Download Biology Answer Key

ITL Public School
FIRST TERM (2015 -16)
Date: 21/09/15
Class: XI
Marking Scheme Biology (044)
Time: 3 hrs
M. M: 70
General Instructions:
1. All questions are compulsory
2. The question paper consists of four sections A,B,C and D. Section A contains 5 questions of 1 mark
each, Section B consists of 5 questions of 2 marks each, Section C consists of 12 questions of 3 marks
Section D consists of 1 value based question of 4 marks and Section E consists of 5 questions of 3
marks each.
3. There is an internal choice in one question of 2 marks, one question of 3 marks and all the three
questions of 5 marks.
4. Wherever necessary, the diagrams drawn should be neat and properly labeled.
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Section A
Name two hormones that regulate calcium level in blood.
PTH and TCT
Which tissue is afflicted by Myasthenia Gravis? What is the underlying cause?
Neuromuscular junction, autoimmune disorder
What do grey and white matter in brain represent?
Unmyelinated cell bodies and dendrites comprise grey matter while myelinated axons
makeup white matter.
How many molecules of ATP and NADH2 are synthesized in one turn of Kreb’s cycle?
4 NADH2 and 1 ATP are produced
Categorise human vertebrae on the basis of their location giving the specific number in each
category.
Cervical – 7, thoracic – 12, lumbar – 5 , sacral – 1, coccygeal – 1
Section B
Why and where is aldosterone produced? What factors stimulate its secretion?
From Adrenal cortex, so that it causes reabsorption of Na+ and water from the distal
parts of the tubule. This increases GFR and blood pressure
Low GFR activates JG cells to release rennin which converts angiotensinogen to
angiotensin I and II . Angiotensin II activates adrenal cortex to release aldosterone.
Which cell organelles are involved in photorespiration? In which cell organelle substrate for
photorespiration is used?
Three cell organelles are chloroplast, mitochondria and peroxisome.
The substrate for photorespiration is glycolic acid which is oxidized in peroxisome to
produce glyoxylic acid and glycine.
What is the function and importance of Eustachian tube?
Opening and closing of eustachian tube equalizes atmospheric pressure in the middle
ear, closing of Eustachian tube protects the middle ear from unwanted pressure
fluctuations and loud sounds.
Why is glomerular filtrate hypertonic and hypotonic in descending and ascending limb of
loop of Henle, respectively? What is the effect of ADH on collecting tubule?
The descending loop is permeable to water but impermeable to electrolytes.The
ascending limb is impermeable to water but allows transport of electrolytes actively.
ADH reabsorbs water from collecting tubule, preventing diuresis., increase in blood
pressure.
a) In old age people often suffer from stiff and inflamed joints. What is this condition called?
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What are the possible reasons for these symptoms?
b) Give two examples of synovial joints found in hindlimbs.
Gout – due to accumulation of uric acid crystals
b) hinge – knee joint, saddle joint – carpal and metacarpal
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Section C
Label A- F given in the figure of human skull below:
a- Parietal bone, B- Temporal Bone, C – Occipital Bone, D – Maxilla, E – Mandible, F –
Spenoid bone
Differentiate between aerobic respiration and combustion.
Aerobic respiration – energy produced in the form of ATP, biochemical process, energy
is relesed in stepwise manner,
Combustion – energy produced in the form of heat and light, physical process, lot of
energy produced
What are the assumptions made during the calculation of net gain of ATP?
Sequential , orderly pathway functioning with one substrate forming the next with
glycolysis, TCA cycle and ETS
NADH synthesized in glycolysis is transferred into the mitochondria
None of the intermediates in the pathway are utilized to synthesise any other compound
Only glucose is being respired
i) What is the chemical nature of the white solid material usually found in bird droppings?
ii) How much urine is excreted in a day by a normal healthy human and what is the GFR
value for the same? What do these values indicate about excretion of waste in humans?
Explain the process.
Uric acid, urine – 1.5 litres GFR value - 125ml/min, nearly 99 % of filtrate is
reabsorbed by the renal tubule. , glucose, amino acids, Na + in the filtrate are
reabsorbed actively
What are the two types of Diabetes? Give examples of Hyperglycemic and hypoglycemic
hormone in humans.
Diabetes insipidus- deficiency of ADH and diabetes mellitus- deficiency of insulin
Hyperglycemic- Glucagon and hypoglycemic hormone – insulin
Deficiency of Calcium in body would cause tetany, explain with the help of diagram.
Mechanism of muscle contraction
i) A person suffering from severe Cold and Cough had a difficulty in maintaining body
balance. Which part of the body might be affected for poor coordination and balance?
ii) Distinguish between blind spot and yellow spot of eye.
Inner Ear
Blind spot – Photoreceptor cells are not present, optic nerve arise from here
Yellow spot – macula lute ahs only cone cells , resolution is greatest
What is the difference between the photoreceptor cells of the eye? How do you perceive the
colour of an object?
Rod cells – Rhodopsin Protein, more in no. Sensitive to dim light, Night blindness,
cylindrical
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Cone cells – Iodopsin protein, Comp low, Sensitive to light , colour blindness, conical
There are three types of cones which possess their own characteristic photopigments
that respond to red, greem , blue lights.
Name the hormones released by ovary. How do these hormones regulate different functions
of female reproductive system?
Ovary releases estrogen and progesterone. Corpus luteum releases progesterone which
maintains endometrium for pregnancy
Follicular cells in ovary release estrogen which stimulates pituitary to release FSH and
also determines secondary sexual characters.
A test tube containing water, Carbon dioxide and isolated chloroplasts was illuminated. A
gas started evolving, on the basis of this experiment answer the following questions:
i) Name the gas evolved and how would it be identified?
ii) From which raw material the gas is evolved?
ii) Explain the process by which it is evolved.
iii) In which wavelength of light, would the gas stop evolving and in which wavelength
it would be maximum?
i) Oxygen , by bringing a burning matchstick near the mouth of test tube
ii) Water ii) It is evolved due to photosynthesis iii) green light, Blue and red
wavelength
Explain any three internal and three external factors that determine the rate of
photosynthesis.
Internal Factors – number, size, age, orientation of leaves, mesophyll cells, chloroplast,
internl CO2 conc, amount of chlorophyll
External factors – sunlight, temperature, CO2 conc. water
Describe the location of JGAand counter current system in human kidney. Draw labeled
diagram of nephron showing blood vessels, duct , renal corpuscle and tubule.
The afferent arteriole and DCT forms JGA
The opposite flow of blood in limbs of vasa recta forms counter current with henle’s
loop.
List the different groups of hormones secreted by adrenal cortex. Give the specific region of
secretion and one major function of each. Name the disorder that may occur in human if the
adrenal cortex is damaged.
Adrenal cortex secretes corticoids
Zona Glomerulosa – Aldosterone- mineralcorticoid
Zona Fasciculata – cortisol – glucocorticoid
Mineralcorticoids regulate the balance of water and electrolytes in body
Glucocorticoids stimulate lipolysis, gluconeogenesis, proteolyis. Produce nti inflamtory
reactions, suppress immune response, stimulates RBC production. Addison’s disease
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i) Name theT3 and T4 components of Thyroid hormone. Explain their specific action.
ii) Name the disorders caused due to imbalance of thyroid hormone in body. Also mention
the effects of the disorders.
Triiodothyronine, tetraiodothyronine
Regulate BMR, control metabolism of carbohydrate, protein , fats
Influence maintenance of water and electrolyte balance
They support process of RBC formation
Deficiency – Hypothyroidism, oversecretion – hyperthyroidism
Hypothyroidism – causes defective development and maturation of growing baby
leading to stunted growth, mental retardation, low intelligence, abnormal skin, deaf
mutism, irregular menstrual cycle. Hyperthyroidism affects body physiology
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Section D
Due to deforestation the increasing concentration of CO2 will effect the rate of
photosynthesis.
i) How will CO2 concentration effect the rate of photosynthesis in C3 and C4 plants?
ii) If the plant productivity increases should we continue with deforestation? Give
reasons in support of your answer.
i)
C3 plants will show increase in photosynthesis because the CO2 saturation is
450 ul/l, but in C4 plants it is 360 ul/l . Thus current CO2 levels are limiting
for C3 plants.
ii)
No. because besides productivity of planats deforestation has other hrmful
effects on envt – global warming, disturbed geological cycles.
Section E
What is EMP pathway? Where does it occur and why is it called so? What are the end
products? Trace the fate of these products in aerobic and anaerobic respiration.
Embden, Meyerhof and Parnas is Glycolysis
In Cytoplasm , 2 molecules of ATP, 2 molecules of NADH, 2 molecules of Pyruvate
G;ycolysis – 3marks
OR
Explain chemiosmosis hypothesis for ATP production in respiration.
Explanation – 3m , digramatic flowchart – 2m
Name the photosynthetic mechanism adapted to help plants growing in dry conditions.
Explain the mechanism giving reasons why this adaptation is beneficial to such plants?
Hatch and Slack pathway / C4 cycle – 3+2 m explanation with flow chart
OR
a) What is photorespiration? How does this process result in loss to the plants?
b) Describe Van Neil’s experiment and his conclusion regarding photosynthesis.
a) Photorespiration occurs when RuBP reacts with Oxygen instead of CO2 and uses
ATP
Reactions – 2m
b) Van Neil performed experiment using purple and green bacteria
He demonstrated that photosynthesis light dependent process in which hydrogen from
water releases oxygen
Explain what is meant by resting membrane potential of a neuron? How do ion channels and
sodium potassium pumps contribute to the resting potential Describe the role of Na+ and K+
ions in the conduction of nerve impulses.
Resting membrane potential is when Na- K ion channels are impermeable and Positive
charge is outside the axoplasm and negative charge is inside
Digram – 3 m
OR
Draw a labeled diagrams of human ear and cochlea and label the following parts
i) Ear ossicles
ii) organ of Corti
iii) otolith orgn
iv) Scala vestibule
v) Reissner’s membrane
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