GSEB 2024 Biology Question Paper with Answer and Solution

(A) The $Spleen$ is known as the 'graveyard of erythrocytes' because it removes old and damaged red blood cells from circulation. Additionally, it acts as a large reservoir of erythrocytes, storing them and releasing them into the bloodstream when the body requires an increased oxygen-carrying capacity, such as during exercise or hemorrhage.

(B) $Meloidogyne \ incognita$ is a nematode that infects the roots of tobacco plants,causing a significant reduction in yield. This infection is prevented using $RNA$ interference $(RNAi)$ technology.

(A) Initially,$9$ biodiversity hotspots were identified in the world. Later,$25$ more hotspots were added to the list,bringing the total number of biodiversity hotspots to $34$. Therefore,$25$ more hotspots were added. However,based on the provided options,the question likely refers to the addition of $9$ hotspots in a specific context or a revision. Given the standard $NCERT$ context,the total is $34$. If the question implies the most recent additions to the original list of $25$,the answer is $9$.

(D) $Clarias \text{ } gariepinus$ (African catfish) is an invasive species introduced illegally for aquaculture purposes in India. It is harmful to indigenous catfish species because it competes with them for food and habitat, and it is also predatory in nature, leading to a decline in the population of native catfish.

(D) According to the $NCERT$ textbook diagram representing the global biodiversity of major plant taxa,the pie chart shows the distribution of different plant groups.
In this diagram,the largest portion represents Angiosperms $(Y)$,which constitute the majority of plant species.
The portion labeled $X$ represents Algae.
Therefore,$X$ is Algae and $Y$ is Angiosperm.

(D) In situ conservation involves the protection of plants and animals within their natural habitats.
$A$,$B$,and $C$ (National Parks,Biosphere Reserves,and Wildlife Sanctuaries) are examples of in situ conservation.
$D$ (Zoological parks) is an example of ex situ conservation,where organisms are kept in a protected environment outside their natural habitat for care and breeding.
Therefore,the correct answer is $D$.

(A) The Amazon rain forest,often referred to as the '$Lungs$ of the planet',is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle. This large-scale deforestation is the primary cause of biodiversity loss in this region,which is categorized as habitat loss and fragmentation.

(C) Alexander Von Humboldt observed that within a region,species richness increased with increasing explored area,but only up to a limit. This relationship is described by the equation $S = CA^z$,where $S$ is species richness,$A$ is area,$Z$ is the slope of the line (regression coefficient),and $C$ is the $Y$-intercept. This fundamental concept in ecology was established by the German naturalist and geographer Alexander Von Humboldt.

(D) The transgenic cow 'Rosie', produced in $1997$, was the first transgenic cow to produce human protein-enriched milk.
Rosie's milk contained the human alpha-lactalbumin protein.
The concentration of this human protein in her milk was $2.4 \text{ gm}$ per litre.
Therefore, the correct option is $D$.

(B) The full form of $G.E.A.C.$ is Genetic Engineering Approval Committee.
This committee is responsible for making decisions regarding the validity of research involving genetically modified organisms $(GMOs)$ and the safety of introducing genetically modified organisms for public services.

(D) $BT$ cotton is a genetically modified or transgenic crop that expresses the $cry$ gene from the bacterium $Bacillus$ $thuringiensis$.
This gene produces an insecticidal protein that provides resistance against specific lepidopteran,coleopteran,and dipteran pests.
Therefore,it is a transgenic plant and is insect-resistant.
However,it is not resistant to all insecticides; it is specifically engineered to target certain pests,and its resistance is limited to those specific insect groups.
Thus,the statement that it is resistant to all insecticides is incorrect.

(A) Genetic engineering,specifically the creation of transgenic animals,has significant applications in medicine and research.
$1$. Transgenic mice are used to test the safety of vaccines,such as the polio vaccine,before they are administered to humans. This ensures that the vaccine is safe and effective.
$2$. Transgenic models are also used to study human diseases,including heart-related conditions,to develop new treatments.
While options $A$ and $B$ are both scientifically valid applications,in the context of standard $NCERT$ biology curriculum,the use of transgenic mice for vaccine safety testing is a primary example cited for the application of biotechnology in medicine.

(D) The correct answer is $D$. $\alpha-1$ antitrypsin is a proteinase inhibitor used to treat emphysema. Emphysema is a chronic respiratory disorder in which alveolar walls are damaged due to which respiratory surface is decreased. This protein is produced through transgenic animals (specifically sheep) to treat this deficiency.

(D) Mature insulin consists of two short polypeptide chains: chain $A$ and chain $B$.
These two chains are linked together by two inter-chain disulphide bonds.
Additionally,there is an intra-chain disulphide bond within chain $A$.
Therefore,the correct answer is $D$.

(A) Golden rice is a genetically modified crop developed to combat vitamin deficiency. It is engineered to produce high levels of beta-carotene,which is a precursor to $Vitamin \ A$. When consumed,the human body converts this beta-carotene into $Vitamin \ A$. Therefore,the correct option is $A$.

(B) The $Bt$ toxin produced by the bacterium $Bacillus \text{ } thuringiensis$ exists in an inactive protoxin form within the bacterial cell.
It only becomes active when it is ingested by an insect, where the alkaline $pH$ of the insect's gut solubilizes the crystals and converts the protoxin into its active toxic form.
Therefore, the bacteria remain unharmed because the toxin is not in its active state while inside the bacterial cell.

(D) The corn borer is controlled by the protein encoded by the gene $cry I Ab$.
This gene is derived from the bacterium $Bacillus thuringiensis$.
When the corn borer ingests the plant tissue containing this protein,the toxin is activated in the alkaline gut of the insect,leading to its death.
Therefore,the correct option is $D$.

(D) In the context of cloning vectors like $pBR322$,$BamH I$,$Hind III$,and $Sal I$ are specific restriction endonuclease recognition sites. The term $amp^R$ stands for ampicillin resistance,which is a gene that provides resistance to the antibiotic ampicillin. Therefore,$amp^R$ is the antibiotic resistance gene.

(C) The correct answer is $C$.
Ethidium Bromide $(EtBr)$ is a fluorescent dye used to stain $DNA$ in agarose gel electrophoresis.
When exposed to ultraviolet $(UV)$ light,the $EtBr$ molecules intercalate between the base pairs of the $DNA$,causing the $DNA$ bands to fluoresce orange,which allows for the visualization and study of $DNA$ fragments.

(D) Restriction endonucleases are enzymes that recognize specific nucleotide sequences in $DNA$ and make cuts at these specific positions within the $DNA$ molecule.
Option $A$ describes the function of $PCR$ (Polymerase Chain Reaction).
Option $B$ describes the function of exonucleases.
Option $C$ describes the function of $DNA$ ligase.
Therefore,the correct option is $D$.

(A) The restriction endonuclease $EcoRI$ recognizes the specific palindromic sequence $5'-GAATTC-3'$.
It cleaves the phosphodiester bond between the bases $G$ (Guanine) and $A$ (Adenine) on both strands of the $DNA$ molecule.
This specific cleavage results in the formation of sticky ends or cohesive ends,which are essential for recombinant $DNA$ technology.
Therefore,the correct site of cleavage for $EcoRI$ is between $G$ and $A$.

(C) During the process of $DNA$ isolation,the final step involves the precipitation of purified $DNA$. This is achieved by adding chilled ethanol to the $DNA$ solution. The chilled ethanol reduces the solubility of $DNA$ in the aqueous solution,causing it to precipitate out as fine threads,which can then be collected by spooling.

(B) The plasmid $pBR322$ is a widely used cloning vector in $E. coli$.
It contains two antibiotic resistance genes: $amp^R$ (ampicillin resistance) and $tet^R$ (tetracycline resistance).
The $amp^R$ gene contains recognition sites for the restriction endonucleases $Pst$ $I$ and $Pvu$ $I$.
The $tet^R$ gene contains recognition sites for $Bam$ $HI$ and $Sal$ $I$.
Therefore,the correct option is $B$.

(B) In the gene gun method (also known as biolistics or microprojectile bombardment),cells are bombarded with high-velocity microparticles of gold or tungsten coated with $DNA$. These heavy metals are used because they are inert and do not react with the biological tissues,ensuring the safe delivery of the alien $DNA$ into the host cell. Therefore,the correct option is $B$.

(B) According to the $10\%$ law of energy transfer proposed by Lindeman, only about $10\%$ of the energy available at one trophic level is transferred to the next trophic level. The remaining $90\%$ of the energy is lost as heat during metabolic processes or remains in the form of chemical energy in the biomass that is not consumed. Due to this significant loss of energy at each step, the number of trophic levels in a grazing food chain is typically limited to $4$ or $5$.

(A) Humus is a dark-colored,amorphous substance formed by the process of humification during decomposition.
$(P)$ Humus acts as a reservoir of nutrients and possesses colloidal properties,which help in retaining moisture and nutrients in the soil.
$(Q)$ It is rich in nutrients like nitrogen,phosphorus,and potassium,which are released slowly into the soil.
$(R)$ Humus is highly resistant to microbial action and undergoes decomposition at a very slow rate,but it is not impossible to decompose. Therefore,statement $(R)$ is incorrect.
Thus,statements $(P)$ and $(Q)$ are correct.

(D) The population density $(N)$ is influenced by four primary factors: natality $(B)$,mortality $(D)$,immigration $(I)$,and emigration $(E)$.
The formula for population density at time $t+1$ is given by: $N_{t+1} = N_t + [(B + I) - (D + E)]$.
Natality $(B)$ refers to the number of births in a population during a given period,which adds individuals to the population.
Immigration $(I)$ refers to the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration,which also adds individuals to the population.
Since both natality and immigration contribute to an increase in the number of individuals,an increase in these rates will lead to an increase in the overall population density.

(B) The provided age pyramid shows a base (pre-reproductive age group) that is narrower than the middle section (reproductive age group).
This shape is characteristic of a declining population,where the number of individuals in the reproductive age group is higher than those in the pre-reproductive age group,leading to a decrease in the population over time.

(B) The rate of decomposition is controlled by the chemical composition of detritus and climatic factors.
Detritus rich in nitrogen and water-soluble substances like sugars decomposes faster.
Conversely,detritus rich in lignin and chitin decomposes much slower because these substances are complex,resistant to enzymatic degradation,and require specific microbial enzymes that are not easily produced by all decomposers.
Therefore,the correct option is $B$.

(C) In an aquatic ecosystem like a lake,the trophic levels are organized as follows:
$1$. The first trophic level consists of producers,which are phytoplankton,algae,and submerged plants.
$2$. The second trophic level consists of primary consumers,which feed on the producers. In a lake,these are zooplankton.
$3$. The third trophic level consists of secondary consumers,such as small fishes.
$4$. Therefore,the second trophic level is represented by zooplankton.

(D) The pyramid of energy is always upright because energy flow is unidirectional and some energy is lost as heat at each trophic level. This statement is $True$ $(T)$.
$(B)$ The pyramid of number in a sea is generally upright (e.g.,many small phytoplankton support fewer zooplankton,which support even fewer small fish). This statement is $False$ $(F)$.
$(C)$ The pyramid of biomass in a sea is generally inverted because the biomass of phytoplankton (producers) is smaller than the biomass of zooplankton and fish (consumers) at any given time. This statement is $True$ $(T)$.
$(D)$ In most ecosystems,the pyramid of energy is always upright,and the pyramid of number is often upright. This statement is $False$ $(F)$.
Therefore,the sequence is $T, F, T, F$.

(B) The Detritus Food Chain $(DFC)$ begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms,mainly fungi and bacteria. These organisms meet their energy and nutrient requirements by degrading dead organic matter or detritus. These are also known as saprotrophs ($SAPRO$ = to decompose).

(C) The incident solar radiation consists of various wavelengths of light.
Photosynthetically active radiation $(PAR)$ refers to the spectral range of solar radiation from $400 \ nm$ to $700 \ nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
It is observed that $PAR$ constitutes less than $50$ % of the total incident solar radiation reaching the Earth's surface.
Therefore, the correct option is $C$.

(A) $Homo \text{ } habilis$ is considered the first human-like hominid. Their brain capacity ranged between $650 \text{ } CC$ and $800 \text{ } CC$. They did not eat meat. Therefore, the correct option is $A$.

(C) Lobefins were fish with stout and strong fins that could move on land and go back to water.
In $1938$,a fish caught in South Africa happened to be a Coelacanth,which was thought to be extinct.
These animals,called lobefins,evolved into the first amphibians that lived on both land and water.
Therefore,the correct answer is $C$ (Amphibians).

(D) Charles $Darwin$ observed a variety of small black birds in the Galapagos Islands,now known as $Darwin's$ finches. He realized that many varieties of finches existed on the same island. All the varieties,he conjectured,evolved on the island itself. From the original seed-eating features,many other forms with altered beaks arose,enabling them to become insectivorous and vegetarian finches. This process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation.

(B) According to the Hardy-Weinberg principle,$p + q = 1$,where $p$ is the frequency of the dominant allele and $q$ is the frequency of the recessive allele.
Given that the frequency of the $M$ allele $(p)$ is $0.8$,we can calculate the frequency of the recessive allele $(q)$ as:
$q = 1 - p = 1 - 0.8 = 0.2$.
The frequency of the homozygous recessive genotype is represented by $q^2$.
Therefore,$q^2 = (0.2)^2 = 0.04$.
Converting this to a percentage: $0.04 \times 100 = 4\%$.
Thus,the correct option is $B$.

(C) The concept of saltation was proposed by Hugo de Vries. He defined saltation as a single-step,large mutation that leads to speciation. Unlike Darwin's theory of gradual evolution through small variations,de Vries emphasized that evolution occurs through sudden,discontinuous variations or mutations.

(C) The brain capacity of Neanderthal man was approximately $1400 \text{ cc}$.
Neanderthals lived in near east and central Asia between $100,000$ to $40,000$ years back.
They used hides to protect their body and buried their dead.
Their cranial capacity was significantly larger than that of $Homo \text{ habilis}$ and $Homo \text{ erectus}$.

(A) Divergent evolution occurs when organisms with a common ancestor evolve different traits to adapt to different environments,resulting in homologous structures.
$1$. Thorn of Bougainvillea and tendril of Cucurbita are homologous structures because both are modified branches,representing divergent evolution.
$2$. Flippers of Penguins and Dolphins,Octopus and human eye,and Sweet potato and potato are examples of convergent evolution,where unrelated organisms evolve similar traits due to similar environmental pressures,resulting in analogous structures.
Therefore,the correct option is $A$.

(D) According to evolutionary biology and the fossil record, modern humans, $Homo \text{ } sapiens$, appeared approximately $75,000$ to $10,000$ years ago during the Ice Age.
While earlier forms of $Homo \text{ } sapiens$ existed before this, the emergence of modern human behavior and widespread dispersal is generally categorized within this timeframe in standard textbooks.
Thus, option $D$ is the correct answer.

(B) Contact inhibition is a regulatory mechanism that functions to keep the cells growing to a layer one cell thick (a monolayer).
Normal cells in the body exhibit this property,which prevents them from dividing uncontrollably when they come into contact with neighboring cells.
In contrast,cancer cells (neoplastic cells) lose this property,which allows them to continue dividing and piling up on top of each other,eventually forming a tumor.

(D) $\alpha-1$ antitrypsin is a protein produced by the liver that protects the lungs from damage caused by inflammation.
It is used to treat emphysema, a condition where the air sacs in the lungs are damaged, leading to breathing difficulties.
This protein inhibits the enzyme elastase, which can break down lung tissue if left unchecked.
Therefore, the correct option is $D$.

(D) Among the options provided, $Gonorrhoea$, $Syphilis$, and $Trichomoniasis$ are caused by bacteria or protozoa and can be completely cured if detected early and treated with appropriate antibiotics or medications.
However, $Hepatitis-B$ is a viral infection. While vaccines are available for prevention, there is no definitive cure for chronic $Hepatitis-B$ infection, as the virus can persist in the body. Therefore, it is considered not completely curable.

(D) The chemical structure shown in the image represents Morphine.
Morphine is an alkaloid extracted from the latex of the poppy plant,Papaver somniferum.
It is a potent sedative and painkiller,which is very useful in patients who have undergone surgery.
It acts on the central nervous system to relieve pain and induce sleep.

(B) Interferons are proteins secreted by virus-infected cells which protect non-infected cells from further viral infection.
These proteins act as a cytokine barrier in the innate immune system.
Therefore,the secretion of interferon is a cytokine barrier.

(B) In the process of spermatogenesis,the $2n$ (diploid) spermatogonia undergo mitosis to form primary spermatocytes,which are also $2n$ (diploid).
These primary spermatocytes then undergo meiosis $I$ to form secondary spermatocytes,which are $n$ (haploid).
Secondary spermatocytes undergo meiosis $II$ to form spermatids ($n$,haploid),which eventually differentiate into spermatozoa ($n$,haploid).
Therefore,only the primary spermatocytes are diploid $(2n)$.

(C) The correct matching is as follows:
- $(p)$ Leydig cells are responsible for the secretion of androgens (testosterone).
- $(q)$ Sertoli cells provide nutrition to the developing spermatozoa.
- $(r)$ Corpus luteum is an endocrine structure that secretes progesterone.
- $(s)$ Bulbourethral gland secretes a fluid that helps in the lubrication of the penis.
Therefore,the correct sequence is $(p-iii), (q-iv), (r-ii), (s-i)$,which corresponds to option $(C)$.

(B) The process of ovulation is triggered by a rapid surge in the secretion of Luteinizing Hormone $(LH)$ from the anterior pituitary gland. This phenomenon is known as the $LH$ surge. This surge occurs towards the middle of the menstrual cycle (around the $14^{th}$ day) and induces the rupture of the Graafian follicle,leading to the release of the secondary oocyte (ovum). Therefore,the correct option is $B$.

(B) The $Bulbourethral$ glands (also known as $Cowper's$ glands) are a pair of small exocrine glands in the male reproductive system.
Their primary function is to secrete a clear,alkaline fluid into the urethra before ejaculation.
This secretion helps in the lubrication of the penis during coitus and also neutralizes the acidic environment of the urethra caused by urine,thereby protecting the sperm.

(A) The large holes in 'Swiss cheese' are caused by the production of a large amount of $CO_2$ by the bacterium $Propionibacterium$ $sharmanii$.
During the fermentation process, this bacterium releases carbon dioxide gas, which gets trapped in the cheese curd, creating the characteristic large holes.