect non target organisms/beneficial
insects are conserved/they aid in IPM problems/ no negative impact on plants or
other animals = 1+1=2
Why are some molecules called bioactive molecules? Give two examples of such
molecules?
Ans:-Microbes/bacteria fungus are used in their production = I
e.g. Citric acid - acetic acid
Butyric acid
- lactic acid
Ethanol
- lipase
Streptokinase
- cyclosporine A(Any two)=1 = 1 =2
Mention the product and its use produced by each of the microbes listed below:
(i) Streptococcus
(ii)Lactobacillus
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2
3
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1
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(iii)Saccharomyces cerevisiae
Ans:(i)Streptokinase, clot buster/dissolves clot
from blood vessels= ½ + ½
(ii)Lactic acid, coagulates milk/partial digestion of milk proteins= ½ + ½
(iii)Ethyl alcohol + CO2, ferments dough to make bread/idli= ½ + ½
Mention the information that the health workers derive by measuring BOD of a
water body.
A measure of organic waste matter present in the water, greater the BOD more is its
polluting potential=1/2+1/2
Mention the role of cyanobacteria as a biofertilizer.
(a biological organism) that fixes atmospheric nitrogen =1
Name the source of cyclosporine-A. How does this bioactive molecule function in
our body?
Trichoderma polysporum =1
Immunosuppressant , used in organs transplant patient = ½+1/2
How does activated sludge get produced during sewage treatment?
b)explain how this sludge is used in biogas production.
Ans:a)when BOD of sewage water is reduced, the effluent passes to settling tank
where, bacterial flocs are allowed to sediment and this sediment is activated
sludge=1/2x3
b) the major part of sludge is pumped into anaerobic sludge digester, here other
anaerobic bacteria digest the flocs,during this digestion biogas is produced=1/2x3
11 PRINCIPLES OF BIOTECHNOLOGY
Q): A recombinant DNA is formed when sticky ends of vector DNA and foreign
DNA join. Explain how the sticky ends are formed and get joined.
Ans: Restriction enzymes cut the DNA sequence a little away from the centre of the
palindrome site but between the same two bases on the opposite strands, leaving
single stranded portions at the ends. These overhanging stretches are called sticky
ends on each strand. They form hydrogen bonds with the complementary cut
counterparts, facilitates the action of ligase enzymes to join the foreign and vector
DNA strands.
Name and explain the techniques used in th separation and isolation of DNA
fragments to be used in recombinant DNA technology
.
Ans: Gel Electrophoresis.=1/2
DNA fragments of the agarose gel are negatively charged molecules
and they
move towards the anode. The separated DNA fragments can be visualised after
staining with ethidium bromide followed by exposure to UV radiation,
Separated fragments are extracted from the gel by elution.=1/2x5=21/2
(A) Name the source of Taq polymerase. Explain the advantage of its use in
biotechnology
(B) Expand the name of the enzyme ADA. Why is this enzyme essential in the
human body? Suggest a gene therapy for its deficiency.
Ans: (A) Thermus aquaticus
It is a thermostable DNA polymerase, does not get denatured and remain active
during PCR.
(B) Adenosine deaminase, this enzyme is essential for immune system to function`,
its deficiency can be cured by gene therapy, lymphocytes from the patients are
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extracted and cultured , functional ADA cDNA are introduced into lymphocyte
using a vector, lymphocytes are returned to the patient.
Q): Biotechnologists refer to Agrobacterium tumefaciens as a
natural genetic engineer of plants. Give reasons to support
the statement.
Ans: Can transfer gene naturally/ Can deliver a piece of TDNA/
has tumour inducing plasmid
What are recombinant proteins? How do bioreactors help
in their production?
Ans: Any protein produced by genetically altered gene in a
host.
Bioreactors can be thought of as vessels in which raw
biologically converted into specific products./ A
bioreactor provides the optimal conditions for achieving
the desired product by providing optimum growth
conditions.
): If a desired gene is identified in an organism for some
experiments, explain the process of the following:
(I) Cutting this desired gene at specific location.
Ans:
- Identifying the restriction nuclease that recognises the
palindromic nucleotide sequence of the desired gene.
- The restriction endonuclease inspects the DNA
sequences- finds and recognises the site.
- Cuts of the double helix at the specific point- a little
away from the centre of the palindromic site- between
the same two bases on the opposite strand.
- Makes the overhanging stretch single stranded portion
as a sticky end. 2
(II) Synthesis of multiple copies of this desired gene.
Ans:
- By PCR/ Polymerase Chain Reaction.
- Desired gene is synthesised in vitro.
- DNA is denatured.
- Annealed using two sets of primers.
- Thermostable Taq polymerasa extends the primers
using nucleotides.
- Amplified fragments are ligated. 3
(I) Mention the number of primers required in each cycle of polymerase chain
reaction(PCR). Write the role of primers and DNA polymerase in PCR.
(II) Give the characteristic feature and source organism
of the DNA polymerase used in PCR.
Ans:
(I) 2 sets of primers.
DNA polymerisation/extends the primers using the
nucleotides.
(II) Thermostable/ remain active during high temp.
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induced denaturation of DNA.
Thermus aquaticus.
(I) Describe the characteristics a cloning vector must possesss.
Ans:
- Should have ori/ origin of relication.1/2
- Has selectable marker, genes encoding for an
antibiotic resistance/ genes encoding for alphagalactosidase.1
- Has cloning site/ recognition site, for the
restriction enzyme to recognise. 1
ii)Why DNA cannot pass through the cell membrane?
Explain. How is a bacterial cell made ‘competent’ to
take up recombinant DNA from the medium?
Ans: DNA is a hydrophilic molecule.1
Bacterial cell is made competent by treating with
specific concentration of ca ion/divalent ions
incubating them on ice heat shock for a short
period and placing it back on ice again.1 1/2
A recombinant vector with a gene of interest inserted within the gene of α
galactosidase enzyme, is introduced into a bacterium.explain the method that would
help in selection of recombinant colonies from non-recombinant ones
b) Why is this method of selection referred to as insertional inactivation?
Ans: bacteria is grown in a medium with chromogenic substrate, colonies
formed show blue colour – no recombinants =1/2x3=1 ½
b)gene for the enzyme is inactivated by insertion = 1/2
How is the amplification of a gene sample of interest carried out using PCR
polymerase chain reaction?
ds DNA is denatured at high temperature to unzip them, annealing using two sets of
primers, amplification in the direction of 5’--3’ using Taq polymerase. this
enzyme is thermo stable, 1 billion times amplified in 30 cycles =1/2x6=3
labeled illustration to be evaluated in lieu of the explanation 1/2x6=3
Chap 12 BIOTECHNOLOGY AND ITS APPLICATIONS
a) Mention the cause and body system affected by ADA deficiency in humans.
b) Name the vector used for transferring ADA-DNA into the recipient cells in
humans. Name the recipient cells.
a) defective gene into producing ADA, immune system is affected =1/2+1/2
b) a retroviral vector is used, recipient cells are lymphocytes = ½+1/2
a) Tobacco plants are damaged severely when infested with Meloidegyne
incognitia.name and explain the strategy that is adapted to stop this infestation.
b) Name the vector used for introducing the nematode specific gene in tobacco plant.
a)nematode specific gene introduced into host plant, produced ds RNA, RNAi
initiated, specific mRNA of the nematode silenced and parasite dies. =1/2x4=2
b)Agrobacterium tumefaciens =1
Chap 13 ORGANISM AND POPULATIONS
Explain brood parasitism with the help of an example.
Koel is a parasitic bird has evolved the technique of laying eggsin the nest of a crow
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=1, its eggs bear resemblences to those of crow =1+1=2
a) List any three ways of measuring population density of a habitat.
b) Mention the essential information that can be obtained by studying the population
density of an organism.
a) by physical counting, percent cover or total biomass, from relative density,
counting pug marks, counting faecal pellets (any three) 1/2x3
b) Status of habitat, whether competition for survival exists or not, whether
population is increasing or declining, natality, mortality, emigration, immigration.
The following graph represents the organismic response to certain environmental
condition (e.g. temperature)
Which one of these,’ a’ or ‘b’ depicts conformers?
What does the other line graph depict?
How do these organisms differ from each other with reference to homeostasis?
Mention the category to which humans belong.
Ans: i) a = conformers = ½
ii)response of the regulators =1/2
iii)maintain homeostasis by physiological means, others either migrate, or suspend
activities = 1/2x3
iv)regulators =1/2
Water is very essential for life. write any three features both for plants and animals
which enable them to survive in water scarce environment
Ans:plants: ephemeral mode(complete life cycle in short period)/deep tap
roots/deciduous leaves/waxy cuticle/sunken stomata/ succulence to store water/C4
pathway of photosynthesis(any three)= 1/2x3
Animals:no sweating/uricotelic/deposition of fat in sub epidermal layer/burrowing
nature/thick skin/body covered with scales (any three) 1/2x3=11/2
How do organisms cope with stressful external environmental conditions which are
localized or short duration?
Migrate temporarily from the stressful habitat to a hospitable area/ suspended
activities/form thick walled spores/form dormant seeds/hibernate during
winter/aestivate during summer/planktons diapauses (any six)=1/2x6=3
Chap 14
ECOSYSTEM
3
3
3
3
1
2
3
Name the pioneer and the climax species in a water body. Mention the changes
observed in the biomass and the biodiversity of the successive seral communities
developing in the water body.
Ans : pioneer species; phytoplanktons =1/2
Climax species; forest/trees = ½
There will be gradual increase in the biomass = ½
Free floating angiosperms/ rooted hydrophytes/sedges/grasses=1/2
Construct a pyramid of biomass starting with phytoplankton. Label three trophic
levels. Is the pyramid upright or inverted? Why?
fish/crustaceans/other=1/2
zooplanktons
=1/2
phytoplanktons
=1/2
the pyramid of biomass is generally inverted, because the biomass of fishes, and
other aqutic animals far exceeds that of phytoplanktons =1/2x3
Write a difference between net primary productivity and gross productivity.
Gross productivity – rate of production of organic matter during photosynthesis = ½
Net primary productivity – available biomass for the consumption to heterotrophs/
GPP-R=NPP=1/2
4
2
3
1
2
Identify the type of the given ecological pyramid and give one example each of
pyramid of number and pyramid of biomass in each cases.
Ans: inverted pyramid =1
Inverted pyramid of biomass in a lake – phytoplankton--- zooplankton-- fish1/2
Inverted pyramid of number – tree-- insects -- birds = 1/2
5
1
2
List the features that make a stable biological community.
Should not show too much variations in productivity from year to year
Must be either resistant or resilient to occasional disturbance( natural/man made)
Must also be resistant to invasion by alien species.(any two)1+1
Chap 15 BIODIVERSITY AND CONSERVATION
Alien species are highly invasive & are a threat to indigenous species. Substantiate
this statement with 3 examples.
Nile perch introduced into lake Victoria in east Africa led to the extinction of cichlid
fish.
Parthenium/lantana/Eichhornia invasive plants & poses a threat to indigenous
species.
Introduction of African catfish aquaculture is threat to Indian catfishes.
(any three) = 1x3=3
Taking one example of each of habitat loss & fragmentation, explain how the two
are responsible for biodiversity loss.
2
3
3
3
b) Explain two different ways of biodiversity conservation.
a)habitat loss: amazon rain forest destroyed for soyabean cultivation/ for growing
grass land for grazing cattle/ colonization of pacific islands – extinction of 2000
species of native birds =1
fragmentation: b human activity – migratory birds & animals are affected.
b)exsitu:1/2 threatened organisms are taken out from the natural habitat and placed
in special setting with care and protected =1/2 eg: zoological park/ botanical garden
=1/2
insitu: ½ , threatened organisms are conserved in their natural habitat = ½, eg.
national parks/ biosphere reserves = 1/2
Name the unlabeled areas ‘a’ and ‘b’ of the pie chart representing the biodiversity of
plants showing their proportionate number of species of major taxa.
1
A= fungi, b = angiosperm=1/2+1/2
4
5
6
7
State the biodiversity in modern agriculture.
A source of hybrids, GM plants, biopesticides, organic farming, bio fertilizer,
improved varieties of plants, disease resistance plants or any other relevant use.(any
two)
2
1
The above graph shows species – area relationship.write the equation of the curve
‘a’ and explains.
Ans: S=CAZ=1
I)
within the region, species richness increases with increasing explored
area but only upto a limit = ½
II)
relationship between species richness and area for a wide variety of taxa
turns out to be rectangular hyperbola =1/2
Differentiate between in situ and ex situ approaches of conservation of biodiversity.
In situ
ex situ
Protection of endangered species – protection of exdangered species by removing
Of plants and animals =1/2
them from the natural habitat=1/2
by protecting the natural habitat/
by placing under special care =1/2
ecosystem=1/2
India has more than 50000 strains of rice. mention the level of biodiversity it
represents.
1
1
2
3
4
5
6
7
Genetic biodiversity
Chap 16
ENVIRONMENTAL ISSUES
Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters?
Lead in petrol inactivates the catalyst, harmful pollutants are converted to lesser
harmful pollutants (Co2, H2O) =1/2+1/2=1
How did Ahmed khan, plastic manufacturer from Bangalore, solve the ever
increasing problem of accumulating plastic waste?
Collected waste plastics- recycled- powdered to form polyblend, blended with
bitumen, used in road laying, increased road life by a factor of three/ more durable =
1/2x4=2
a) What depletes ozone in stratosphere? How does it affect human life?
b) Explain biomagnifications of DDT in an aquatic food chain. How does it affect
the bird population?
a)chlorofluorocarbons (CFCs)
=1
UV (B) damages DNA causing mutation, skin cancer, inflammation of cornea,
cataract, aging of skin, snow blindness
2
(any two)
½+1/2=1
b)if DDT leaches from the agricultural field gets into the water body, it gets into the
food chain-- zoo planktons -- small fish -- large fish -- any fish eating bird//
concentration of DDT increases, along the food chain, reaching a high level in the
top carnivore bird=
11/2
DDT concentration disturbs ca++ metabolism- egg shells become thin ---
premature breaking resulting in decline in bird population
11/2
Explain the cause of algal bloom in water body. How does it affect an ecosystem?
Effluents from home/industries/chemical fertilizers/agriculture/sewage,bring or add
nutrients to the water body which enhances algal growth = ½+1/2
Effects – reduces oxygen content/BOD increases, deterioration of water quality,
affects all aquatic life forms, toxicity of water increases (any two0=1/2+1/2
Explain any three measures which will control vehicular air pollution in Indian
cities.
Use of CNG as the fuel, use of unleaded petrol, low sulphur petrol/ diesel, use of
catalytic converter in the vehicles, phasing out of old vehicles(any three) = 1x3
Ornithologists observed decline in the bird population in an area near a lake after the
setting of an industrial unit in the same area. Explain the cause responsible for the
decline observed.
Toxicants like DDT entered the trophic levels of the food chain, accumulated as it
can neither be metabolized nor be excreted, toxicants disturb Ca metabolism, result
in thinning of egg shells, premature breaking of eggs, population declined=1/2x6=3
Particulate and gaseous pollutants along with harmless gases are released from the
thermal power plants.
i)name any two harmless gases released.
ii)name the most widely used device of removing particulate pollutants from the air
Explain how the device is used.
Ans:i)niyrogen,oxygen = ½+1/2
ii)electrostatic precipitator = ½
electrode wires at several thousand volts produce corona
1
2
5
2
3
3
3
release electrons attach dust particles & make it negatively charge =1/2
8
9
10
collected plates grounded & attract charged dust particles =1/2
How do algal blooms affect the life in water bodies?
Ans: pollutes water/deterioration of the water quality/oxygen depletion/water
becomes toxic/BOD increases =1/2
Fish mortality/death of aquatic organism=1/2
i) State the consequence if the electrostatic precipitator of a thermal plant fails to
function.
ii) Mention any four methods by which the vehicular air pollution can be controlled.
i)Particulate matter will pollute the air=1
ii) use of CNG/phasing out of old vehicles/use of unleaded petrol/use of low sulphur
fuel/use of catalytic converters/application of stringent pollution level norms (any
four) 1+2=3
How is snow blindness caused in humans?
High dose of UV-B radiation, inflammation of cornea=1/2+1/2
3
1
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