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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

18001.

Question : Destruction of forest leads to increase ofCO_2 heat in the atmosphere, Recently the Govt of India instituted an award for individuals or communities from rural areas that showed extra ordinary courage and dedication in protecting wildlife. Comment on deforestation and reforestation.

Answer»

Solution :Deforestation is the conversion of forested AREA into non-forested areas.
Reforestation is the conversion or RESTORING a FOREST that once existed but was removed at some point of TIME in the past.
Discussion
18002.

Question : Destruction of forest leads to increase ofCO_2 heat in the atmosphere, Recently the Govt of India instituted an award for individuals or ommunities from rural areas that showed extra ordinary courage and dedication in protecting wildlife. Identify the award.

Answer»

SOLUTION :AMRITA Devi BISHNOI Wildlife Protection Award.
Discussion
18003.

Question : Despite high level of heterozygosity the progeny derived from seed of a cross pollinated plant was found to be completely uniform One reason for this may be completely uniform One reason for this may the phenomenon of

Answer»

Parthenocarpy
Apoximis
Induced mutation
Polyploidy

Solution :Because apomixis is a ABNORMAL kind of sexual REPRODUCTION in which egg or other cells ASSOCIATED with egg (synergids, antipodals, etc) developm into embryo with FERTILIZATION and with or without MEIOSIS.
Discussion
18004.

Question : Despite havingthe great biodiversity why Amazon rain forest inunderthe risk of desertification.

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Solution :The soil is not fertile but thecontiuousfalling of leaves from the vegeatation cover the soil. Deforestation reduces this enerichment . In the deforseted areas WHENTHE rain water FALLS DIRECTLY on to the soil CAUSES reosion . Moreover ,deforestion does not allow recylingof essential nutrientsfor the plants . Hencethe rainforests and theirneighourhood areas are underthe threat of DESERTIFICATION.
Discussion
18005.

Question : Desired improved varieties of economically useful crops are raised by

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Migration
Biofertiliser
Hybridisation
Natural selection

Answer :C
Discussion
18006.

Question : Design a role play in which five classes of immunoglobulins show different functions to provide immunity to human body. (Hint: Give at least one dialogue showing the function for each class of immunoglobulin. In addition to these five members, human body, patho gens, p cells etc. may be involved in the role play).

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Solution :Human body : I am well protected against you Mr. Pathogen.
Pathogen : How will you protect yourself against me?
Human body: I will call my warriors and they will introduce themselves before you. (Then calls the immunoglobulins)
IgG :I help in the stimulation of phagocytes.
IGA : I protect the body from inhaled and ingested pathogens.
IGM: Activation of B cells is my duty.
IgD:I will be seen in lymphocyte SURFACE as receptors.
IgE : Allergic response needs a mediator and I will LOOK after that JOB.
Discussion
18007.

Question : Desertification is due to

Answer»

DEFORESTATION 
SOIL-erosion due to WATER 
Soil erosion due to wind 
Very HIGH TEMPERATURE and low rainfall 

Solution :Deforestation
Discussion
18008.

Question : Desert grasses often roll their leaves due to presence of

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oily surface
bulliform cells
spines
None of these

SOLUTION :DESERT grasses often ROLL their leaves due to the presence of buliform cells. These are big-sized, thin WALLED and alrge vacuolated cells that FREQUENTLY occur towards the lower epidermis.
Discussion
18009.

Question : Desert national park (Jaisalmar) is famous for _____.

Answer»


ANSWER :GREAT INDIAN BASTARD
Discussion
18010.

Question : Desert lizards bask in the sun when their body temperature drops below the comfort zone, but move into shade when the ambient temperature starts increasing. This is an example of

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morphological ADAPTATION
PHYSIOLOGICAL adaptation
BEHAVIOURAL adaptation
anatomical adapatation

Answer :C
Discussion
18011.

Question : "Desert lizards are conformer hence they cope with the stressful environment by behavioral adaptations". How?

Answer»

Solution :(a) They bask in the SUN and absorb heat when their BODY temperature drops below the comfort ZONE in winter.
(b) They move to SHADE when the AMBIENT temperature starts increasing.
Discussion
18012.

Question : Desert can be converted into greenland by planting :

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Oxylophytes
Psammophytes
Halophytes
Tropical trees

Answer :B
Discussion
18013.

Question : Desert biome does not support much vegetation as it lacks

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SUFFICIENT light
Favouratble TEMPERATURE
Sufficient water
Sufficient NUTRIENTS

ANSWER :C
Discussion
18014.

Question : Desert animals have the capability of forming ........ urine.

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Hypotonic
Isometic 
CONCENTRATED 
DILUTE 

ANSWER :C
Discussion
18015.

Question : Desert adaptations.

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Solution :(1)The adaptations to suit desert life are called desert adaptations.The animals LIKE camel living in deserts show physiologivcal adaptations such as losing minimum water through urine.(2)Water is stored in muscles,water cells of STOMACH and CONNECTIVE tissues of the hump.(3)In the kidney,there is longer LOOP of henle in the nephrons for more REABSORPTION of water.
Discussion
18016.

Question : Describe the mutual relationship between the fig and wasp and comment on the phenomenon that operates in this relationship.

Answer»

Solution :Wasps present in the FIGS is an example of mutualism where both the INTERACTING species are benefitted from the obligate association. Wasps ACTS as a pollinating agents for figs inturn larvae of wasps are NOURISHED and protected by fruits of figs.
Discussion
18017.

Question : Describlethe structureof dict embryo with the help of a label led diagrma.

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Solution :
It consists of an embryonal AXIS and twocotyledons.
The portion of embryonal axis above the levelof COTYLEDONS is theEpicotly whichterminateswith theplumuleor stem tip .
Thecylinderical portion belowthe level of cotyledonsis HYPOCOTYLS thatterminates at its lower end is the radicalor roottip . The root tip is covered by root CAP .
Discussion
18018.

Question :Deseribe in detail on population interaction

Answer»

Solution :Organisms belonging to different populations interact for food, shelter, MATING or for other necessities. The interaction may be intra specific (interaction within the members of same species) or interspecific (among organisms of different species). The intra-specific association is OBSERVED for all livelihood processes like feeding, territoriality, breeding and protection.
Interspecific associations or interactions can be: Neutral: where different species LIVE together but do not affect each other.
Positive: it is a symbiotic relationship in which no organism in an association is HARMED and either one or both may be benefitted. It is of two types Mutualism and Commensalism. Negative: One or both of the interacting organisms will be affected as in case of competition, PREDATION and parasitism
Discussion
18019.

Question : Describlerivet popper hypothesis.

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Solution :It was givenby Stanford ecolgoist Paul Ehrlich . In an airpalne(ecosystem) all parts are joinedtogether usingthousands of river (SPECIES) if everypassengertreavellingin it starts to becomes extinct ) , it may not AFFECT flight SAFETY (prtoperfundtioning) ofthe ecosystem ) initially , but as more and morerivetsareremoved , the planebecomes DANGEROUSLY weak overa periodof time. Furthermore , whichrivet is removedmay also becritical , seriousthreatto flight safety thanloss of a few RIVETS on the seatsor windows insidethe plance .
Discussion
18020.

Question : Describle the experiment that helpedlouis pasteur to dismiss thetheory of spontaeous generation of life .

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SOLUTION :Louispasteur showed thatlife comesonly frompre- existing LIFE in thefollowing manner
1. he demonstated that in pre-sterilised flasks , life did not come from killed yeast.
2. in Another flask opento air ,new organisms arose fromkilled yeast .
this led PASTEUR to dismissthetheory of spontaneous generation of life .
Discussion
18021.

Question : Describle internal structure of anther by mentioning about typical stamen

Answer»

Solution :Two parts of a typical STAMEN are shown in the figure below. The long and slender stalk is called the filament and the terminal generally bilobed structure is called the anther. The proximal END of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in FLOWERS of different species. Collecting a stamen each from ten flowers the large variation in size is seen in nature. Careful observation of each stamen under a dissecting microscope elucidate the range in shape and attachment of anthers in different flowers.

A typical angiosperm anther is bilobed with each lobe having two the ca, i.e., they are dithecous.
Often a longitudinal GROOVE runs lengthwise separating the the ca. Anther consists of four microsporangia located at the corners
The microsporangia develop further and becomes pollen sacs.
Pollen sacs are packed with pollen GRAINS
Discussion
18022.

Question : Describe various theories of origin of life.

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Solution :Life on earth appeared 500 million years after its formation, about 4 billion year ago.
In order to explain origin of life on the earth different theories were given by different thinkers and scientists.
(i) Theory of special creation : It states that God has created life by his divine act of creation Le. the earth, light, plants and animals are all being created by the supernatural power.
This theory has three connotations : (a) All living organisms or species that we see today were created as such. (b) Diversity was always the same since creation and will remain same in future also. (c) Earth is about 4000 years old.
(ii) Theory of panspermia : It was given by EARLY Greek thinkers which states that the life on earth arose from the spores or panspermia, which came from outer space and developed into living forms.
(iii) Theory of spontaneous generation : It states that life originated from NON - living matter automatically.
This theory is also known as theory of abiogenesis or autobiogenesis.
For long time it was believed that life came out of decaying and rotting matter like straw, mud, etc.
Louis Pasture (in 1860) rejected the theory of spontaneous generation and demonstrated that life came from pre-existing life.
In his experiment, he kept killed yeast cells in pre-sterilized FLASK and another flask (opened into air).
The life did not evolved in the former but new living organisms evolved in the letter flask.
(iv) Theory of chemical evolution : This theory was given by Oparin and Haldane.
According to them, the FIRST form of life came from pre - existing, non - living organic molecule (eg. RNA, PROTEIN etc) and chemical evolution was followed by the formation of life, Le. formation of diverse organic molecules were formed from inorganic constituents.
The conditions on the earth favouring chemical evolution were high temperature, volcanic storms and reducing atmosphere containing `CH_4, NH_3, etc`.
Discussion
18023.

Question : Describe various valves in the human heart.

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Solution : Human HEART has following maiil valves :
(1) Tricuspid valve: Tricuspid valve is present between the right atrium and right ventricle. It has THREE cusps or flaps. It prevents the backflow of blood into right atrium.
(2) Bicuspid valve: Bicuspid valve, also called mitral valve is present between the left atrium and left ventricle. It has two flaps. It prevents the backflow of blood in left atrium. Both tricuspid and bicuspid valves are attached to papillary muscles with TENDINOUS chords or chordae ten.dineae to prevent valves from turning back into atria at the time of systole.
(3) Semilunar valve : These are present at the opening of pulmonary artery and systemic aorta. They prevent the back flow of blood when ventricles undergo systole.
(4) Thebesian valve : Thebesian valve is present at the opening of the coronary SINUS.
(5) Eustachian valve : Eustachian valve is present at the opening of inferior vena cava.
Discussion
18024.

Question : Describe various steps in breeding a new genetic variety of a crop.

Answer»

Solution :The main steps in breeding a new genetic variety of a crop are as follow :
(i) Collection of variability : Genetic variability is the root of any breeding programme.
In many crops pre-existing genetic variability is available from wild relatives of the crop.
Collection and preservation of all the different wild varieties, species and relatives of the cultivated species is a pre-requisite.
The entire collection having all the diverse alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents : The germplasm is evaluated so as to identify plants with desirable combination of characters.
The selected plants are multiplied and used in the process of hybridisation. Purelines are created wherever desirable and possible.
(iii) Cross hybridisation among the selected parents : The desired characters have very often to be combined from two different plants (parents).
For example high protein quality of one parent may need to be combined with disease resistance from another parent. This is possible by cross hybridising the two parents to PRODUCE hybrids that genetically combine the desired characters in one plant.
This is a very time consuming and tedious process since the pollen grains from the desirable plant CHOSEN as male parent have to be collected and placed on the stigma of the flowers selected as female parent.
Also it is not necessary that the hybrids do combine the desirable characters, usually only one in few hundred to a thousand crosses shows the desirable combination.
(iv) Selection and testing of superior recombinant : This step consists of selecting among the progeny of the hybrids, those plants that have the desired character combination.
The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny.
This step YIELDS plants that are superior to both of the parents.
These are self pollinated for several generations till they reach a state of uniformity so that the characters will not segregate in the progeny.
(v) Testing, release and commercialisation of new cultivars: The newly selected lines are evaluated for their yield and other AGRONOMIC traits of quality, disease resistance etc.
This evaluation is done by growing these in the research fields and recording their performance under ideal fertiliser application, irrigation and other crop management practices.
The evaluation in research field is followed by testing the materials in farmer.s fields for at least three growing seasons at several locations in the country. Representing all the agroclimatic zones where the crop is usually GROWN.
The material is evaluated in comparison to the best available local crop cultivar a check or reference cultivar.
Discussion
18025.

Question : Describe various methods used in 'In situ conservation'.

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Solution :In situ (on site) conservation is the conservation and protection of the whole ECOSYSTEM and its biodiversity at all levels in order to protect the threatened species.
However, it is not economically feasible to conserve all the biological wealth at all the existing ecosystem.
Methods used in in situ conservation are :
Biodiversity hotspots : Biodiversity hot spots is an approach for in situ method of conservation.
Eminent conservationists have identified CERTAIN regions for the maximum protection these regions are called biodiversity hotspots.
These are regions with very high levels of species richness, high degree of ENDEMISM (species confined to a region and not found anywhere else) and accelerated habitat loss.
Initially 25 biodiversity hotspots were identified.
Now there are 34 hotspots all over the WORLD.
Three hotspots are in India i.e., Western Ghats and Sri Lanka, Indo-Burma and Eastern Himalaya.
If all the biodiversity hotspots are put together, they cover less than `2%` of the earth.s land area but harbour extremely high diversity.
Ongoing mass extinction could be reduced by `30%` through strict protection of these hot spots.
Protected Areas : Protected areas are especially dedicated areas for protection and MAINTANANCE of ecologically unique and biodiversity rich regions. Protected areas are classified as
Discussion
18026.

Question : Describe various levels of biodiversity.

Answer»

Solution :Levels of BIODIVERSITY : The important levels of biodiversity are (i) Genetic diversity (ii) Species diversity (iii) Ecological diversity.
(1) Genetic diversity : It is the diversity at genetic LEVEL or at subspecies level i.e. below species level in a single species.
For example there are about 1000 varieties of MANGO [Magnifera indica] and 50,000 strains of rice.
There are variations in the concentration of chemical in the medicinal plants, Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces.
The genetic diversity it can adopt better to the changed environmental conditions.
The low diversity leads to UNIFORMITY.
The genetic variability is therefore, considered to be the raw material for speciation.
(ii) Species diversity : The measurement of species diversity is its richness i.e. the number of species per unit area.
The greater is the species richness the more will be the species diversity.
In nature the number and kind of species as well as the number of individual per species vary and this leads to greater diversity.
For example the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
(iii) Ecological diversity : At the ecosystem level, India for instance with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows has a greater ecosystem diversity then a Scandinavian country like Norway.
It is the diversity at COMMUNITY level.
It can be of 3 types :
Alpha `(alpha)` diversity : It is diversity of organisms within same community.
Beta `(beta)` diversity : It is diversity between communities.
Gamma `(gamma)` diversity : Diversity over the entire geographical area.
Discussion
18027.

Question : Describe various laws based on monohybrid experiment.

Answer»

Solution :The study of inheritance of a single pair of alleles or factors of a trait at a time (monohybrid cross) is called ONE gene inheritance.
= Based on his observations on monohybrid crosses, MENDEL proposed two general rules in order to consolidate his understanding of inheritance in monohybrid crosses.
= These rules are called the principles or laws of inheritance.
= They are :
=Law of Dominance (First Law) : (i) Characters are controlled by discrete units called factor. (ii) Factors OCCUR in pairs. (iii) In a dissimilar pair of factors, one member of the pair is dominant while the other is recessive.
= This law is USED to explain the expression of only one of the parental characters in a monohybrid cross in the `F_1` GENERATION and the expression of both in the `F_2` generation. It also explains the proportion of 3 : 1 ratio obtained in the `F_2` generation.
=Law of Segregation (Second Law) :This law states that though the parents contain two alleles during gamete formation the factors or alleles of a pair segregate from each other, such that gamete receives only one of the two factors.
= Hence, the alleles do not show any blending and both the characters are recovered as such in the `F_2` generation, though one of these is not seen in the `F_1` generation
Discussion
18028.

Question : Describe various enzymes involved for DNA Replication.

Answer»

Solution :The process of replication required a set of catalysts (enzymes) as given below:
DNA Dependent DNA Polymerase : It is the main enzyme which uses a DNA template to catalyse the polymerisation of deoxynucleotides.
These enzymes are highly efficient enzyme as they have to catalyse polymerisation of a large number of nucleotides in a very short time.
E. coli that has only `4.6 xx 10^(6)` bp (Compare it with human WHOSE diploid content is `6.6 xx 10^(9)` bp) completes the process of replication within 38 minutes, that means the average rate of polymerisation has to be approximately 2000 bp per second.
Not only do these polymerases have to be fast, but they also have to catalyse the reaction with high degree of accuracy.
Any mistake during replication would result into mutations.
Furthermore energetically replication is a very expensive process.
Deoxyribonucleoside triphosphates serve dual purposes. In addition to acting as substrates they provide energy for polymerisation reaction (the two terminal PHOSPHATES in a deoxynucleoside triphosphates are high-energy phosphates, same as in case of ATP).
In prokaryotes these are three types of DNA polymerases i.e. DNA polymerase I, II and III whereas in eukaryotes five different DNA polymerases have been identified i.e. DNA polymerases `alpha, beta, gamma, delta and epsilon`.
These enzyme also help in removing mismatched nucleotides by a mechanism called proof reading.
Helicase : It unwinds the DNA strand, i.e. separates the two strands from one point, for the formation of replication fork.
Topoisomerase : The unwinding of DNA creates a tension in DNA strands, which gets released by the enzyme topoisomerase.
DNA Ligase : It facilitates the joining of DNA strands together by catalysing the formation of phosphodiester bond.
It plays a role in repairing single strand breaks in duplex DNA.
In addition to DNA dependent DNA polymerases, many additional enzymes are required to complete the process of replication with high degree of accuracy.
For long DNA molecules since the two strands of DNA cannot be separated in its entire length (due to very high energy requirement) the replication within a small opening of the DNA helix. REFERRED to as replication fork.
`5. rarr3. `
The DNA - dependent DNA polymerases catalyse polymerisation only in one direction that is `5.RARR 3.`.
This creates some additional complications at the (parental strands) replicating fork.
Consequently, on one strand (the template with polarity 3.`rarr` 5.), the replication is continuous.
While on the other (the template with polarity Newly 5. `rarr` 3.), it is discontinuous.
The discontinuously synthesised fragments are later joined by the enzyme DNA ligase.
DNA polymerases on their own cannot initiate the process of replication.
Also the replication does not initiate randomly at any place in DNA.
There is a definite region in E. coli DNA where the replication originates.
Such regions are termed as origin of replication.
It is because of the requirement of the origin of replication that a piece of DNA if needed to be propagated during recombinant DNA procedures requires a vector.
The vectors provide the origin of replication.
In eukaryotes, the replication of DNA takes place at S-phase of the cell cycle.
The replication of DNA and cell division cycle should be highly coordinated.
A failure in cell division after DNA replication results into polyploidy (a chromosomal anomaly).
Discussion
18029.

Question : Describe various causes of biodiversity losses in detail.

Answer»

Solution :Human activities have ACCELERATED the rate of extinction of species from the EARTH.
The four main causes also CALLED the Evil Quartet are RESPONSIBLE for the LOSS of biodiversity.
Discussion
18030.

Question : Describe various biogeographical evidences.

Answer»

Solution :Adaptive Radiation : The process of evolution of different species starting from a point ih a geographical area and finally radiating to other area of geography (habitats) is called adaptive radiation.

Example of adaption radiation are :
(i) Darwin.s Finches: Darwin observed an amazing DIVERSITY of creatures in Galapagos island.
There he saw the small black birds that amazed him the most later called as Darwin finches. Koala
They represent one of the best examples of adaptive radiation.
He observed that there were many varieties of finches in the same island and all the varieties have evolved on the island itself from original seed EATING finches.
He explained that after originating from a common ancestral seed eating stock the finches must have radiated to different geographical areas and under gene adaptive changes, especially in the type of beaks.
Therefore, due to the alterations in beaks gradually, some become insectivorous and some vegetarian.
Living in ISOLATION for long the new kind of finches emerged that could function and survive in new habitat.
(ii) Marsupials of Australia : These are another example of adaptive radiation.

A variety of marsupials (pouched mammals) each different from the other, evolved from an ancestral stock, but all within the Australian island continent.
(iii) Adaptive convergence I CONVERGENT Evolution: When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats)
and two or more groups of unrelated animals come to resembles each other for similar mode of life or habitat it is called adaptive convergence or convergent evolution.
(iv) Adaptive convergence in mammals : Australia marsupials and placental mammals in North America provide another example of convergent evolution.
Despite the temporal and geographical separation, Marsupials in Australia and placental mammals in North America have produced varieties of species living in similar habitat with similar ways of living.

They are not related but resemble each other because they fill similar niches in each continent.
e.g. placental wolf and Tasmanian wolf MARSUPIAL.
Discussion
18031.

Question : Describe various biochemical evidences or molecular evidences ofevolution.

Answer»

Solution :Among diverse organisms, the similarities in proteins and genes performing a common function indicates common ancestry.
The metabolic process, in different organism are also similar, thus also points in same shared ancestry.
Evidences from Embryology (How embryology helps in the study ofevolution) : Organisms that show common descent show embryological patters on which they later build their adult patterns.
This was first observed by Von Baer.
Later Ernest Haeckel reinterpreted Baer.s law in forms of recapitulation theory in the light of evolution.
The theory ofrecapitulation or biogenetic law states that ontogeny (development ofembryo) recapitulates phylogeny (ancestral sequence).
This means that the life history of an animal reflects its evolutionary history.
For example during the life history, frog.s tadpole larva resembles fishes the ancestors of Amphibia.
The presence of gill clefts in all vertebrate embryos including human provides a strong evidence in support of organic evolution.
In the same line of argument, similarities in proteins and genes performing a giving function among diverse organisms give clues to common ancestry.
These biochemical similarities point to the same shared ancestry as structural similarities among diverse organisms.
Man has bred selected plants and animals for agriculture, horticulture sports or security.
Man has domesticated many wild animals and crops.
This intensive breeding programme has created breeds that differ from other breeds. (eg. dogs) but STILL are of the same group.
Another interesting observation supporting evolution by natural selection comes from England.
In collection of moths made in 1850s in before industrialization set in it was observed that there were more white-winged moths on tree than dark winged or melanised moths.
However, in the collection carried out from the same area but after industrialization Le. in 1920, there were more dark winged moths in the same area i.e. the proportion was reversed.
The explanation put forth for this observation was that .predators will spot a moth against a contrasting background.
During post industrialization PERIOD the tree trunks became dark DUE to industrial smoke and soots.
Under this condition the white winged moth did not survive to predators, dark winged or melanised moth survived.
Before industrialization set in thick growth of almost white-coloured lichens covered the trees in the background the white winged moth survived but the dark coloured moth were picked out by predators.
Lichens can be used as industrial pollution indicators.
They will not grow in areas that are polluted.
Hence, moths that were able to camouflage themselves Le. hide in the background, survived.
This understanding is supported by the fact that in areas where industrialization did not occur ego in rural areas the count of melanic moth was low.
This showed that in a mixed population those that can better adapt, survive and increase in population SIZE.
No variant is completely wiped out.
Similarly, excess use of herbicides, pesticides etc has only resulted in selection of resistance varieties in much lesser time scale.

This is also true for microbes against which we employ antibiotics or drugs against eukaryotic organisms / cells.
Hence, resistant organisms / cells are appearing in a time scale of months or years and not centuries.
This also tells us that evolution is not a directed process in the sense of determinism.
These are EXAMPLES of evolution by anthropogenic action.
It is a stochastic process based on chance events in nature or chance mutation in the organism.
Discussion
18032.

Question : Describe tRNA as adapter molecule.

Answer»

Solution :The PRESENCE of an ADAPTER molecule which could read the CODE and WOULD bind to specific amino acids during translation was proposed by FRANCIS Crick in 1961.
tRNA was known before genetic code and was called SRNA (soluble RNA) but later its role as an adapter molecule was reported.
Discussion
18033.

Question : Describe T.S. of the spinal cord.

Answer»

Solution :(1) The spinal cord is covered externally by three meninges viz. DURA mater, arachnoid membrane and PIA mater.
(2) Dorsoventrally there are two fissures, the shallow dorsal or posterior fissure and the deeper ventral or anterior fissure.
(3) From dorsal fissure a dorsal septum extends inside.
(4) Neurocoel or central canal is situated in the centre of spinal cord.

(5) The central canal is filled with cerebrospinal fluid and is LINED by cuboidal epithelial cells called layer of ependyma.
(6) There is inner grey and outer white matter in the spinal cord. This grey matter is in the shape of 'H' with two dorsolateral horns and two ventrolateral horns.
(7) Dorsal horns form dorsal roots and ventral horns form ventral roots.
(8) White matter is divided into three columns, viz., the dorsal funiculi, ventral funiculi and LATERAL funiculi on either side.
(9) Ascending and descending tracts of nerve fibres arise from dorsal and ventral roots of the spinal cord. Ascending tracts are sensory while descending tracts are motor in nature.
Discussion
18034.

Question : Describe Transforming Principle.

Answer»

Solution :Transforming Principle : In 1928, Frederick GRIFFITH, in a series of experiment with streptococcus pneumoniae (bacterium responsible for pneumonia), witnessed a miraculous transformation in the bacteria.
During the course of his experiment, a living organism (bacteria) had changed in physical form.
When streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate some produced smooth shiny colonies (S) while others produce rough colonies (R).
This is because the .S. strain bacteria have a mucous (polysaccharide) coat, while R strain does not.
Mice infected with the strain (virulent) DIE from pneumonia infection but mice infected with the R strain do not develop pneumonia.
`"S strain "rarr" Inject into mice "rarr" mice die"`
`"R strain "rarr" Inject into mice "rarr" mice live"`
Griffith was able to kill bacteria by heating them.
He observed that heat killed S strain bacteria injected into mice did not kill them.
`"S strain (heat killed) "rarr" Inject into mice "rarr" mice live "`
`"S strain (heat killed) "+ "R strain (live) "rarr" Inject into mice "rarr" mice die "`
When he injected a mixture of heat-killed S and live R bacteria the mice died.
Moreover, he recovered living S bacteria from the dead mice.
He concluded that the R strain bacteria had somehow been TRANSFORMED by the heat killed S strain bacteria.
Some .transforming principle transferred from the heat-killed S strain, had enabled the R strain to synthesise a smooth polysaccharide coat and become virulent.
This MUST be due to the transfer of the genetic material.
However, the biochemical nature of genetic material was not DEFINED from his experiments.
Discussion
18035.

Question : Describe three factors which affect on decomposition.

Answer»

Solution :(a) Decomposition is LARGELY an oxygen requiring process hence it REQUIRES more oxygen
(b) Detritus rich in chitin and lignin has SLOW rate of decomposition
(c) Detritus rich in NITROGEN and water soluble substance has faster decomposition
(d) Temperature and soil moisture are most important factors
(E) Warm and moist environment favour decomposition
(f) Low temperature, dryness and anerobiosis inhibit decomposition
Discussion
18036.

Question : Describe theory of natural selection? Who gave this theory?

Answer»

Solution : Charles Darwin made a sea VOYAGE around the world between 1831-1836 in a sailship HMS Beagle.
During that period Darwin explored the fauna and flora of a number of continents and islands.
Based on his observation, he concluded the following: (i) There has been gradual evolution of life form with new forms arising at different periods of history of earth. (ii) Varying degrees of similarities can be observed between existing life forms and those which existed million of YEARS ago. (Hi) Population of all organisms have variations in characteristics, which make them adapt to better environment.
The characteristics which enable some population or individuals to survive better in natural conditions (foods, climate, physical factors would outbreed other survival of fittest).
Thus fitness of the individual, according to Darwin, refers ULTIMATELY to the reproductive fitness.
Such fit individuals leave more progeny than others.
Thus those organisms, which are better fit or adapt well, will survive more in nature and get selected by nature.
This is called natural selection.
Branching descent (eg. Darwin finches) and natural selection are the two key concepts of Darwinian theory of evolution.
Alfred Wallace, a naturalist worked in Malay Archipelago, came to a similar conclusions like Darwin.
Thus they both jointly propounded the theory of .Natural selection. in 1858.
It is based on following observation which are factual: (a) There are limited natural resources. Cb) Population are STABLE in size except for seasonal fluctuations. (c) Varying characteristics in members of a population i.e. no two members of a population are identical even though they look superficially similar. (d) Variations are generally INHERITED. (e) Population size has two facts Le. theoretically it grows exponentially if everybody reproduced rnaximally and in reality, population size is limited due to the competition among the individual for resources.
Those which are better adapted could survive and will reproduce at the cost of others i.e. who are less adapted in the environment.
Discussion
18037.

Question : Describe the wall layers of a pollen grain.

Answer»

Solution :The outer layer called EXINE is thick and made of CELLULOSE, sporopollenin and pollenkitt. The inner layer intine is THIN, uniform and made of PECTIN.
Discussion
18038.

Question : Describe the wobble hypothesis.

Answer»

SOLUTION :(1) Wobble HYPOTHESIS was proposed by Crick in 1966.
(2) According to this hypothesis, in the codon-anticodon pairing the third base may not be complementary.
(3) This third base is CALLED a wobble base.
(4) The position at which wobble base is present is called wobble position.
(5) Due to wobble base pairing, the codon and anticodon do not match PERFECTLY. In spite of this, the required amino acid is brought perfectly during translation.

(6) Wobble base pairing brings about the economy of t-RNA. Here, amino acid valine is CODED by GUU, GUC, GUA and GUG.
Discussion
18039.

Question : Describe the various steps involved in the process of deconmposition of detritus.

Answer»

Solution :Detritus : are raw materials for decomposition
Eg :- Dead plant remains such as leaves, bark, flower and dead ANIMALS. Steps in the process of decomposition :
(1) Fragmentation : The process of breaking down detritus into smaller particles. Eg : Earthworm
(2) Leaching : Water soluble inorganic NUTRIENTS go down into the soil HORIZON and get precipitated as unwanted salts.
(3) Cataboism : The process by which bacterial and fungal ENZYMES degrade detritus into simpler inorganic substances.
(4) Humification : The process that leads to ACCUMULATION of a dark coloured amorphous substance called Humus that is highly resistant to microbial action and undergoes decomposition on a extremely slow rate.
(5) Mineralisation : The process by which humus is degraded by microbes and inorganic nutrients are released.
Discussion
18040.

Question : Describe the various stages of decomposition process

Answer»

Solution :a. Fragmentation - The breaking down of detritus into smaller particles by detritivores like bacteria, fungi and earth worm is known as fragmentation. These detritivores secrete certain substances to enhance the fragmentation process and increase the surface area of detritus particles.
b. Catabolism. The decomposers produce some EXTRACELLULAR enzymes in their surroundings to break down complex organic and inorganic compounds in to simpler ones. This is called catabolism.
C. Leaching or Eluviation - The movement of decomposed, WATER soluble organic and inorganic compounds from the surface to the lower layer of soil or the carrying away of the same by water is called leaching or eluviation.
d. Humification - It is a process by which simplified detritus is changed into dark COLOURED amorphous substance called humus. It is highly resistant to microbial action, therefore decomposition is very slow. It is the reservoir of nutrients.
e. MINERALISATION - Some microbes are involved in the release of inorganic nutrients from the humus of the soil, such process is called mineralisation.
Discussion
18041.

Question :Describe the usage of Nirodh/ condom as contraceptive method of family planning ?

Answer»

Solution :This method is available for both males and females. This method affects both male and female properly. This protects STIS.
In this method ovum and sperms are revented from PHYSICALLY meeting with the help of barriers.
(i)Physical method : Condoms are barriers made of thin rubber / LATEX sheath that are used to cover the penis in the males or vagina and cervix in the female, just before coitus so that the ejaculated semen would not enter into the female reproductive tract. This can prevent conception.

Nirodh is a popular BRAND of condom for male. Use of condom has increased in recent years due to its additional benefit of protecting the user from contracting STIs and AIDS.
It can be self inserted and thereby gives privacy to the user.
Diaphragms cervical CAPS and vaults are also barriers Condom for female made of rubber that are inserted into female reproductive tract to cover the cervix during coitus.
They prevent conception by blocking the entry of sperms through the cervix. They are reusable.
(ii) Chemical method : Spermicidal creams, jellies and foams are usually used and along with these barriers to increase their CONTRACEPTIVE efficiency.
Discussion
18042.

Question : Describe the two situations in which the independent assortment of genes results in 50 per cent recombination.

Answer»

SOLUTION : (a) If gene pairs are PRESENT on separate CHROMOSOME pairs. (B) If genes are present on same chromosome but are placed at long DISTANCE
Discussion
18043.

Question : Describe the T.S. oftestis and explain the process of spermatogenesis.

Answer»

Solution :I. T.S. of testis:
II. Process of spermtogenesis :
(1) In the processof spermatogenesis , primordialgerm cellsor germinal cells ofthe seminifieroustubulespass throughthree phases, vizs, phase ofmultiplication, phase of growthand phase ofmaturation.
(i) Multiplicationphase : Primordialgermcells undergomitoticdivisionsto producemany diploid (2n) SPERMATOGONIA .
(ii) Growthphase :Spermatogonisum accumulatesnutrientsand growsin size,givingrise toprimaryspermatocyte (2n).
(iii) Maturation phase :The primaryspermatocyteundergoesfirstmeioticdivisionor maturationdivision.Exchangeof geneticmaterialoccursbetweenhomologouschromosomes INEACH sper-matocyte.
(2) Themeioticdivisiongives rise tosecondary spermatocytewhich is haploid(n).At the endof firstmeiotic divisiontwo secondaryspermatocytes are formedwhile at the end of secondmeiotic divisionfour haploidspermatidsare formed.
(3) SPERMATIDS are nonmotile. They undergo spermiogenesisand form motilespermatozoan(sperm).The changestaking place duringspermiogeneisare as follows :
(i)Increase in length .
(ii) Formationof proxinaland distal centriole.
(iii) Distal centriole formsthe axialfilament.
The various STAGESOF spermatogenesis.
Discussion
18044.

Question : Describe the T.S. of human testic and explain the process of spermatogenesis.

Answer»

Solution :Histological structure of testis :
(a) The external covering of testis is a fibrous connective tissue CALLED tunica albuginea.
(b) Then there is an incomplete pertioneal covering called tunica vaginalis.
© Interior to this there is a covering called tunica vascularis formed by capillaries.
(d)The testis si composed of many seminiferous tubules that are lined by cuboidal germinal epithelial cells.
(e) In the seminiferous tubulas various stages of developing SPERMS are seen as spermatogenesis takes place here. These are spermatogonia, primary and secondary spermatocytes, spermateds and sperms.
(f) Interrupted between germinal eptihelium are large PYRAMIDAL subtentacular cells, nurse cells or sertoli cells PROVIDE nourishment to the sperms till maturation.
(g) In between the seminiferous tubules there are itnerstitial cells of leyding which are endorine in nature. They secrete testosterone.
Spermatogenesis : The process by which sperms are formed is called spermatogenesis.
(a) In the testis, i.e, male gonads there are seminferous tubules which are lined by germinal epithelium.
(b) Cells of germinal epithelium UNDERGO spermatogenesis and form sperms.
(c ) In between the germinal cells there are nurse cells or cells of sertoli which provide nourishment to teh develping sperms.
Discussion
18045.

Question : Describe the translator mechanism of cross pollination.

Answer»

Solution :Pollination in Calotropis:
(i) This mechanism found in members of Asclepiadaceae.

(ii) The flowers are bisexual with 5 stamens forming gynostegium (union of stigma with the ANDROECIUM).
(iii) The stigma is large and 5 - angled and is receptive on the underside.
(iv) Each stamen at its back possesses a brightly coloured hood like outgrowth enclosing horn shaped NECTAR.
(v) The pollen in each anther LOBE of a stamen unites into a mass, forming a pollinium.
(vi) Pollinia are attached to a clamp or CLIP like stickly structure called corpusculum.
(vii) The filamentous or thread like part arising from each pollinium is called retinaculum.
(viii) The whole structure looks like inverted letter 'Y' and is called translator.
(ix) When the insect visits the flower for nectar, the translator gets attached to the PROBOSCIS or leg of the visitor.
(x) During the visit to the next flower the pollinia come in contact with the receptive stigma carrying out pollination.
Discussion
18046.

Question : Describe the tools used in rDNA technology.

Answer»

Solution :(1) In rDNA technology, various enzymes and vectors are used as the tools in the procedure.
(2) The different enzymes that are used are : restriction endonucleases, DNA ligase, reverse transcriptase, DNA polymerase, alkaline phosphatases, etc.
(3) The restriction endonucleases are used as biological or molecular scissors.
(4) They are able to CUT a DNA molecule at a specific point.
(5) Vectors are DNA molecules. They are used to transfer genetic MATERIAL into another cell.
(6) Vectors are either PLASMID or bacteriophage DNA or artificial DNA or cosmid.
(7) Vectors are low molecular weight DNA having the capacity to multiply independently of the genomic DNA. These are THEREFORE used to make multiple copies of desired DNA fragments.
Discussion
18047.

Question : Describe the technique of DNA fingerprinting.

Answer»

Solution :Technique of DNA Fingerprinting : Alec Jeffreys initially developed DNA fingerprinting also known as DNA typing or DNA profiling to find out markers for the inherited diseases.
He used a satellite DNA as probe that shows very high degree of polymorphism and called it variable number of Tandem Repeats (VNTRs).
The technique INVOLVED southern blot hybridisation using radiolabelled VNTR as a probe. The technique has the following steps:
(i) DNA isolations : DNA is extracted from the cells in a high speed centrifuge.
(ii) Amplification : Amplification many copies of the extracted DNA can be made by the use of polymerase chain reaction.
(ii) Digestion : Digestion of DNA by restriction endonucleases.
(iv) Separation : Separation of DNA fragments by electrophoresis.
(v) Southern Blotting : Transfer of separated DNA fragments to synthetic MEMBRANES (like nylon or nitrocellulose).
(vi) Hybridisation : With the help of radiolabelled VNTR probe (SMALL segments of DNA which help to detect the presence of gene in a long DNA sequence) which gets attached to single stranded VNTRs having complementatry nucleotide sequences.
(vii) Autoradiographic Exposure to X-Ray films : Detection of hybridised DNA fragments by autoradiography.

Schematic representation of DNA fingerprinting : Few representative chromosomes have been shown to contain different copy number of VNTR. For the sake of understanding different colour schemes have been used to trace the origin of each band in the gel. The two alleles (paternal and maternal) of a chromosome also contain different copy numbers of VNTR. It is clear that the banding pattern of DNA from CRIME scene matches with individual B, and not with A.
This shows many dark bands of different sizes.
A small DNA sequence is arranged tandemly in many copy numbers, which varies from chromosome to chromosome in an individual.
The number of repeats show very high degree of polymorphism.
As the size of VNTR varies from 0.1 - 20 kb.
Consequently, after the hybridisation with VNTR probe, the autoradiogram gives many bands of different sizes.
Thus these bands will give characteristic pattern for an individual DNA.
The VNTRs of two persons may be of same length and sequence at certain sites, but vary at other sites.
Therefore it differs from person to person in a population except in the case of monozygotic (identical) twins.
The VNTR belong to a class of satellite DNA known as minisatellite and are essential for DNA of fingerprinting.
The sensitivity of this technique has been increased by using PCR (Polymerase Chain Reaction).
Applications of DNA fingerprinting : (a) Used as a tool in forensic investigations. (b) To settle paternity disputes.(c) To study evolution by determining the GENETIC diversities among population.
Discussion
18048.

Question : Describe the structure of tRNA.

Answer»

Solution :Structure of tRNA : The tRNA has a secondary structure LIKE clover leal.
But its THREE dimensional structure depicts it as an inverted L-shaped molecule, tRNA has five arms or loops as follows:
(i) Anticodon loop : It has bases complementary to the code.
(ii) AMINO acid acceptor end : At his end, amino acids bind.
(iii) T-loop : It helps in BINDING to ribosome.
(iv) D-loop : It helps in binding aminoacyl synthetase.
(v) Variable loop : it is variable in both nucleotide COMPOSITION and in length.
tRNAs are specific for each amino acid.
For initiation, there is another specific tRNA that is another specific RNA that is referred to as initiator tRNA.
There are no tRNAs for stop codons.
In figure, the secondary structure of tRNA has been depicted that looks like a clover leaf.
Discussion
18049.

Question : Describe the structure of the heart wall.

Answer»

Solution :1. The heart wall is COMPOSED of three layers, viz. outer epicardium, middle MYOCARDIUM and inner endocardium.
2. Epicardium is composed of single layer of mesothelium that has flat epithelial cells.
3. Myocardium is composed of cardiac muscle FIBRES. These muscle fibres PERFORM the functions of systole and diastole by showing contraction and relaxation of muscle wall of the heart.
4. Endocardium is composed of single layer of flat epithelial cells called ENDOTHELIUM.
Discussion
18050.

Question : Describe the structure of polynucleotide chain of DNA or RNA ?

Answer»

Solution :A nucleotide is composed of a nitrogenous base, pentose sugar and phosphate group.
Pentose Sugar : Two types of sugar are PRESENT a GIVEN below : (a) Ribose (in case of RNA) (b) Deoxyribose (in case of DNA).
Nitrogenous Base : It is a nitrogen containing ORGANIC molecule having similar physical properties of a base.
There are two types of nitrogenous bases : (a) Purines (Adenine and Guanine). (b) Pyrimidines (Cytosine, Uracil and Thymine) Out of the Pyrimidins, Cytosine is common for both DNA and RNA, while Thymine is present in DNA and Uracil is present in RNA.
A nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage to form a nucleoside, such as adenosine or deoxyadenosine, guanosine or deoxyguanosine, cytidine or deoxycytidine and uridine or deoxythymidine.
When a phosphate group is linked to 5. - OH of a nucleoside through phosphoester linkage, a corresponding nucleotide (or deoxynucleotide depending upon the type of sugar present) is formed.
Two nucleotides are linked through 3. - 5. phosphodiester linkage to form a DINUCLEOTIDE.
More nucleotides can be joined in such a manner to form a polynucleotide chain.
A polymer thus formed has at one end a free phosphate moiety at 5.-end of ribose sugar, which is referred to as 5.-end of polynucleotide chain.
Similarly, at the other end of the polymer the ribose has a free `3-OH` group which is referred to as 3.-end of the polynucleotide chain.
The backbone in a polynucleotide chain is formed DUE to sugar and phosphate.
The nitrogenous bases linked to sugar moiety project from the backbone.
In RNA, every nucleotide residue has an additional `-OH` group present at 2.-Position in the ribose.
Also, in RNA the uracil is found at the place of thymine (5-methyl uracil, another chemical name for thymine).
Discussion