AIPMT 1996 Biology Question Paper with Answer and Solution

(B) In bacteria,the sex factor is known as the $F$-factor or $F$-plasmid (Fertility factor).
This plasmid contains the genes necessary for the formation of the sex pilus,which is required for the process of conjugation.
During conjugation,the $F$-plasmid is transferred from the donor cell $(F^+)$ to the recipient cell $(F^-)$,thereby converting the recipient into a donor cell.
Therefore,the correct option is $B$.

(B) Bacteria are prokaryotic organisms. The genetic material in bacteria is typically a single,large,circular $DNA$ molecule,which is often referred to as the bacterial chromosome or nucleoid.
Unlike eukaryotes,it is not enclosed within a nuclear membrane and does not contain histones.

(B) The $Influenza$ virus belongs to the family $Orthomyxoviridae$.
It is an enveloped virus that contains a segmented,single-stranded $RNA$ genome.
Unlike some other viruses,it does not contain $DNA$ as its genetic material.
Therefore,the correct option is $RNA$.

(A) Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
In this relationship,the fungus helps the plant in the absorption of essential nutrients like phosphorus from the soil,while the plant provides carbohydrates (food) to the fungus.
Since both organisms benefit from this association,it is classified as a symbiotic relationship (mutualism).

(D) Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont).
They are very slow-growing organisms,often taking many years to cover a small surface area.
They are known to be pollution indicators,especially for $SO_2$ (sulfur dioxide),as they do not grow in polluted areas.
They serve as a primary food source for reindeer in the Arctic tundra.
Therefore,the statement that they grow rapidly at a rate of $2 \ cm$ per year is false.

(A) Bryophytes are known as the amphibians of the plant kingdom because they can live in soil but are dependent on water for sexual reproduction. Specifically,the male gametes (antherozoids) require a film of water to swim to the female sex organ (archegonium) for fertilization. While they are found in moist and shady habitats,their classification as 'amphibians' is primarily due to this critical dependence on water for the completion of their life cycle.

(B) Elaters are hygroscopic,elongated,spindle-shaped cells found within the spore capsule of certain liverworts.
They respond to changes in humidity by twisting and untwisting,which helps in the mechanical dispersal of spores.
Among the given options,$Marchantia$ is a liverwort that possesses elaters in its capsule.
$Riccia$ lacks elaters,while $Funaria$ and $Sphagnum$ are mosses that possess a different structure called a peristome for spore dispersal.

(A) The evolution of the seed habit is a significant event in plant evolution.
It was first observed in certain heterosporous pteridophytes,such as $Selaginella$ and $Salvinia$.
In these plants,the development of the zygote into young embryos takes place within the female gametophytes retained on the parent sporophytes.
This precursor to the seed habit is considered an important step in evolution.

(B) Blue-green algae,also known as $Cyanobacteria$,are photosynthetic prokaryotic organisms.
They lack a well-defined nucleus and membrane-bound organelles.
According to the $Whittaker$ classification system,they are placed under the Kingdom $Monera$,which consists of all prokaryotic organisms.
Therefore,they are classified as prokaryotes.

(D) Radial symmetry is a body plan in which the body can be divided into identical halves by any plane passing through the central axis.
This type of symmetry is typically found in organisms that are sessile (attached to a substrate) or free-floating,such as Cnidarians and adult Echinoderms.
Because these organisms do not move actively in a specific direction,radial symmetry allows them to detect food or threats from any direction in their environment.
Therefore,it is generally associated with a sessile mode of life.

(D) true coelom is defined as a body cavity that is completely lined by the mesoderm on all sides.
In triploblastic animals,the mesoderm splits to form the coelomic cavity.
This cavity is lined by the parietal peritoneum (derived from mesoderm) on the body wall side and the visceral peritoneum (derived from mesoderm) on the gut wall side.
Therefore,the correct answer is that it is lined by mesoderm on both sides.

(C) Nephridia are the excretory organs in earthworms $(Pheretima)$.
Flame cells (protonephridia) are the specialized excretory cells found in Platyhelminthes (e.g.,liver flukes like $Fasciola$ $hepatica$).
Both structures perform the function of excretion and osmoregulation.
Therefore,flame cells are functionally analogous to nephridia.

(B) Sponges (Phylum $Porifera$) are characterized by the presence of a water transport or canal system.
$1$. They possess flagellated collar cells,also known as $choanocytes$,which line the spongocoel and the canals. This is a defining feature of all sponges.
$2$. Option $A$ is incorrect because some sponges,like $Spongilla$,are freshwater.
$3$. Option $C$ is incorrect because the skeleton varies; some have only spicules,some only spongin fibers,and some have neither.
$4$. Option $D$ is incorrect because while many reproduce by budding,it is not a universal feature for all species in the phylum.

(B) The genus $Casuarius$,commonly known as the Cassowary,is a large flightless bird belonging to the family $Casuariidae$.
These birds are native to the tropical rainforests of New Guinea,nearby islands,and northeastern Australia.
Among the given options,Australia is the primary region where these birds are naturally found and well-documented.

(A) Pneumatic bones are hollow,air-filled bones that reduce body weight,which is an essential adaptation for flight in birds.
Among the given options,the pigeon ($Columba$ $livia$) belongs to the class $Aves$.
Birds possess pneumatic bones to facilitate flight.
Therefore,the correct answer is $A$.

(B) The coconut fruit is a drupe. In a drupe,the pericarp is well-differentiated into an outer thin epicarp,a middle fleshy or fibrous mesocarp,and an inner stony endocarp. In coconut,the mesocarp is fibrous and is the source of coir.

(A) Sclereids are a type of sclerenchyma cells that are typically short,irregular in shape,and possess extremely thick,lignified cell walls with narrow lumens.
Option $A$ is incorrect because elongated,elastic cells with pointed ends are characteristic of sclerenchyma fibers,not sclereids.
Option $B$ is correct as sclereids possess highly thickened,lignified walls.
Option $C$ is correct as sclereids provide grit to the pulp of fruits like guavas and pears.
Option $D$ is correct as they are commonly referred to as stone cells due to their hardness.

(A) Lysosomes are membrane-bound vesicular structures formed by the process of packaging in the Golgi apparatus.
These organelles are rich in hydrolytic enzymes (hydrolases - lipases,proteases,carbohydrases) that are optimally active at the acidic $pH$ of the lysosome.
These enzymes are capable of digesting carbohydrates,proteins,lipids,and nucleic acids.

(B) Cholera is caused by the bacterium $Vibrio$ $\text{cholerae}$, which leads to severe diarrhea and vomiting. This results in a massive loss of water and electrolytes from the body, leading to dehydration. Saline drips (containing $NaCl$ solution) are administered to replace the lost water and electrolytes. Specifically, $Na^+$ ions are crucial because they help in maintaining osmotic balance and retaining water in the body, thereby preventing circulatory collapse due to dehydration.

(D) The human neural system is divided into the Central Neural System $(CNS)$ and the Peripheral Neural System $(PNS)$.
The $PNS$ is further divided into the Somatic Neural System and the Autonomic Neural System $(ANS)$.
The Somatic Neural System relays impulses from the $CNS$ to skeletal muscles,which are under conscious control.
The Autonomic Neural System $(ANS)$ transmits impulses from the $CNS$ to the involuntary organs and smooth muscles of the body.
The $ANS$ consists of two divisions: the sympathetic neural system and the parasympathetic neural system.
These systems regulate the visceral organs (involuntary organs) and operate independently of conscious control.

(B) The cornea is an avascular tissue,meaning it lacks blood vessels. Because it is not directly connected to the circulatory system,it is not easily accessed by the immune system's cells. This lack of direct immune surveillance makes the cornea an 'immune-privileged' site,significantly reducing the risk of transplant rejection and making corneal transplantation highly successful.

(C) $1$. $Glucagon$ is secreted by the pancreas and increases blood glucose levels by stimulating glycogenolysis and gluconeogenesis.
$2$. $Cortisol$ is a glucocorticoid secreted by the adrenal cortex that stimulates gluconeogenesis,lipolysis,and proteolysis,thus playing a major role in carbohydrate metabolism.
$3$. $Insulin$ is secreted by the pancreas and decreases blood glucose levels by facilitating cellular glucose uptake and utilization.
$4$. $Aldosterone$ is a mineralocorticoid secreted by the adrenal cortex. Its primary function is to regulate water and electrolyte balance (sodium and potassium) in the body,not carbohydrate metabolism.

(A) In a living cell,macromolecules are constantly undergoing turnover.
Proteins are the most dynamic macromolecules in the cell,as they are continuously synthesized and degraded (turnover) to maintain cellular functions and respond to environmental changes.
While nucleic acids and carbohydrates also undergo turnover,proteins exhibit the highest rate of metabolic flux and structural modification,making them the most dynamic in both physical and chemical terms.

(A) Polysaccharides are complex carbohydrates formed by the polymerization of many monosaccharide units.
$1$. Starch is a storage polysaccharide in plants.
$2$. Glycogen is a storage polysaccharide in animals.
$3$. Cellulose is a structural polysaccharide found in plant cell walls.
Sucrose,maltose,and lactose are disaccharides,while glucose,fructose,and galactose are monosaccharides.
Therefore,the correct group is Starch,Glycogen,and Cellulose.

(B) Lampbrush chromosomes are a special type of chromosome found in the growing oocytes (immature eggs) of most animals,except mammals.
They are observed during the $Diplotene$ stage of $Meiosis-I$.
During this stage,the chromosomes are highly extended and exhibit a characteristic 'lampbrush' appearance due to the presence of lateral loops of chromatin,which are sites of active transcription.

(C) During the $Pachytene$ stage of $Prophase-I$ of meiosis, the exchange of genetic material between non-sister chromatids of homologous chromosomes takes place. This process is known as $Crossing$ $over$.
$Synapsis$ refers to the pairing of homologous chromosomes, while $Chiasmata$ are the $X$-shaped structures formed at the sites where crossing over has occurred.

(A) The $S$ phase (Synthesis phase) is a critical stage of the cell cycle occurring during interphase. During this phase,$DNA$ replication takes place. As a result,the amount of $DNA$ per cell doubles,although the number of chromosomes remains the same (the sister chromatids are formed).

(D) In plants,water moves from a region of higher water potential to a region of lower water potential.
In the root cortex,water moves from cell to cell along a water potential gradient.
As water moves from the soil into the root hair and then through the cortical cells towards the xylem,each successive cell has a slightly lower water potential than the previous one,creating a gradient that facilitates the passive movement of water.

(C) The movement of mineral ions from the soil into the root cells can occur through two main processes: active and passive absorption.
Passive absorption is the process where mineral ions move into the root cells along the concentration gradient without the expenditure of metabolic energy $(ATP)$.
Since diffusion is a passive process that occurs along the concentration gradient,the movement of mineral ions into root cells via diffusion is termed as passive absorption.

(C) Plant nutrients are classified into two categories based on their quantitative requirements: macronutrients and micronutrients.
$1$. Macronutrients are required in large amounts (usually $ > 10 \text{ mmol kg}^{-1}$ of dry matter). Examples include Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulphur, Potassium, Calcium, and Magnesium.
$2$. Micronutrients or trace elements are required in very small amounts (usually $ < 10 \text{ mmol kg}^{-1}$ of dry matter). Examples include Iron, Manganese, Copper, Molybdenum, Zinc, Boron, Chlorine, and Nickel.
Among the given options, Calcium, Magnesium, and Nitrogen are macronutrients, whereas Manganese $(Mn)$ is a micronutrient.

(C) Essential mineral elements for plants are those that are absolutely necessary for supporting normal growth and reproduction.
Criteria for essentiality include:
$1$. The plant cannot complete its life cycle without the element.
$2$. The element is directly involved in the metabolism of the plant.
$3$. The requirement of the element is specific and not replaceable by another element.
Potassium $(K)$,Iron $(Fe)$,and Zinc $(Zn)$ are well-established essential micronutrients or macronutrients.
Iodine $(I)$ is not considered an essential mineral element for higher plants,although it may be found in some marine algae.

(B) In the Calvin cycle,which occurs in the stroma of chloroplasts,the primary $CO_2$ acceptor is a $5$-carbon ketose sugar called Ribulose $1,5$-bisphosphate $(RuBP)$.
This reaction is catalyzed by the enzyme Ribulose bisphosphate carboxylase-oxygenase $(RuBisCO)$.
$PEP$ is the primary $CO_2$ acceptor in $C_4$ plants,while $PGA$ is the first stable product of the Calvin cycle.

(B) Chlorophyll $a$ $(C_{55}H_{72}O_5N_4Mg)$ is the primary photosynthetic pigment.
Its structure consists of a porphyrin head and a phytol tail.
The porphyrin head is composed of four pyrrole rings $(I, II, III, IV)$ linked by methine bridges.
In chlorophyll $a$,the carbon atom $3$ of pyrrole ring $II$ is attached to a methyl group $(-CH_3)$.
In contrast,chlorophyll $b$ has an aldehyde group $(-CHO)$ at the same position.

(A) Photorespiration is a process that occurs in $C_3$ plants when the enzyme $RuBisCO$ acts as an oxygenase instead of a carboxylase.
This happens primarily when the concentration of $O_2$ is high and the concentration of $CO_2$ is low in the vicinity of the enzyme.
Under these conditions,$RuBisCO$ binds with $O_2$ instead of $CO_2$,leading to the formation of one molecule of phosphoglycerate and one molecule of phosphoglycolate,which initiates the photorespiratory pathway.
Therefore,high $O_2$ and low $CO_2$ concentrations induce photorespiration.

(A) The Calvin cycle,also known as the $C_3$ cycle,is the light-independent reaction of photosynthesis.
It involves the fixation of $CO_2$ into organic compounds.
The process consists of three main stages: carboxylation,reduction,and regeneration.
During the reduction phase,$3$-phosphoglyceric acid ($3$-$PGA$) is reduced to glyceraldehyde-$3$-phosphate $(G3P)$ using $ATP$ and $NADPH$.
Because this step involves the reduction of carbon compounds,the Calvin cycle is collectively referred to as reductive carboxylation.

(A) The Law of Limiting Factors was proposed by $F.F. Blackman$ in $1905$.
According to this law,if a chemical process is affected by more than one factor,then its rate will be determined by the factor which is nearest to its minimal value,and this factor is known as the limiting factor.

(B) Fermentation is a type of anaerobic respiration that occurs in the absence of oxygen.
In this process,glucose is incompletely oxidized into various products depending on the organism.
Common products of fermentation include ethanol (alcohol),lactic acid,or other organic compounds like butyric acid.
Therefore,option $B$ is the correct answer.

(A) The Krebs cycle,also known as the citric acid cycle or $TCA$ cycle,occurs in the mitochondrial matrix of eukaryotic cells. During this process,acetyl-$CoA$ is oxidized to produce $CO_2$,$ATP$,$NADH$,and $FADH_2$.

(D) Oxidative phosphorylation is the metabolic pathway in which cells use enzymes to oxidize nutrients,thereby releasing energy which is used to produce $ATP$.
In this process,the electron transport chain $(ETC)$ facilitates the transfer of electrons from $NADH$ and $FADH_2$ to oxygen.
The energy released during this electron transfer is used to pump protons across the inner mitochondrial membrane,creating an electrochemical gradient.
Finally,$ATP$ synthase utilizes this gradient to phosphorylate $ADP$ into $ATP$.
Therefore,the final product of this process is $ATP$.

(C) Pellagra is a deficiency disease caused by a lack of $Vitamin B_3$ (Niacin or Nicotinamide).
Symptoms of Pellagra are often described by the '$4Ds$': Dermatitis (thick,pigmented skin),Diarrhea,Dementia (irritability,confusion),and Death.
Swollen lips (cheilosis) and glossitis are also common clinical features associated with this deficiency.
Therefore,the correct pair is Nicotinamide - Pellagra.

(B) High blood cholesterol is primarily caused by the consumption of saturated fats.
Vegetable oils,such as groundnut oil,are rich in unsaturated fatty acids,which help in lowering low-density lipoprotein $(LDL)$ cholesterol levels in the blood.
In contrast,desi ghee,butter,red meat,and margarine contain high levels of saturated fats or trans fats,which increase the risk of cardiovascular diseases by raising cholesterol levels.

(A) The correct match is $Maltose - Maltase$.
$Maltase$ is a specific enzyme that hydrolyzes the disaccharide $Maltose$ into two molecules of $Glucose$.
$Lactose$ is broken down by $Lactase$,not $Renin$.
$Starch$ is primarily broken down by $Amylase$ (Steapsin is another name for pancreatic lipase,which acts on fats).
$Casein$ is a milk protein primarily acted upon by $Renin$ in infants or $Pepsin$ in adults,not $Chymotrypsin$.

(C) The Expiratory Reserve Volume $(ERV)$ is defined as the additional volume of air that a person can expire by a forcible expiration.
This averages about $1000 \, ml$ to $1100 \, ml$ in some contexts,but in many standard physiology references,it is cited as approximately $1500 \, ml$ depending on the individual's lung capacity.
Residual Volume $(RV)$ is the volume of air remaining in the lungs even after a forcible expiration,which is approximately $1100 \, ml$ to $1200 \, ml$.
Total Lung Capacity $(TLC)$ is the total volume of air accommodated in the lungs at the end of a forced inspiration,which is approximately $5000 \, ml$ to $6000 \, ml$.
Therefore,$1500 \, ml$ is most appropriately associated with the Expiratory Reserve Volume $(ERV)$ in this context.

(D) The transport of respiratory gases is primarily carried out by $R.B.C.$ and blood plasma.
$1.$ $R.B.C.$ (Red Blood Cells) contain hemoglobin, which binds with $O_2$ to form oxyhemoglobin and also carries a portion of $CO_2$ as carbaminohemoglobin.
$2.$ Blood plasma transports $O_2$ in a dissolved state (about $3\%$) and $CO_2$ in dissolved form (about $7\%$) as well as in the form of bicarbonates (about $70\%$).
$3.$ $W.B.C.$ (White Blood Cells) are primarily involved in the immune response and do not play a significant role in the transport of respiratory gases.
Therefore, both $R.B.C.$ and plasma are responsible for the transport of $O_2$ and $CO_2$.

(D) The $Spleen$ is an organ in vertebrates that acts as a filter for the blood. It receives oxygenated blood directly from the splenic artery, which is a branch of the celiac trunk originating from the dorsal aorta. Unlike the liver (which receives deoxygenated blood via the hepatic portal vein) or the lungs (which receive deoxygenated blood from the heart for oxygenation), the spleen primarily receives oxygenated blood to support its metabolic functions and immune activities.

(C) An individual that exhibits both male and female sexual characteristics is known as a $Gynandromorph$.
In such organisms,one part of the body displays male characteristics while the other part displays female characteristics due to abnormal chromosomal distribution during early development.
$Hermaphrodite$ refers to an organism that has both male and female reproductive organs,but $Gynandromorph$ specifically refers to the mosaic expression of sexual traits.

(A) In $Codominance$,the alleles of a gene pair are both expressed in the heterozygous condition. This means that neither allele is dominant over the other,and both produce their independent effects simultaneously in the phenotype. $A$ classic example is the $ABO$ blood grouping system in humans,where individuals with the $I^A I^B$ genotype express both $A$ and $B$ antigens on their red blood cells.

(D) Klinefelter syndrome is a genetic disorder in males caused by the presence of an extra $X$ chromosome,resulting in a karyotype of $47, XXY$.
This condition occurs due to the non-disjunction of chromosomes during meiosis.
Individuals with this syndrome exhibit masculine development but also show feminine characteristics such as gynaecomastia (development of breast tissue) and are sterile.

(B) In this scenario,the father is affected and passes the trait to all his daughters but none of his sons.
Since the father passes his $X$ chromosome to all his daughters and his $Y$ chromosome to all his sons,the trait must be located on the $X$ chromosome.
Because all daughters are affected,the trait must be dominant,as a single copy of the dominant allele on the $X$ chromosome inherited from the father is sufficient to express the disease in the daughters.
If it were recessive,the daughters would be carriers (assuming the mother is normal),but they would not necessarily show the disease unless the mother was also a carrier. Thus,the pattern of inheritance is $X$-linked dominant.

(A) $DNA$ fingerprinting is a technique used to identify individuals based on their unique genetic makeup.
It primarily relies on $DNA$ polymorphism,specifically $Restriction$ $Fragment$ $Length$ $Polymorphism$ $(RFLP)$.
These variations in the length of $DNA$ fragments,generated by restriction enzymes,occur due to differences in the nucleotide sequences at specific loci in the genome.
Since these patterns are highly individual-specific,they serve as the fundamental basis for $DNA$ profiling.

(B) In the process of protein synthesis,translation is terminated when the ribosome encounters a stop codon on the mRNA molecule.
There are three stop codons: $UAA$,$UAG$,and $UGA$.
These codons do not code for any amino acid and are recognized by release factors rather than tRNA molecules.
Among the given options,$UAA$ is a stop codon.

(C) Okazaki fragments are short,newly synthesized $DNA$ fragments that are formed on the lagging template strand during $DNA$ replication.
They are synthesized in the $5' \rightarrow 3'$ direction and are later joined together by the enzyme $DNA$ ligase to form a continuous strand.
Therefore,Okazaki fragments are observed during the process of $DNA$ replication.

(D) $DNA$ $Ligase$ is the enzyme responsible for joining the ends of two $DNA$ strands by forming phosphodiester bonds. It acts as a 'molecular glue' in $DNA$ replication and repair processes to seal nicks in the sugar-phosphate backbone.

(D) $DNA$ and $RNA$ are nucleic acids composed of nucleotides.
Both contain the nitrogenous bases Adenine $(A)$,Guanine $(G)$,and Cytosine $(C)$.
However,$DNA$ contains Thymine $(T)$ as its fourth base,whereas $RNA$ contains Uracil $(U)$ instead of Thymine.
Therefore,Uracil is the nitrogenous base present in $RNA$ but not in $DNA$.

(C) Evolutionary convergence,also known as convergent evolution,is the process whereby organisms not closely related (not monophyletic) independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
For example,the wings of butterflies and birds are analogous structures that evolved independently to serve the function of flight.
Therefore,it represents the development of common traits in a group of distantly related organisms.

(D) Allen's rule states that animals living in colder climates have shorter extremities (ears,tails,limbs) compared to those living in warmer climates.
This is an adaptation to minimize the surface area to volume ratio,thereby reducing heat loss from the body.
Bergmann's rule relates to body size,Gloger's rule relates to pigmentation,and Jordan's rule relates to the number of vertebrae in fish.

(D) The $Cro-Magnon$ man ($Homo$ $sapiens$ $fossilis$) is considered the direct ancestor of modern humans ($Homo$ $sapiens$ $sapiens$).
They lived about $34,000$ years ago and were anatomically very similar to modern humans,possessing a large cranial capacity of approximately $1,600$ $cc$.

(B) According to the Oparin-Haldane hypothesis,the origin of life occurred through chemical evolution.
$1$. Simple inorganic molecules like water,ammonia,and methane were present in the primitive atmosphere.
$2$. These reacted to form simple organic compounds like amino acids.
$3$. These simple organic compounds polymerized to form complex macromolecules like proteins and nucleic acids.
$4$. Therefore,the sequence is: Ammonia (simple inorganic/organic precursor) $\rightarrow$ Amino acids $\rightarrow$ Proteins $\rightarrow$ Nucleic acids.

(C) Vestigial organs are anatomical structures that have lost their original ancestral function through evolution.
In humans,the $coccyx$ (tailbone) is a remnant of an ancestral tail.
The $nictitating$ $membrane$ (plica semilunaris) is a vestigial fold of tissue in the corner of the eye.
The $vermiform$ $appendix$ is a vestigial structure related to the cecum,which was once used for cellulose digestion.
The $ear$ $muscles$ (auricular muscles) are vestigial muscles that were once used to move the pinna.
Therefore,the group containing only vestigial organs is $coccyx$,$nictitating$ $membrane$,$vermiform$ $appendix$,and $ear$ $muscles$.

(C) Retroviruses are known to cause cancer in humans and animals.
These viruses possess viral oncogenes,denoted as $v$-oncogenes,in their genome.
When these viruses infect a host cell,the $v$-oncogenes can transform normal cells into cancerous cells by disrupting the regulation of the cell cycle.
Therefore,the presence of $v$-oncogenes is the primary reason for their oncogenic potential.

(A) Hypersensitivity to an allergen is known as an allergy.
An allergy is an exaggerated response of the immune system to certain antigens present in the environment.
This occurs due to the aberrant (abnormal) functioning of the immune system,where it reacts to harmless substances like pollen,dust,or dander as if they were dangerous pathogens.
Therefore,it is associated with the aberrant functioning of the immune system.

(D) $1$. $Tetanus$ is caused by the bacterium $Clostridium$ $tetani$.
$2$. $Typhoid$ is caused by the bacterium $Salmonella$ $typhi$.
$3$. $Whooping$ $cough$ is caused by the bacterium $Bordetella$ $pertussis$.
$4$. $Sleeping$ $sickness$ is caused by the protozoan $Trypanosoma$ $brucei$.
$5$. $Syphilis$ is caused by the bacterium $Treponema$ $pallidum$.
$6$. $AIDS$ is caused by the $Human$ $Immunodeficiency$ $Virus$ $(HIV)$.
$7$. $Measles$ is caused by the $Measles$ $virus$ (a $Paramyxovirus$).
$8$. $Rabies$ is caused by the $Rabies$ $virus$ (a $Lyssavirus$).
Therefore,both $Measles$ and $Rabies$ are viral diseases.

(B) Passive immunity was discovered by $Emil \text{ } von \text{ } Behring$ and $Shibasaburo \text{ } Kitasato$ in $1890$. They demonstrated that immunity could be transferred from an immunized animal to a non-immunized one through the serum, which contained antibodies. $Emil \text{ } von \text{ } Behring$ was awarded the first Nobel Prize in Physiology or Medicine in $1901$ for his work on serum therapy, particularly its application against diphtheria.

(A) The correct answer is $A$.
$1$. Rabies is caused by the Rabies virus (Lyssavirus).
$2$. Mumps is caused by the Mumps virus (Paramyxovirus).
$3$. Cholera is caused by the bacterium Vibrio cholerae.
$4$. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
$5$. Typhoid is caused by the bacterium Salmonella typhi.
$6$. Tetanus is caused by the bacterium Clostridium tetani.
$7$. $AIDS$ is caused by the Human Immunodeficiency Virus $(HIV)$,but Syphilis is caused by the bacterium Treponema pallidum.
Therefore,both diseases in option $A$ are viral.

(B) Long-term cultural evolution in humans is primarily driven by the ability to sustain larger populations through advancements in agriculture. The transition from hunting-gathering to settled agriculture allowed for a significant increase in food production. This surplus food provided the stability required for the development of complex societies,technologies,and cultural structures. Therefore,the scale of food production is the fundamental basis for long-term cultural evolution.

(C) The dog $(Canis \text{ } lupus \text{ } familiaris)$ is widely considered to be the first animal domesticated by humans. Archaeological evidence suggests that this domestication occurred during the Paleolithic era, likely as a result of a symbiotic relationship where wolves scavenged near human camps, eventually leading to a mutualistic bond.

(C) Pasteurization is a process of heating milk to a specific temperature to kill harmful bacteria without significantly altering its nutritional value or taste.
In the batch pasteurization method (also known as Low Temperature Long Time or $LTLT$),milk is heated to $63^o \,C - 65^o \,C$ for about $30$ minutes.
This process effectively destroys pathogens like Mycobacterium tuberculosis and other non-spore-forming bacteria.
Therefore,the correct option is $C$.

(NONE) The term 'antibiotic' was coined by Selman Waksman in $1942$. This statement is true.
Alexander Fleming discovered the first antibiotic, Penicillin, from the fungus Penicillium notatum. This statement is true.
Antibiotics are chemical substances produced by some microbes which can kill or retard the growth of other (disease-causing) microbes. They are not necessarily effective against every type of germ; they are often specific to certain groups of bacteria. However, the statement 'Every antibiotic is effective against a specific type of germ' is generally considered a correct description of their selective toxicity.
Actually, all the provided statements are scientifically accurate based on standard biological literature. If this is a multiple-choice question where one must be 'not true', there might be a context-specific error. However, based on $NCERT$, all these facts are correct.

(C) Biological control refers to the use of biological methods for controlling plant diseases and pests. In this process,one organism is used to control or destroy another organism (the pest) by utilizing its natural physiological processes,predatory behavior,or parasitic nature. This method is environmentally friendly and reduces the reliance on toxic chemical pesticides.

(A) In ecology,an ecological niche describes the functional role and position of a species within its environment. It includes how an organism uses the resources available in its habitat,its interactions with other species,and its specific requirements for survival and reproduction. While a habitat is the 'address' where an organism lives,the niche is its 'profession' or functional role.

(D) Forests are reservoirs of genetic diversity,known as germplasm.
When forest areas are destroyed or reduced significantly,the wild relatives of cultivated crops and various landraces are lost.
Since these wild varieties contain essential genes for disease resistance,drought tolerance,and high yield,their loss (loss of germplasm) severely hinders crop breeding programs.
While other options like desertification or starvation may occur,the most significant long-term biological impact in the context of environmental science and agriculture is the loss of genetic diversity required for future crop improvement.

(B) In a typical ecosystem, the food chain follows the $10\%$ law of energy transfer, where energy decreases at each trophic level.
Producers (plants) occupy the first trophic level and possess the highest biomass and population size to support all subsequent levels.
As we move up the trophic levels from primary consumers to tertiary consumers, the number of individuals and the available energy significantly decrease.
Therefore, producers have the largest population in a food chain.

(A) In ecological succession,the climax community represents the final,stable stage of an ecosystem that remains relatively unchanged unless disturbed.
While factors like soil type,nutrient availability,and biotic interactions influence the rate of succession,the ultimate nature and composition of the climax community are primarily determined by the regional climate (temperature and precipitation patterns).
Thus,climate is the most significant factor that dictates the potential vegetation of a climax community.

(C) The correct pair is $C$. The Little Rann of Kutch in Gujarat is famous as the only habitat for the Indian Wild Ass ($Equus$ $hemionus$ $khur$).
- Gir Forest is famous for the Asiatic Lion,not the Tiger.
- Kaziranga National Park is famous for the One-horned Rhinoceros,not the Elephant.
- Banas Wildlife Sanctuary is not primarily known for the Musk Deer,which is typically found in high-altitude Himalayan regions.

(D) When sewage is discharged into water bodies,it contains high levels of organic matter.
Microorganisms like bacteria decompose this organic matter,a process that requires a significant amount of oxygen.
This leads to a sharp decrease in the $BOD$ (Biochemical Oxygen Demand) and a corresponding depletion of dissolved oxygen in the water.
As a result,aquatic organisms like fish,which rely on dissolved oxygen for respiration,die due to suffocation.

(D) The worst nuclear power plant accident occurred at the Chernobyl nuclear power plant in Ukraine in $1986$.
The Bhopal gas tragedy,which involved the leakage of Methyl Isocyanate $(MIC)$ gas,occurred in Bhopal,India,in $1984$.
Therefore,the correct sequence is $1986$ in Ukraine and $1984$ in Bhopal.

(B) The $USA$ is historically and currently one of the largest contributors to global greenhouse gas emissions due to its high level of industrialization,energy consumption,and transportation infrastructure. While other countries like China have recently surpassed the $USA$ in annual emissions,in the context of standard biology and environmental science textbooks,the $USA$ is frequently cited as a major contributor.