AIPMT 1997 Biology Question Paper with Answer and Solution

(B) Viruses are obligate parasites that lack their own metabolic machinery. They consist of genetic material,which is either $DNA$ or $RNA$,enclosed in a protein coat. Because they lack the cellular machinery targeted by antibiotics (such as cell wall synthesis or bacterial protein synthesis),they are not affected by antibiotics. Therefore,the statement that viruses contain either $DNA$ or $RNA$ is correct.

(B) Lichens are symbiotic associations between fungi (mycobiont) and algae or cyanobacteria (phycobiont).
In the majority of lichen associations,the fungal partner belongs to the class Ascomycetes,and the algal partner is either a green alga or a blue-green alga (cyanobacteria).
Therefore,most lichens consist of blue-green algae and Ascomycetes.

(B) In the plant kingdom,$Bryophytes$ are divided into liverworts and mosses.
$Mosses$ (class $Bryopsida$) are characterized by the presence of a leafy gametophyte stage.
They also possess multicellular and branched rhizoids,which help in anchorage and absorption of water and minerals.
Therefore,these features are characteristic of some bryophytes (specifically mosses).

(C) Bryophytes are land-dwelling plants that exhibit a significant evolutionary advancement over algae.
One of the key differences is the structure of their reproductive organs.
In bryophytes,the female reproductive organ,known as the archegonium,is multicellular and flask-shaped,and it is protected by a jacket of sterile cells.
In contrast,algae typically have unicellular reproductive organs that lack such a protective sterile layer.
Therefore,the presence of an archegonium surrounded by sterile cells is a characteristic feature that distinguishes bryophytes from algae.

(C) Brown algae,belonging to the class $Phaeophyceae$,are characterized by the presence of specific pigments that give them their distinct brown color.
These algae contain chlorophyll $a$,$c$,and carotenoids,specifically the xanthophyll pigment known as $Fucoxanthin$.
$Fucoxanthin$ masks the green color of chlorophyll,resulting in shades ranging from olive green to brown.
Phycocyanin and Phycoerythrin are characteristic pigments of red and blue-green algae,respectively.

(A) Ulothrix is a genus of filamentous green algae. In Ulothrix,sexual reproduction occurs through the fusion of flagellated gametes that are morphologically similar. Such gametes are known as isogametes. Therefore,Ulothrix filaments produce isogametes.

(B) Heterospory is the production of two different types of spores (microspores and megaspores). This phenomenon is a precursor to the seed habit in plants. In the context of plant morphology and evolution,the development of seeds is closely associated with the evolution of the $Bract$ (or specialized leaf-like structures) that protect the developing sporangia. Among the given options,the $Bract$ is the structure most commonly associated with the evolutionary context of seed-bearing plants.

(D) In plants,$Xylem$ is primarily responsible for the transport of water and minerals from roots to other parts of the plant (unidirectional). $Phloem$ is responsible for the translocation of organic solutes (mainly sucrose) from the source (leaves) to the sink (roots,fruits,storage organs,etc.). This transport is bidirectional,meaning it can move upwards and downwards depending on the plant's requirements.

(A) In angiosperms,the $Sieve$ $tube$ $elements$ are the main conducting cells of the phloem. During their development and maturation,they lose their nucleus,ribosomes,and vacuoles to facilitate the efficient transport of food materials. This process makes them enucleated at maturity,while they remain associated with companion cells that regulate their metabolic activities.

(D) The basement membrane is a thin,fibrous,extracellular matrix of tissue that separates the lining of an internal or external body surface from underlying connective tissue.
It is not composed of cells itself.
Instead,it is a specialized extracellular matrix secreted by the epithelial cells (basal lamina) and the underlying connective tissue cells (reticular lamina).
Therefore,it is a product of epithelial cells and connective tissue cells,rather than being composed of the cells themselves.

(A) The germinal epithelium is the layer of cells that lines the gonads (testes and ovaries) and is responsible for the production of gametes.
It is composed of a single layer of cuboidal epithelial cells.
Therefore,the germinal epithelium is a specialized form of cuboidal epithelium.

(C) In eukaryotic animal cells,protein synthesis is primarily carried out by ribosomes.
Ribosomes are found in the cytoplasm (either free or attached to the rough endoplasmic reticulum) and also within the mitochondria (mitochondrial ribosomes).
Therefore,protein synthesis occurs in both the cytoplasm and the mitochondria.

(C) The process of $ATP$ synthesis in both chloroplasts and mitochondria is explained by the $Chemiosmotic$ $hypothesis$.
This hypothesis was proposed by $Peter$ $Mitchell$ in $1961$.
It states that $ATP$ synthesis is linked to the development of a proton gradient across the membrane (thylakoid membrane in chloroplasts and inner mitochondrial membrane in mitochondria).
The movement of protons back across the membrane through the $ATP$ $synthase$ enzyme complex provides the energy required for the phosphorylation of $ADP$ to $ATP$.

(B) The centromere is a specialized $DNA$ sequence of a chromosome that links a pair of sister chromatids. During mitosis,spindle fibers attach to the centromere via the kinetochore. Therefore,the centromere is an integral part of the chromosome structure.

(A) The basic functional and structural unit of the human kidney is the $Nephron$. Each kidney contains approximately $1$ million nephrons. $A$ nephron consists of a renal corpuscle (glomerulus and Bowman's capsule) and a renal tubule. The $Loop$ $of$ $Henle$ is a part of the nephron,not the entire unit. $Nephridia$ are excretory organs found in annelids like earthworms. Therefore,the correct answer is $Nephron$.

(B) The kidney of an adult frog is of the $Mesonephric$ type.
In amphibians,the larval stage possesses a $Pronephric$ kidney,while the adult stage develops a $Mesonephric$ kidney.
$Metanephric$ kidneys are characteristic of higher vertebrates like reptiles,birds,and mammals.
Therefore,the correct option is $B$.

(A) Ureotelic animals are those that excrete nitrogenous waste in the form of urea.
In these animals,ammonia produced during metabolism is converted into urea in the liver through a series of biochemical reactions known as the Ornithine cycle (also called the Urea cycle).
This cycle involves the conversion of ammonia and carbon dioxide into urea using $ATP$.
Therefore,the correct option is $A$.

(A) The $Vagus$ nerve is the $10th$ cranial nerve,denoted as $X$ in Roman numerals. It is the longest cranial nerve and plays a crucial role in the parasympathetic nervous system,regulating heart rate,gastrointestinal peristalsis,and sweating.

(A) The sympathetic nervous system is part of the autonomic nervous system that prepares the body for 'fight-or-flight' responses.
It increases the heart rate (heartbeat) to pump more blood to muscles.
Conversely,it inhibits the digestive system,including the secretion of digestive juices and saliva,to divert energy toward physical activity.
Therefore,among the given options,only the heartbeat is stimulated by the sympathetic nervous system.

(C) In frogs,the cranium (brain box) is a bony structure that protects the brain. The roof of the cranium is formed by a pair of fused bones known as the $Fronto-parietals$. These bones cover the dorsal surface of the cranium,while the floor is primarily formed by the $Parasphenoid$ bone.

(A) In frogs,the middle ear communicates with the inner ear through an opening called the $Fenestra$ $ovalis$ (also known as the oval window).
This opening is covered by the stapes (columella auris) and allows the transmission of sound vibrations from the middle ear to the fluid-filled inner ear.
Therefore,it acts as the gateway between the middle ear and the inner ear.

(C) In mammals,the light-sensitive pigments in the retina are known as photopigments. These consist of an opsin (a protein) and retinal (an aldehyde of vitamin $A$). The most well-known photopigment in the rod cells of the retina is $Rhodopsin$ (also known as visual purple). When light strikes the retina,it causes the dissociation of retinal from opsin,which triggers the generation of action potentials in the ganglion cells,leading to vision. Therefore,the correct answer is $Rhodopsin$.

(A) Nissl's granules (also known as Nissl bodies) are large granular bodies found in neurons.
They are composed of rough endoplasmic reticulum $(RER)$ with clusters of free ribosomes and are the site of protein synthesis.
Since they contain ribosomes,they are rich in $RNA$ and are responsible for the synthesis of proteins required for the maintenance and repair of the neuron.

(C) Thyroxine (a thyroid hormone),adrenaline (an adrenal medulla hormone),and melanin (a skin pigment) are all synthesized from the amino acid $Tyrosine$.
$Tyrosine$ acts as a precursor for the synthesis of catecholamines (like adrenaline and noradrenaline),thyroid hormones (like thyroxine),and the pigment melanin.

(D) $E. coli$ (Escherichia coli) is a prokaryotic organism.
In all prokaryotes,the genetic material consists of a single,circular,double-stranded $DNA$ molecule.
Therefore,the genetic material in $E. coli$ is double-stranded $DNA$.

(C) In animal cells,protein synthesis occurs primarily in the cytoplasm on ribosomes,which may be free or attached to the rough endoplasmic reticulum. Additionally,mitochondria contain their own $DNA$,$RNA$,and ribosomes,allowing them to perform protein synthesis independently within the organelle. Therefore,protein synthesis takes place in both the cytoplasm and mitochondria.

(C) An enzyme is composed of a protein part called the apoenzyme and a non-protein part called the cofactor.
Cofactors are of three types:
$1$. Prosthetic groups: These are organic compounds that are tightly bound to the apoenzyme.
$2$. Coenzymes: These are organic compounds that are loosely bound to the apoenzyme,often acting as transient carriers of chemical groups.
$3$. Metal ions: These are inorganic ions that form coordination bonds with side chains of the apoenzyme.
Therefore,a coenzyme is defined as a loosely bound organic cofactor.

(A) All enzymes,including amylase,rennin,and trypsin,are proteins in nature. Enzymes are biological catalysts that speed up chemical reactions in living organisms,and their chemical structure is primarily composed of amino acid chains,making them proteins. While rennin and trypsin are proteolytic (protein-digesting) enzymes,amylase is a carbohydrate-digesting enzyme. Therefore,the only common feature among them is that they are all proteins.

(B) In higher plants,cell division occurs without the presence of centrioles.
Centrioles are characteristic of animal cells and some lower plant groups (like certain algae and bryophytes).
During mitosis in higher plants,the spindle apparatus is formed by microtubules organized by microtubule-organizing centers (MTOCs) that lack centrioles.
Cell plates are formed during cytokinesis,centromeres are present on chromosomes,and spindle fibers are essential for chromosome movement,all of which are observed in higher plants.

(A) The number of cells produced after $n$ mitotic divisions is given by the formula $2^n$.
Here,we need to find $n$ such that $2^n = 128$.
Since $128 = 2^7$,we have $2^n = 2^7$.
Therefore,$n = 7$.
Thus,$7$ mitotic divisions are required to produce $128$ cells from a single cell.

(C) During the process of mitosis,the $Telophase$ stage is characterized by the reformation of the nuclear envelope around the daughter chromosomes at each pole. The nucleolus,Golgi complex,and endoplasmic reticulum also reform during this stage. Therefore,the correct option is $C$.

(D) Water potential $(\Psi_w)$ is defined as the sum of solute potential $(\Psi_s)$ and pressure potential $(\Psi_p)$.
In plant cells, $\Psi_w = \Psi_s + \Psi_p$.
Normally, the water potential of plant cells is negative due to the presence of solutes.
However, during the process of guttation, water is forced out of the hydathodes due to root pressure.
Root pressure creates a positive hydrostatic pressure $(\Psi_p > 0)$ in the xylem, which can lead to a positive water potential in the leaf tissues during this specific event.

(A) When a plant cell is placed in a hypotonic solution (water),water enters the cell due to endosmosis.
As water enters,the protoplast expands and pushes against the cell wall.
This pressure exerted by the protoplast against the cell wall is called turgor pressure.
Consequently,the cell wall exerts an equal and opposite pressure on the protoplast,known as wall pressure.
Therefore,the pressure on the cell wall increases as the cell becomes turgid.

(B) Chlorophyll is a green pigment found in the chloroplasts of plants,which is essential for photosynthesis.
Its molecular structure consists of a porphyrin ring with a central metal ion.
The central metal ion coordinated within the porphyrin ring of the chlorophyll molecule is $Mg^{2+}$ (Magnesium ion).
Therefore,the correct option is $B$.

(D) The correct answer is $D$.
$Nostoc$ is a genus of cyanobacteria that is free-living,aerobic,and capable of photosynthesis.
It also possesses specialized cells called heterocysts which are the sites of nitrogen fixation.
$Rhizobium$ is a symbiotic nitrogen fixer.
$Azotobacter$ and $Azospirillum$ are free-living,aerobic nitrogen fixers but they are not photosynthetic.

(C) The deficiency symptoms of essential elements in plants include:
$1$. Chlorosis: Loss of chlorophyll leading to yellowing of leaves.
$2$. Necrosis: Death of tissue,particularly leaf tissue.
$3$. Inhibition of cell division: Leading to stunted growth.
$4$. Delay in flowering: If the concentration of essential elements is low.
$5$. Shortening of internodes.
All options $A$,$B$,$C$,and $D$ are recognized deficiency symptoms in $NCERT$ Biology. However,if the question implies selecting the most general term or if there is a discrepancy in the provided options,'Stunting' is a result of the inhibition of cell division. Given the standard $NCERT$ list,all these are valid symptoms. If this is a multiple-choice question where one must be excluded,please note that all listed options are standard deficiency symptoms.

(A) In the light-dependent reactions of photosynthesis,the $Z$-scheme involves both photosystems.
$Photosystem-II$ $(PS-II)$ absorbs light and initiates the electron transport chain,leading to the photolysis of water.
The electrons are then transferred to $Photosystem-I$ $(PS-I)$.
$Photosystem-I$ $(PS-I)$ is responsible for the final reduction of $NADP^+$ to $NADPH$ using the electrons received from the electron transport chain and protons from the stroma.
Therefore,$NADPH$ is produced by the activity of $Photosystem-I$.

(C) In the $Krebs$ cycle (also known as the Citric Acid Cycle),the enzyme $Succinate$ $dehydrogenase$ catalyzes the oxidation of $Succinic$ $acid$ to $Fumaric$ $acid$.
During this specific reaction,$FAD$ (Flavin Adenine Dinucleotide) acts as an electron acceptor and gets reduced to $FADH_2$.
This is the only step in the $Krebs$ cycle where $FAD$ is used as an electron carrier instead of $NAD^+$.
Therefore,the correct conversion is $Succinic$ $acid$ to $Fumaric$ $acid$.

(C) The mechanism of $ATP$ synthesis in both chloroplasts (during photophosphorylation) and mitochondria (during oxidative phosphorylation) is explained by the Chemiosmotic Hypothesis.
This hypothesis was proposed by Peter Mitchell in $1961$.
It states that $ATP$ synthesis is linked to the development of a proton gradient across the membranes (thylakoid membrane in chloroplasts and inner mitochondrial membrane in mitochondria).
The movement of protons across the membrane through the $F_0-F_1$ ATPase enzyme complex provides the energy required for the phosphorylation of $ADP$ to form $ATP$.

(D) Plants that flower multiple times a year regardless of the specific photoperiod (day length) are known as day-neutral plants. Since the tree flowers in October,January,and July in North India,it experiences vastly different day lengths and temperatures during these months. Because it flowers consistently despite these environmental variations,it is considered to be both photo-insensitive and temperature-insensitive. Therefore,it is a day-neutral plant that does not rely on specific environmental triggers like photoperiod or vernalization to initiate flowering.

(D) Phytochrome exists in two interconvertible forms: $Pr$ (inactive form,absorbs red light) and $Pfr$ (active form,absorbs far-red light).
When a plant is exposed to continuous red light,the $Pr$ form is converted into the $Pfr$ form.
However,the $Pfr$ form is unstable and undergoes degradation or reversion back to $Pr$.
In a state of continuous red light,the plant maintains a dynamic equilibrium where the rate of synthesis of $Pr$ and the rate of degradation/conversion of $Pfr$ reach a steady state,ensuring the plant can continue to respond to light stimuli.

(B) Gibberellins are plant growth regulators that play a crucial role in seed germination.
In germinating cereal seeds,gibberellins are released from the embryo and diffuse into the aleurone layer.
This triggers the synthesis of hydrolyzing enzymes,such as $\alpha$-amylase,which break down stored starch into simple sugars to provide energy for the growing embryo.
Therefore,the correct answer is the production of hydrolyzing enzymes in germinating seeds.

(D) The human large intestine contains a symbiotic microflora,primarily consisting of bacteria such as $Escherichia \ coli$.
These bacteria play a crucial role in the synthesis of certain vitamins,most notably Vitamin $K$ and various $B$-complex vitamins (such as $B_{12}$ and biotin).
Vitamin $K$ is essential for the synthesis of blood clotting factors in the liver.
Therefore,among the given options,Vitamin $K$ is the correct answer.

(D) The pancreas is a vital organ in the digestive system that secretes pancreatic juice into the small intestine.
Pancreatic juice contains various enzymes such as pancreatic amylase (for carbohydrates),trypsin and chymotrypsin (for proteins),and pancreatic lipase (for fats).
If the pancreas is removed,these essential enzymes are no longer secreted into the digestive tract.
Consequently,the digestion of carbohydrates,proteins,and fats will be severely impaired or remain undigested.
Therefore,the correct answer is $D$ (All of the above).

(D) In a frog, the tongue is bifid and muscular. It is attached to the $Hyoid$ apparatus at the anterior end of the mouth cavity. This attachment allows the frog to flip its tongue out rapidly to catch prey.

(B) The diffusion membrane of the lungs is extremely thin and is composed of three major layers:
$1$. The thin squamous epithelium of the alveoli.
$2$. The endothelium of the alveolar capillaries.
$3$. The basement substance (basement membrane) in between them.
Therefore,the exchange of gases occurs through the alveolar epithelium and the capillary endothelium.

(A) White blood cells (leukocytes) have a relatively short lifespan compared to red blood cells. While the lifespan varies depending on the specific type of leukocyte (e.g.,neutrophils live for a few days,while some lymphocytes can live for years),the general lifespan for most circulating white blood cells is considered to be less than $10$ days. Therefore,the most appropriate option is $A$.

(A) White blood cells $(WBCs)$ are classified into two main categories based on the presence or absence of granules in their cytoplasm: granulocytes and agranulocytes.
$1$. Granulocytes contain granules in their cytoplasm and include neutrophils,eosinophils (acidophils),and basophils.
$2$. Agranulocytes lack distinct granules in their cytoplasm and include lymphocytes and monocytes.
Therefore,lymphocytes are agranulocytes.

(D) living fossil is an extant taxon that closely resembles related species known only from the fossil record.
$Ginkgo$ $biloba$,also known as the maidenhair tree,is a unique species of gymnosperm with no close living relatives.
It has remained virtually unchanged for millions of years,making it a classic example of a living fossil.

(B) The $t-RNA$ (transfer $RNA$) acts as an adapter molecule during protein synthesis.
It has an anticodon loop that recognizes the codon on $m-RNA$ and a $3'$ end that carries the specific amino acid corresponding to that codon.
Thus,it picks up amino acids from the cytoplasm and transports them to the ribosome for polypeptide chain assembly.

(C) To measure $DNA$ synthesis precisely,scientists use radioactive labeling of nucleotides that are specifically incorporated into $DNA$ strands.
$DNA$ contains the nitrogenous base $Thymine$,whereas $RNA$ contains $Uracil$.
Therefore,radioactive $Thymine$ (often labeled as $^3H-Thymine$) is used to specifically track $DNA$ synthesis without interference from $RNA$ synthesis.
This technique is commonly used in experiments like the pulse-chase labeling to study the cell cycle and replication.

(B) $1$. $Homo$ $neanderthalensis$ fossils are primarily found in Europe and parts of Western Asia,not South America.
$2$. Neanderthal man ($Homo$ $neanderthalensis$) and Cro-Magnon man ($Homo$ $sapiens$ $fossilis$) lived during the late Pleistocene epoch and there is evidence of their co-existence for a period before Neanderthals went extinct.
$3$. $Australopithecus$ fossils were discovered in Africa,not Australia.
$4$. $Homo$ $habilis$ (the 'handy man') appeared before $Homo$ $erectus$ in the evolutionary timeline.
Therefore,the correct statement is that Neanderthal man and Cro-Magnon man co-existed for some time.

(A) The common ancestry of humans and chimpanzees is supported by molecular and cytogenetic evidence. Specifically,the banding patterns observed in chromosomes $3$ and $6$ of humans and chimpanzees show a high degree of similarity,indicating a shared evolutionary history. This chromosomal homology provides strong evidence for their close phylogenetic relationship.

(C) Poliomyelitis (Polio) is a viral disease that has been the target of global eradication programs. Due to widespread vaccination campaigns (such as the Pulse Polio Programme),the incidence of polio has decreased significantly worldwide. It is considered one of the diseases that can be completely eradicated in the near future.

(A) Smallpox (Variola virus) was officially declared eradicated from India in $1977$ by the World Health Organization $(WHO)$. While India has been declared polio-free,smallpox is the only disease that has been completely eradicated globally and from India.

(A) Diphtheria is a serious bacterial infection caused by the bacterium $Corynebacterium$ $\text{diphtheriae}$.
It is primarily caused by the secretion of a potent exotoxin by the living bacteria that colonize the host's throat and upper respiratory tract.
This toxin inhibits protein synthesis in the host cells, leading to cell death and the formation of a characteristic greyish pseudomembrane in the throat.

(D) Exposure to high levels of ionizing radiation causes acute radiation syndrome.
Common symptoms include nausea,vomiting,hair loss (alopecia),and skin damage such as redness (erythema) or ulcers.
Therefore,the combination of skin ulcers,nausea,and hair loss is a characteristic indicator of radiation exposure.

(B) Opiates are drugs that are derived from the opium poppy plant ($Papaver$ $somniferum$).
$Morphine$ is a potent analgesic and a classic example of an opiate narcotic.
$Barbiturates$ are depressants but not opiates.
$Amphetamines$ are stimulants.
$LSD$ ($Lysergic$ $acid$ $diethylamide$) is a hallucinogen.
Therefore, the correct option is $B$.

(B) $Interferons$ are a group of signaling proteins made and released by host cells in response to the presence of several viruses. They are a type of cytokine that helps the immune system fight viral infections. Among the given options,$Measles$ is a viral disease,while $Typhoid$,$Tetanus$,and $Malaria$ are caused by bacteria and a protozoan,respectively. Therefore,the production of $Interferons$ indicates a viral infection like $Measles$.

(C) Pebrine is a serious disease that affects silkworms $(Bombyx \ mori)$.
It is caused by a protozoan parasite known as $Nosema \ bombycis$.
This disease is transmitted through the eggs of the infected moth or through contaminated food.
Therefore,the correct option is $C$.

(D) High milk-yielding breeds of cows are obtained through advanced animal breeding techniques like $MOET$ ($Multiple$ $Ovulation$ $Embryo$ $Transfer$ $Technology$).
$1$. $Superovulation$: Hormonal treatment is given to induce the production of more than one egg per cycle.
$2$. $Artificial$ $insemination$: Semen from a superior bull is used to fertilize the eggs.
$3$. $Use$ $of$ $surrogate$ $mothers$: The fertilized embryos are transferred to surrogate mothers for further development.
Therefore, all these methods are used in combination to improve the breed.

(A) Honey is naturally acidic in nature. Its $pH$ typically ranges between $3.2$ and $4.5$. This acidity is primarily due to the presence of organic acids,such as gluconic acid,which are produced during the enzymatic conversion of nectar into honey by bees. This acidic environment helps in preserving honey by inhibiting the growth of most microorganisms.

(D) The top five cereals in the world based on annual production are Maize,Wheat,Rice,Barley,and Sorghum.
All these five cereals belong to the botanical family 'Gramineae' (now officially known as 'Poaceae').
Therefore,all five cereals are members of the same family,Poaceae.
Thus,the correct option is $D$.

(B) Parthenocarpy is the development of fruit without fertilization,which results in seedless fruits.
For many fruits like grapes and bananas,seedlessness is a desirable trait that increases their economic value.
However,for fruits like pomegranates,the edible part is the juicy seed coat (aril).
If a pomegranate is produced via parthenocarpy,it will be seedless,meaning it will lack the edible arils,thereby significantly decreasing its economic value.

(D) Foundation species are organisms that play a major role in creating,modifying,or maintaining the physical structure of an ecosystem. By doing so,they significantly influence the environmental conditions and the availability of resources for other species,thereby contributing to the overall properties and stability of the ecosystem. Examples include corals in coral reefs or trees in a forest.

(D) Primary productivity is the rate at which biomass or organic matter is produced per unit area over a time period by plants during photosynthesis.
Tropical rainforests are characterized by high temperature,abundant rainfall,and year-round sunlight,which provide ideal conditions for plant growth.
These factors lead to the highest net primary productivity among all terrestrial ecosystems.
Therefore,the correct option is $D$.

(D) The full form of $MAB$ is $Man$ and $Biosphere$ Program.
It is an intergovernmental scientific program launched by $UNESCO$ in $1971$ to establish a scientific basis for the improvement of relationships between people and their environments.

(B) The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic.
It is most prominent over Antarctica because the extremely cold temperatures during the polar winter lead to the formation of polar stratospheric clouds.
These clouds provide surfaces for chemical reactions that convert inactive chlorine into active forms,which then destroy ozone molecules when sunlight returns in the spring.

(A) The concentration of carbon dioxide $(CO_2)$ in the Earth's atmosphere is approximately $0.03\%$ to $0.04\%$.
Among the given options,$0.0314\%$ is the most accurate representation of the standard atmospheric concentration of $CO_2$ (often cited as approximately $314 \ ppm$ in historical contexts or standard textbook references).
Therefore,option $A$ is the correct answer.

(D) The depletion of the ozone layer allows more ultraviolet $(UV)$ radiation,specifically $UV-B$,to reach the Earth's surface.
Increased exposure to $UV-B$ radiation is known to cause various skin-related issues,including premature aging of the skin,skin cancer,and damage to $DNA$ in skin cells.
Therefore,as the ozone layer continues to deplete,the incidence of skin-related diseases is expected to rise.

(D) Phosphate pollution in water bodies is primarily caused by the discharge of untreated or partially treated sewage and the runoff from agricultural fields where phosphate-rich fertilizers are used.
These sources contribute to eutrophication,which leads to excessive growth of algae and depletion of dissolved oxygen in the water.