Ahsec Class 12 Biology Solved Question Paper - 2026| ASSEB BOARD
2026
BIOLOGY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: 3 hours
The figures in the
margin indicate full marks for the questions.
PART-I
(Botany)
(Marks: 35)
1. What is sporopollenin? 1
Ans:- Sporopollenin is a highly tough and
resistant organic polymer that forms the outer layer (exine) of pollen grains.
It protects them from high temperatures, strong acids, and enzymes.
2. Who
proposed mutation theory? 1
Ans:- Hugo de Vries proposed the mutation
theory of evolution.
3. Name
one free-living nitrogen-fixing bacteria. 1
Ans:- Azotobacter (other common examples
include Clostridium or Beijerinckia).
4. What
is the function of DNA ligase? 1
Ans:- DNA ligase acts like "molecular
glue." It joins DNA fragments (such as Okazaki fragments) together by
forming phosphodiester bonds during DNA replication and repair.
5. Write
briefly about the principles of biotechnology. 2
Ans:-
Modern biotechnology is primarily based on two main techniques:-
(i) Genetic Engineering: The technique of altering the
chemistry of genetic material (DNA and RNA) to introduce phenotypic (observable
trait-related) changes in organisms.
(ii) Bioprocess Engineering: Maintaining sterile
(contamination-free) conditions in chemical engineering processes to enable the
large-scale growth of only the desired microorganisms or eukaryotic cells for
the production of biotechnological products such as antibiotics, vaccines, and
enzymes.
Or
What is genetically modified crop?
Mention its advantages. 2
Ans:-Plants whose genes have been altered
using genetic engineering techniques are known as Genetically Modified (GM)
crops.
Advantages:-
(i) They are more tolerant to abiotic
stresses (cold, drought, salinity, heat).
(ii) They reduce reliance on chemical
pesticides (e.g., pest-resistant crops like Bt cotton).
(iii) They help reduce post-harvest
losses and enhance nutritional value (e.g., Vitamin A-enriched Golden Rice).
6. What
is triple fusion? Write the significance of it. 2
Ans:- The process in which a male gamete
fuses with the diploid secondary nucleus (formed by the fusion of two polar
nuclei) within the embryo sac to form a triploid (3n) Primary Endosperm Nucleus
(PEN) is called triple fusion.
Significance: It results in the formation of the
endosperm, which provides essential nutrition and food to the developing embryo
during seed germination.
7. What
do you mean by false fruit? Give two examples of false fruit. 2
Ans:- A fruit in which parts of the flower
other than the ovary (such as the thalamus, receptacle, or calyx) contribute to
fruit formation is called a false fruit (pseudocarp).
Examples: Apple and strawberry (in both, the
thalamus contributes significantly to the edible part).
Or
What is tapetum? Write its role in
the formation of pollen grain. 2
Ans:- The tapetum is the innermost
nutritive layer of the anther wall that surrounds the sporogenous tissue.
Role in pollen grain formation:-
(i) It provides nourishment to the
developing microspores (pollen grains).
(ii) It secretes sporopollenin (for
the tough outer layer 'exine') and pollenkitt (in insect-pollinated plants).
(iii) It secretes the enzyme
'callase', which dissolves the callose wall holding the microspore tetrad (a
cluster of four microspores) together, thereby releasing individual pollen
grains.
8.
"Pyramid of energy is always upright.” Explain. 2
Ans:- According to the 10% law of energy
transfer, only about 10% of energy is transferred from one trophic level to the
next, while the rest is lost as heat during respiration and metabolic
activities.
Since energy is progressively lost at
each successive trophic level as one moves from producers to top carnivores,
producers always possess the highest amount of energy. For this reason, the
pyramid of energy is always upright and never inverted.
9.
Explain briefly (any two): 2x2=4
(a) Biopiracy
(b) Bt cotton
(c) Gene gun
(d) PCR
10. Write
the scientific names and uses of the following plants (any three):
(1⁄2+1⁄2)×3=3
(a) Sissoo
(b) Cinchona
(c) Atropa
(d) Holong
11. What are
biopesticides? Write briefly on biopesticides with examples. 1+2=3
12. Discuss
about the chemical evolution of life on the earth. 4
Or
Describe the facts on which Darwin's
theory is based. 4
13. Describe
the structure of ecosystem. 4
Or
Describe the process of energy flow
in different trophic levels in the ecosystem. 4
14. Write an
account of biotechnological application in medicine. 5
Or
What is recombinant DNA technology?
Write about the process of recombinant DNA technology. 5
PART-II
(Zoology)
(Marks: 35)
1. Fill
in the blanks (any two): 1×2=2
(a) Fertilization takes place in the fallopian tube.
(b) Down's syndrome disorder was
first described by Langdon Down (1866).
(c) DNA
ligase enzyme is used to join discontinuously synthesized fragments
of DNA.
(d) Malaria is caused by the bite of
infected female Anopheles mosquito.
2. Answer
any two of the following questions: 1×2=2
(a) What is an allele?
Ans:- An allele is an alternative form or
variant of a gene that is located at the same locus on homologous chromosomes
and controls contrasting traits of a characteristic.
(b) What is mutation?
Ans:- A mutation is a sudden and heritable
change in the nucleotide sequence of an organism's DNA, which can lead to
alterations in traits.
(c) What is DNA replication?
Ans:- DNA replication is the biological
process by which a cell creates identical copies of its DNA molecules prior to
cell division.
(d) What is transgenic animal?
Ans:- An animal whose genome has been
modified by inserting a foreign gene using genetic engineering techniques is
called a transgenic animal.
3. Answer
any four of the following questions: 2×4=8
(a) What is menstrual cycle?
Ans:- Definition: The cyclical reproductive cycle
occurring in female primates (such as humans, apes, and monkeys), involving
physiological and structural changes in the ovaries and uterus, is called the
menstrual cycle.
Key points: It repeats at an average interval of
approximately 28/29 days. It begins with the shedding of the endometrial lining
of the uterus (menstruation) and includes phases such as the follicular
(proliferative) phase, ovulation, and the luteal (secretory) phase.
(b) What is meant by linkage?
Ans:- Definition: Linkage refers to the physical
association of genes located on the same chromosome or their tendency to be
inherited together during meiosis.
Key points: Linked genes—discovered by T.H.
Morgan in *Drosophila*—do not segregate independently (do not show independent
assortment) during gamete formation unless crossing over occurs. The strength
of linkage is inversely proportional to the distance between the genes on the
chromosome.
(c) Write the composition of a
polynucleotide chain.
Ans:- A polynucleotide chain (such as DNA
or RNA) is a polymer composed of repeating units called nucleotides.
Each nucleotide consists of three
main chemical components:-
(i) A Nitrogenous Base: Heterocyclic rings classified as
purines (adenine and guanine) and pyrimidines (cytosine, thymine in DNA, or
uracil in RNA).
(ii) A pentose sugar: A 5-carbon sugar—specifically
deoxyribose in DNA and ribose in RNA.
(iii) A phosphate group: Attached to the 5-carbon of the
sugar; it imparts a negative charge to the backbone and forms phosphodiester
bonds between adjacent nucleotides.
(d) Mention the different symptoms of
malaria.
(e) What are the four major factors
which affect the population density?
(f) What is splicing?
4. Write
the difference between (any two): 2x2=4
(a) Spermatogenesis and Oogenesis
(b) Monohybrid and Dihybrid cross
(c) Deoxyribonucleic acid (DNA) and
Ribonucleic acid (RNA)
(d) Innate and Acquired immunity
5. Draw a
labelled diagram of a DNA double-helical structure. 3
Or
Draw a labelled diagram of the
matured human sperm. 3
6. What is
DNA fingerprinting? Mention its applications. 1+2=3
Or
What is biodiversity? Write the
causes of biodiversity losses. 3
7. Write
down the systematic position of muga silkworm. 3
Or
Name any three diseases of silkworm
with causative organisms. 3
8. Explain
Mendel's law of dominance using monohybrid Cross. 5
Or
Discuss the stages in the life cycle
of malarial parasite. 5
9. Describe
the process of gametogenesis. 5
Or
Describe the mechanism of
transcription. 5
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