AHSEC| CLASS 12| BIOLOGY| SOLVED PAPER - 2024| H.S. 2ND YEAR
2024
BIOLOGY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate
full marks for the questions.
PART-I
(BOTANY)
MARKS
- 35
PART-II
(ZOOLOGY)
MARKS
- 35
Part-I
(Botany)
1. Name the bacterium used in pesticides. 1
Ans:- The
bacterium commonly used in pesticides is Bacillus thuringiensis (Bt). It is
widely recognized for its effectiveness as a biopesticide and is safe for
humans, making it a popular choice in agricultural pest control.
2. Who first coined the term 'mutation'?
1
Ans:- The
term 'mutation' was first coined by scientist Hugo de Vries in the early 20th
century. He introduced the term while studying variations in plant species,
particularly the evening primrose, and exploring the concept of genetic
changes.
3. Give an example of adaptive
radiation. 1
Ans:- An
example of adaptive radiation is the diversification of Darwin's finches on the
Galapagos Islands. These birds evolved from a common ancestor into different
species, each of which adapted to different ecological habitats, such as
different beak shapes for different food sources.
4. What is gene therapy? 1
Ans:- Gene
therapy is a medical technique that involves altering genes inside a patient's
cells to treat or prevent disease. It may involve replacing, inactivating, or
introducing genes into cells to correct genetic disorders or enhance
therapeutic effects.
5. Answer the following: 2x4=8
(a) Write the biotic component of an ecosystem.
Ans:- The biotic components of an
ecosystem include all living organisms, such as plants, animals, fungi, and
microorganisms such as bacteria. These organisms interact with each other and
with their environment, affecting the structure and function of the ecosystem.
(b) Name one homologous and one analogous organ of plant.
Ans:- An example of a homologous organ
in plants is the leaf of a flowering plant and the leaf of a coniferous plant,
because they share the same evolutionary origin. An example of a homologous
organ is the flower of a cactus and the flower of a hibiscus; both perform
similar functions in reproduction but have evolved independently.
(c) Define fermentation. Name one microorganism used in industrial
fermentation.
Ans:- Fermentation is a metabolic
process that converts sugar into acids, gases, or alcohol in the absence of
oxygen. It is commonly used in food production and biofuel production. A
microorganism used in industrial fermentation is Saccharomyces cerevisiae,
commonly known as baker's yeast, which is used in baking and brewing.
(d) Mention the different kinds of pollination.
Ans:- Different types of pollination include:-
(i) Self-pollination: Pollen from the
same flower fertilises its ovule.
(ii) Cross-pollination: Pollen from one
flower fertilises the ovule of another flower.
(iii) Wind pollination: Pollen is
carried to other flowers by the wind.
(iv) Insect pollination: Pollinators
such as bees and butterflies transfer pollen between flowers.
(v) Water pollination: Pollen is spread
through water.
6. Write short notes on: (any two) 2x2=4
(a) Embryo sac
Ans:- The embryo sac is the female
gametophyte in flowering plants, which develops within the ovule. It arises
from a single functional megaspore, which is formed through meiotic division of
the megaspore mother cell, resulting in the formation of four megaspores, only
one of which survives. The surviving megaspore undergoes three mitotic
divisions to form a mature embryo sac containing seven cells and eight nuclei:
three antipodal cells at the chalazal end, two synergids and an egg cell at the
micropylar end, and a central cell with two polar nuclei. The embryo sac plays
a vital role in fertilization, as it contains the egg cell that fuses with a
male gamete to form a zygote.
(b) Antibiotic
Ans:- Antibiotic is a type of
antimicrobial substance that inhibits the growth of bacteria or destroys them.
They are mainly used to treat bacterial infections and are classified into
different categories based on their mechanism of action. Common classes include
penicillins, which inhibit cell wall synthesis; tetracyclines, which inhibit
protein synthesis; and quinolones, which interfere with DNA replication. While
antibiotics are effective against bacterial infections, they are not effective
against viral infections and can lead to antibiotic resistance if misused.
(c) Ecological succession
Ans:- Ecological succession refers to
the gradual process by which ecosystems change and evolve over time. It occurs
in two main types: primary succession, which occurs in lifeless areas where
soil has not yet formed (for example, after a volcanic eruption), and secondary
succession, which occurs in areas where the ecosystem has been disturbed but
soil remains (for example, after a forest fire). Succession involves a series of
stages characterized by different communities of plants and animals, eventually
leading to a stable climax community. This process is essential for ecosystem
resilience and biodiversity.
7. Write the scientific name with the
utility of the following plants: (any two) 2+2=4
(a) Neem
Ans:- (i) Scientific name: Azadirachta
indica (A. Juss)
(ii) Utility:
(a) Widely used in traditional medicine due to its antimicrobial
properties, which treat diseases such as infections and skin ailments.
(b) Acts as a natural insecticide and fertilizer, making it valuable
in agriculture for pest control and soil health.
(b) Rauwolfia
Ans:- (i) Scientific name: Rauwolfia
serpentina
(ii) Utility:
(a)
Known primarily for its use in treating hypertension due to the presence of
reserpine, which helps lower blood pressure.
(b)
Also used in traditional medicine due to its sedative properties, which aid in
anxiety and insomnia management.
(c) Cinchona
Ans:- (i) Scientific name: Cinchona
officinalis
(ii) Utility:
(a)
Historically important for its bark, which contains quinine, an effective
treatment for malaria.
(b)
Additionally, it is used for its antipyretic properties to reduce fever.
(d) Sal
Ans:- (i) Scientific name: Shorea
robusta
(ii) Utility:
(a)
Its wood is highly valued for its durability and is commonly used in
construction and furniture making.
(b)
Sal is also known for its medicinal properties, including wound healing and
anti-inflammatory effects.
8. How is genetically engineered insulin
produced? 3
Ans:- Production of Genetically
Engineered Insulin:-
Genetically engineered insulin, commonly known as recombinant
insulin, is produced using advanced biotechnology techniques.
This process involves several major steps:-
(i) Understanding the insulin structure:
Insulin consists of two polypeptide chains, chain A and chain B, linked by
disulfide bonds.
(ii) Preparation of DNA sequences:
Scientists synthesize DNA sequences that correspond to the amino acid sequences
of the insulin chains.
(iii) Insertion into plasmids: These DNA
sequences are inserted into a plasmid vector, a small circular DNA molecule
that can replicate independently within bacterial cells, usually derived from
E. coli.
(iv) Transformation of E. coli: The
plasmid containing the insulin gene is introduced into E. coli cells through a
process called transformation, allowing the bacteria to express the insulin
gene.
(v) Production of insulin chains: The
transformed E. coli use their cellular machinery to transcribe and translate
the inserted DNA, producing chain A and chain B of insulin separately.
(vi) Extraction of insulin chains: After
production, insulin chains are extracted from the bacterial cells, ensuring
purity by handling each chain separately.
(vii) Formation of disulfide bonds: The
final step involves combining chain A and chain B through disulfide bond
formation, resulting in functional human insulin.
This method allows large-scale production of insulin that is more
pure and less likely to cause allergic reactions than animal-derived insulin.
Or
Describe the various types of ecological pyramids. 3
Ans:- Types of Ecological Pyramids:-
Ecological pyramids visually represent the relationships between
different trophic levels in an ecosystem.
There are three main types:-
(i) Pyramid of numbers: This pyramid
shows the number of different organisms at each trophic level in a food chain.
This usually forms an upright pyramid shape in predatory food chains
(reflecting larger organisms at higher levels) but may be inverted in parasitic
food chains, where there are fewer large parasites than their hosts.
(ii) Pyramid of biomass: This
representation shows the total mass (fresh or dry weight) of living matter at
each trophic level. In terrestrial ecosystems, this pyramid usually appears
upright; however, in aquatic ecosystems, it may be inverted or spindle-shaped
due to the high turnover rates of phytoplankton compared to large consumers.
(iii) Pyramid of energy: This pyramid
shows the amount of energy available at each trophic level, showing that energy
decreases as one goes up the food chain due to energy loss at each level (as
per the 10% rule)
9. Draw and describe the different parts
of a complete flower. 1+2=3
Ans:- A
complete flower consists of several main parts, each of which performs specific
functions in the plant's reproductive process. Below is a detailed description
of these parts, along with a diagrammatic representation.
Parts of a complete flower:-
Diagram of a complete flower:-
Description of each part:-
(i) Calyx (Sepals):
(a) Description: The outermost whorl of
the flower, consisting of the sepals.
(b) Function: Protects the developing
bud and is often green, although some may be coloured. The sepals help shield
the inner floral structures until the flower blooms.
(ii) Corolla (Petals):
(a) Description: The second whorl, made
up of petals that are usually coloured and fragrant.
(b) Function: Attracts pollinators such
as bees and butterflies, making the process of pollination easier.
(iii) Stamen (Pistil):
(a) Description: Male reproductive part,
consisting of two components:
1. Anther: produces pollen.
2. Filament: supports the anther,
positioning it to maximize exposure to pollinators.
(b) Function: Responsible for the
production and dispersal of pollen, which contains the male gametes needed for
fertilization.
(iv) Gynocium (Pistil or Carpel):
(a) Description: Female reproductive
part, consisting of:
1. Stigma: sticky upper surface that
catches pollen.
2. Style: a tube that connects the
stigma to the ovary.
3. Ovary: contains the ovules (female
gametes); after fertilization, it develops into the fruit.
(b) Function: Facilitates fertilization
by allowing pollen to travel down the style to reach the ovary where the ovules
are fertilized.
(v) Receptacle:
(a) Description: The thickened part of
the stem from which the flower emerges.
(b) Function: Supports all parts of the
flower and attaches them to the plant.
Additional Notes:-
(i) A flower is considered complete if all four of its main parts
are present: sepals, petals, stamens, and pistil. If any of these parts are
missing, it is classified as an incomplete flower.
(ii) Examples of complete flowers include roses, hibiscus, and
tulips, which have all the necessary structures for reproduction present.
Understanding these components is essential to study plant biology
and their reproductive strategies.
Or
Explain the Hardy-Weinberg principle. 3
Ans:- The Hardy-Weinberg principle is a
foundational concept in population genetics that describes genetic equilibrium
within a population. It states that allele frequencies in a population will
remain constant over generations in the absence of evolutionary influences.
The main components of the principle are as follows:-
(i) Genetic equilibrium: The principle
asserts that allele frequencies (the relative frequency of different alleles at
a genetic locus) remain constant over time, leading to what is known as genetic
equilibrium. This means that, under certain conditions, the gene pool of a
population does not change, allowing predictions to be made about genotype
frequencies based on allele frequencies.
(ii) Mathematical representation: The
Hardy-Weinberg principle can be expressed mathematically through two main
equations:-
(iii) Assumptions for equilibrium: For a
population to be in Hardy-Weinberg equilibrium, several assumptions must be
met:
(a) No mutation: No new alleles enter
the gene pool.
(b) Random mating: Individuals mate
regardless of their genotype.
(c) No gene flow: there is no migration
of individuals into or out of the population.
(d) Infinite population size: the
population is large enough to prevent random fluctuations in allele frequencies
(genetic drift).
(e) No natural selection: all genotypes
have equal chances of surviving and reproducing.
In essence, the Hardy-Weinberg principle
serves as a mathematical model that assesses whether a population is evolving
by comparing observed genetic variation against expected frequencies under
ideal conditions.
10. Write an account on biotechnological
application in agriculture. 4
Ans:-
Biotechnology has revolutionized agriculture by providing innovative solutions
to increase crop production, improve pest resistance, and overcome nutritional
deficiencies.
Some of the major applications of biotechnology in agriculture are
as follows:-
(i) Genetically Modified Organisms (GMOs): Biotechnology enables the creation of genetically modified crops
that have properties not found in their natural counterparts. For example,
crops such as Bt cotton and Bt corn are engineered to express proteins from the
bacteria Bacillus thuringiensis, making them resistant to specific pests. This
reduces the need for chemical pesticides, leading to safer farming practices
and lower environmental impact.
(ii) Disease Resistance: Biotechnology
plays a vital role in developing crops that are resistant to diseases. A
notable example is the genetically engineered papaya that is resistant to the
papaya ringspot virus, which previously threatened the Hawaiian papaya
industry. This innovation not only saved the industry but also ensured food
security in the region.
(iii) Nutritional enrichment: Biotechnological
methods are used to enhance the nutritional profile of crops. For example,
golden rice has been genetically modified to contain high levels of
beta-carotene, which alleviates vitamin A deficiency in populations that rely
heavily on rice as a staple food. Such bio-fortified crops can significantly improve
public health outcomes.
(iv) Environmental adaptation:
Biotechnology is also focused on developing crops that can thrive in
challenging environmental conditions, such as drought or high salinity.
Research is underway to create varieties that require less water and that can
withstand extreme weather conditions, which is increasingly important in the
context of climate change.
In short, biotechnology in agriculture
not only enhances productivity and sustainability but also contributes
significantly to food security and nutritional health around the world.
Or
Write briefly on modern synthetic theory of evolution. 4
11. Describe the carbon cycle in ecosystem
with diagram. 5
Or
Describe the process of tissue culture. 5
Part-II
(Zoology)
1. Fill in the blanks: (any two) 1x2=2
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