BiologyQ1–14 of 14 questions
Page 1 of 1 · English
1
BiologyEasyMCQAIIMS · 1987
The wing in $Pinus$ seed originates from
A
Integument
B
Adaxial surface of ovuliferous scale
C
Bract scale
D
Cone axis
Solution
(B) The wing of the $Pinus$ seed is derived from the adaxial surface of the ovuliferous scale. As the seed matures,a thin,papery layer of the ovuliferous scale tissue separates and remains attached to the seed coat $(testa)$,forming a wing that aids in wind dispersal.
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2
BiologyMediumMCQAIIMS · 1987
Fusiform initials form:
A
Vascular rays
B
Tracheary elements
C
Ray parenchyma
D
Phloem parenchyma
Solution
(B) Fusiform initials are elongated cells in the vascular cambium that divide to produce the axial system of the secondary xylem and secondary phloem. These include tracheary elements (tracheids and vessels),fibres,and axial parenchyma. Therefore,the correct option is $B$.
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3
BiologyMediumMCQAIIMS · 1987
Stomata open at night and close during the day in
A
Xerophytes
B
Gametophytes
C
Mesophytes
D
Hydrophytes
Solution
(A) Stomata that open at night and close during the day are known as $scotoactive$ stomata.
This mechanism is an adaptation to reduce water loss through transpiration in arid environments.
These are typically found in succulent plants such as $Opuntia$,$Aloe$,and $Bryophyllum$,which are classified as $Xerophytes$.
This mechanism is an adaptation to reduce water loss through transpiration in arid environments.
These are typically found in succulent plants such as $Opuntia$,$Aloe$,and $Bryophyllum$,which are classified as $Xerophytes$.
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4
BiologyMediumMCQAIIMS · 1987
What is the cause of excurrent habit in Pinus?
A
Presence of gibberellin
B
Presence of apical dominance
C
High concentration of cytokinin
D
High concentration of $ABA$
Solution
(B) The excurrent habit in $Pinus$ refers to the conical shape of the tree,where the main stem grows continuously and the lateral branches are shorter,giving the tree a pyramidal appearance.
This growth pattern is primarily controlled by apical dominance,a phenomenon where the terminal bud (apical bud) suppresses the growth of lateral buds due to the high concentration of the hormone auxin produced at the apex.
Therefore,the presence of apical dominance is the direct cause of the excurrent habit in $Pinus$.
This growth pattern is primarily controlled by apical dominance,a phenomenon where the terminal bud (apical bud) suppresses the growth of lateral buds due to the high concentration of the hormone auxin produced at the apex.
Therefore,the presence of apical dominance is the direct cause of the excurrent habit in $Pinus$.
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5
BiologyEasyMCQAIIMS · 1987
The pigment involved in red-far red light interconversion is
A
Cytochrome
B
Xanthophyll
C
Lycopene
D
Phytochrome
Solution
(D) $Phytochrome$ is a proteinaceous pigment that exists in two interconvertible forms: $Pr$ (which absorbs red light at $660 \ nm$) and $Pfr$ (which absorbs far-red light at $730 \ nm$).
This interconversion between $Pr$ and $Pfr$ forms acts as a biological switch,allowing plants to sense light quality and regulate various developmental processes such as flowering and seed germination.
This interconversion between $Pr$ and $Pfr$ forms acts as a biological switch,allowing plants to sense light quality and regulate various developmental processes such as flowering and seed germination.
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6
BiologyMediumMCQAIIMS · 1987
The main difference between brown fat and white fat is that the cells of brown fat:
A
Are multicoloured
B
Have more mitochondria
C
Are polygonal in shape
D
All the above
Solution
(B) Brown adipose tissue $(BAT)$ is specialized for thermogenesis. The cells of brown fat contain a large number of mitochondria,which give the tissue its characteristic brown color and are responsible for the uncoupling of oxidative phosphorylation to produce heat instead of $ATP$. In contrast,white adipose tissue $(WAT)$ contains fewer mitochondria and is primarily used for energy storage.
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7
BiologyMediumMCQAIIMS · 1987
The appearance of albumin in the urine is most likely due to
A
Increase in the blood pressure
B
Decrease in the blood osmotic pressure
C
Damage to the Malpighian corpuscles
D
Damage to the proximal convoluted tubules
Solution
(C) Normally,albumin cannot pass through the filtration slits of the glomerulus due to its large molecular size.
However,in pathological conditions such as kidney disease,inflammation,or damage to the Malpighian corpuscles (glomerulus and Bowman's capsule),the filtration membrane becomes compromised.
This damage increases the permeability of the filtration barrier,allowing large protein molecules like albumin to leak into the filtrate,a condition known as albuminuria.
However,in pathological conditions such as kidney disease,inflammation,or damage to the Malpighian corpuscles (glomerulus and Bowman's capsule),the filtration membrane becomes compromised.
This damage increases the permeability of the filtration barrier,allowing large protein molecules like albumin to leak into the filtrate,a condition known as albuminuria.
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8
BiologyEasyMCQAIIMS · 1987
Which of the following cranial nerves in humans is both sensory and motor?
A
Olfactory
B
Trigeminal
C
Optic
D
Auditory
Solution
(B) The correct answer is $B$. The Trigeminal nerve $(V)$ is a mixed nerve,meaning it contains both sensory and motor fibers. It is responsible for sensation in the face and motor functions such as biting and chewing. In contrast,the Olfactory $(I)$,Optic $(II)$,and Auditory $(VIII)$ nerves are purely sensory.
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9
BiologyMediumMCQAIIMS · 1987
The endodermal derivatives include:
A
Thyroid
B
Pineal gland
C
Spleen
D
Pituitary
Solution
(A) The endoderm is the innermost germ layer formed during gastrulation.
It gives rise to the epithelial lining of the gastrointestinal tract,the respiratory system,and several glands.
The thyroid gland is derived from the endoderm of the pharyngeal floor.
The pineal gland and pituitary gland are derivatives of the ectoderm (neuroectoderm),while the spleen is derived from the mesoderm.
It gives rise to the epithelial lining of the gastrointestinal tract,the respiratory system,and several glands.
The thyroid gland is derived from the endoderm of the pharyngeal floor.
The pineal gland and pituitary gland are derivatives of the ectoderm (neuroectoderm),while the spleen is derived from the mesoderm.
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10
BiologyEasyMCQAIIMS · 1987
$EDTA$ is widely used in tissue cultures; it is a:
A
Hormone
B
Vitamin
C
Buffer
D
Nutrient
Solution
(C) $EDTA$ (Ethylenediaminetetraacetic acid) acts as a chelating agent and is often used in tissue culture media to maintain the stability of the medium by acting as a buffer. It helps in maintaining the $pH$ of the culture medium,which is essential for the optimal growth of plant tissues.
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11
BiologyMediumMCQAIIMS · 1987
Holoblastic cleavage may occur in eggs which are
A
Oligolecithal only
B
Mesolecithal only
C
Macrolecithal only
D
Oligolecithal and mesolecithal both
Solution
(D) Holoblastic cleavage refers to the complete division of the egg.
It occurs in eggs with low to moderate amounts of yolk.
$1$. Oligolecithal eggs (e.g.,Amphioxus,mammals) contain very little yolk,resulting in equal holoblastic cleavage.
$2$. Mesolecithal eggs (e.g.,amphibians) contain a moderate amount of yolk,resulting in unequal holoblastic cleavage.
Therefore,holoblastic cleavage occurs in both oligolecithal and mesolecithal eggs.
It occurs in eggs with low to moderate amounts of yolk.
$1$. Oligolecithal eggs (e.g.,Amphioxus,mammals) contain very little yolk,resulting in equal holoblastic cleavage.
$2$. Mesolecithal eggs (e.g.,amphibians) contain a moderate amount of yolk,resulting in unequal holoblastic cleavage.
Therefore,holoblastic cleavage occurs in both oligolecithal and mesolecithal eggs.
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12
BiologyMediumMCQAIIMS · 1987
Immune deficiency syndrome in humans could develop as a consequence of
A
$AIDS$ virus infection
B
Defective liver
C
Defective thymus
D
Weak immune system
Solution
(A) Immune deficiency syndrome,specifically $AIDS$ ($Acquired$ $Immuno$ $Deficiency$ $Syndrome$),is caused by the $Human$ $Immunodeficiency$ $Virus$ $(HIV)$.
$HIV$ targets and destroys $Helper$ $T$-lymphocytes ($CD4^+$ cells),which are essential for the proper functioning of the immune system.
As the number of these cells declines,the body loses its ability to fight off infections and cancers,leading to the syndrome of immune deficiency.
Therefore,$AIDS$ virus infection is the primary cause of this specific syndrome.
$HIV$ targets and destroys $Helper$ $T$-lymphocytes ($CD4^+$ cells),which are essential for the proper functioning of the immune system.
As the number of these cells declines,the body loses its ability to fight off infections and cancers,leading to the syndrome of immune deficiency.
Therefore,$AIDS$ virus infection is the primary cause of this specific syndrome.
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13
BiologyMediumMCQAIIMS · 1987
The release of phosphates and nitrates into water bodies (i.e., rivers and lakes) leads to:
A
Increased algae growth
B
Increased growth of decomposers
C
Nutrient enrichment
D
Reduced algae growth
Solution
(C) The release of phosphates and nitrates into water bodies leads to a process known as $Eutrophication$.
These nutrients act as fertilizers for aquatic plants and algae, causing their excessive growth, which is known as an algal bloom.
This phenomenon is fundamentally a form of nutrient enrichment in aquatic ecosystems.
Therefore, the most direct and encompassing consequence among the given options is nutrient enrichment.
These nutrients act as fertilizers for aquatic plants and algae, causing their excessive growth, which is known as an algal bloom.
This phenomenon is fundamentally a form of nutrient enrichment in aquatic ecosystems.
Therefore, the most direct and encompassing consequence among the given options is nutrient enrichment.
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14
BiologyEasyMCQAIIMS · 1987
Reserpine, an alkaloid or drug extracted from the roots of which of the following plants, cures mental disorders and reduces or checks blood pressure?
A
Rauwolfia serpentina
B
Ferula asafoetida
C
Atropa belladonna
D
Digitalis purpurea
Solution
(A) The correct answer is $A$.
Reserpine is an indole alkaloid extracted from the roots of the plant $Rauwolfia$ $serpentina$ (commonly known as Sarpagandha).
It belongs to the family $Apocynaceae$.
It is medically used to treat high blood pressure (hypertension) and certain mental disorders like schizophrenia by acting as a tranquilizer.
Reserpine is an indole alkaloid extracted from the roots of the plant $Rauwolfia$ $serpentina$ (commonly known as Sarpagandha).
It belongs to the family $Apocynaceae$.
It is medically used to treat high blood pressure (hypertension) and certain mental disorders like schizophrenia by acting as a tranquilizer.
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