AIIMS 2005 Biology Question Paper with Answer and Solution

(B) The correct answer is $B$.
$1$. Nephridia in earthworm are excretory organs.
$2$. Malpighian tubules in cockroach are the primary excretory organs.
$3$. Urinary tubules (nephrons) in rat are the functional units of the kidney responsible for excretion.
Since all three structures perform the function of excretion,they are functionally similar.

(C) Silverfish (insect),scorpion (arachnid),dragonfly (insect),and prawn (crustacean) all belong to the phylum $Arthropoda$.
The defining characteristics of all arthropods include the presence of jointed appendages and a chitinous exoskeleton,which provides protection and support.
Option $A$ is incorrect because scorpions and prawns do not have three pairs of legs.
Option $B$ is incorrect because insects have one pair of antennae,while arachnids have none.
Option $D$ is incorrect because insects do not have a cephalothorax (they have a distinct head,thorax,and abdomen).

(A) Mustard belongs to the family $Brassicaceae$ (also known as $Cruciferae$).
Key characteristics of this family include:
$1$. Flowers are $tetramerous$ (parts in fours).
$2$. Androecium consists of $six$ stamens,arranged in two whorls ($tetradynamous$ condition: $2$ outer short and $4$ inner long).
$3$. Gynoecium is $bicarpellary$ (two carpels),syncarpous,and superior.
$4$. The fruit is typically a $siliqua$ or $silicula$.

(C) . Sieve tube elements are specialized cells in the phloem that are responsible for the translocation of food. During their maturation,they lose their nuclei and other organelles to facilitate the flow of sap,but they retain a thin layer of cytoplasm along the cell wall.

(A) The correct answer is $A$. Lysosomes are single-membraned organelles,not double-membraned. They are small vesicles formed by the budding off from the trans-face of the Golgi apparatus and contain various hydrolytic enzymes (acid hydrolases) that are active at acidic $pH$. The other statements are correct: Endoplasmic reticulum is a network of tubules involved in transport and synthesis; Leucoplasts are plastids that lack pigments and contain $DNA$ and ribosomes; Sphaerosomes are single-membrane-bound organelles involved in lipid metabolism.

(B) Glyoxysomes are specialized peroxisomes found in plants,particularly in the fat-storing tissues of germinating seeds.
They contain enzymes for the glyoxylate cycle,which converts stored lipids into carbohydrates (gluconeogenesis) to provide energy for the developing embryo.
Castor seeds are oil-rich seeds,and their endosperm contains significant amounts of lipids.
Therefore,glyoxysomes are abundantly found in the endosperm of castor seeds,whereas wheat endosperm is primarily starchy.

(B) Gibberellins promote seed germination by inducing the synthesis of hydrolytic enzymes such as $\alpha$-amylase,protease,and lipase in the aleurone layer of the endosperm.
These enzymes break down stored food reserves (starch,proteins,and lipids) into simpler,soluble forms that are transported to the developing embryo to support its growth.
Therefore,the correct option is $B$.

(D) The correct option is $D$.
$1$. Gastrin is secreted by $G$-cells in the stomach lining and stimulates the gastric glands to secrete $HCl$ and pepsinogen,not specifically targeting oxyntic cells in the manner described.
$2$. Inhibin is secreted by Sertoli cells and acts on the anterior pituitary to inhibit $FSH$ secretion,not the hypothalamus.
$3$. Enterokinase is an enzyme secreted by the intestinal mucosa (duodenum) that activates trypsinogen into trypsin; it does not target the gall bladder.
$4$. Atrial Natriuretic Factor $(ANF)$ is secreted by the atrial wall of the heart in response to increased blood pressure. It acts on the juxtaglomerular apparatus $(JGA)$ to inhibit the release of renin,thereby acting as a vasodilator and reducing blood pressure.

(A) The correct statement is that when water is not available,camels do not produce urine but store urea in their tissues to maintain osmotic balance.
Camels are adapted to desert environments where they produce nearly dry feces and highly concentrated urine to conserve water.
In conditions of extreme water scarcity,they rely on metabolic water and accumulate urea in their tissues to prevent water loss.

(B) In the provided diagram,the labels are as follows:
$1$. The thigh bone is labeled as 'Femu',which is a misspelling of 'Femur'.
$2$. The lateral bone of the lower leg is labeled as 'Fibul',which is a misspelling of 'Fibula'.
$3$. The medial bone of the lower leg is correctly labeled as 'Tibia'.
$4$. The ankle bones are labeled as 'Tarsa',which is a misspelling of 'Tarsals'.
$5$. The toe bones are correctly labeled as 'Phalanges'.
Comparing the labels with the anatomical positions:
- The label 'Femu' points to the Femur (correct bone,incorrect spelling).
- The label 'Fibul' points to the Fibula (correct bone,incorrect spelling).
- The label 'Tibia' points to the Tibia (correct bone,correct spelling).
- The label 'Tarsa' points to the Tarsals (correct bone,incorrect spelling).
- The label 'Phalanges' points to the Phalanges (correct bone,correct spelling).
However,looking at the anatomical orientation of the left hindlimb:
- The Fibula is the lateral bone,and the Tibia is the medial bone. In the diagram,the labels for 'Fibula' and 'Tibia' are swapped. The label 'Fibul' is pointing to the medial side (Tibia),and the label 'Tibia' is pointing to the lateral side (Fibula).
- Therefore,the bones that are wrongly labeled in terms of their anatomical position are the Fibula and the Tibia. Among the given options,the most appropriate choice identifying the mislabeled bones is 'Femur and fibula' (due to the spelling error and positional swap) or 'Tibia and tarsals'. Given the standard interpretation of this specific diagram in textbooks,the labels for 'Femur' and 'Fibula' are the ones typically highlighted as having errors.

(B) Glyoxysomes are specialized peroxisomes found in plants, particularly in the fat-storing tissues of germinating seeds.
They contain enzymes for the glyoxylate cycle, which converts stored fatty acids into carbohydrates (sugars) required for the growth of the embryo.
Castor seeds $(Ricinus communis)$ are oil-rich seeds, and their endosperm contains abundant glyoxysomes to facilitate the conversion of fats into energy and building blocks during germination.
Therefore, the correct option is $B$.

(B) The process of synapsis,which involves the pairing of homologous chromosomes,begins during the $Zygotene$ stage.
When synapsis is complete all along the length of the chromosomes,the bivalents are fully formed.
Following the completion of synapsis,the cell enters the $Pachytene$ stage.
In the $Pachytene$ stage,the bivalent chromosomes become clearly visible as tetrads,and the process of crossing over occurs between non-sister chromatids of homologous chromosomes.

(C) The Assertion is correct because fungi are cosmopolitan and found in air,water,soil,and on animals and plants.
However,the Reason is incorrect because fungi are heterotrophic organisms that completely lack photosynthetic pigments such as chlorophyll,carotenoids,fucoxanthin,and phycoerythrin.
These pigments are characteristic of algae,not fungi.
Fungi obtain nutrients through saprophytic,parasitic,or symbiotic modes of nutrition.

(C) The Assertion is correct because the duck-billed platypus and the spiny ant-eater (echidna) are prototherian mammals that lay eggs (oviparous) but possess mammary glands.
The Reason is incorrect because,while mammals generally have $7$ cervical vertebrae,the number of cranial nerves in mammals is $12$ pairs,but this specific anatomical feature is not the defining characteristic that classifies them as mammals. Furthermore,the statement implies these are the reasons for their classification as mammals,which is scientifically inaccurate; they are classified as mammals due to the presence of mammary glands,hair,and a diaphragm.

(A) In eukaryotic cells,extranuclear $DNA$ is primarily found in mitochondria and chloroplasts (plastids). These organelles contain their own genome. Mitochondrial $DNA$ is inherited through the egg cytoplasm because the egg provides the bulk of the cytoplasm to the zygote,whereas the sperm contributes primarily nuclear $DNA$.

(C) Mitochondria and chloroplasts are considered semi-autonomous organelles because they contain their own $DNA$ and ribosomes,which allow them to synthesize some of their own proteins.
They are formed by the division of preexisting organelles.
However,the statement that they 'lack protein-synthesizing machinery' is incorrect because they possess $70S$ ribosomes,which are essential for protein synthesis.
Therefore,the Assertion is correct,but the Reason is incorrect.

(B) In a typical enzyme-catalyzed reaction,the velocity increases with substrate concentration until it reaches a maximum $(V_{max})$ and then plateaus.
However,the provided graph shows that after reaching a certain point,the reaction velocity decreases as the substrate concentration increases.
This decline in reaction rate at higher substrate concentrations is a characteristic indicator of the presence of an enzyme inhibitor in the reaction mixture,which interferes with the enzyme's activity.

(D) Many cells,such as animal cells,function properly and undergo mitotic division even in the absence of plastids. Plastids are organelles found primarily in plant cells and algae,responsible for photosynthesis and storage,but they are not essential for the basic cellular processes of metabolism or mitosis in all cell types.

(A) $C_4$ plants are more efficient than $C_3$ plants because they have evolved a mechanism to minimize photorespiration.
In $C_4$ plants,the initial $CO_2$ fixation occurs in mesophyll cells via the enzyme $PEP$ carboxylase,which has a high affinity for $CO_2$ and does not bind with $O_2$.
The $CO_2$ is then transported to bundle sheath cells,where it is released at a high concentration,ensuring that the enzyme $RuBisCO$ functions primarily as a carboxylase rather than an oxygenase.
This spatial separation effectively suppresses photorespiration,making the $C_4$ pathway more efficient in terms of carbon fixation and energy utilization compared to the $C_3$ pathway.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(C) The $CO_2$ compensation point is defined as the specific atmospheric concentration of $CO_2$ at which the rate of photosynthesis exactly equals the rate of respiration in a plant.
At this point,the net exchange of $CO_2$ between the plant and the atmosphere is zero,meaning the $CO_2$ produced by respiration is entirely consumed by photosynthesis.
The Assertion is correct.
The Reason states that the compensation point is reached when $CO_2$ uptake is less than that generated through respiration,which is incorrect.
At the compensation point,the rate of $CO_2$ uptake is exactly equal to the rate of $CO_2$ release (respiration).
Therefore,the Assertion is correct,but the Reason is incorrect.

(B) The thymus is an organ located in the upper anterior portion of the chest cavity just behind the sternum.
The thymus continues to grow between birth and puberty and then begins to atrophy.
Proportional to thymic size,thymic activity is most active before puberty.
Upon atrophy,the size and activity are dramatically reduced,and the organ is primarily replaced with fat.
The atrophy is due to the increased circulating level of sex hormones,and chemical or physical castration of an adult results in the thymus increasing in size and activity.
In contrast,other options are incorrect: Thyroid hyperactivity causes hyperthyroidism,not cretinism (which is caused by hypothyroidism); Parathormone increases blood calcium levels by mobilizing it from bones; and Delta cells of the pancreas secrete somatostatin,not a hormone that stimulates glycolysis.

(A) Regeneration is broadly classified into two types: Morphallaxis and Epimorphosis.
$1$. Morphallaxis involves the reorganization of existing body tissues to form a complete organism from a small fragment,as seen in Hydra.
$2$. Epimorphosis involves the proliferation of cells at the site of injury to replace lost parts,such as limb regeneration or the formation of new Planarians from body fragments.
Therefore,the regeneration of two transversely cut equal pieces of a Hydra into two small Hydras is a classic example of Morphallaxis.

(A) Senescence refers to the period of decline in biological functions associated with aging,where age-related defects become apparent.
The programmed senescence theory suggests that aging is genetically controlled,involving the sequential activation (switching on) and inactivation (switching off) of specific genes throughout an individual's lifespan.
Therefore,the Reason correctly explains why senescence occurs as a manifestation of these genetic changes.
Thus,both Assertion and Reason are correct,and the Reason is the correct explanation of the Assertion.

(C) Telomerase is a specialized enzyme that adds specific nucleotide sequences to the ends of eukaryotic chromosomes,known as telomeres.
It is a ribonucleoprotein complex,meaning it consists of both a protein component ($TERT$ - Telomerase Reverse Transcriptase) and an $RNA$ component ($TERC$ - Telomerase $RNA$ Component) that serves as a template for the synthesis of telomeric $DNA$ repeats.

(D) Double fertilization is a characteristic feature of angiosperms.
It involves two fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) in the central cell to form a triploid primary endosperm nucleus ($PEN$,$3n$).
Both male gametes are delivered to the embryo sac by the same pollen tube.

(B) In a normal $28$-day menstrual cycle:
$1$. The menstrual phase occurs from day $1-5$.
$2$. The follicular (proliferative) phase occurs from day $6-13$,during which the endometrium regenerates.
$3$. Ovulation (release of egg) occurs on the $14^{th}$ day.
$4$. The luteal (secretory) phase occurs from day $15-28$,where the endometrium secretes nutrients for implantation due to high progesterone levels.
Therefore,the regeneration of the endometrium typically occurs between days $5$ and $10$ (proliferative phase),making option $B$ the correct match.

(C) The middle piece of a human sperm contains numerous mitochondria arranged spirally around the axial filament.
This axial filament runs through the entire length of the sperm tail and possesses the characteristic $9+2$ arrangement of microtubules (axoneme).
Therefore,a cross-section at the midpoint of the middle piece reveals both the mitochondria and the $9+2$ arrangement of microtubules.

(B) Grain colour in wheat is an example of polygenic inheritance involving $3$ gene pairs $(n = 3)$.
In the $F_2$ generation of a trihybrid cross,the total number of possible combinations is $4^n = 4^3 = 64$.
The parental phenotypes (extreme phenotypes) are represented by the genotypes $AABBCC$ (darkest) and $aabbcc$ (lightest).
The proportion of individuals resembling either parent is given by the formula $(1/4)^n$.
Substituting $n = 3$,we get $(1/4)^3 = 1/64$.
Since $1/64$ is approximately $0.0156$,which is $1.56\%$,this value is less than $5\%$.

(A) The "cri-du-chat" syndrome is a genetic disorder caused by a partial deletion of the short arm ($p$ arm) of chromosome $5$.
This structural chromosomal abnormality leads to characteristic symptoms, including a high-pitched cry in infants that sounds like a cat, which is why it is named "cri-du-chat" (French for "cry of the cat").
Therefore, the correct mechanism is deletion.

(D) Somaclonal variation refers to the genetic variations observed in plants that are regenerated from tissue culture.
These variations arise due to the stress of the culture environment,the use of growth regulators,or the duration of the culture period.
Since plants raised through tissue culture are clones of the parent,any deviation from the parent's genotype is termed as somaclonal variation.
Therefore,the correct answer is $D$.

(A) $1$. Analyze the pedigree: An affected father (Generation $1$) passes the trait to his daughters (Generation $2$),but not to his sons. This is characteristic of $X$-linked inheritance.
$2$. In Generation $2$,an affected female marries an unaffected male and produces both affected and unaffected offspring of both sexes. This indicates that the trait is dominant because it appears in every generation and affected individuals have affected parents.
$3$. Since an affected father passes the trait to all his daughters and the trait appears in both males and females in subsequent generations,it follows the pattern of $X$-linked dominant inheritance.

(C) The primary source of all genetic variation is $Mutation$.
$Mutation$ refers to a sudden, heritable change in the $DNA$ sequence of an organism.
While $Independent \text{ } assortment$ and $Recombination$ (during meiosis) shuffle existing alleles to create new combinations, they do not create new alleles.
$Mutation$ is the ultimate process that introduces entirely new alleles into a population's gene pool, thereby serving as the fundamental source of genetic diversity.

(C) $Bt$ in "$Bt$-cotton" refers to the bacterium $Bacillus$ $thuringiensis$, not just a general term for biotechnology. Thus, option $A$ is incorrect.
Somatic hybridization involves the fusion of protoplasts, not complete plant cells (which include cell walls). Thus, option $B$ is incorrect.
$Hirudin$ is an anticoagulant protein originally found in leeches. Its gene has been transferred into $Brassica$ $napus$ (rapeseed) to produce it in seeds. Thus, option $C$ is correct.
$Flavr$ $Savr$ tomato was engineered to have delayed ripening by inhibiting ethylene production, not enhancing it. Thus, option $D$ is incorrect.

(B) Somaclonal variations are genetic variations observed in plants regenerated from tissue culture. These variations occur during the process of callus differentiation when cells undergo rapid division and reorganization in an artificial culture medium.

(C) An ecological niche describes the functional role of an organism in its environment,including its habitat,food sources,and interactions with other species.
$A$. $Vallisneria$ is a submerged plant,but 'pond' is a habitat,not a niche.
$B$. 'Desert' is a habitat,not a niche.
$C$. Plant lice (aphids) feed on the sap of specific leaves; the leaf surface acts as their specific micro-habitat and functional site for feeding,which represents their ecological niche.
$D$. 'Dense forest' is a habitat,not a niche.
Therefore,option $C$ is the most accurate representation of a specific ecological niche.

(C) The provided image shows an inverted pyramid of biomass. In an aquatic ecosystem like a lake,the biomass of phytoplankton (producers) is much smaller than the biomass of zooplankton and small fish (primary consumers),and even smaller than the biomass of large fish (secondary consumers). Therefore,the pyramid of biomass in a lake is typically inverted.

(B) $Prosopis$ is a deep-rooted perennial tree, which is able to absorb water from either the water table or moist strata. It is typically found in desert scrub forests.
$Saccharum$ is a common grass found in grasslands and tropical savannahs.
Both $Shorea \text{ } robusta$ and $Acacia \text{ } catechu$ are trees found in tropical deciduous forests.
In tropical deciduous forests, vegetation includes broad-leaved trees, which shed their leaves during the dry season.

(C) The correct answer is $(c)$.
Cryopreservation is an ex-situ conservation method where biological materials such as tissue cultures, embryos, animal cells/tissues, and spermatozoa are preserved at $-196^{\circ}C$ using liquid nitrogen $(N_2)$.
Ex-situ conservation refers to the conservation of organisms outside their natural habitats.
Other examples of ex-situ conservation include botanical gardens, zoological parks, wildlife safari parks, and gene banks.
Wildlife sanctuaries, biosphere reserves, and national parks are examples of in-situ conservation methods.

(A) The introduction of high-yielding varieties (HYVs) has led to the widespread adoption of a limited number of genetically uniform crop strains.
This practice replaces the traditional,diverse landraces and local varieties that were naturally adapted to various environmental conditions.
As a result,the genetic diversity within agricultural crops is significantly reduced,making the entire crop population more vulnerable to pests,diseases,and changing environmental conditions.

(C) Conservation of biodiversity is classified into two types: $In-situ$ (on-site) and $Ex-situ$ (off-site).
$In-situ$ conservation involves protecting species within their natural habitats, such as Wildlife Sanctuaries, National Parks, and Biosphere Reserves.
$Ex-situ$ conservation involves protecting species outside their natural habitats, such as botanical gardens, zoological parks, and cryopreservation (storing gametes or embryos at very low temperatures, e.g., $-196^{\circ}C$ in liquid nitrogen).
Therefore, cryopreservation is an $Ex-situ$ conservation method.

(A) $DDT$ (Dichlorodiphenyltrichloroethane) is a non-biodegradable pollutant.
These substances are persistent in the environment because they cannot be broken down naturally or by the metabolic activities of microorganisms.
Due to their chemical stability,they accumulate in the food chain and are not recycled back into the atmosphere or soil in a harmless form.

(C) Haemophilia is a sex-linked recessive disorder caused by the deficiency of blood clotting factor $VIII$ (Haemophilia $A$) or factor $IX$ (Haemophilia $B$).
In patients with haemophilia,the blood clotting mechanism is impaired because the cascade of reactions required for fibrin formation is interrupted due to the absence of these specific clotting factors.
The Assertion is correct because haemophilia is indeed characterized by the failure to produce functional clotting factor $VIII$.
The Reason is incorrect because the primary defect in haemophilia is not a low concentration of platelets or a deficiency in prothrombin production; rather,it is a genetic deficiency of specific clotting factors. Platelet counts in haemophiliacs are typically normal.

(C) In humans,sex determination is based on the $XY$ type. Males produce two types of gametes: $50\%$ carrying the $X$ chromosome and $50\%$ carrying the $Y$ chromosome. Females produce only one type of gamete,all carrying the $X$ chromosome. Therefore,the sex of the child is determined by the sperm (male gamete) that fertilizes the egg. Thus,the Assertion is correct.
Sex in humans is not a polygenic trait; it is determined by the presence or absence of the $Y$ chromosome,specifically the $SRY$ gene located on it. The Reason statement is scientifically incorrect because sex determination in humans is primarily a monogenic trait controlled by the $Y$ chromosome,not a polygenic trait.

(A) $DNA$ replication and transcription occur inside the nucleus in eukaryotic cells. After transcription,the $mRNA$ is processed and exported from the nucleus into the cytoplasm. In the cytoplasm,the $mRNA$ binds to ribosomes,where translation (protein synthesis) takes place using available amino acids and $tRNA$. This flow of genetic information from $DNA$ to $RNA$ to protein is known as the Central Dogma. Since the Reason correctly explains why translation must occur in the cytoplasm (due to the presence of necessary machinery),the Assertion and Reason are both correct,and the Reason is the correct explanation.

(D) The Assertion is incorrect because the tail-expressing genes have not completely disappeared; humans possess vestigial structures like the coccyx (tailbone),which are remnants of ancestral tails. Furthermore,genes are not lost simply due to disuse.
The Reason is incorrect because Lamarck's theory is known as the 'Theory of Inheritance of Acquired Characters'. The 'Theory of Continuity of Germ Plasm' was proposed by August Weismann,which specifically refuted Lamarckism by stating that changes in somatic cells are not inherited.

(A) Comparative biochemistry provides strong evidence for the common ancestry of living beings. The presence of similar biochemical molecules such as proteins,enzymes,hormones,and blood groups across diverse species suggests a shared evolutionary origin.
Furthermore,the genetic code is universal,meaning that the same codons specify the same amino acids in almost all living organisms,from bacteria to humans. This universality is a powerful piece of evidence supporting the theory that all life on Earth evolved from a common ancestor. Therefore,the Reason correctly explains the Assertion.

(A) Darwin's finches on the Galapagos Islands exhibit a remarkable diversity in beak morphology,which is an adaptation to the specific food sources available in their respective niches,such as large seeds,insects,or cactus fruits.
This phenomenon is a classic example of adaptive radiation,where a single ancestral species evolves into multiple new forms to exploit different ecological niches.
The ancestral seed-eating finches migrated from the South American mainland to the Galapagos Islands.
Upon arrival,they encountered various isolated habitats that were free from competitors,allowing them to diversify and adapt to different diets over time.
Therefore,the Reason correctly explains why the finches evolved different beak shapes as described in the Assertion.

(B) An insect bite causes tissue damage,which triggers an inflammatory response at the site of the injury.
This response is mediated by the release of chemical mediators known as alarm chemicals.
$Histamine$ is released by mast cells and basophils,which causes vasodilation and increased capillary permeability,leading to redness and swelling.
$Kinins$ (such as bradykinin) are polypeptides that also promote vasodilation,increase vascular permeability,and stimulate pain receptors.
Therefore,the correct combination of alarm chemicals involved in this process is $histamine$ and $kinins$.

(C) An antibody molecule is $Y-$shaped and consists of four polypeptide chains: two identical heavy $(H)$ chains and two identical light $(L)$ chains. The antigen-binding site,also known as the paratope,is located at the variable region of the antibody. This site is formed by the interaction between the variable domain of one heavy chain $(V_H)$ and the variable domain of one light chain $(V_L)$. Therefore,the antigen-binding site is found between one heavy and one light chain.

(A) The success of an organ transplant depends on the proper matching of histocompatibility antigens present on the surface of all body cells.
Because the transplanted tissue contains foreign antigens,it is recognized as 'non-self' by the recipient's immune system.
These antigens stimulate the recipient's $T-$cells and antibodies to attack the graft,leading to rejection.
Therefore,patients undergoing organ transplantation are administered immunosuppressive drugs to suppress the immune response and prevent the rejection of the transplanted tissue.

(A) $1$. The graph shows the relationship between the weight of the Khapra beetle larvae and the concentration of cholesterol in their diet.
$2$. At $0 \, \mu g/g$ cholesterol,the growth is minimal or zero,indicating that cholesterol is necessary for the development of these larvae.
$3$. As the concentration of cholesterol increases,the weight of the larvae increases,showing that cholesterol is an essential dietary requirement for the Khapra beetle.
$4$. Option $A$ is the most accurate interpretation because the graph demonstrates that without cholesterol,the larvae do not grow,confirming it is an essential nutrient.

(D) $Agrobacterium$ $tumefaciens$ is a soil-inhabiting,plant-pathogenic bacterium that infects broad-leaved crops such as tomato,soybean,sunflower,and cotton,but it does not infect cereals.
Tumor formation (crown galls) is induced by the transfer of its $Ti$ plasmid $DNA$ into the host plant's genome.
The $T-DNA$ segment of the $Ti$ plasmid is responsible for tumor induction.
Because this gene transfer occurs naturally without human intervention,the bacterium is known as the 'natural genetic engineer' of plants.
Since the Assertion incorrectly states that it is associated with all cereal and pulse crops,and the Reason is also factually incorrect regarding the mechanism of gene transfer (it uses $Ti$ plasmid,not the chromosomal genome),both statements are incorrect.

(A) In recombinant $DNA$ technology,human genes are inserted into host organisms like bacteria or yeast to produce large quantities of desired proteins.
Bacteria and yeast are preferred as host cells because they have a very short generation time and multiply rapidly,allowing for the creation of a large population of cells in a short period.
This large population of cells expresses the inserted gene,leading to the efficient production of the recombinant protein.
Therefore,the Reason correctly explains why human genes are transferred into these organisms.

(B) The Assertion is correct because Kerala has the highest sex ratio in India (approximately $1084$ females per $1000$ males according to recent census data).
The Reason is also a factually correct statement regarding the demographic trend in India,as the population is indeed increasing at a rapid rate.
However,the Reason does not explain why Kerala has the highest sex ratio.
Therefore,both statements are correct,but the Reason is not the correct explanation for the Assertion.

(B) The Assertion is correct because diesel vehicles are a major source of suspended particulate matter $(SPM)$,which is harmful to human health.
The Reason is also correct because catalytic converters are used in automobiles to reduce the emission of poisonous gases like carbon monoxide $(CO)$ and nitrogen oxides $(NO_x)$ by converting them into less harmful gases like carbon dioxide $(CO_2)$ and nitrogen $(N_2)$.
However,catalytic converters are ineffective at reducing the emission of $SPM$ (particulate matter).
Therefore,while both statements are true,the Reason does not explain why $SPM$ is released by diesel vehicles.

(B) The Assertion is correct because global warming is a well-documented phenomenon caused by the increase in the concentration of greenhouse gases like $CO_2$,$CH_4$,and $CFCs$ in the atmosphere.
These greenhouse gases trap heat by preventing the escape of long-wave infrared radiations into space,leading to a rise in global temperatures.
The Reason is also a scientifically correct statement regarding the depletion of the ozone layer,which allows more $UV$ radiation to reach the earth's surface.
However,the depletion of the ozone layer is not the cause of global warming; therefore,the Reason is not the correct explanation for the Assertion.

(A) Methane is produced by incomplete biomass combustion and anaerobic decomposition by methanogens.
Carbon dioxide contributes about $60\%$ to total global warming,while methane $(CH_4)$ and chlorofluorocarbons $(CFCs)$ contribute $20\%$ and $14\%$ respectively.
Nitrous oxide $(N_2O)$ contributes $6\%$ to total global warming.
Efficient engines,such as multi-point fuel injection engines,improve combustion efficiency,thereby reducing the emission of unburnt hydrocarbons like methane in automobile exhausts.
Therefore,both the Assertion and the Reason are correct,and the Reason explains why methane emissions from vehicles are controlled.