ZOOM INTERNATIONAL SCHOOL

(Senior Secondary : Affiliated to CBSE, Delhi)

QUESTION BANK (Term I)
(Session: – 2024-2025)
Class: – XII
Subject: – Biology (Code: –044)

SECTION–A
Multiple Choice Questions (MCQs): (1 mark each)
1. The coconut water from tender coconut is
a) cellular endosperm.
b) free nuclear endosperm.
c) both cellular and nuclear endosperm.
d) free nuclear embryo.
2. Which of the following statements are true related to Seed X and Y?

(i) Seed X is dicot and endospermic or albuminous.

(ii) Seed X is dicot and non-endospermic or non-albuminous.
(iii) Seed Y is monocot and endospermic or albuminous.
(iv) Seed Y is monocot and non-endospermic or non-albuminous.
Choose the correct option with the respect to the nature of the seed
a) (i), (iii)
b) (ii), (iii)
c) (i), (iv)
d) (ii), (iv)
3. During the development of embryo, which of the following occurs first?
a) Differentiation of organ b) Differentiation of tissue
c) Differentiation of organ system d) Differentiation of cells

4. ―Cleistogamous flowers are invariably autogamous‖, because –

a) These flowers do not open at all.
b) There is no chance of cross – pollen landing on the stigma.
c) These flowers have exposed anthers and stigma.
d) These flowers are wind pollinated.
5. In the figure of anatropous ovule given below, choose the correct option for the characteristic
distribution of cells within the typical embryo sac

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 Number of cells at chalazal Number of cells at Number of nuclei left in
end micropylar end central cell
a) 3 2 3
b) 3 3 2
c) 2 3 3
d) 2 2 4

6. Mature Graafian follicle is generally present in the ovary of a healthy human female around:
a) 5 – 8 days of the menstrual cycle b) 11 – 17 days of the menstrual cycle
c) 18 – 23 days of the menstrual cycle d) 24 – 28 days of the menstrual cycle

7. What would happen if corpus luteum is not degenerated

a) Progesterone will not be secreted
b) Endometrium will disintegrate
c) Proliferation of endometrium will take place
d) Ovulation will take place

8. Seminal plasma, the fluid part of semen, is contributed by.

i. Seminal vesicle ii. Prostate gland
iii. Urethra iv. Bulbourethral gland
a) i and ii b) i, ii and iv
c) ii, iii and iv d) i and iv

9. Figure A shows the front view of the human female reproductive system and Figure B
shows the development of a fertilized human egg cell
Figure A Figure B

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Identify the correct stage of development of human embryo (Figure B) that takes place at the site
X, Y and Z respectively in the human female reproductive system (Figure A).
Choose the correct option from the table below:

X Y Z
a) Morula Fertilized egg Blastocyst
b) Underutilized egg Fertilized egg Morula
c) Blastocyst Fertilized egg Unfertilized egg
d) Fertilized egg Morula Blastocyst

10. The correct sequence of hormone secretion from beginning of menstruation is

a) FSH, progesterone, estrogen.
b) estrogen, FSH, progesterone.
c) FSH, estrogen, progesterone.
d) estrogen, progesterone, FSH

11. During parturition, a pregnant woman is having prolonged labour pains and child birth has to
be fastened. It is advisable to administer a hormone that can
a) increase the metabolic rate.
b) release glucose in the blood.
c) stimulate the ovary.
d) activate smooth muscles.

12. A female undergoing IVF treatment has blocked fallopian tubes. The technique by which the
embryo with more than 8 blastomeres will be transferred into the female for further
development is
a) ZIFT
b) GIFT
c) IUT
d) AI

13. An IUD recommended to promote the cervix hostility to the sperms is:
a) CuT b) Multiload 375
c) LNG-20 d) Cu 7

14. Which of the following statements is correct

a) Surgical methods of contraception do not prevent gamete formation
b) In E.T techniques, embryos are always transferred into the uterus
c) Oral pills are very popular contraceptives among the rural women
d) All STDs are not completely curable.

15. The mode of action of the copper ions in an IUD is to

a) increase the movement of sperms.
b) decrease the movement of the sperms.
c) make the uterus unsuitable for implantation.
d) make the cervix hostile to the sperms.

16. In Antirrhinum, RR is phenotypically red flowers, rr is white and Rr is pink. Select the correct
phenotypic ratio in F1 generation when a cross is performed between RR X Rr:
a) 1 red: 2 Pink: 1 white
b) 2 Pink: 1 white
c) 2 Red: 2 Pink
d) All Pink

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17. What is the pattern of inheritance in the above pedigree chart?

a) Autosomal dominant
b) Autosomal recessive
c) Sex -linked dominant
d) Sex -linked recessive

18. Choose the chromosome in humans that possesses least number of genes.
a) 21 b) Autosome c) X-chromosome d) Y-chromosome

19. Rajesh and Mahesh have defective haemoglobin due to genetic disorders. Rajesh has too
few globin molecules while Mahesh has incorrectly functioning globin molecules.Identify the
disorder they are suffering from.

a) A
b) B
c) C
d) D

20. A cross is made between tall pea plants having green pods and dwarf pea plants having
yellow pods. In the F2 generation, out of 80 plants how many are likely to be tallplants?
a) 15
b) 20
c) 45
d) 60

21. If Meselson and Stahl's experiment is continued for sixth generations in bacteria, the ratio of
Heavy strands 15N/15N : Hybrid15N/14N : light 14N/14N containing DNA in the sixth
generation would be
a) 1:1:1
b) 0:1:7
c) 0:1:15
d) 0:1:31

22. Two important RNA processing events lead to specialized end sequences in most human
mRNAs: ____(i)____ at the 5‘ end, and ____(ii)____ at the 3‘ end. At the 5‘end the most
distinctive specialized end nucleotide, ____(iii)____ is added and a sequence of about 200
____(iv)____ is added to the 3‘ end.
a) (i) Initiator codon (ii) Promotor (iii) Terminator codon (iv) Release factors
b) (i). Promotor (ii) Elongation (iii) Regulation (iv) Termination.
c) (i) Capping (ii) Polyadenylation (iii) mGppp (iv) Poly(A).
d) (i) Repressor (ii) Co repressor (iii) Operon (iv) sRelease factors
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23. AUG on the mRNA will result in the activation of which of the following tRNA having correct
combination of amino acids:

Site A Site B
a) UAC Methionine
b) Methionine UAC
c) Methionine AUG
d) AUG Methionine

24. The correct feature of double helical structure of DNA as given by Watson and Crick is:
a) Right-handed helix, pitch is 3.4 nm b) Left-handed helix, pitch is 3.8nm
c) Right-handed helix, pitch is 3.8nm d) Left-handed helix, pitch is 3.4 nm

25. Select the incorrect pair:

a) Polygenic inheritance: Haemophilia b) Linkage: Drosophila
c) Incomplete dominance: Antirrhinum d) Pleiotropy: Phenylketonuria

26. Observe structures A and B given below. Which of the following statements are correct?

a) A is having 2'-OH group which makes it less reactive and structurally stable, whereas B is
having 2'-H group which makes it more reactive and unstable.
b) A is having 2'-OH group which makes it more reactive and structurally unstable,
whereas B is having 2'-H group which makes it less reactive and structurally stable.
c) A and B both have -OH groups which make it more reactive and structurally stable.
d) A and B both are having -OH groups which make it less reactive and structurally stable.

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27. There was a mix-up at the hospital after a fire accident in the nursery division. Which of these
children belong to the parents?

a) All of the children b) Children 2, 3 & 6

c) Children 1 & 3 d) Children 2 & 4

28. A person with sickle cell anaemia is

a) More prone to malaria b) More prone to typhoid
c) Less prone to malaria d) Less prone to typhoid

29. The substance produced by a cell in viral infection that can protect other cells from further
infection is
a) Serotonin b) Colostrum
c) Interferon d) Histamine

30. Which scientist proposed the concept of the inheritance of acquired traits?
a) Charles Darwin b) Jean-Baptiste Lamarck
c) Gregor Mendel d) Alfred Russel Wallace

31. The term ―homologous structures‖ refers to structures that:

a) Have similar functions but different evolutionary origins.
b) Have similar structures but different functions.
c) Have both similar structures and functions.
d) Have neither similar structures nor functions.

32. The theory of evolution supported by the experiment conducted by Louis Pasteur is
a) Spontaneous generation theory
b) Life comes only from pre-existing life
c) Abiogenesis of life
d) Big bang theory

33. The idea that evolution occurs in small, incremental steps over long periods of time is known
as:
a) Gradualism
b) Punctuated equilibrium
c) Speciation
d) Adaptive radiation

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34. According to the Hardy-Weinberg principle, the frequency of alleles in a population will
remain constant if:
a) Mutation occurs at a high rate.
b) Genetic drift is absent.
c) Natural selection is intense.
d) Gene flow is restricted.

35. The immune response that occurs immediately upon exposure to an antigen is called:
a) Cell-mediated immunity
b) Active immunity
c) Passive immunity
d) Innate immunity

36. The transmission of a disease from an infected mother to her unborn child is called:
a) Vertical transmission
b) Horizontal transmission
c) Zoonotic transmission
d) Mechanical transmission

Assertion Reasoning type questions: (1 mark each)

Question No. 1 to 14 consist of two statements – Assertion (A) and Reason (R).
Answer these questions selecting the appropriate option given below:
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true and R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.
1) Assertion: Parturition is induced by a complex neuro endocrine meachanism.
Reason: At the end of gestation period, the maternal pituitary releases prolactin which
causes uterine contractions.
Ans. c)

2) Assertion: When the two genes in a dihybrid cross are situated on the same chromosome,
the proportion of parental gene combinations is much higher than non-parental type.
Reason: Higher parental gene combinations can be attributed to crossing over between two
genes.
Ans. c)

3) Assertion: Megaspore mother cell undergoes meiosis to produce four megaspores.

Reason: Megaspore mother cell and megaspore are both haploid.
Ans. c)

4) Assertion: The region outside the seminiferous tubule is called interstitial spaces, which
contain Leydig‘s cells.
Reason: Leydig‘s cells synthesise and secrete testicular hormones called androgen.
Ans. b)

5) Assertion: Very often persons suffering from STDs do not go for timely detection and proper
treatment.
Reason: Absence or less significant symptoms in the early stages of STDs and the social
stigma attached to the disease.
Ans. a)

6) Assertion: Lactational amenorrhea is the natural method of contraception.

Reason: It increases the phagocytosis of sperm.
Ans.c)

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7) Assertion: Saheli, an oral contraceptive for females, contains a steroidal preparation.
Reason: It is a ―once a week‖ pill with very few side effects.
Ans.d)

8) Assertion: ZIFT is practised where oviducts are normal.

Reason: ET is practised in case of blockage of oviducts.
Ans. b)

9) Assertion: Accumulation of phenylalanine in the brain results in the mental retardation in

phenylketonuria.
Reason: The affected person lacks phenylalanine which is therefore not converted to
tyrosine.
Ans. c)

10) Assertion: Primary transcripts in eukaryotes are non-functional.

Reason: Methyl guanosine triphosphate is attached to 5′-end of mRNA.
Ans. b)

11) Assertion: An organism with lethal mutation may not even develop beyond the zygote stage.
Reason: All types of gene mutations are not lethal.
Ans. b)

12) Assertion: Ganja is obtained from Cannabis sativa/ hemp plant.

Reason: It is hallucinogenic, alters perception, causes illusion, and damages cardiovascular
system.
Ans. b)

SECTION–B
Short Answer (SA) type questions: (2 marks each)
1. How many pollen grains and ovules are likely to be formed in the anther and the ovary of an
angiosperm bearing 25 microspore mother cells and 25 megaspore mother cells
respectively?
Ans. Since each microspore, mother cell gives rise to a tetrad containing 4 pollen grains each
therefore 25 microspore mother cells will give 100 pollen grains. Each megaspore mother cell
gives rise to a single megaspore which on development becomes ovule therefore 25
megaspore mother cells will give 25 ovules.
2. Gynoecium of a flower may be apocarpous or syncarpous. Explain the difference in ovary
with the help of an example each.
Ans.
a. Carpels are fused (syncarpous), e.g.: Papaver.
b. Carpels are free (apocarpous), e.g.: Michelia.

(a) (b)

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The gynoecium of Papaver is multicarpellary and syncarpous (pistils are fused together); the ovary
can be unilocular to multilocular. The gynoecium of Michelia is multicarpellary and apocarpus
(pistils are free) and the ovary are always unilocular.
3. Study the transverse section of human ovary given below and answer the questions that
follow:

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 hormone produced by D.

Ans. a) FSH and LH.

b) Estrogen.
c) Maintenance of uterine endometrium.

4. Explain the role of two accessory glands in human male reproductive system.

Ans. Male accessory glands produce seminal plasma. It helps in motility of sperms. They also
secrete fluid that enters the urethra. They contribute to the production of semen and provide
sperms to immobile sperms and help in their movement.
5. a) Mention the problems that are taken care of by Reproduction and Child Health Care
programme.
b) What is amniocentesis and why there is a statutory ban on it? follow copy
Ans. a) Uncontrolled population growth, social evils like sex abuse, sex related crimes, STDs.
b) Foetal sex determination tests based on chromosomal pattern in the amniotic fluid, to study
chromosomal abnormalities in the foetus banned to illegally check female foeticide.

6. What happens when chromatids fail to segregate during cell division cycle? Explain your
answer with an example.
Ans. Failure of segregation of chromatids during cell division cycle results in the gain or loss of
chromosome called aneuploidy- Down‘s syndrome results in the gain or extra copy of
chromosome 21 or Turner‘s syndrome results due to loss of one of the X- chromosomes in
human female.
7. Sickle cell anaemia in humans is a result of point mutation. Explain.
Ans. Point mutation is a genetic mutation in which a single nucleotide base is changed, inserted or
deleted from a sequence of DNA or RNA. In sickle-cell anaemia single point mutation occurs.
This point mutation occurs in the beta-haemoglobin gene. It converts a GAG codon (sixth
codon) into GUG codon which encodes the amino acid valine rather than glutamic acid.
8. Name the scientists and write how did they explain Mendel‘s laws after the chromosomes
were discovered?
Ans. Walter Sutton and Theodore Boveri proposed the chromosomal theory of inheritance. This
theory states that individual genes are found at specific locations on chromosomes, and that

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 the behaviour of chromosomes during meiosis can explain why genes are inherited
according to Mendel's laws.

9. Mention the role of histone proteins in packaging of DNA to form the structure of Chromatin
fibre.
Ans. Histones are positively charged proteins rich in basic amino acids such as lysine and
arginine.
 Role of histones in DNA packaging to form Chromatin fibre :
8 histone protein units form histone octamer. DNA is negatively charged and wraps around
positively charged histone octamer to stabilise the charge.
DNA wrapper around the histone octamer forms a nucleosome. Nucleosomes on DNA form a
‗beads on string‘ appearance, where the nucleosome forms the beads and the linker DNA is
seen as the string. This nucleosome further condenses to attain a higher order structure
called chromatin fibre.

10. A small stretch of DNA that codes for a polypeptide is given below
3‘--- --- --- --- CAT CAT AGA TGA AAC--- --- --- --- 5‘

a) Which type of mutation could have occurred in each type resulting in the following mistakes
during replication of the above original sequence?

i. 3‘… … … …CAT CAT AGA TGA ATC… … …5‘

ii. 3‘… … … …CAT ATA GAT GAA AC… … … 5‘
b) How many amino acids will be translated in each of the above two cases?
Ans. a) i. Point mutation/ single base substitution
ii. point mutation/ single base deletion
b) i. 4 amino acids ii. 4 amino acids

11. With the help of an algebraic expression, how did Hardy-Weinberg explain that in each
population the frequency of occurrence of alleles of a gene is supposed to remain the same
through generation.

Ans. Hardy-Weinberg equation states that the frequency of occurrence of alleles of a gene is
constant. The gene pool remains constant. The total sum of allelic frequencies is 1.

Let the individual frequencies be p, q of alleles A and a respectively.

Then the frequency of AA is square of p. Similarly, for aa it is square of q and for Aa it is 2pq.
Hence p2 + 2pq + q2 = 1. It is the binomial expansion for (p+q)2 = 1. Any change in this
equation signifies evolution.

12. How does Darwin‘s finches illustrate adaptive radiation?

Ans. According to Darwin's observation, it was found there were many verieties of finches on the
same island. From the original seed-eating features, many forms with altered beaks arose,
enabling then to become insectivorous and vegetarian finches . This process of evolution of
different species in a given geographical area starting from a point and literally radiating to
other areaes of geography is called adaptive radiation.

13. Differentiate between -

(a) Benign and Malignant tumors
(b) Viral oncogenes and proto-oncogenes

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Ans.
(a)

BENIGN TUMOR MALIGNANT TUMOR

A slow growing, self-contained tumor that is A usually fast growing, often fatal tumor that
not seriously harmful. invades surrounding tissue and sheds cells that
spread throughout the body, creating new tumor.
Fibroid in the uterus, lipomas in skin Lung cancer, breast cancer

(b)
VIRAL ONCOGENES PROTO-ONCOGENES
Viral oncogenes are derived from the Proto-oncogenes oncogenes are normal genes
genetic material of certain cancer-causing (cellular oncogenes) present in the genome of all
viruses, such as retroviruses. These cells. They play essential roles in regulating cell
viruses can insert their genetic material growth, division, and differentiation. When these
into the host cell's DNA, including genes genes are mutated or abnormally activated, they
that promote cell growth and division. can become oncogenes and contribute to cancer
development.

14. Differentiate between opioids and cannabinoids based on them

a) Specific receptor site in human body.
b) Mode of action in human body.

Ans.
Opioids Cannabinoids
Specific receptor site in Receptors of opioids are Receptors are in the brain only.
human body. in the GI tract and CNS.

Mode of action in human Act as depressant and Affects the cardiovascular

body. slows down the body system of the body.
functions.

15. List two diseases that spread through inhaling droplets or aerosols. Write one prominent
symptom for each one of them.

Ans. Diseases that spread through inhaling droplets or aerosols are Diphtheria and common cold.
Symptoms of Diphtheria- Sore throat and swollen lymph nodes.
Symptoms of common cold- Nasal congestion and sneezing.

SECTION–C
Long Answer (LA-I) type questions: (3 marks each)
1. The embryo sac in female gametophyte is seven celled and eight nucleated structure. Justify
the statement with the help of a labelled diagram.

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Ans.

Female gametophyte

2. Apomixis mimics sexual reproduction, do you agree? Justify your answer. Also state how
does apomixis differ from polyembryony.
Ans. Apomixis (Apo- without, mixis- fusion) is a mode of reproduction in some plants which results
in the formation of seeds without genetic fusion. So, apomixis is a form of asexual
reproduction that mimics sexual reproduction and produces seeds without fertilisation.

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3. Explain double fertilization in an angiosperm.
Ans. It is a characteristic feature of flowering plants.
In this process, out of the two sperm nuclei, one
sperm nucleus fuses with the egg nucleus to
form an embryo (syngamy) and other fuses with
the secondary nucleus to form an endosperm
(triple fusion). Because two kinds of fusion-
syngamy and triple fusion- take place, the
process is known as double fertilization.

4. Explain three different modes of pollination that occur in a chasmogamous flower.

Ans.
(i) Autogamy- It is a type of self-pollination where the transfer of pollen grains from the
anther to the stigma takes place within the same flower
(ii) Geitonogamy- Geitonogamy is the type of self-pollinations where the transfer of pollen
grains from the anther to the stigma takes place between different flowers in the same
plant.
(iii) Xenogamy-Xenogamy is the cross-pollination where the pollen grain transfer occurs
across the flowers of two different plants. In other words, the transfer of pollen from the
anther of one plant to the stigma of another plant.

5. Draw a labelled diagram to show interrelationship of four

necessary ducts in a human male reproductive system.

Ans. The male accessory ducts (vasa efferentia, epididymis, vas

deferens, and rete testis) serve to store spermatozoa and to
transport them outside urethra during ejaculation.

6. Explain the events in a normal woman during her menstrual cycle on the following days:
a) Pituitary hormone levels from 8 to 12 days.
b) Uterine events from 13 to 15 days.
c) Ovarian events from 16 to 23 days.

Ans. a) FSH and LH levels- low.

b) Endometrium is highly vascularised, proliferative phase of uterine lining.
c) Formation of corpus luteum, secretion of progesterone.

7. Name the stage of the human embryo at which it gets implanted. Explain the process of
implantation.

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Ans. The embryo gets implanted at blastocyst stage. The trophoblast gets attached to the
endometrium uterine wall of mother by a process called implantation.

8. What are STDs? State 3 symptoms of STDs? Give two simple principles to prevent
infections.
Ans. According to the Centers for Disease Control and Prevention (CDC), sexually transmitted
diseases (STDs) are which get transmitted from one person to another through sexual
intercourse.
 Redness, intense itching, pain or swelling near the vagina, penis or anus
 Vaginal discharge with a bad odor or that is a different amount or color than your usual
discharge
 Painful sex

The risks of STDs can be reduced through the following methods:

 Use condoms: During sexual intercourse use of male or female condoms is highly effective
in reducing STD transmission.
 Have fewer sexual partners: Before you have sex with a new partner, get tested together
and share your results.
9.
a) Explain the mode of action of Cu++ releasing IUDs as a good contraceptive. How is
hormone releasing IUD different from it?
b) Why is ‗Saheli‘ a preferred contraceptive by women (any two reasons)?

Ans.
a) The copper IUD‘s primary mechanism of action is to prevent fertilization. Copper acts as a
spermicide within the uterus. The presence of copper increases the levels of copper ions,
prostaglandins, and white blood cells within the uterine and tubal fluids.
Intra-Uterine Device is inserted by doctors or expert nurses in the uterus through the
vagina. These Intra Uterine Devices are presently available as the non-mediated IUDs,
copper-releasing IUDs (CuT) and the hormone-releasing IUDs. IUDs increase phagocytosis
of sperms within the uterus and the Cu ions released suppress sperm motility and the
fertilizing capacity of sperms.
The hormone-releasing IUDs, in addition, make the uterus unsuitable for implantation and
the cervix hostile to sperms.

b)
i. The use of ―Saheli‖ pills inhibits the processes of ovulation as well as implantation.
ii. Women can prevent an untimely or unplanned pregnancy when they use these pills.

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10. A true-breeching homozygous pea plant with green pods and axial flowers as dominant
characters, is crossed with recessive homozygous pea plant having yellow pods and terminal
flowers. Work out the cross up to F2 generation giving the phenotypic ratios of F1 and F2
generations respectively.

Ans.

11. Why males are heterogametic? Can there be female heterogamety. Give example if any.
Ans. In humans, males are referred to as heterogametic because they have an X and a Y sex
chromosome. Whereas, females comprise of two X chromosomes and are hence referred to
be homogametic.

In case of birds, two different types of gametes are produced by females, i.e., female
heterogamety. In these organisms, the females have one Z and one W chromosome,
whereas males have a pair of Z-chromosomes besides the autosomes.

12. When Morgan conducted dihybrid cross on Drosophila like Mendel did with pea plants, the
ratios deviated significantly from that Mendel‘s F2 ratio. Write the explanation, Morgan and
his group gave to the observations they obtained from their experiment.

Ans. When two genes in a dihybrid cross were located on the same chromosome they did not
segregate independently.

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 When Morgan conducted dihybrid cross on Drosophila like Mendel did, Morgan and his
group kenw that the genes were located on the x-chromosome and saw quickly that when
the two genes in a dihybrid cross were situated on the same chromosome, the proportion of
parental gene combinations were much higher than non-parental combinations
(recombinants).

Morgan attributed this due to the physical association or linkage of the two genes and coined
the term ‗linkage‘ to describe the physical association of genes on a chromosome and the
term ‗recombination‘ to describe the generation of non-parental gene combination. Morgan
and his group also found that even when genes were grouped on the same chromosome,
some genes were tightly linked while others were loosely linked. This physical association of
two genes was termed linkage.

13. Work out monohybrid cross up to F1 by taking a suitable example to show the following
phenotypes.
(i) F1 represents only one of the parents.
(ii) F1 with both the parental characteristics.
Ans.
i.

ii. In Humans - Inheritance of blood

14. Construct a complete transcription unit with promoter and terminator on the basis of the
hypothetical template strand given below:

ATGCATGCATAC

Write the RNA strand transcribed from the above transcription unit along with its polarity.

Ans.
Template Strand: 3‘—Promoter – ATGCATGCATAC – Teminator 5‘
Coding strand : 5‘___________ TACGTACGTATG __________3‘

RNA transcribed: 5‘ UACGUACGUAUG 3‘

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15.
a) What do ‗Y‘ and ‗B‘ stand for in ‗YAC‘ and ‗BAC‘ used in HGP? Mention their role in the
project.
b) Write the percentage of the total human genome that codes for proteins and the percentage
of discovered genes whose functions are known as observed during HGP.
c) Expand ‗SNPs‘ identified by scientists in HGP.

Ans.
a) In Human Genome Project (HGP), ‗YAC‘ Y stands for Yeast and in ‗BAC‘ B stands for
bacteria. These are used as a vector for cloning foreign DNA.
b) The percentage of the total human genome that codes for proteins are less than 2%. The
percentage of discovered genes whose functions are known is more than 50%.
c) ‗SNPs‘ stands for Single Nucleotide Polymorphism in HGP.

16. Compare and contrast the theories of evolution proposed by Darwin and Hugo De Vries.
Ans.

DARWIN'S THEORY OF NATURAL SELECTION DEVRIES THEORY OF MUTATION

Minor variation causes evolution. Mutation causes evolution.

Darwinian variations are small and directionless. Mutations are random and directionless.
Evolution is gradual. Sudden mutations caused evolution.

17.
a) State the hypothesis which S.L. Miller tried to prove in the laboratory with the help of the
set-up given below.
b) Name the organic compound
observed by him in the liquid water at
the end of his experiment.
c) A scientist simulated a similar set
up and added CH4, NH3 and water
vapour at 800℃. Mention the important
component that is missing in his
experiment?

Ans.
a) Chemical evolution – First form of
life originated from pre-existing non-
living organic molecules.
b) Amino acids.
c) H2.

18. How do normal cells get transformed into cancerous neoplastic cells? Elaborate by giving
three examples of inducing agent.

Ans. Transformation of normal cells into cancerous neoplastic cells may be induced by following
physical, chemical or biological agents causing DNA damage:

• Ionizing radiations like X-rays and gamma rays.

• Non-ionizing radiations like UV.
• Chemical carcinogens present in tobacco smoke.
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 • Cellular oncogenes (c-onc) or proto-oncogenes, when activated under certain conditions
cause cancer. Viruses with oncogenes can transform normal cells to cancerous cells.

19. Discuss the roles of B-lymphocytes and T-lymphocytes in generating immune responses.

Ans. Role of B-lymphocytes and T-lymphocytes in the immune response:

i. B-cells (B-lymphocytes) and T-cells (T lymphocytes) comprising the immune system are
produced in the bone marrow. T-cells differentiate in the thymus.
ii. B-lymphocytes are responsible for humoral immunity. It produces antibodies in response to
foreign substances (antigens) such as pathogens in the blood. Antibodies are called as
immunoglobulins. They are specific for each antigen. There is more than one antibody for
an antigen. Antibodies bind antigens but do not destroy them. This is attacked through
other mechanisms.
iii. T-lymphocytes are responsible for cell-mediated immunity. It responds to pathogens by
producing three types of cells: killer T-cells, helper T-cell and suppressor T-cells. T
lymphocytes either help B-lymphocytes to produce antibodies or kill the pathogen directly
(killer T-cells).
iv. Both B- and T-cells produce memory cells when stimulated. These have long lives and form
the basis of acquired immunity.

20. The outline structure of a drug is given below:

a) Which group of drugs does this represent?

b) What are the modes of consumption of these drugs?
c)Name the organ of the body which is affected by the
consumption of this drug.

Ans. a) Cannabinoids.
b) By smoking or oral ingestion.
c) Cannabinoids generally affect the cardiovascular system of the body.

21. Principle of vaccination is bassed on the property of ―memory‖ of the immune system. Taking
one suitable example, justify the statement.
Ans. When an organism (pathogen) enters human body, B-lymphocyte starts producing antibodies
and memory cells. The memory cells give faster response whenever in future new infection
with the same pathogen takes place. Same principle is used for the vaccination process.
In vaccination process dead, weakened or inactivated micro-organism is introduced into
human body either orally or injected, this generates immune response and formation of
memory cells which take care of any future infection.

SECTION–D
Case-Based type questions: (4 marks each)

1. A typical anther is bilobed. It is a tetragonal structure consisting of four microsporangia.

These microsporangia form pollen sac which on maturity gets filled with pollen grains. Pollen
grains represents the male gametophytes, their cell wall is very hard. Pollen grains of many
species cause severe allergies which cause various diseases in human beings.
a) Name a species which is a major cause of pollen allergy in India. Mention the symptoms
caused by it.
b) What is the study of pollen grain known as?
c) Mention the location of prominent pollen grain aperture. Mention its function.
OR

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 Tom grows strawberries in raised beds in his backyard. He notices that while some plants
produce large, juicy berries, others produce small and often misshapen berries.
a) What factors could be causing the variability in berry size and shape among Tom‘s
strawberry plants?
b) What strategies can Tom employ to promote more uniform berry development in his
strawberry plants?

Ans. a) Parthenium which is also known as carrot grass, is a major cause of pollen allergy in India.
It may lead to allergic respiratory problems, contact dermatitis, etc in animals and humans.
b) Study of pollen grains is called palynology.
c) Exine is the outer most layer of pollen, made up of sporopollenin. The prominent pollen
grain aperture called germ pore, through which pollen tube ooze out.
OR
a) Variability in berry size and shape in strawberries can be due to uneven pollination.
Strawberries can produce fruits without pollination (parthenocarpic), but fully developed
fruits with seeds require pollination. Poor pollination due to inadequate pollinators,
excessive heat or cold during flowering, or improper spacing of plants can result in smaller
or misshapen berries.
b) Tom can enhance pollination by encouraging bees to visit his garden through planting
pollinator-attracting flowers. Hand-pollination by transferring pollen between flowers can
ensure better fruit set. Proper spacing of plants to allow for adequate airflow and light
penetration, along with consistent watering and appropriate fertilization, can also improve
berry size and quality.

2. Emily, a 17-year-old high school student, experiences irregular menstrual cycles and wants to
understand the possible reasons behind it.
a) What could be the potential causes of irregular menstrual cycles in Emily‘s case?
b) How can Emily manage or address her irregular menstrual cycles?
OR
Chandan, a 16-year-old student, is curious about the changes he‘s experiencing during
puberty and seeks clarification on the process of spermatogenesis.
a) Explain the process of spermatogenesis to Chandan.
b) What factors influence spermatogenesis?

Ans.
a) Irregular menstrual cycles in adolescents like Emily can be attributed to hormonal changes
during puberty. The hypothalamus-pituitary-ovarian axis is still maturing, leading to
variability in hormone production. Stress, diet, exercise levels, and underlying medical
conditions such as polycystic ovary syndrome (PCOS) can also contribute to irregular
periods.
b) Emily can maintain a healthy lifestyle with balanced nutrition and regular exercise, which
can help regulate hormonal balance. Keeping track of her menstrual cycles using a
calendar or app can provide insights into patterns. If irregularities persist or cause
discomfort, consulting a healthcare provider for evaluation and possible treatment is
advisable.
OR

a) Spermatogenesis is the process by which spermatogonia (stem cells in the testes) undergo
multiple rounds of mitosis and meiosis to eventually form mature sperm cells. It begins with
spermatogonia dividing and differentiating into primary spermatocytes, which undergo
meiosis I to form secondary spermatocytes, followed by meiosis II to produce spermatids.
Spermatids mature into spermatozoa (sperm cells) in the epididymis.

19
 b) Spermatogenesis is influenced by hormonal regulation, primarily by follicle-stimulating
hormone (FSH) and testosterone. Temperature regulation (spermatogenesis occurs best at
slightly cooler than body temperature), nutrition, and overall health also impact sperm
production.

3. Priya, aged 35, and Rohan, aged 37, have been married for six years and have been
unable to conceive. Priya has irregular menstrual cycles (ranging from 35 to 40 days) and
reports occasional pelvic pain. Rohan's semen analysis reveals low sperm count and poor
motility.
a) Discuss the potential causes of infertility in Priya and Rohan, considering their age and
clinical findings.
b) Suggest appropriate treatment options for Priya and Rohan, taking into account their
specific infertility issues and

OR

When principles of experiments on peas were repeated using other traits in other plants, it was
found that sometimes the F1 had a phenotype that did not resemble either of the two parents
and was in between the two.
a) What was the phenotypic ratio of F2 generation, when heterozygous (Rr) plant was selfed?
b) Which plant shows incomplete inheritance?
c) What was the genotype and the phenotype of F1 generation, when homozygous dominant
plant (RR) and homozygous recessive plants(rr) were crossed?

Ans.
a) Causes of Infertility:
Priya: ovarian factors (e.g., polycystic ovary syndrome) and hormonal imbalances.
Rohan: male factors such as low sperm count, poor sperm motility (asthenospermia), and
potential causes like varicocele or infections.

b) Treatment Options:
For Priya: ovulation induction with medications or assisted reproductive technologies (ART)
such as IVF.
For Rohan: Recommend lifestyle modifications (e.g., avoiding heat exposure), medications
to improve sperm count and motility, surgical correction of varicocele if indicated, or ART
procedures like intrauterine insemination (IUI) or IVF with intracytoplasmic sperm injection
(ICSI).

OR
a) 1:2:1
b) Antirrhinum sp.
c) Genotype-Rr, phenotype-pink.

4. RNA was the first genetic material. There is now enough evidence to suggest that essential
life process evolved around RNA.
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 a) Name the more reactive nucleic acid.
b) Give one evidence suggesting that RNA used to be the genetic material rather than DNA.
c) Give two examples of RNA acting as a catalyst.
d) ―DNA has evolved from RNA with chemical modifications that makes it more stable.‖ What
is the chemical modification referred here?

OR

The data below shows the concentration of nicotine smoked by a smoker taking 10 puffs/ minute.

a) With reference to the above graph explain the concentration of nicotine in blood at 10
minutes.
b) How will this affect the concentration of carbon monoxide and haem bound oxygen at 10
minutes?
c) How does cigarette smoking result in high blood pressure and increase in heart rate?
d) How does cigarette smoking result in lung cancer and emphysema?

Ans.

a) RNA (ribonucleic acid) is generally considered more reactive compared to DNA

(deoxyribonucleic acid). This is primarily due to the presence of a hydroxyl group (-OH) on
the 2' carbon of the ribose sugar in RNA, which makes RNA more susceptible to hydrolysis
and chemical modifications.
b) One evidence is the discovery of ribozymes, which are RNA molecules capable of catalyzing
specific biochemical reactions. The presence of ribozymes indicates that RNA can not only
store genetic information but also catalyze reactions, suggesting a dual role as both genetic
material and catalyst in early life forms.
c) Ribozymes are RNA molecules that act as catalysts. Two well-known examples are:
1. Ribosomal RNA (rRNA): Part of the ribosome, which is responsible for protein synthesis.
rRNA catalyzes the formation of peptide bonds between amino acids during translation.
2. Group I and Group II Introns: These are self-splicing RNA molecules found in certain
genes. They catalyze their own removal from pre-mRNA during RNA processing,
demonstrating RNA's catalytic activity.
d) The chemical modification referred as in DNA, the ribose sugar in RNA is modified to
deoxyribose. This modification involves the removal of a hydroxyl group (-OH) from the 2'
carbon of the ribose sugar, resulting in deoxyribose. This change contributes to the greater
stability of DNA compared to RNA because it reduces the susceptibility to hydrolysis and
other chemical reactions that can degrade the molecule over time.
OR

a) Concentration of nicotine is maximum at 10 minutes/ conc. of nicotine increases steadily in

the blood to reach 45mg/cm3.
b) The Concentration of CO will increase resulting in reduced concentration of haem bound
oxygen.
c) Nicotine results in stimulating the adrenal gland which results in release of adrenaline / nor -
adrenaline in the blood resulting in increase of blood pressure and heart rate.
21
 d) Chemical carcinogens present in tobacco smoke are the major cause of lung cancer.
The cigarette smoke irritates the air passages of the lungs causing them to produce mucus
which causes cough resulting in enlarging air spaces/ reduce surface area/lose their elasticity
(any point can be mentioned) thus difficulty in breathing causing emphysema.

SECTION–E
Long Answer-II (LA-II) type questions: (5 marks each)

1. Trace the development of male gametophyte of angiosperm up to two cell stage with Suitable
example.
OR
Draw self-explanatory schematic representation of oogenesis.

Ans. Angiosperms are distinguished by the presence of seeds in the enclosing fruit, which are
derived from a flower‘s ovary. The male gametophyte is found in the stamens‘ anthers,
whereas the female gametophyte is found in the pistil‘s ovules.

Four pollen sacs (locules) in the anther contain many microspore mother cells, each of which
goes through meiosis to create four microspores in a tetrad. The microspore is the beginning
for male gametophyte production. The cytoplasm of the microspore is uniformly dispersed at
first, with a haploid nucleus in the centre. Later on, a huge vacuole grows in the centre,
pushing the nucleus to the side.

During pollen development, many flowering plants, including the model species Arabidopsis
and maize, undergo two mitotic divisions. A huge vegetative cell and a much smaller
generative cell result from the initial division.

OR

22
2. What is co-dominance? Explain with reference to ABO blood type in human beings.

OR
What is a repressor molecule? Explain how can a gene be made to induce the metabolic
process?

Ans. Codominance is a heterozygous condition in which both alleles at a gene locus are fully
expressed in the phenotype. Alleles which show an independent effect are called as
Codominant alleles. In codominance, neither phenotype is completely dominant.

Example:
i. The gene I is in charge of ABO blood types in humans. Sugar polymers protrude from the
surface of the plasma membrane of red blood cells, and the kind of sugar is controlled by
gene I.
ii. IA, IB, and I are the three alleles of the gene (I). Alleles IA and IB create a slightly different
type of sugar, whereas allele I produce no sugar at all.
iii. The allele IA is codominant with the allele IB.
iv. Both IA and IB are completely dominant to the allele I.
v. When a person has both IA and IB antigen on their surface, their blood type is AB. AB
blood type in humans is an example of codominance. In AB blood type the phenotypic
effect of both IA and IB alleles is observed.
OR

A repressor is an RNA or DNA binding protein that prevents the expression of genes by attaching
to the operator. A repressor protein binding to the DNA prevents the RNA polymerase from
attaching to the promoter
and transcribing the genes
into mRNA or messenger
RNA.
Repressor proteins include
lac repressor, which
prevents the expression of
the lac operon in E. coli.

3. A cross between a normal couple resulted in a son who was haemophilic and a normal
daughter. In course of time, when the daughter was married to a normal man, to their
surprise, the grandson was also haemophilic.
a) Represent this cross in the form of a pedigree chart.
b) Give the genotypes of the daughter and her husband.
c) Write the conclusion you draw of the inheritance pattern of this disease.

OR

(a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked
with them for their experiments. Explain the correlation between linkage and recombination
with respect to genes as studied by them.
(b) How did Sturtevant explain gene mapping while working with Morgan?

23
Ans.
a)

b) Genotype of daughter- XXH

Genotype of husband- XY

c) Haemophilia is a sex-linked recessive disease. Here, it is transmitted from the carrier

female to the sons. From the above pedigree chart, it can be observed that the disease is
being transmitted from the carrier female to her daughter (carrier) and son (affected). The
carrier daughter transmits this disease to the grandson. This pattern of inheritance is called
crisscross inheritance.
OR
(a) Thomas Hunt Morgan and his colleagues worked with Drosophila melanogaster for their
experiments
They observed that the proportion of parental gene combinations were much higher than the
non-parental type in two genes in a dihybrid cross which are situated on the same
chromosome. Morgan attributed this due to the physical association or linkage of the two
genes and coined the term linkage to describe this physical association of genes on a
chromosome and the term recombination to describe the generation of non-parental gene
combinations. Even when genes were grouped on the same chromosome, some genes were
very tightly linked (showed very low recombination) while others were loosely linked (showed
higher recombination).

(b) While working with Morgan, Alfred Sturtevant used the frequency of recombination between
gene pairs on the same chromosome as a measure of the distance between genes and
‗mapped‘ their position on the chromosome, thus explaining gene mapping.

4. Where does the process of megasporogenesis start in an angiosperm? Describe the process
up to the formation of embryo sac.
OR
Read the following statement and answer the questions that follow:
―A guava fruit has 200 viable seeds‖.
(a) What are viable seeds?
(b) Write the total number of:
(i) Pollen grains
(ii) Gametes in producing 200 viable guava seeds.
(c) Prepare a flowchart to depict the post-pollination events leading to viable-seeds
production in a flowering plant.

Ans.
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 Nucleus/Ovules.
A single MMC/ megaspore mother cell differentiates in the micropylar region of the nucleus,
MMC undergoes meiosis, to produce four (haploid) megaspores, one of the megaspores
functional, the nucleus of functional megaspore undergoes free nuclear division, to form 2
nucleate- 4 nucleate-8 nucleate embryo sac, cell wall formation occurs in six of 8 nuclei, two
polar nuclei occur in the large central cell to form 8 nucleate and 7 celled embryo- sac.

OR
(a) Seeds that remain alive / gives rise to new plant / ability to germinate.
(b) i.200.
ii. 600 gametes / 400 male gametes / 200 female gametes.
(c) Flowchart depicting the post pollination events:

25
5. Trace the events from copulation to zygote formation in a human female.

OR

a) Identify the parts labelled 1,2,3 in the diagram given.

b) Draw a labelled diagram of a human blastocyst.
c) What is parturition and how is it induced at the end of pregnancy
in a human female?

Ans. Events from copulation to zygote formation:

i) During copulation (coitus) semen is released by the penis into
the vagina (insemination).
ii) The motile sperms swim rapidly, pass through the cervix, enter the uterus, and finally reach
the ampullary region of the fallopian tube.
iii) The ovum released by the ovary is also transported to the ampullary region where fertilization
takes place.
iv) Fertilisation can only occur if the ovum and sperms are transported simultaneously to the
ampullary region. This is the reason why not all copulations lead to fertilisation and
pregnancy.
v) The process of fusion of a sperm with an ovum is called fertilisation.
vi) During fertilisation, a sperm encounters the zona pellucida layer of the ovum and induces
changes in the membrane that block the entry of additional sperms. Thus, it ensures that only
one sperm can fertilise an ovum.
vii) The secretions of the acrosome help the sperm enter the cytoplasm of the ovum through the
zona pellucida and the plasma membrane.
viii) This induces the completion of the meiotic division of the secondary oocyte.
ix) The second meiotic division is also unequal and results in the formation of a second polar
body and a haploid ovum (ootid).
x) Soon the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid
zygote.
OR

a) 1. Placenta villi 2. Umbilical cord 3. Embryo.

b) Human blastocyst

c) Vigorous contraction of the uterus at the end of pregnancy causes delivery of the foetus by
the process known as parturition. It is induced by a complex neuroendocrine mechanism.
The signals originate from the fully developed foetus and the placenta which induces uterine
contractions known as foetal ejection reflex. This triggers release of oxytocin from the
maternal pituitary which acts on the uterine muscle and causes stronger uterine contractions,
that in turn stimulates further secretion of oxytocin. The stimulatory reflex continues causing
stronger contractions which leads to the expulsion of the baby out of the uterus through the
birth canal known as parturition.

26
6. a) List any two reasons other than physical and congenital disorders for causing infertility in
couples.
b) Explain how IVF as a technique helped childless couples in having children.
c) Compare GIFT with ICSI.

OR

A normal couple has a colour-blind child, whereas a child suffering from thalassemia is born
to normal parents. Compare the pattern of inheritance of these two traits in the said cases.
State the reasons how is it possible.

Ans. a) Reasons for infertility

(i) Sexually transmitted infections
(ii) Steroid drug abuse
b) IVF – Fertilization outside the body in test tube is called invitro fertilization. In such a method,
ova are collected from female and sperms are collected from male. Both sperm and ovum are
fused in stimulated conditions in laboratory to form a zygote. Zygote or embryo up to 8 celled
stages are transferred into fallopian tube known as ZIFT whereas embryo more than 8 celled
stage are transferred into uterus called IUT.
c)
GIFT ICSI

1. In vivo fertilization occurs. 1. In vitro fertilization occurs.

2. Sperms naturally reach up to ovum and 2. Sperms are injected within ovum
penetrate with ovum. artificially by microneedle.
3. Usually used when female can provide 3. Usually used when male partner suffers
suitable environment but cannot produce from low production of sperms or non-motile
viable ova. sperm production.

OR

This is because colour blindness is a sex-linked recessive disorder whereas thalassemia is

an autosome linked recessive. Colour blindness: Red-green colour blindness means that a
person cannot distinguish shades of red and green (usually blue-green), but their ability to
see is normal. There are no serious complications; however, those affected may not be
considered for certain occupations involving transportation or the Armed Forces where colour
recognition is required. Males are affected more often than females, because the gene is
located on the X chromosome.

Thalassemia: Thalassemia is an autosomal recessively inherited disorder transmitted to the

offspring when both the parents are heterozygous or careers for the disease Alpha
Thalassemia is controlled by two closely linked genes HBA1 and HBA2 located on
chromosome 16 beta Thalassemia is controlled by a single gene HBB located on
chromosome 11.

27
7.
a) A DNA segment has a total of 1000 nucleotides, out of which 240 of them are adenine
containing nucleotides. How many pyrimidines bases this DNA segment possess?
b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.
OR
a) How and at what stage does Plasmodium enter a human body?
b) With the help of a flow chart only shows the stages of asexual reproduction in the life cycle of
the parasite in the infected human.
c) Why does the victim show symptoms of high fever?

Ans. a) A = T, A = 240 hence, T = 240

A + T = 240 + 240 = 480
so, G + C = 1000 - 480 = 520 G = C,
so, C = 520/2 = 260
so, pyrimidines = C + T = 260 + 240 = 500
Purine A and G always pair with T and C respectively.
A/G = T/C = 1 (Chargaff rule).
b)

OR
a) Sporozoite stage enters human body along with saliva of female Anopheles mosquito as it
bites to suck blood.
b) Asexual phases of the life history of plasmodium in the body of a human:

28
c) When the parasite attacks red blood cells, it leads to its rupture with the release of
haemozoin, which is a toxin. As the haemozoin is released into blood, symptoms (high fever)
of malaria appear.
8. A youth in his twenties met with an accident and succumbed to the injuries. His parents
agreed to donate his organs. List any two essential clinical steps to be undertaken before
any organ transplant. Why is the transplant rejected sometimes? What views would you
share with your health club members to promote organ donation?
OR
Name the cells HIV attacks first, when it enters a human body. How does this virus replicate
further to cause immunodeficiency in the body?
Ans. Organ transplantation involves the removal of damaged/injured tissues or organs from the
body of a person and their substitution by similar tissues/organs from a donor. Tissue
matching, blood group matching are essential clinical steps before undertaking any
graft/transplant. Transplantation may result in the rejection of transplanted organs as the
immune system recognises the protein in the transplanted tissue or organs as foreign and
initiates cellular immunity. We should raise and promote awareness about organ donation,
about need of organ and tissue donors. There are lakhs of people waiting for organ donation
and many people die daily while waiting for transplant. Organs and tissues from one donor
can save up to 40-50% lives. So, we should encourage and get registered for organ donation
to save many lives.
OR
The HIV virus attacks the macrophages first in human body. The further replication of virus
causes immuno deficiency in the following way
 RNA is replicated to form viral DNA by the enzyme reverse transcriptase.
 Viral DNA gets incorporated into the host cell‘s DNA and directs the infected cells to produce
viruses.
 Macrophages continue to produce virus particles and function as HIV factories.
 The virus particles enter helper T-lymphocytes in the blood, where they continue to replicate
and produce viral progenies.
29
 The number of helper T-lymphocytes progressively decreases in the body of the infected
person.
 With the decrease in number of T-cells, the immunity also decreases. The person is unable
to produce any immune response even against common bacteria like Mycobacterium,
parasites like Toxoplasma, viruses, and fungi.
9. a) How do the observations made during moth collection in pre- and post – industrialised era
in England support evolution by natural selection?
b) Explain the phenomenon that is well represented by Darwin‘s finches other than natural
selection.
OR
a) Rearrange the following in the correct order of their appearance on earth between two
million years and 40,000 years back.
Neanderthals, Australopithecus, Homo erectus, and Homo habilis.
b) Which one of the above
i) had the largest brain size.
ii) ate fruits.
c) State what does the study of fossils indicate.
d) Rearrange the following group of plants according to their evolution from Palaeozoic to
Cenozoic periods.
Rhynia; Arborescent lycopods; Conifers; Dicotyledons.
Ans. a) Industrial melanism:
▪ In England, before industrialisation, white-winged moths were more in number than dark-
winged moths.
▪ But after industrialisation, dark-winged moths became more in number than white winged
moths.
▪ This is because during industrialisation, the tree trunks covered by white lichens became
dark due to deposition of dust and coal particles.
▪ As a result, white-winged moths could be easily picked up by predators from the dark
background and dark-winged moths survived.
b) The process of evolution of different species in each geographical area starting from a point,
radiating to other areas of geography (habitats) is called adaptive radiation. Finches evolved
in the same island from original seed eating features. Many other altered beaks arose
enabling them to became insectivorous and vegetarian finches.
OR
a) The correct sequence of their appearance is Australopithecus → Neanderthals→ Homo
erectus→ Homo habilis.
b) i) The brain sizes were as follows:
1. Neanderthals - 1400 cc
2. Australopithecus - 466 cc
3. Homo erectus - 900 cc
4. Homo habilis - 650−800 cc
So, Neanderthals had the largest brain size.
ii) Two million years ago, Australopithecus probably lived in East African grasslands.
Evidence shows they hunted with stone weapons and ate fruits.
c) They are evidence of evolution and they represent extinct. The life forms varied over time and
certain life forms were restricted to certain geological time spans.
d) Rhynia ⇒Arborescent Lycopods ⇒ Conifers ⇒ Dicotyledon.

*****

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