BiologyQ1–60 of 61 questions
Page 1 of 2 · English
1
BiologyMediumMCQAIIMS · 1999
The basic unit of classification / taxonomy is
A
Genus
B
Species
C
Family
D
Order
Solution
(B) The correct answer is $B$.
Species occupies a key position in biological classification.
It is considered the fundamental or basic unit of classification/taxonomy because it represents a group of individual organisms with fundamental similarities.
Species occupies a key position in biological classification.
It is considered the fundamental or basic unit of classification/taxonomy because it represents a group of individual organisms with fundamental similarities.
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2
BiologyMediumMCQAIIMS · 1999
The Linnaeus system of plant classification is:
A
Artificial
B
Natural
C
Phylogenetic
D
None of the above
Solution
(A) The Linnaeus system of classification is considered $Artificial$ because it is based on only one or two morphological characters of plants,such as the number of stamens and carpels,rather than considering the entire range of plant characteristics or evolutionary relationships.
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3
BiologyMediumMCQAIIMS · 1999
'Peptidoglycan' is a characteristic constituent of the cell wall of
A
Eubacteria and unicellular eukaryotes
B
Bacteria and cyanobacteria
C
Archaebacteria and eukaryotes
D
All members of 'monera' and 'protista'
Solution
(B) Peptidoglycan,also known as murein,is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria,forming the cell wall.
Cyanobacteria are a phylum of bacteria that obtain their energy through photosynthesis and possess a cell wall containing peptidoglycan.
Therefore,both bacteria (eubacteria) and cyanobacteria are characterized by the presence of peptidoglycan in their cell walls.
Archaebacteria lack peptidoglycan in their cell walls,and eukaryotes (like fungi or plants) have cell walls made of chitin or cellulose,respectively.
Cyanobacteria are a phylum of bacteria that obtain their energy through photosynthesis and possess a cell wall containing peptidoglycan.
Therefore,both bacteria (eubacteria) and cyanobacteria are characterized by the presence of peptidoglycan in their cell walls.
Archaebacteria lack peptidoglycan in their cell walls,and eukaryotes (like fungi or plants) have cell walls made of chitin or cellulose,respectively.
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4
BiologyEasyMCQAIIMS · 1999
One of the major components of the bacterial cell wall is a polymer called:
A
Peptidoglycan
B
Cellulose
C
Chitin
D
Xylan
Solution
(A) The bacterial cell wall is primarily composed of a polymer known as Peptidoglycan (also called murein).
It consists of sugars and amino acids that form a mesh-like layer outside the plasma membrane of most bacteria,providing structural support and protection.
It consists of sugars and amino acids that form a mesh-like layer outside the plasma membrane of most bacteria,providing structural support and protection.
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5
BiologyEasyMCQAIIMS · 1999
Hormogonia are the vegetatively reproducing structures of
A
Ulothrix
B
Spirogyra
C
Oscillatoria
D
Chlamydomonas
Solution
(C) Hormogonia are short,motile or non-motile segments of filaments that break off from the parent filament to form new colonies.
These structures are characteristic of certain filamentous cyanobacteria (blue-green algae).
Among the given options,$Oscillatoria$ is a filamentous cyanobacterium that reproduces vegetatively through the formation of hormogonia.
$Ulothrix$,$Spirogyra$,and $Chlamydomonas$ are green algae and do not produce hormogonia.
These structures are characteristic of certain filamentous cyanobacteria (blue-green algae).
Among the given options,$Oscillatoria$ is a filamentous cyanobacterium that reproduces vegetatively through the formation of hormogonia.
$Ulothrix$,$Spirogyra$,and $Chlamydomonas$ are green algae and do not produce hormogonia.
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6
BiologyEasyMCQAIIMS · 1999
The primary grouping of protozoan protists is based on:
A
Locomotor organelles
B
Size and shape
C
Mode of feeding
D
Mode of reproduction
Solution
(A) Protozoan protists are primarily classified into four major groups based on their locomotor organelles,which are structures used for movement.
These groups are:
$1$. Amoeboid protozoans (using pseudopodia).
$2$. Flagellated protozoans (using flagella).
$3$. Ciliated protozoans (using cilia).
$4$. Sporozoans (lacking specialized locomotor organelles in the infectious stage).
These groups are:
$1$. Amoeboid protozoans (using pseudopodia).
$2$. Flagellated protozoans (using flagella).
$3$. Ciliated protozoans (using cilia).
$4$. Sporozoans (lacking specialized locomotor organelles in the infectious stage).
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7
BiologyEasyMCQAIIMS · 1999
The infective stage of $Trypanosoma$ $gambiense$ is:
A
Metacyclic
B
Crithidial
C
Leptomonas
D
Leishmania
Solution
(A) The infective stage of $Trypanosoma$ $gambiense$ is the metacyclic form.
These forms are developed within the lumen of the salivary glands of the tsetse fly (the vector).
When the fly bites a human, these metacyclic trypomastigotes are injected into the bloodstream, leading to the infection.
These forms are developed within the lumen of the salivary glands of the tsetse fly (the vector).
When the fly bites a human, these metacyclic trypomastigotes are injected into the bloodstream, leading to the infection.
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8
BiologyMediumMCQAIIMS · 1999
Primitive types of stomata are found in the
A
Leaves of moss plants
B
Axis of the moss plant
C
Apophysis of capsule of moss
D
All the above
Solution
(C) The correct answer is $C$. In mosses,the stomata are considered primitive because they lack functional guard cells that regulate opening and closing. These structures are specifically found in the $Apophysis$ region of the moss capsule,which is the sterile basal part of the sporophyte.
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9
BiologyMediumMCQAIIMS · 1999
The prothallus represents:
A
Gametophyte of fern
B
Sporophyte of angiosperm
C
Sporophyte of gymnosperm
D
Sporophyte of fern
Solution
(A) The prothallus is the gametophyte of a fern.
It is exosporic,flat,green,autotrophic,cordate $(heart-shaped)$,multicellular,short-lived,small,reduced,dorsiventral,and a free-living independent non-vascular structure.
It is exosporic,flat,green,autotrophic,cordate $(heart-shaped)$,multicellular,short-lived,small,reduced,dorsiventral,and a free-living independent non-vascular structure.
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10
BiologyEasyMCQAIIMS · 1999
The plant which bears clinging roots is
A
Trapa
B
Orchid
C
Screw pine
D
Podostemon
Solution
(B) In $Orchid$,many short,branched,adventitious roots arise at each node of the weak stem to help the plant climb up its support; these are called clinging roots.
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11
BiologyEasyMCQAIIMS · 1999
Water currents in $Leucosolenia$ are produced by
A
Choanocytes
B
Pinacocytes
C
Archeocytes
D
Thesocytes
Solution
(A) Water currents in $Leucosolenia$ (a type of sponge) are produced by the beating of flagella present on the $Choanocytes$ (also known as collar cells).
These cells line the spongocoel and the canals,and their coordinated flagellar movement creates a constant flow of water,which is essential for respiration,nutrition,and excretion.
These cells line the spongocoel and the canals,and their coordinated flagellar movement creates a constant flow of water,which is essential for respiration,nutrition,and excretion.
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12
BiologyEasyMCQAIIMS · 1999
The middle layer in the body wall of Porifera is:
A
Mesoderm
B
Mesenchyme
C
Mesogloea
D
Mesentery
Solution
(B) In Porifera,the body wall consists of an outer pinacoderm (ectoderm),an inner choanoderm (endoderm),and a gelatinous,non-cellular middle layer known as mesenchyme (or mesohyl).
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13
BiologyMediumMCQAIIMS · 1999
The true statement regarding corals is
A
They form branched colonies
B
Are solitary or colonial polypoid
C
They grow as massive bodies
D
All of these
Solution
(D) Corals belong to the phylum $Cnidaria$ (also known as $Coelenterata$).
They exhibit a $polypoid$ body form,which is sessile and cylindrical.
Corals can exist as solitary individuals or in colonial forms.
Many corals secrete calcium carbonate skeletons,which can grow into massive,branched,or complex structures over time.
Therefore,all the given statements are correct.
They exhibit a $polypoid$ body form,which is sessile and cylindrical.
Corals can exist as solitary individuals or in colonial forms.
Many corals secrete calcium carbonate skeletons,which can grow into massive,branched,or complex structures over time.
Therefore,all the given statements are correct.
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14
BiologyEasyMCQAIIMS · 1999
The medusa of $Obelia$ is:
A
Carnivorous
B
Herbivorous
C
Detritus feeder
D
Omnivorous
Solution
(A) The medusa of $Obelia$ is strictly carnivorous in its feeding habit.
It captures prey using its tentacles and nematocysts.
Its diet primarily consists of minute worms,nematodes,small insects,and crustaceans.
It captures prey using its tentacles and nematocysts.
Its diet primarily consists of minute worms,nematodes,small insects,and crustaceans.
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15
BiologyEasyMCQAIIMS · 1999
The sense organs of $Aurelia$ are known as:
A
Tentilla
B
Tentaculocyst
C
Nematocyst
D
Otolith
Solution
(B) The sense organs of $Aurelia$ (a member of the phylum $Cnidaria$,class $Scyphozoa$) are called $rhopalia$ or $tentaculocysts$.
These structures are marginal sense organs that contain statocysts for equilibrium and sometimes ocelli for light sensitivity.
$Tentilla$ are small tentacles,$nematocysts$ are stinging cells,and $otoliths$ are the calcified structures found within the statocysts.
These structures are marginal sense organs that contain statocysts for equilibrium and sometimes ocelli for light sensitivity.
$Tentilla$ are small tentacles,$nematocysts$ are stinging cells,and $otoliths$ are the calcified structures found within the statocysts.
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16
BiologyEasyMCQAIIMS · 1999
Which one of the following is an example of Platyhelminthes?
A
Trypanosoma
B
Schistosoma
C
Plasmodium
D
Wuchereria
Solution
(B) $Schistosoma$ is a genus of trematodes,commonly known as blood flukes,which belong to the phylum Platyhelminthes.
$Trypanosoma$ belongs to the phylum Protozoa (Protista).
$Plasmodium$ belongs to the phylum Protozoa (Protista).
$Wuchereria$ belongs to the phylum Aschelminthes (Nematoda).
$Trypanosoma$ belongs to the phylum Protozoa (Protista).
$Plasmodium$ belongs to the phylum Protozoa (Protista).
$Wuchereria$ belongs to the phylum Aschelminthes (Nematoda).
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17
BiologyMediumMCQAIIMS · 1999
In the life history of the liver fluke,the following stages are present: $(1)$ Cercaria,$(2)$ Metacercaria,$(3)$ Sporocyst,$(4)$ Redia,$(5)$ Miracidium. What is their proper sequence?
A
$2-1-3-5-4$
B
$5-3-4-1-2$
C
$5-4-2-1-3$
D
$5-4-3-1-2$
Solution
(B) The life cycle of the liver fluke ($Fasciola$ $hepatica$) involves several larval stages that occur in a specific order.
$1$. The cycle begins with the $Miracidium$ larva,which hatches from the egg.
$2$. The $Miracidium$ penetrates the intermediate host (snail) and transforms into a $Sporocyst$.
$3$. The $Sporocyst$ then develops into $Redia$ larvae.
$4$. The $Redia$ larvae produce $Cercaria$ larvae.
$5$. Finally,the $Cercaria$ encysts to form the $Metacercaria$,which is the infective stage for the primary host.
Therefore,the correct sequence is $5 \to 3 \to 4 \to 1 \to 2$.
$1$. The cycle begins with the $Miracidium$ larva,which hatches from the egg.
$2$. The $Miracidium$ penetrates the intermediate host (snail) and transforms into a $Sporocyst$.
$3$. The $Sporocyst$ then develops into $Redia$ larvae.
$4$. The $Redia$ larvae produce $Cercaria$ larvae.
$5$. Finally,the $Cercaria$ encysts to form the $Metacercaria$,which is the infective stage for the primary host.
Therefore,the correct sequence is $5 \to 3 \to 4 \to 1 \to 2$.
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18
BiologyMediumMCQAIIMS · 1999
Rhabdites occur in
A
Planaria/Dugesia
B
Fasciola
C
Taenia
D
Echinococcus
Solution
(A) Rhabdites are rod-shaped structures found in the epidermis of many turbellarian flatworms,such as $Planaria$ $(Dugesia)$.
These structures are secreted by specialized cells called rhabdite cells.
When the animal is irritated or threatened,these rhabdites are discharged to form a protective mucus layer,which helps in defense and locomotion.
$Fasciola$,$Taenia$,and $Echinococcus$ belong to the class Trematoda and Cestoda,which are parasitic and lack these specific epidermal structures.
These structures are secreted by specialized cells called rhabdite cells.
When the animal is irritated or threatened,these rhabdites are discharged to form a protective mucus layer,which helps in defense and locomotion.
$Fasciola$,$Taenia$,and $Echinococcus$ belong to the class Trematoda and Cestoda,which are parasitic and lack these specific epidermal structures.
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19
BiologyEasyMCQAIIMS · 1999
The order of metamorphosis in the housefly is
A
Egg,nymph,pupa and adult
B
Egg,larva,nymph and adult
C
Egg,larva,pupa and adult
D
Egg,pupa,larva and adult
Solution
(C) The housefly undergoes complete metamorphosis (holometabolous development).
The life cycle consists of four distinct stages:
$1$. Egg: The female lays eggs in decaying organic matter.
$2$. Larva (Maggot): The egg hatches into a legless larva.
$3$. Pupa: The larva transforms into a pupa within a protective casing.
$4$. Imago (Adult): The final stage where the adult fly emerges from the pupa.
Therefore,the correct order is $Egg \rightarrow Larva \rightarrow Pupa \rightarrow Adult$.
The life cycle consists of four distinct stages:
$1$. Egg: The female lays eggs in decaying organic matter.
$2$. Larva (Maggot): The egg hatches into a legless larva.
$3$. Pupa: The larva transforms into a pupa within a protective casing.
$4$. Imago (Adult): The final stage where the adult fly emerges from the pupa.
Therefore,the correct order is $Egg \rightarrow Larva \rightarrow Pupa \rightarrow Adult$.
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20
BiologyMediumMCQAIIMS · 1999
Open circulatory system is not a physiological hindrance in a $Cockroach$ because
A
Heart is simple but chambered
B
Blood is colourless
C
Circulatory and respiratory systems are not connected
D
Excretion occurs through $Malpighian$ tubules
Solution
(C) In a $Cockroach$, the circulatory system is of the open type, meaning the blood $(haemolymph)$ flows through body cavities $(haemocoel)$ and bathes the tissues directly.
Unlike vertebrates, where the circulatory system is responsible for transporting respiratory gases ($O_2$ and $CO_2$), the $Cockroach$ has a separate, highly efficient tracheal system for respiration.
The tracheal system consists of a network of tubes that deliver oxygen directly to the tissues and remove carbon dioxide.
Because the circulatory system is not involved in gas exchange, the lack of closed vessels does not hinder its physiological function.
Unlike vertebrates, where the circulatory system is responsible for transporting respiratory gases ($O_2$ and $CO_2$), the $Cockroach$ has a separate, highly efficient tracheal system for respiration.
The tracheal system consists of a network of tubes that deliver oxygen directly to the tissues and remove carbon dioxide.
Because the circulatory system is not involved in gas exchange, the lack of closed vessels does not hinder its physiological function.
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21
BiologyMediumMCQAIIMS · 1999
In which of the following organisms is the foot displaced to the neighborhood of the mouth and divided into arms?
A
Ostrea
B
Pila
C
Sepia
D
Chiton
Solution
(C) In $Sepia$ (a member of the class $Cephalopoda$),the foot is significantly modified. It is displaced to the region surrounding the mouth and is divided into $8$ to $10$ arms or tentacles,which are used for capturing prey and locomotion. This is a characteristic feature of cephalopods.
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22
BiologyEasyMCQAIIMS · 1999
Aristotle's lantern is connected with
A
Respiration
B
Mastication
C
Excretion
D
Support
Solution
(B) Aristotle's lantern is a complex jaw apparatus found in sea urchins (class $Echinoidea$,phylum $Echinodermata$).
It consists of five calcareous teeth used for scraping and grinding food,which is the process of mastication.
It consists of five calcareous teeth used for scraping and grinding food,which is the process of mastication.
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23
BiologyEasyMCQAIIMS · 1999
Basket star belongs to which class?
A
Ophiuroidea
B
Echinoidea
C
Asteroidea
D
Crinoidea
Solution
(A) The basket star,scientifically known as $Gorgonocephalus$,belongs to the class $Ophiuroidea$ within the phylum $Echinodermata$.
Members of this class are characterized by a central pentagonal disc and five elongated,highly branched arms that are used for filter feeding.
Members of this class are characterized by a central pentagonal disc and five elongated,highly branched arms that are used for filter feeding.
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24
BiologyMediumMCQAIIMS · 1999
The vertebrae of birds are characteristically
A
Heterocoelous
B
Acoelous
C
Opisthocoelous
D
Amphicoelous
Solution
(A) The vertebrae of birds are characteristically $Heterocoelous$.
In a $Heterocoelous$ vertebra,the centrum has a saddle-shaped articular surface,where one face is convex in one direction and concave in the other,allowing for significant flexibility of the neck while preventing rotation.
This structure is a unique adaptation in birds that provides stability and mobility to the cervical region.
In a $Heterocoelous$ vertebra,the centrum has a saddle-shaped articular surface,where one face is convex in one direction and concave in the other,allowing for significant flexibility of the neck while preventing rotation.
This structure is a unique adaptation in birds that provides stability and mobility to the cervical region.
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25
BiologyEasyMCQAIIMS · 1999
Weberian ossicles are found in
A
Frogs
B
Snakes
C
Fishes
D
Birds
Solution
(C) The Weberian ossicles are a chain of small bones found in certain freshwater fishes,such as carps and catfishes.
These bones connect the swim bladder (air bladder) to the inner ear (auditory capsule).
They function to transmit vibrations from the swim bladder to the ear,thereby enhancing the fish's sense of hearing.
These bones connect the swim bladder (air bladder) to the inner ear (auditory capsule).
They function to transmit vibrations from the swim bladder to the ear,thereby enhancing the fish's sense of hearing.
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26
BiologyMediumMCQAIIMS · 1999
The flower of $Hibiscus$ is:
A
Actinomorphic and epigynous
B
Actinomorphic and hypogynous
C
Zygomorphic and hypogynous
D
Zygomorphic and epigynous
Solution
(B) The flower of $Hibiscus$ (China rose) exhibits radial symmetry,meaning it can be divided into two equal radial halves in any radial plane passing through the center; this condition is known as actinomorphic.
Furthermore,the ovary in $Hibiscus$ is superior,meaning the gynoecium occupies the highest position while the other floral parts (sepals,petals,and stamens) are situated below it. This condition is known as hypogynous.
Therefore,the flower is actinomorphic and hypogynous.
Furthermore,the ovary in $Hibiscus$ is superior,meaning the gynoecium occupies the highest position while the other floral parts (sepals,petals,and stamens) are situated below it. This condition is known as hypogynous.
Therefore,the flower is actinomorphic and hypogynous.
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27
BiologyMediumMCQAIIMS · 1999
Vascular cambium and cork cambium are examples of
A
Lateral meristem
B
Apical meristem
C
Elements of xylem and phloem
D
Intercalary meristem
Solution
(A) Lateral meristems occur laterally in the axis,parallel to the sides of stems and roots.
They are responsible for secondary growth,which increases the girth of the plant.
The vascular cambium (including fascicular,interfascicular,and extrastelar cambium) and the cork cambium (phellogen) are primary examples of lateral meristems.
They are responsible for secondary growth,which increases the girth of the plant.
The vascular cambium (including fascicular,interfascicular,and extrastelar cambium) and the cork cambium (phellogen) are primary examples of lateral meristems.
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28
BiologyEasyMCQAIIMS · 1999
Cystoliths, sometimes deposited in plant cells, are crystals of (aggregation of)
A
Calcium oxalate
B
Calcium carbonate
C
Magnesium carbonate
D
Glucosides
Solution
(B) The correct answer is $B$.
Cystoliths are specialized structures found in the epidermal cells of certain plants, such as $Ficus$ \text{ } $bengalensis$ (Banyan tree).
These structures consist of an aggregation of $CaCO_3$ (calcium carbonate) crystals, which often appear in a grape-like cluster attached to the cell wall by a cellulose stalk.
Cystoliths are specialized structures found in the epidermal cells of certain plants, such as $Ficus$ \text{ } $bengalensis$ (Banyan tree).
These structures consist of an aggregation of $CaCO_3$ (calcium carbonate) crystals, which often appear in a grape-like cluster attached to the cell wall by a cellulose stalk.
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29
BiologyEasyMCQAIIMS · 1999
Blood does not clot inside the blood vessels due to the presence of
A
Heparin
B
Fibrinogen
C
Vitamin $K$
D
Thrombin
Solution
(A) The liver produces an anticoagulant,a hetero-polysaccharide known as heparin.
This substance prevents the coagulation of blood within the blood vessels by inhibiting the action of thrombin and other clotting factors.
This substance prevents the coagulation of blood within the blood vessels by inhibiting the action of thrombin and other clotting factors.
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30
BiologyMediumMCQAIIMS · 1999
The main organelle involved in the modification and routing of newly synthesized proteins to their destinations is:
A
Chloroplast
B
Mitochondria
C
Lysosome
D
Golgi apparatus
Solution
(D) The $Golgi$ $apparatus$ is the primary organelle responsible for the modification, sorting, and packaging of proteins synthesized by the $Endoplasmic$ $reticulum$.
After proteins are synthesized in the $Rough$ $Endoplasmic$ $reticulum$ $(RER)$, they are transported to the $Golgi$ $apparatus$ in vesicles.
Within the $Golgi$ $apparatus$, these proteins undergo modifications such as glycosylation and are then sorted and routed to their specific destinations, such as the plasma membrane, lysosomes, or for secretion outside the cell.
After proteins are synthesized in the $Rough$ $Endoplasmic$ $reticulum$ $(RER)$, they are transported to the $Golgi$ $apparatus$ in vesicles.
Within the $Golgi$ $apparatus$, these proteins undergo modifications such as glycosylation and are then sorted and routed to their specific destinations, such as the plasma membrane, lysosomes, or for secretion outside the cell.
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31
BiologyEasyMCQAIIMS · 1999
Regarding the sequence of the cell cycle,which one is correct?
A
$G_1, G_2, S$ and $M$
B
$S, G_1, G_2$ and $M$
C
$G_1, S, G_2$ and $M$
D
$G_2, S, G_1$ and $M$
Solution
(C) The cell cycle is a series of events that take place in a cell leading to its division and duplication of its $DNA$ to produce two daughter cells.
It consists of two main phases: Interphase and $M$-phase (Mitosis).
Interphase is further divided into three sub-phases: $G_1$ phase (Gap $1$),$S$ phase (Synthesis),and $G_2$ phase (Gap $2$).
The sequence of these phases is $G_1 \rightarrow S \rightarrow G_2 \rightarrow M$.
Therefore,the correct sequence is $G_1, S, G_2$ and $M$.
It consists of two main phases: Interphase and $M$-phase (Mitosis).
Interphase is further divided into three sub-phases: $G_1$ phase (Gap $1$),$S$ phase (Synthesis),and $G_2$ phase (Gap $2$).
The sequence of these phases is $G_1 \rightarrow S \rightarrow G_2 \rightarrow M$.
Therefore,the correct sequence is $G_1, S, G_2$ and $M$.
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32
BiologyMediumMCQAIIMS · 1999
Which of the following helps in the absorption of water and mineral salts?
A
Mycorrhiza
B
Anabaena
C
Nostoc
D
None of these
Solution
(A) Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
In this association,the fungal hyphae have a very large surface area that helps in the absorption of water and mineral salts from the soil,which are then provided to the plant.
In return,the plant provides the fungus with sugars and other organic nutrients.
Therefore,the correct option is $A$.
In this association,the fungal hyphae have a very large surface area that helps in the absorption of water and mineral salts from the soil,which are then provided to the plant.
In return,the plant provides the fungus with sugars and other organic nutrients.
Therefore,the correct option is $A$.
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33
BiologyMediumMCQAIIMS · 1999
The enzyme which converts glucose to glucose-$6$-phosphate is
A
Phosphorylase
B
Glucose-$6$-phosphate
C
Hexokinase
D
Glucose synthetase
Solution
(C) In the first step of glycolysis,glucose is phosphorylated to glucose-$6$-phosphate by the enzyme hexokinase in the presence of $ATP$ and $Mg^{2+}$ ions.
This reaction is irreversible and consumes one molecule of $ATP$.
This reaction is irreversible and consumes one molecule of $ATP$.
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34
BiologyMediumMCQAIIMS · 1999
Bud dormancy is induced by
A
$ABA$
B
$IAA$
C
Ethylene
D
Gibberellic acid
Solution
(A) $ABA$ (Abscisic acid) acts as a plant growth inhibitor.
It plays a crucial role in inducing bud dormancy,especially as winter approaches,to protect the plant from harsh environmental conditions.
Therefore,$ABA$ is responsible for the induction of dormancy in buds.
It plays a crucial role in inducing bud dormancy,especially as winter approaches,to protect the plant from harsh environmental conditions.
Therefore,$ABA$ is responsible for the induction of dormancy in buds.
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35
BiologyEasyMCQAIIMS · 1999
Liver in our body stores
A
Vitamin $A$
B
Vitamin $D$
C
Vitamin $B_{12}$
D
All of these
Solution
(D) The liver plays a crucial role in the storage of various fat-soluble and water-soluble vitamins.
Specifically,the liver cells (hepatocytes) are capable of synthesizing Vitamin $A$ from its precursor,carotene.
Furthermore,the liver acts as a primary storage site for Vitamin $A$,Vitamin $D$,and Vitamin $B_{12}$ in the human body.
Therefore,all the given options are correct.
Specifically,the liver cells (hepatocytes) are capable of synthesizing Vitamin $A$ from its precursor,carotene.
Furthermore,the liver acts as a primary storage site for Vitamin $A$,Vitamin $D$,and Vitamin $B_{12}$ in the human body.
Therefore,all the given options are correct.
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36
BiologyEasyMCQAIIMS · 1999
The protein which prevents coagulation of blood in the blood vessel is
A
Platelets
B
Globular protein
C
Albumin
D
Heparin
Solution
(D) Heparin is a natural anticoagulant produced by the liver and mast cells.
It prevents the clotting of blood inside the blood vessels by inhibiting the formation of thrombin from prothrombin.
Therefore,it keeps the blood in a fluid state within the circulatory system.
It prevents the clotting of blood inside the blood vessels by inhibiting the formation of thrombin from prothrombin.
Therefore,it keeps the blood in a fluid state within the circulatory system.
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37
BiologyMediumMCQAIIMS · 1999
The heart beat increases at the time of interview due to
A
Corticotrophic hormone
B
Hyper secretion of renin
C
Secretion of adrenaline
D
Antidiuretic hormone secretion
Solution
(C) The correct answer is $C$. During stressful situations like an interview,the body triggers the 'fight-or-flight' response. The adrenal medulla secretes the hormone adrenaline (epinephrine) into the bloodstream. Adrenaline acts on the heart to increase the heart rate and the strength of cardiac contractions to prepare the body for immediate action.
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38
BiologyEasyMCQAIIMS · 1999
The end product of the ornithine cycle is:
A
Urea
B
Ammonia
C
Uric acid
D
Carbon dioxide
Solution
(A) The ornithine cycle,also known as the urea cycle,is a metabolic pathway that converts toxic ammonia into urea in the liver.
This process is essential for ureotelic animals to safely excrete nitrogenous waste.
Therefore,the end product of the ornithine cycle is urea.
This process is essential for ureotelic animals to safely excrete nitrogenous waste.
Therefore,the end product of the ornithine cycle is urea.
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39
BiologyEasyMCQAIIMS · 1999
Which of the following is not found in birds?
A
Pectoral girdle
B
Pelvic girdle
C
Hind limb
D
Fore limb
Solution
(D) The correct answer is $D$. In birds,the fore limbs are modified into wings to facilitate flight. Therefore,they do not possess typical fore limbs as seen in other tetrapods.
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40
BiologyEasyMCQAIIMS · 1999
Which of the following glands plays a key role in the metamorphosis of a frog's tadpole?
A
Adrenal
B
Thymus
C
Pancreas
D
Thyroid
Solution
(D) . The $Thyroid$ gland plays a key role in the metamorphosis of a frog's tadpole. The $Thyroid$ hormones, specifically $Thyroxine$, initiate and regulate the process of metamorphosis. Metamorphosis is the biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation, transforming the larva into an adult.
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41
BiologyMediumMCQAIIMS · 1999
Which of the following hormones is a derivative of an amino acid?
A
Estrogen
B
Epinephrine
C
Progesterone
D
Prostaglandin
Solution
(B) Epinephrine is an amino acid derivative. Specifically,it is derived from the amino acid tyrosine. It belongs to the class of catecholamines,which are synthesized in the adrenal medulla. In contrast,Estrogen and Progesterone are steroid hormones,and Prostaglandins are fatty acid derivatives.
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42
BiologyEasyMCQAIIMS · 1999
Conn's disease is caused by the over-secretion of
A
$ADH$
B
$ACTH$
C
Aldosterone
D
Oxytocin
Solution
(C) Conn's disease,also known as primary hyperaldosteronism,is a condition characterized by the excessive production of the hormone aldosterone by the adrenal glands.
This over-secretion leads to an increase in the reabsorption of sodium and water in the kidneys,which results in an increase in blood volume and blood pressure.
Therefore,the correct option is $C$.
This over-secretion leads to an increase in the reabsorption of sodium and water in the kidneys,which results in an increase in blood volume and blood pressure.
Therefore,the correct option is $C$.
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43
BiologyMediumMCQAIIMS · 1999
Edaphology is the study of the relationship between:
A
Plant and biosphere
B
Animal and ecosystem
C
Soil and living organisms
D
Soil and biosphere
Solution
(C) Edaphology is a branch of soil science that focuses on the influence of soils on living things,particularly plants. It examines the relationship between soil properties and the organisms that inhabit or depend on the soil environment. Therefore,it is defined as the study of the relationship between soil and living organisms.
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44
BiologyMediumMCQAIIMS · 1999
Assertion : Birds have one ovary.
Reason : This reduces the body weight for flight.
Reason : This reduces the body weight for flight.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(A) Birds typically possess only a single functional ovary (the left one) as an evolutionary adaptation to reduce body weight,which facilitates efficient flight. Therefore,the assertion is correct,and the reason provides a valid explanation for this anatomical feature.
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45
BiologyMediumMCQAIIMS · 1999
Assertion : Higher plants have meristematic regions for indefinite growth.
Reason : Higher plants have root and shoot apices.
Reason : Higher plants have root and shoot apices.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(A) The root apex and shoot apex are meristematic in nature.
These meristematic tissues are embryonic in origin.
They are primary in origin because they develop from embryonic tissues and primary in function because they form the primary structure of the plant,such as the root apex and shoot apex,which persist throughout the life of the plant.
Because these meristematic regions remain active throughout the plant's life,higher plants exhibit the feature of indefinite growth.
Therefore,the Reason correctly explains the Assertion.
These meristematic tissues are embryonic in origin.
They are primary in origin because they develop from embryonic tissues and primary in function because they form the primary structure of the plant,such as the root apex and shoot apex,which persist throughout the life of the plant.
Because these meristematic regions remain active throughout the plant's life,higher plants exhibit the feature of indefinite growth.
Therefore,the Reason correctly explains the Assertion.
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46
BiologyMediumMCQAIIMS · 1999
Assertion : Enzymes have active sites and substrates have reactive sites on their surface respectively.
Reason : Active and reactive sites push the enzyme and substrate molecules away from each other.
Reason : Active and reactive sites push the enzyme and substrate molecules away from each other.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(C) Enzymes are biocatalysts that increase the speed of a chemical reaction without themselves undergoing any permanent chemical change.
Enzymes possess specific regions known as active sites that bind to the substrate molecules to form an enzyme-substrate complex.
These active sites are designed to attract and hold the substrate,not push them away.
Therefore,the Assertion is correct,but the Reason is incorrect because it describes a repulsive force,whereas the interaction is based on specific binding and attraction.
Enzymes possess specific regions known as active sites that bind to the substrate molecules to form an enzyme-substrate complex.
These active sites are designed to attract and hold the substrate,not push them away.
Therefore,the Assertion is correct,but the Reason is incorrect because it describes a repulsive force,whereas the interaction is based on specific binding and attraction.
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47
BiologyMediumMCQAIIMS · 1999
Assertion: Waxy and cutin coating on plant parts reduce the transpiration.
Reason: These adaptations are found in xerophytes.
Reason: These adaptations are found in xerophytes.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(A) Waxy and cutin coatings on the surface of leaves and stems act as a barrier to water loss,thereby significantly reducing the rate of transpiration.
This structural adaptation is a characteristic feature of xerophytes,which are plants adapted to survive in environments with limited water availability.
Since the presence of these coatings is a direct evolutionary adaptation to minimize water loss in dry habitats,the Reason correctly explains the Assertion.
This structural adaptation is a characteristic feature of xerophytes,which are plants adapted to survive in environments with limited water availability.
Since the presence of these coatings is a direct evolutionary adaptation to minimize water loss in dry habitats,the Reason correctly explains the Assertion.
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48
BiologyMediumMCQAIIMS · 1999
Assertion : Light is a very important factor in transpiration.
Reason : Light induces stomatal opening and darkness closing of stomata. Therefore,transpiration increases in light and decreases in dark.
Reason : Light induces stomatal opening and darkness closing of stomata. Therefore,transpiration increases in light and decreases in dark.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(A) Light is a critical environmental factor affecting the rate of transpiration.
Most plants have stomata that open in response to light to facilitate $CO_2$ intake for photosynthesis.
When stomata open,the pathway for water vapor loss increases,thereby increasing the rate of transpiration.
Conversely,in the dark,stomata close to conserve water,which significantly reduces transpiration.
Since the reason directly explains the mechanism by which light influences transpiration,the Reason is the correct explanation of the Assertion.
Most plants have stomata that open in response to light to facilitate $CO_2$ intake for photosynthesis.
When stomata open,the pathway for water vapor loss increases,thereby increasing the rate of transpiration.
Conversely,in the dark,stomata close to conserve water,which significantly reduces transpiration.
Since the reason directly explains the mechanism by which light influences transpiration,the Reason is the correct explanation of the Assertion.
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49
BiologyMediumMCQAIIMS · 1999
Assertion: Mitochondria helps in photosynthesis.
Reason: Mitochondria have enzymes for dark reaction.
Reason: Mitochondria have enzymes for dark reaction.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(D) The Assertion is incorrect because mitochondria are the sites of cellular respiration,not photosynthesis. Photosynthesis occurs in chloroplasts.
The Reason is also incorrect because the enzymes for the dark reaction (Calvin cycle) are located in the stroma of the chloroplast,not in the mitochondria.
Therefore,both the Assertion and the Reason are incorrect.
The Reason is also incorrect because the enzymes for the dark reaction (Calvin cycle) are located in the stroma of the chloroplast,not in the mitochondria.
Therefore,both the Assertion and the Reason are incorrect.
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50
BiologyMediumMCQAIIMS · 1999
Assertion : Muscle fibres of $SA$ node possess the lowest rhythmicity among all cardiac muscles.
Reason : Due to this fact,it can initiate excitatory waves at the highest rate.
Reason : Due to this fact,it can initiate excitatory waves at the highest rate.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If the Assertion is incorrect but the Reason is correct.
Solution
(D) The $SA$ node (sinoatrial node) is known as the natural pacemaker of the heart. It consists of specialized cardiac muscle fibres that possess the highest rhythmicity,not the lowest. Because of this high rhythmicity,it can generate excitatory impulses at the fastest rate,which sets the pace for the entire heart. Since the assertion states that the $SA$ node has the lowest rhythmicity,the assertion is incorrect. However,the reason correctly identifies that it initiates excitatory waves at the highest rate. Therefore,the assertion is incorrect,but the reason is correct.
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51
BiologyMediumMCQAIIMS · 1999
Sporogony of the malarial parasite occurs in
A
Liver of man
B
$RBCs$ of man
C
Stomach wall of mosquito
D
Salivary glands of mosquito
Solution
(C) The life cycle of the malarial parasite $(Plasmodium)$ involves two hosts: humans and female $Anopheles$ mosquitoes.
Sporogony refers to the sexual phase of the life cycle where sporozoites are formed.
This process occurs within the stomach wall of the female $Anopheles$ mosquito.
After fertilization and development,the sporozoites migrate to the salivary glands of the mosquito to be transmitted to a new human host.
Sporogony refers to the sexual phase of the life cycle where sporozoites are formed.
This process occurs within the stomach wall of the female $Anopheles$ mosquito.
After fertilization and development,the sporozoites migrate to the salivary glands of the mosquito to be transmitted to a new human host.
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52
BiologyEasyMCQAIIMS · 1999
$Nepenthes$ $khasiana$ is a/an:
A
Fungicidal and wetland plant
B
Insectivorous and endangered plant
C
Fungicidal and endangered plant
D
Insectivorous and wetland plant
Solution
(B) $Nepenthes$ $khasiana$, commonly known as the pitcher plant, is an insectivorous plant found in the Khasi hills of Meghalaya, India.
It is classified as an endangered species due to habitat loss and over-collection.
Therefore, it is both an insectivorous and an endangered plant.
It is classified as an endangered species due to habitat loss and over-collection.
Therefore, it is both an insectivorous and an endangered plant.
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53
BiologyEasyMCQAIIMS · 1999
What does the cumulus cover?
A
Ovary
B
Ovum
C
Embryo
D
All of these
Solution
(B) The cumulus oophorus (or cumulus ovaricus) is a cluster of follicular cells (membrana granulosa cells) that surrounds the oocyte (ovum) in the Graafian follicle. Therefore,the cumulus covers the ovum.
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54
BiologyMediumMCQAIIMS · 1999
If a homozygous red-flowered plant is crossed with a homozygous white-flowered plant,the offspring would be
A
Half red-flowered
B
Half white-flowered
C
All red-flowered
D
Half pink-flowered
Solution
(C) According to Mendel's law of dominance,when a homozygous dominant plant (red-flowered,$RR$) is crossed with a homozygous recessive plant (white-flowered,$rr$),the $F_1$ generation offspring will all be heterozygous $(Rr)$.
Since the allele for red color is dominant over the allele for white color,all $F_1$ offspring will exhibit the red-flowered phenotype.
Since the allele for red color is dominant over the allele for white color,all $F_1$ offspring will exhibit the red-flowered phenotype.
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55
BiologyMediumMCQAIIMS · 1999
The monosomic condition in human beings depicted as $XO$ is referred to as
A
Criminal syndrome
B
Down's syndrome
C
Klinefelter's syndrome
D
Turner's syndrome
Solution
(D) The monosomic condition in human beings represented as $XO$ is known as Turner's syndrome.
Individuals with Turner's syndrome have a $45$ chromosome count,specifically $44 + XO$ genotype.
This condition arises due to the absence of one $X$ chromosome,which is caused by the non-disjunction of sex chromosomes during gametogenesis in the parents.
Individuals with Turner's syndrome have a $45$ chromosome count,specifically $44 + XO$ genotype.
This condition arises due to the absence of one $X$ chromosome,which is caused by the non-disjunction of sex chromosomes during gametogenesis in the parents.
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56
BiologyMediumMCQAIIMS · 1999
If a boy's father has haemophilia and his mother has one gene for haemophilia,what is the chance that the boy will inherit the disease (in $\%$)?
A
$25$
B
$50$
C
$75$
D
$100$
Solution
(B) Haemophilia is an $X$-linked recessive disorder.
The father's genotype is $X^hY$ (affected) and the mother's genotype is $X^HX^h$ (carrier,as she has one gene for haemophilia).
When we cross the parents $(X^HX^h \times X^hY)$:
- The possible genotypes for the offspring are $X^HX^h$ (carrier daughter),$X^hX^h$ (affected daughter),$X^HY$ (normal son),and $X^hY$ (affected son).
- Among the sons,$50\%$ will be normal $(X^HY)$ and $50\%$ will be affected $(X^hY)$.
- Therefore,the chance that the boy will inherit the disease is $50\%$.
The father's genotype is $X^hY$ (affected) and the mother's genotype is $X^HX^h$ (carrier,as she has one gene for haemophilia).
When we cross the parents $(X^HX^h \times X^hY)$:
- The possible genotypes for the offspring are $X^HX^h$ (carrier daughter),$X^hX^h$ (affected daughter),$X^HY$ (normal son),and $X^hY$ (affected son).
- Among the sons,$50\%$ will be normal $(X^HY)$ and $50\%$ will be affected $(X^hY)$.
- Therefore,the chance that the boy will inherit the disease is $50\%$.
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57
BiologyMediumMCQAIIMS · 1999
The food chain in which microbes split energy-rich compounds of the producer community is:
A
Parasitic food chain
B
Detritus food chain
C
Predators food chain
D
Producer food chain
Solution
(B) The $Detritus$ food chain $(DFC)$ begins with dead organic matter.
Microbes (decomposers) break down these energy-rich compounds from the producer community into simpler substances.
These decomposers are then consumed by detritivores,which may subsequently be eaten by larger predators.
Microbes (decomposers) break down these energy-rich compounds from the producer community into simpler substances.
These decomposers are then consumed by detritivores,which may subsequently be eaten by larger predators.
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58
BiologyMediumMCQAIIMS · 1999
Assertion : In hemianatropous ovule,the funicle lies parallel to body of ovule.
Reason : Here,body of ovule is rotated by $90^o$.
Reason : Here,body of ovule is rotated by $90^o$.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If the Assertion is incorrect but the Reason is correct.
Solution
(D) In a hemianatropous ovule,the body of the ovule is rotated by $90^o$ with respect to the funicle.
As a result,the body of the ovule lies at a right angle $(90^o)$ to the funicle,not parallel to it.
Therefore,the Assertion is incorrect because the funicle is perpendicular to the body of the ovule,while the Reason is correct as it accurately describes the rotation of the ovule body.
As a result,the body of the ovule lies at a right angle $(90^o)$ to the funicle,not parallel to it.
Therefore,the Assertion is incorrect because the funicle is perpendicular to the body of the ovule,while the Reason is correct as it accurately describes the rotation of the ovule body.
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59
BiologyMediumMCQAIIMS · 1999
Assertion: The genetic complement of an organism is called genotype.
Reason: Genotype is the type of hereditary properties of an organism.
Reason: Genotype is the type of hereditary properties of an organism.
A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
C
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.
Solution
(A) The Assertion is correct because the genotype refers to the entire genetic makeup or the genetic complement of an organism.
The Reason is also correct because the genotype represents the hereditary information (alleles) that determines the traits of an organism.
Since the genotype is defined as the genetic complement,the Reason provides a valid explanation for why the term is used to describe the hereditary properties of an organism.
Therefore,both are correct and the Reason is the correct explanation of the Assertion.
The Reason is also correct because the genotype represents the hereditary information (alleles) that determines the traits of an organism.
Since the genotype is defined as the genetic complement,the Reason provides a valid explanation for why the term is used to describe the hereditary properties of an organism.
Therefore,both are correct and the Reason is the correct explanation of the Assertion.
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60
BiologyMediumMCQAIIMS · 1999
Wings of pigeon,mosquito,and bat show:
A
divergent evolution
B
atavism
C
convergent evolution
D
all of these
Solution
(C) Wings of pigeons (birds),mosquitoes (insects),and bats (mammals) are analogous organs,meaning they perform the same function (flight) but have different anatomical structures and embryonic origins.
This similarity in function,which has developed in distantly related groups,is an adaptation to the same environmental pressure (the need for flight).
Therefore,this phenomenon is known as analogy or convergent evolution.
This similarity in function,which has developed in distantly related groups,is an adaptation to the same environmental pressure (the need for flight).
Therefore,this phenomenon is known as analogy or convergent evolution.
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