AHSEC| CLASS 11| BIOLOGY| SOLVED PAPER - 2019| H.S.1ST YEAR
2019
Biology
(Theory)
Times: 3 hours
Full marks: 70
Part - I (Botany)
1. Who proposed binomial nomenclature? 1
Ans: Carolus Linnaeus.
2. Fusion of two nuclei in sexual cycle is called Plasmogamy. (Fill in the blank) 1
3. What is the common name of phaeophycean algae? 1
Ans: Brown algae.
4. Potato is a modification of root. (Write True or False) 1
5. Name the proposer(s) of cell theory. 1
Ans: Schleiden and Schwann.
6. Define and distinguish (any four): (1+1)x4=8
(a)
Prokaryotic and eukaryotic cells
Ans:
Difference between Prokaryote and Eukaryotic cells:-
Prokaryotic
cells
(i) lack of a
nuclear membrane
(ii) They
contain 70S ribosomes
(iii) export
ribosome no other organelle is present
Eukaryotic
cells
(i) having a
real nucleus
(ii) They
contain 80S ribosomes
(iii) All the
organs are present.
(b) Heartwood
and Sapwood
Ans: Difference
between Heart wood and Sap wood:-
Heart wood
(i) The dark
colored area situated in the middle of the trunk of a tree is called heart
wood.
(ii) It gives
mechanical strength to the torso.
Sap wood
(i) The light
colored area of the trunk of a tree is called sap wood.
(ii) It is
less durable like wood.
(c)
Antheridia and archegonia
Ans:
Antheridium: The male reproductive organ present in bryophytes,
pteridophytes and gymnosperms is known as antheridium. The antheridium occurs
at the apex of the male gametophore. It is usually a club-shaped, tall, stalked
structure. It consists of a jacket within which a large number of sperm mother cells
or androcytes are present. Each androcytes give rise to an antherozoid. At
maturity they are released from the antheridium.
Archegonium:
It is the female reproductive organ. The archegonium is a flask-shaped body
with a swollen basal part called the venter and a thin tube called the neck.
The venter puts an egg in it.
(d) Tracheid’s
and Vessels
Ans: Difference
between Tracheid’s and Vessels:-
Tracheid’s
(i) These are
elongated or tube-like cells.
(ii) They are
dead and without protoplasm.
Vessels
(i) These are
long cylindrical tube-like cells.
(ii) These are
living cells.
(e) Cyclic
and non-cyclic phosphorylation’s
Ans: Difference
between Cyclic and Non-cyclic Photophosphorylation: -
Cyclic Photophosphorylation:
(i) Includes
only photo system I.
(ii) The
electron removed from the chlorophyll is returned to the same chlorophyll in a
cyclic manner.
Non-cyclic
Photophosphorylation:
(i) Both
photosystem I and II are involved.
(ii) The
electrons removed from chlorophyll never return to the same chlorophyll.
(f) Macro and
micro-nutrients for plants.
Ans: Macro:
Macronutrients are nutrients present in large quantities in plant tissues.
Examples of macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur,
potassium, calcium and magnesium etc.
Micronutrients:
The nutrients which are required in very small amounts are called
micronutrients. Examples of micronutrients are iron, copper, zinc, boron etc.
7. Answer briefly any three of the following: 3x3=9
(a) What is
meant by heterospory? Write the significance of heterospory.
Ans: Most
pteridophytes produce only one type of spore. But some produce two types of
spores differing in size. The shorter one is known as the microspore and the
longer one is known as the megaspore. They develop within microsporangia and
megasporangia respectively. The phenomenon in which two types of spores are
formed on the same plant is called heterospory.
The first step
towards spore-dwelling is a heterosporous life cycle. The second stage is the
retention of the megaspore within the megasporangium. The third feature is the
transport of sperm nuclei to the female gametophyte. The fourth stage is to
develop a means to protect the embryo by the seed-coat.
Thus,
heterospory is a major step towards evolution as seed-habit is an important
step in evolution.
Examples: Psilotum,
Dryopteris.
(b) What is
hydroponics? Explain the uses and applications of hydroponics.
Ans:
Hydroponics is a technique that involves the cultivation of plants in a
soil-free, defined mineral solution. These methods require purified water and
mineral nutrient salts. By this method the essential elements are identified
and their deficiency symptoms are detected.
Uses and
Applications: Hydroponics has been successfully employed as a technology for
the commercial production of vegetables such as tomato, seedless cucumber and
lettuce.
(c) What are
nuclear pores? State their functions.
Ans: A
nuclear pore is a part of a larger complex of proteins known as the nuclear
pore complex that spans the nuclear envelope. Which is a double membrane around
the nucleus of the kukaryotic cell. Function: Nuclear pore complexes allow the
transport of molecules across the nuclear envelope. This transport involves RNA
and ribosomal proteins moving from the nucleus into the cytoplasm and proteins,
carbohydrates, signaling molecules and lipids moving into the nucleus.
(d) What are
phytohormones? Explain the role of phytohormones in seed germination.
Ans:
Phytohormones are small molecules of different chemical structures. They can be
indole compounds, adenine derivatives, carotenoids, terpenes or derivatives of
gases. Phytohormones are responsible for developing a fruit that contains the
developing seed. The phytohormones gibberellins are involved in the natural
process of breaking dormancy and other aspects of germination. Before the
photosynthetic apparatus is sufficiently developed in the early stages of
germination, the stored energy stores of starch hydrolysis sprout. In
germination, the breakdown of starch into glucose in the endosperm begins soon
after the seed is exposed to water. gibberellins in seeds
It is believed
to induce starch hydrolysis by inducing the synthesis of the enzyme amylase in
embryonic aleurone cells. An amylase then hydrolyses the starch, which is
abundant in many seeds.
(e) Give an
account on the structure and function of embryo sac in angiosperms.
Ans: It
develops from the megaspore of the plant spore. Embryo sac is also called
female gametophyte. It holds both the embryo plant and the endosperm after
fertilization. There are seven haploid cells in the embryo sac. These include
three exponent cells, a central cell, two synergistic cells, and an egg cell.
Function:
(i) The
synergistic cells of the umbilical cord play an important role in guiding the
pollen tubes synergistically.
(ii)
Exponential cells nourish the embryo sac.
(iii) The
substances produced by antipodal cells help in the growth and development of endosperm.
(iv) It contains starch, lipids and proteins in large quantities which are used for the development of embryo and endosperm.
8. Write precise notes on the following (any two): 4x2=8
(a) Various
steps involved in glycolysis
Ans: The
word glycolysis is derived from the Greek words, glycos for sugar and lysis for
splitting. The scheme of glycolysis was given by Embden, Meyerhof and Parnos
and is called the EMP pathway. Glycolysis occurs in the cytoplasm of the cell.
In this process, glucose is partially oxidized to form 2 molecules of pyruvic
acid. Glucose and fructose are phosphorylated to generate glucose - 6 -
phosphate by the enzyme hexokinase. Glucose-6-phosphate then isomerase to
produce fructose 6 phosphate. ATP is used in two steps first to convert glucose
to glucose 6 phosphate and second to convert fructose 6 phosphate to fructose
1, 6, biphosphate. Fructose is split into 1,6- biphosphate dihydroxyacetone
phosphate and 3 phosphoglyceraldehyde (PGAL). In one step NADH+H+ is formed
from NAD+, this is when 3-PGAL is converted to 1, 3-biphosphoglycerate PGAL is
oxidized and converted to BPGA with inorganic phosphate. The conversion of BPGA
to 3- phosphoglyceric acid (PGA) is also an energy-yielding process. Energy is
also stored in this step in the form of ATP, another ATP is synthesized during
the conversion of PEP to pyruvic acid. Pyruvic acid is the major product of
glycolysis.
(b)
Alternation of generation in bryophytes with illustration.
Ans: Alternation
of Generations: The life cycle of mosses consists of two major phases –
gametophytic phase (n) and sporophytic phase (2n), which regularly alternate
each other. The dominant stage i.e., the gametophyte bears the radium and the
archegonium which in turn bears the antherozoid and the egg. They fuse to form
diploid oospores. It develops into an embryo which later forms the sporophytic
plant. The sporophytic plant is diploid and it produces spores by meiosis of
the spore mother cell. Spores are released from the sporophytic plant and they
germinate to produce the gametophytic plant. This alternate cyclical mode of
life cycle is called alternation of generations.
(c)
Importance of meiotic cell division in plants and the denifition of quiescent
stage 
of cell cycle.
Ans: (i)
It helps in keeping the number of chromosomes constant among the organisms
belonging to vicellodes of the same species (where sexual reproduction takes
place).
(ii) It also
brings diversity which is very important for the process of development.
Cells that do
not divide further exit the G1 phase and enter an inactive phase called the Go
phase of the cycle.
(d)
Description on the different stages of Calvin cycle.
Ans: The
different steps involved in the Calvin cycle are:-
(1)
Carboxylation:- of six molecules
In this step
ribulose monophosphate (RUMP) is converted into 6 molecules of ribulose 1, 5 diphosphates
(RuDP). RuDP combines with CO2 to produce twelve (12) molecules of 3
phosphoglyceric acid (PGA).
6RuMP + 6ATP → 6RuDP
+ 6ADP + 6iP
6 RuDP + 6Co2
→ (12) 3- PGA.
(2) Glycoltic
reversal:- In this step PGA is converted.
Phosphoglyceraldehyde.
This happens in two stages. In the first step, PGA is converted to 1, 3
diphosphoglyceric acid (dPGA) in the presence of ATP.
12PGA + 12ATP
→ 12dPGA + 12ADP + 12Pi
In the next
step, dPGA was reduced to phosphoglyceraldehyde (PGAld) in the presence of
NADPH₂.
12dPGA +
12NADP H₂ → 12PGAID + 12NADP.
Of these 12
molecules of PGALD, two are used for the conversion of fructose, i. 6
diphosphate and later glucose, sucrose, starch etc. (3) Regeneration of RUDP-
The remaining 10 molecules of PGALD are used to regenerate 6 molecules of RUDP
in a series of reactions so that the cycle continues in a cyclic manner without
break.
Summary of
Calvin cycle are:-
6RuDP + 6CO₂ +
12APT +12NADPH₂ →
6RuDP + C
H₁₂O6 + 12ADP + 12Pi + 12NADP.
Difference
between Calvin cycle and Hatch and Slack cycle.
Calvin
Cycle:
1. The primary
acceptor of CO is RuDP.
2. The first
stable compound in 3 PGA, which is a three-carbon compound.
3. Contains only
one type of chloroplast.
4. 18 ATP is
used for the synthesis of a sugar molecule.
Hatch and
Slack Cycles
1. The primary
acceptor of CO2 is phosphoenol pyruvic acid (PEP).
2. The first
stable compound is oxaloacetic acid (OAA) which is a four-carbon compound.
3. Contains two
types of chloroplasts.
4. 30ATP is used
for the synthesis of a sugar molecule.
9. Define photoperiodism and vernalization. Based on the
flowering responses, how can you categorize the angiosperms? 3+2=5
Ans: Some plants require light from time to time to
induce flowering. For example, some plants require exposure to light for a period
longer than a well-defined critical period, while others require exposure to
light for less than this critical period before they can begin to flower.
should be done. The former group are called long day plants while the latter
are called short day plants. There are many plants where there is no such
relationship between the duration of exposure to light and the induction of
flowering response, such plants are called day-neutral plants. Therefore, it
can be said that flowering in some plants depends not only on the combination
of day/night light and dark periods, this is called photoperiodism.
Vernalization:
There are plants for which flowering either quantitatively or qualitatively
depends on exposure to low temperatures. This phenomenon is known as globalization.
This prevents
late reproductive development in the growing season and allows sufficient time
for the plant to reach maturity. It refers to the promotion of flowering by a
period of low temperature.
An example of
vernalization is seen in biennial plants. Biennials are monocarpic plants that
normally flower and die in the second season. Beet, cabbage and carrot are some
common biennials. Subjecting a growing biennial plant to cold treatment
stimulates a subsequent photoperiodic flowering response.
On the basis of
flowering responses, angiosperms are classified into long day plants, short day
plants and day neutral plants.
Or
What are
nucleic acids? Mentioning the basic components, draw the structure of a DNA
molecule. 2+3=5
Ans: Nucleic
acids are molecules that allow organisms to transfer genetic information from
one generation to the next. There are two types of nucleic acids:
deoxyribonucleic acid (known as DNA) and ribonucleic acid (known as RNA).
Structure of
Nucleic Acids: Nucleic Acid Components:
sugar - ribose
or deoxyribose
Base + sugar =
nucleoside - N-glycoside bond.
Nucleoside +
phosphoric acid = nucleotide - ester bond.
Condensation
polymer of nucleic acid - nucleotide (nucleotide - nucleotide) phosphor diester
bond.
Watson–Crick
double helical structure of DNA and the forces responsible for the stability of
the helix.
Part - II
(Zoology)
1. Fill in the blanks: 1x5=5
(a) Notochord
is derived Frome embryonic development.
(b) Coelenterates are radially symmetrical
animals.
(c)
Crossing-over takes place in Meiosis cell
division.
(d) The
secondary structure of protein is due to H-bond.
(e) RBC has
the life span of about 100-120 days.
2. Answer very briefly any four of the following: 1x4=4
(a) What is
the function of ink gland?
Ans: The
ink gland used to eject a cloud of black ink to confuse us predators.
(b) Animals
of which phylum contain spicules as their endoskeleton?
Ans: Phylum
Porifera have spicules as their endoskeleton.
(c) What is
the function of gizzard?
Ans: The
function of grinder is mechanical breaking of seeds and other food items.
(d) Name the
tissue where fats are deposited.
Ans: The
tissue in which fat is stored is called adipose tissue.
(e) Write the
name of two sub-plases of M-phase in cell cycle.
Ans: The
names of the two sub-phases of M-phase are karyokinesis and cytokinesis.
(f) Why is
spleen called the graveyard of red blood corpuscles?
Ans: The
dead RBCs are mixed with the spleen. That's why it is called the graveyard of
RBC.
3. Write the differences between the following (any
two): 2x2=4
(a) DNA and
RNA
Ans: The
differences between RNA and DNA are:
(i) RNA
molecule is very small as compared to DNA.
(ii) RNA is
single-stranded, while DNA is double-stranded.
(iii) The
sugar in RNA is ribose, while in DNA it is deoxyribose.
(iv) RNA
contains cresyl while DNA contains thymine.
(b) Exocrine
and endocrine glands
Ans: Endocrine
Gland: This is the gland which does not have a duct system, rather it pours
its secretion directly into the blood. Hormone is a chemical secreted by an
endocrine gland that regulates a specific metabolic function.
Exocrine
Gland: It is a gland which has a duct system to drain its secretion at a
particular place.
(c) Striated
and unstriated muscles
Ans: Striated
muscles
(i) Striae are
present in this tissue
(ii) They are
voluntary in action.
(iii) Lines
are long and cylindrical
(iv)
Multicentric.
Undrawn
muscles
(i) Streaks
are absent.
(ii)
Involuntary in actions.
(iii) Long
with pointed ends.
(iv)
Decentralised.
(d) Small
intestine and large intestine
Ans: Small
intestine
(i) It
consists of three parts.
(ii) Villi are
present.
(iii) Peer's
patches are present.
Large
intestine
(i) It
consists of four parts.
(ii) Villi are
absent.
(iii) Peer
patches are absent.
4. Answer the following briefly (any three): 2x3=6
(a) What is
myogenic heart?
Ans: The
normal activity of our heart is auto regulated by special muscles (nodal
tissue), our heart is called myogenic.
(b) Name the
two covalent bonds responsible for maintenance of a protein structure.
Ans: There
are two covalent bonds: peptide bond and Disulphide bond.
(c) “All
vertebrates are chordates but all chordates are not vertebrates.” Justify the
statement.
Ans: The
notochord occurs during the embryonic period in members of the vertebrate
Brata.
In the adult
the notochord is rewound by the vertebral column, so all vertebrates are
chordates but not all chordate vertebrates.
(d) Write the
economic importance of earthworm.
Ans: Economic
importance of earthworms:
(i) Earthworms
improve soil fertility in various ways and are of immense importance in
agriculture.
(ii) They are
used as fodder and food.
(iii) Many
people earn their livelihood by catching these insects and supplying them to
scientific laboratories.
(iv) Nowadays
they are used to make various medicines for the treatment of many types of
diseases.
(e) How does
conduction of nerve impulses take place through synapse?
Ans: Near
its termination, the axon divides into several branches, each ending in a
synaptic knob. These are the synaptic clefts that separate the membranes of
neurons. The synaptic knob is filled with numerous membranes bound synaptic
vesicles in its cytoplasm. These vesicles secrete chemicals such as adrexialine
and acetylcholine into stones. Whenever a nerve impulse reaches a nerve ending,
its stored chemicals are released into the synaptic cleft. They then diffuse
across the synaptic cleft to reach the dendrites of the next neuron. This
results in the transmission of nerve impulse to the next neuron.
5. Write short notes on (any two): 3x2=6
(a)
Polysaccharides
Ans: Polysaccharides
are long chains of sugars. They are threads (literally a cotton thread) that
contain various monosaccharides as building blocks. For example, cellulose is a
polymeric polysaccharide consisting of only one type of monosaccharide, that
is, glucose. Cellulose is a homopolymer. Starch is one of its forms but is
present in plant tissues as a storehouse of energy. Animals have another type
called glycogen. Inulin is a polymer of fructose. In a polysaccharide chain
(such as glycogen), the right end is called the reducing end and the left end
is called the non-reducing end.
(b) Skeletal
muscles
Ans: Skeletal
muscle tissue is closely associated with the bones of the skeleton. In
specialized muscles such as biceps, striated (striated) skeletal muscle fibers
are bundled together in a parallel fashion. A sheath of tough connective tissue
surrounds many bundles of muscle fibers.
(c) Auditory
mechanism
Ans: The
external car receives the sound waves and directs them to the ear drum. The ear
drum vibrates in response to the sound wave and these vibrations are
transmitted through the ossicles of the ear through the oval window to the
fluid of the cochlea, they generate waves in the lymph. These waves cause
movements in the basilar membrane that help the hair cells to twist, exerting
pressure on the tectorial membrane. Thus, we generate nerve impulses which are
transmitted to the auditory cortex of the brain where the impulses are analyzed
and the sound is recognized.
(d)
Uricotelic animal
Ans: (i)
Animals that excrete a major part of the nitrogenous waste in the form of
semi-solid or solid uric acid are called uricotelic animals.
(ii) e.g.,
Birds, lizards, snakes, terrestrial insects.
6. What is neuron? Describe the sturcture of a myelinated
neuron with a labelled diagram. 1+2+2=5
Ans: The nervous system of all animals is nisis
granules: made up of highly specialized cells called neurons that can detect,
receive, and transmit a variety of stimuli to the cell body. Nuscicus A neuron
is a microscopic structure made up of three major parts, namely the Schwann
cell. Cell body, dendrites and axon. The cell body consists of cytoplasm with
specific cell organelles and some granular bodies called Nissl granules. Small
fibrils that branch repeatedly and exit the cell body also contain Nissl grains
and are called dendrites. These fibers transmit terminal impulses towards the
cell body. The axon is a long fibre, whose distal end is branched. Each branch
ends in a bulb-like structure called a synaptic knob. There are two types of
axons, namely, myelinated and nonmyelinated. Myelinated nerve fibers are
surrounded by Schwann cells, which form a myelin sheath around the axon. The
gap between two adjacent myelin sheaths is called the node of Ranvier.
Or
What is
hormone? Write the chemical nature of hormone. Mention four important functions
of thyroxine hormone. 1+2+2=5
Ans: Hormones
are non-nutritive chemicals that act as intracellular messengers and are
produced in trace amounts.
On the
basis of chemical nature, hormones are classified into different groups-
(i) Peptide,
polypeptide and protein hormones (such as insulin, glucagon etc.)
(ii) Steroids
(such as testosterone, cortisol)
(iii)
Iodothyronine (thyroid hormone)
(iv)
amino-acid derivatives (epinephrine)
Thyroxim
hormones play an important role in this,
(a) regulating
the metabolic rate of the body,
(b) heart and
digestive functions,
(c) muscle
control,
(d)
Development of brain and maintenance of bones.
7. What is circulatory system? Illustrate a cardiac cycle
with suitable diagram. 1+2+2=5
Ans: The system that circulates blood and lymph
through the body, consisting of the heart, blood vessels, blood, lymph and
lymph vessels and glands, is called the circulatory system.
The four chambers
of the heart are in a relaxed state, that is, they are in joint diastole. As
the tricuspid and bicuspid valves are open, blood from the pulmonary veins and
vena cava flows through the left and right atria into the left and right
ventricles, respectively. In this state, the lunar doors are closed. The SAN
now generates an action potential that stimulates both atria to undergo
simultaneous contraction - atrial systole. This increases the flow of blood to
the ventricles by about 30 percent. The action potential is conducted by the
AVN and AV bundle to the ventricular side, from where the bundle of His
conducts it through the entire ventricular musculature. This causes the
ventricular muscles to contract, (ventricular systole), while the atria undergo
relaxation (diastole), coinciding with ventricular systole. Ventricular systole
increases ventricular pressure causing the tricuspid and bicuspid valves to
close in an effort to backflow blood into the atria. As ventricular pressure further
increases, the semilunar valves guarding the pulmonary artery (right side) and
the aorta (left side) are forced open, allowing blood in the ventricles to flow
through these vessels into the circulatory system. The ventricles now relax
(ventricular diastole) and ventricular pressure drops causing the semilunar
valves to close, preventing backflow of blood into the ventricles. As
ventricular pressure falls further, the tricuspid and bicuspid valves are
pushed open by the pressure exerted by the blood in the atria that is being
emptied into them by the veins. The blood now moves freely into the ventricles
once again. The ventricles and atria are now again at rest (combined diastole)
as before. This sequential event in the heart which is repeated cyclically is
called the cardiac cycle.
Or
What is
locomotion? Describe the sliding filament theory of locomotion. 1+4=5
Ans: The
movement which results in change of place from place to place is called
locomotion.
A sarcomere
consists of one light band and half a dark band. It also contains myosin and
actin. As the muscle is stimulated, the actin filament 3 moves over the myosin
filament, reducing the length of the light band. The place where the filament
is slipped is known as the cross bridge. Thus, the total length of the
sarcomere decreases and ultimately the length of myoglobin. A muscle never
extends across a stimulus but always contracts across its length. This
principle of muscle contraction was proposed by H.E. Known as the sliding
filament theory given by In 1954 Huxley and A.F. Huxley.
***
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