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Series : SMA/1

Roll No.

Code No. 57/1/1Candidates must write the Code onthe title page of the answer-book.

Please check that this question paper contains 6 printed pages.

Code number given on the right hand side of the question paper should be written on the titlepage of the answer-book by the candidate.

Please check that this question paper contains 30 questions.

Please write down the Serial Number of the questions before attempting it.

15 minutes time has been allotted to read this question paper. The question paper will be distributedat 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the student will read the question paper only andwill not write any answer on the answer script during this period.

BIOLOGY

[Time allowed : 3 hours] [Maximum marks : 70]

General Instructions:

1. All questions are compulsory.

2. This questions paper consists of four Sections A, B, C and D. Section-A contains 8 questions of

one mark each, Section-B is of 10 questions of 2 marks each, Section-C is of 9 questions of three

marks each and Section-D is of 3 questions of five marks each.

3. There is no overall choice. However, an internal choice has been provided in one questions of

2 marks, one questions of 3 marks and one question of 5 marks weightage. A student has to

attempt only of the alternatives in such questions.

4. Wherever necessary, the diagrams drawn should be neat and properly labelled.

Studymate Solutions to CBSE Board Examination 2011-2012

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STUDYmate

SECTION-A

1. Mention the unique flowering phenomenon exhibited by Strobilanthus kunthiana

(Neelakuranaji). [1]

Ans. It flowers once in 12 years.

2. How does smoking tobacoo in human lead to oxygen deficiency in their body? [1]

Ans. Smoking increases the carbon monoxide content in blood and reduces the

concentration of oxygen bound to haeme group of haemoglobin.

3. A garden pea plant (A) Produced inflated yellow pod, and another plant (B) of the

same species produced constricted green pods. Identify the dominant traits. [1]

Ans. Dominant traits are Green and inflated.

4. Why is Eichhornia crassipes nicknamed as “Terror of Bengal”? [1]

Ans. Eichhornia crassipes is called terror ‘of Bengal’ because it grows very fast in standing

water. It drains oxygen from water thus leading to death of marine life.

5. Write the location and function of the sertoli cells in humans. [1]

Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. They

provide nourishment to developing spermotozoa.

6. Name the following:

(a) The semi-dwarf variety of wheat which is high-yielding and disease-resistant.

(b) Any one inter-specific hybrid mammal. [1]

Ans. (a) Sonalika / Kalyan sova (b) Mule

7. Write the similarity between the wing of a butterfly and the wing of a bat. What do

you infer from the above with reference to evolution? [1]

Ans. Both butter fly and bat use their wings to fly. They are anatomically different. So it is

result of convergent evolution.

8. Write what do phytophagous insects feed on.

Ans. They feed on plants

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SECTION-B

9. Draw a neat labelled sketch of a replicating fork of DNA. [2]

Ans.

35

35 3

5

Discontinuoussynthesis

Template DNA(parental strands)

continuoussynthesis

5 3

Newlysynthesised

strands

10. Where is sporopollenin present in plants? State its significance with reference to itschemical nature? [2]

Ans. Sporopollenin is present in exine layer of wall of pollen grain.

It is an organic polymer and is resistant to oxidation and leaching.

11. (a) Highlight the role of thymus as a lymphoid organ.

(b) Name the cells that are released from the above mentioned gland. Mention howthey help in immunity. [2]

Ans. (a) In thymus immature lymphocytes differnetiate into antigen – sensitivelymphocytes. After maturation in thymus they migrate to secondary lymphoidorgans.

(b) The cells released from thymus are called T-lymphocytes. These lymphocytesare responsible for cell mediated immunity which defends the body againstvirus, fungi and some bacteria which has entered the hosts cells. Helper T cellsstimulate B-cells to produce antibodies and killer T-cells migrate to site ofinfection.

12. Explain the work carried out by Cohen and Boyer that contributed immensely inbiotechnology. [2]

Ans. Stanley Cohen and Herbert Boyer constructed first artificial recombinant DNA. Theydid this by isolating the antibiotic resistant gene by cutting out a piece of DNA froma plasmid which was responsible for giving antibiotic resistance.

13. Why do clown fish and sea anemone pair up? What is this relationship called? [2]

Ans. This interaction is called commensalism. Here the clown fish lives in the tentacles ofsea anemone. The fish gets protected from predators which stay away from stingingtantacles. However anemone does not get any benefit from clown fish.

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14. (a) State the difference between meiocyte and gamete with respect to chromosomenumber.

(b) Why is a whiptail lizard referred to as parthenogenetic? [2]

Ans. (a) Meiocyte (gamete mother cells) is diploid (2n), where as gamete is haploid (n).

(b) Whiptail lizard is said to be parthenogenetic because female gamete undergoesdevelopment to form new organisms without fertilization.

15. Name the plant source of the drug popularly called “smack”. How does it affect thebody of the abuser? [2]

OR

Why is Rhizobium categorized as a ‘symbiotic bacterium’? How does it act as abiofertiliser? [2]

Ans. It is obtained from Papver somniferum.

Smack is a stronger analgesic than morphine. It reduces heart beat, blood pressureand increases blood sugar.

OR

Rhizobium lives in root nodules of leguminous plants. This association is mutuallybeneficial. Rhizobium gets food and shelter and leguminous plant gets nitrogen inreturn. Since Rhizobium is capable of fixing atmospheric nitrogen so it acts asbiofertiliser.

16. (a) State the role of DNA ligase in biotechnology.

(b) What happens when Meloidegyne incognitia consumes cells with RNAi gene?[2]

Ans. (a) Role of DNA ligase in biotechnology is joining of DNA fragments end to end,having same kind of sticky ends.

(b) If Meloidegyne incognitia consumes cells with RNA i gene silencing of specificmRNA occurs due to a complementary ds RNA molecule formation that bindsto and prevents translation of mRNA (silencing) and thus causing death of thenematode.

17. Some organisms suspend their metabolic activities to survive in unfavourableconditions. Explain with the help of any four examples. [2]

Ans. Examples:

(a) In bacteria, fungi and lower plants various kinds of thick walled spore are formedwhich help them to survive unfavourable conditions.

(b) In higher plants, seeds and some other vegetative reproductive propagules serveas a means to tide over period of stress, besides helping in seed dispersal.

(c) Bears going into hibernation during winter.

(d) Snails and fishes go into aestivation to avoid summer related head problemsand dessication. OR

(e) Many zooplankton are known to enter diapause, a stage of suspendeddevelopment.

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18. (a) Name the Protozoan parasite that causes amoebic dysentery in humans.

(b) Mention two diagnostic symptoms of the disease.

(c) How is this disease transmitted to other? [2]

Ans. (a) Entamoeba histolytica.

(b) Symptoms of this disease include constipation, abdominal pain, cramps, stoolswith excessive mucous and blood clots.

(c) Houseflies act as mechanical carriers and serve to transmit the parasite fromfaeces of infected person to food and thus contaminating them.

SECTION-C19. It is established that RNA is the first genetic material. Explain giving three reasons.

[3]

OR

(a) Name the enzyme responsible for the transcription of tRNA and the amino acidthe initiator tRNA gets linked with.

(b) Explain the role of initiator tRNA in initiation of protein synthesis. [3]

Ans. RNA was first genetic material because

(a) Many evidences suggest that essential life processes such as metabolism,translations, splicing, etc. evolved around RNA.

(b) RNA used to act as genetic material as well as catalyst. Many importantbiochemical reactions in living systems are catalysed by RNA.

(c) RNA being catalyst is highly unstable.

OR

(a) RNA polymerase in procaryotes and RNA polymerase III in Eukaryotes isresponsible for transcription of tRNA.

Initiator tRNA gets linked with methionine in eukaryotes and formylatedmethionine in prokaryotes.

(b) Initiator tRNA combines with methionine in presence of amino acyl-tRNAsynthetas enzymes resulting in formation of charged tRNA. Now this initiatortRNA combines with two subunits of ribosome and mRNA forming translationinitiation complex. First mRNA attaches to small subunit of ribosome and chargedinitiator tRNA. The initiator tRNA joins the initiation codon AUG and signals thestart of translation. Now the large subunit of ribosome combines with smallsubunit. Initiator tRNA lies at the P site of the ribosome.

20. State the theory of Biogenesis. How does Miller’s experiment support this theory?[3]

Ans. Oparin and Haldane proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein etc.).

According to them origin of live is abiogenesis first but biogenesis there after.

Miller’s Experiment: That simple organic compounds could be formed in nature inthe manner explained above was experimentally demonstrated in 1953 by

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Stanley L Miller. Miller designed a glass apparatus comprising a gas flask, a condenser,and a liquid flask interconnected with tubes and fitted with sources of energy. Theapparatus simulated the conditions on the primitive earth, including a “reducingatmosphere” and an “ocean”. He circulated in this apparatus a mixture of methane(CH

4), ammonia (NH

3) and hydrogen (H

2) and water vapour (H

2O) at 800°C. These

gases were believed to prevail in the ancient atmosphere. He provided energy for theinteraction of the gases present in the mixture in the form of electric. The electricsparks simulated lightning. Then the gases were condensed in a narrow tube andpassed through a liquid flask. Here, energy was provided as heat with an electricheater. He kept the experiment working continuously for 18 days. A mixture of smallorganic molecules was formed in the gas flask (atmosphere) and was carried bycondensation (rain) to the liquid flask (ocean). He found many simple organiccompounds which included amino acids, such as glycine, alanine and aspartic acid;adenine and simple sugars such as ribose.

21. Name the two different categories of microbes naturally occurring in sewage water.Explain their role in cleaning sewage water into usable water. [3]

Ans. Different microbes, occuring in sewage water are aerobic and anaerobic bacteria,Protozoans, and filamentous fungi.

The primary effluent is passed into large aeration tanks where it is constainlly agitated.This allows abundant growth of aerobic microbes (bacteria and filamentous fungi)into floes which is a mesh like structure. The growth of these microbes reduces BODof effluents. Once the BOD is reduced significantly, then the effluent is passed intosettling tanks where the bacterial floes are allowed to sediment. This sediment iscalled activated sludge. A small part of activated sludge is again introduced into largetanks called anaerobic sludge digesters. Here anaerobic bacteria digest the bacterialand fungi in the sludge. This digestion produces methane, H

2S and CO

2 gas. These

gases form biogas. The effluent from secondary treatment is them released into naturalwater bodies.

22. Write the function of each one of the following:

(a) (Oviducal) Fimbriae (b) Coleoptile

(c) Oxytocin [3]

Ans. (a) (Oviducal) Fimbriae: It receives the ova which gets released on ovulation.

(b) Coleoptile: It is the protective covering of plumule present inside the monocotseed.

(c) Oxytocin:

(i) It causes contraction of uterus at the time of child birth.

(ii) It also helps in production of milk during lactation period.

23. Name the genes responsible for making Bt cotton plants resistant to bollworm attack.How do such plants attain resistance against bollworm attacks? Explain. [3]

Ans. The gene responsible for making Bt cotton plant resistant to bollworms is cryIAC andcryIIAb these genes form protein crystals during a particular phase of their growth.

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These crystals contain insecticidal protein. These crystals exist as inactive prototoxinsbut once an insect ingest the inactive toxin it is converted into active form of toxininside alkaline conditions of gut of insect. This solubilizes the crystals. The activetoxin binds to the surface of midgnt epithelial cells and create pores that cause cellswelling and lysis and causes death of the insect.

24. Study a part of the life cycle of malarial parasite given below. Answer the questionsthat follows: [3]

(a) Mention the roles of ‘A’ in the life cycle of the malarial parasite.

(b) Name the event ‘C’ and the organ where this event occurs.

(c) Identify the organ ‘B’ and name the cells being released from it.

Ans. (a) A is female Anopheles mosquito that act as vector for Plasmodium.

(b) C = fertilization that takes place in mosquito intestine.

(c) B = salivary gland cells which are released sporozoites.

25. Given below is the representation of amino acid composition of the relevant translatedportion of -chain of haemoglobin, related to the shape of human red. [3]

Gene ..... CTC ....

..... GAG ....

mRNA ... GAG...

Val His Leu Thr Pro Glu Glu

1 2 3 4 5 6 7

HbA Peptide

(a) Is this representation indicating a normal human or a sufferer from certainrelated genetic disease? Give reason in support of your answer.

(b) What difference would be noticed in the phenotype of the normal and the suffererrelated to this gene?

(c) Who are likely to suffer more from the defect related to the gene represented themales, the females or both males and females equally? And why?

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Ans. (a) This representation indicates a normal human because in the respective amino

acid chain, Glutamic acid is present at the 6th position.

(b) In the sufferer who exhibit sickle cell trait, defect is caused by the substitution

of Glutamic acid (Glu) by Valine (Val) at the 6th position of Beta globin chain of

the haemoglobin.

(c) Both the males and females suffer equally because sickle cell anaemia is not a

sex linked disease. It is an autosomal disease and sickle shaped RBC will cause

equal deficiency of oxygen in both males and females.

26. By the end of 2002 the public transport of Delhi switched over to a new fuel. Name

the fuel. Why is this fuel considered better? Explain. [3]

Ans. Delhi Government shifted to CNG (Compressed Natural Gas). CNG is better because

it burns more efficiently unlike petrol or diesel, in automobiles and very little of it is

left unburnt. Also CNG is cheaper fuel them petrol and diesel.

27. Draw a schematic sketch of pBR322 plasmid and label the following in it:

(a) Any two restriction sites.

(b) Ori and rop genes

(c) An antibiotic resistant gene.

Ans.

Origin ofreplication

Pvu II

Sal I

Bam HI

RopOri

Pst I

Pvu I

Eco R I

Cla IHind III

Diagrammatic representation of E.coli cloning vector pBR322 showing restriction sites

(Hind III, Eco RI, Bam HI, Sal I, Pvu II, Pst I, Cla I), Ori V and (ampR and tetR). Rop

codes for the proteins involved in the replication of the plasmid.

SECTION-D

28. Explain the carbon cycle with the help of a simplified model. [5]

OR

Explain how does: [5]

(a) a primary succession start on a bare rock and reach a climax community?

(b) the algal bloom eventually choke the water body in an industrial area?

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Ans.

71% carbon is found dissolved in oceans. This oceanic reservoir regulates theamount of CO

2 in the atmosphere.

Fossil fuel also represent a reservois of carbon.

Carbon cyclic occurs through atmosphere, ocean and through dead and livingorganisms.

A considerable amount of CO2 is fixed by process of photosynthesis.

Carbon from plants moves thruogh food chains.

Detritus food chain releases it to soil.

Respiration and combustion of fossil fuels, burning of forest firewood and organicdebris releases CO

2 in atmosphere.

Decomposers pass substantial CO2 to pool by their processing of water materials

and dead organic matter of land or ocean.

Some amount of fixed carbon is lost to sediment and removed from circulation.

Human activities have significantly influenced carbon cycle. Deforestation andmassive burning of fossil fuel has significantly increased the rate of release ofCO

2 into atmosphere.

OR(a) Such a succession is called Xerarch succession.

In this succession,

(i) Pioneer specie is lichens which secrete acids to dissolve rock causingweathering and soil formation.

(ii) Next seral stage will be bryophytes which can hold in the small amount ofsoil.

(iii) Bryophytes are then succeeded by grasses.

(iv) Grasses eventually will pave way for bigger trees which will form stableclimax community. This remains stable as long as the environment remainsunchanged.

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(b) Effluent from industries contains large amounts of nutrients. This causesexcessive growth of free-floating algae causing algal bloom. Algae startsconsuming oxygen for its own consumption. This will decrease BOD of waterbody. This reduced BOD eventually causes death of all aquatic life thus chokingthe water body.

29. [5]

(i) Identify the figure that illustrates ovulation and mention the stage of oogenesisit represents.

(ii) Name the ovarian hormone and the pituitary hormone that have caused theabove mention event.

(iii) Explain the changes that occur in the uterus simultaneously in anticipation.

(iv) Write the difference between ‘c’ and ‘h’.

(v) Draw a labelled sketch of the structure of a human ovum prior to fertilization.

OR

How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac inan angiosperm? Draw a labelled diagram of mature embryo sac. [5]

Ans. (i) (a) f = stage of ovulation

(b) Meiosis I of oogenesis is completed.

(ii) Ovarian hormone = estrogen

Pituitary hormone = Luetenizing hormone

(iii) Endometrium lining gets thickened and vascularized.

(iv) c = Developing graffian follicle

h = Degenerating corpus luteum(v)

Human ovum prior to fertilization

OR

The nucleus of the functional megaspore divides mitotically to form two nucleiwhich move to the opposite poles, forming the 2-nucleate embryo sac. Two moresequential mitotic nuclear divisions result in the formation of the 4-nucleateand later the 8-nucleate stages of the embryo sac.

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These mitotic divisions are strictly free nuclear, that is, nuclear divisions are

not followed immediately by cell wall formation. After the 8-nucleate stage, cell

walls are laid down leading to the organisation of the typical female gametophyte

or embryo sac.

Six of the eight nuclei are surrounded by cell walls and organised into cells; the

remaining two nuclei, called polar nuclei are situated below the egg apparatus

in the large central cell.

There is a characteristic distribution of the cells within the embryo sac. Three

cells are grouped together at the micropylar end and constitute the egg apparatus.

The egg apparatus, in turn, consists of two synergids and one egg cell.

The synergids have special cellular thickenings at the micropylar tip called filiform

apparatus, which play an important role in guiding the pollen tubes into the

synergid.

Three cells are at the chalazal end and are called the antipodals. The large

central cell, as mentioned earlier, has two polar nuclie. Thus, a typical angiosperm

embryo sac, at maturity, though 8-nucleate is 7-celled.

30. What is the inheritance pattern observed in the size of starch grains and seed shape

of Pisum sativum? Workout the monohybrid cross showing the above traits. How

does this pattern of inheritance deviate from that of Mendelian law of dominance?

[5]

OR

State the aim and describe Messelson and Stahl’s experiment. [5]

Ans. A round seed has well developed starch grains whereas wrinkled seeds don’t have

starch grains. So, a cross between two will give to an intermediate situations.

Suppose R is allele for round shape and r is allele for wrinkled.

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Rr

R r

R r Gametes

F (intermediate)1

Parents

gametes

RoundRR

Wrinkledrr

R rR RR Rrr Rr rr

Round intermediate wrinkled1 : 2 : 1

This is an example of incomplete dominance. Whereas in Mendelian inheritance wehave complete dominance.

OR

Matthew Meselson and Franklin Stahl performed the following experiment in 1958:

(i) They grew E. coli in a medium containing 15NH4Cl (15N is the heavy isotope of

nitrogen) as the only nitrogen source for many generations. The result was that15N was incorporated into newly synthesised DNA (as well as other nitrogencontaining compounds). This heavy DNA molecule could be distinguished fromthe normal DNA by centrifugation in a cesium chloride (CsCl) density gradient(Please note that 15N is not a radioactive isotope, and it can be separated from14N only based on densities).

(ii) Then they transferred the cells into a medium with normal 14NH4Cl and took

samples at various definite time intervals as the cells multiplied, and extractedthe DNA that remained as double-stranded helices. The various samples wereseparated independently on CsCl gradients to measure the densities of DNA.

(iii) Thus, the DNA that was extracted from the culture one generation after thetransfer from 15N to 14N medium [that is after 20 minutes; E. coli divides in 20minutes] had a hybrid or intermediate density. DNA extracted from the cultureafter another generation [that is after 40 minutes, II generation] was composedof equal amounts of this hybrid DNA and of ‘light’ DNA.

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SECTION-A1. Cucurbits and papaya plants bear staminate and pistillate flowers. Mention the

categories they are put under separately on the basis of the type of flowers they bear.

Ans. Cucurbits are monoecious and papaya is Dioecious.

4. What is the interaction called between cuscuta and shoe flower blush?

Ans. Parasitism

5. When do the oogenesis and the spermatogenesis initiate in human females and malesrespectively?

Ans. Oogenesis is initiated during the embryonic development, spermatogenesis begins atpuberty.

7. State the significance of the study of fossils in evolution.

Ans. Study of fossils indicates the geological period in which various life forms were arisen.The calculation of geological period can be done via radioactive dating.

SECTION-B13. Draw a schematic diagram of a part of double stranded dinucleotide DNA chain having

all the four nitrogenous bases and showing the correct polarity.

Ans.

14. Name the parasite that causes filariasis in human. Mention its two diagnosticsymptoms. How is this disease transmitted to others?

Ans. Wuchereria bancrofti and Wuchereria malayi causes filariasis in humans.

The two diagnostic symptoms are

Code No. 57/1/2

Studymate Solutions to CBSE Board Examination 2011-2012

UNCOMMON QUESTIONS ONLY

Series : SMA/1

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1. Chronic inflammation of the organs in which they live for many years.

2. The genital organs are also often affected resulting in gross deformities.

Pathogens are transmitted to a healthy person through the bite by the female mosquitovectors.

15. Name the source of streptokinase. How does this bio-reactor molecule function inour body?

OR

How do mycorrhizae act as biofertilizers? Explain. Name a genus of fungi that formsa mycorrhizal association with plants.

Ans. Streptokinase produced by the bacterium streptococcus and modified by geneticengineering is used as a clot buster for removing clots from the blood vessels ofpatients who have undergone myocardial infection leading to heart attack.

OR

Mycorrhizae are associations between fungi and the roots of higher plants. The fungihelp the plant in the absorption of essential nutrients from the soil while the plant inturn provides the fungi with energy yielding carbohydrates.

Boletus is the soil fungus that forms a mycorrhizal association with plants.

SECTION-C19. Write the function of each of the following

(a) Middle piece in human sperm.

(b) Tapetum in anthers.

(c) Luteinizing hormone in human males.

Ans. (a) The middle piece possesses numerous mitochondria, which produces energyfor the movement of tail that facilitate sperm motility essential for fertilisation.

(b) Microsporangium are surrounded by 4 wall layers, epidermis, endothecium,middle layer and tapetum. Outer 3 wall layers performs the function of protectionand help in dehiscence of anther to release the pollen. The innermost wall layeris the tapetum, it nourishes the developing pollen grains. Cells of the tapetumpossess dense cytoplasm and generally have more than one nucleus.

(c) Luteinizing hormone acts at the Leydig cells and stimulates the synthesis andsecretion of androgens.

26. How does an algal bloom cause eutrophication of a water body? Name the weed thatcan grow in such a eutrophic lake.

Ans. Presence of large amounts of nutrrients in waters also causes execessive growth ofplanktonic algae called an algal bloom which imparrts a distinct colour to the waterbodies. Algal blooms causes deterioration of the water quality and fish mortality.

Eutrophication is the natural aging of a lake by nutrient enrichment of its water.Streams draining into the lake increases nutrients such as nitrogen and phosphorouswhich encourage the growth of aquatic organisms. As the lake’s fertility increases,

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plant and animal life burgeons, and organic remains begin to be deposited on thelake bottom. Over the centuries as silt and organic debris pile up, the lake growsshallower and warmer, with warm-water organisms supplanting those that thrive ina cold environment marsh plants take root in the shallows and begin to fill in theoriginal lake basin. Eventually, the lake gives way to large masses of floating plants,finally converting into land.

Eichhornia crassipes water hyacinth can grow in entrophic lake.

28. (a) Draw a ‘pyramid of numbers’ of a situation where a large population of insectsfeed upon a very big tree. The insects in turn, are eaten by small birds which inturn are fed upon by big birds.

(b) Differentiate giving reasons, between the pyramid of biomass of the abovesituation and the pyramid of numbers that you have drawn.

OR

(a) What are the two types of desirable approaches to conserve biodiversity? Explainwith examples bringing out the difference between the two types.

(b) What is the association between the bumble bee and its favourite orchid ophrys?

How would extinction or change of one would affect the other?

Ans. (a) Pyramid of Number

Large birds

Small birds

Insects

Tree

This is spindle shaped pyramid.

Pyramid of biomass

Large birds

Small birds

Insects

Tree

This is irregular shaped pyramid.

(b) In case of pyramid of number for first two steps number increases but them itdecreases.

Whereas in pyramid of biomass there is no clear trend.

OR

(a) Two types of desirable approaches to conserve biodiversity are:

(i) In-situ conservation: In-situ conservation is the most appropriate methodto maintain species of wild animals and plants in their natural habitats.This approach includes protection of total ecosystems through a networkof protected areas. These are the biogeographical areas where biologicaldiversity along with natural/cultural resources are protected, maintainedand managed.

The common natural habitats (protected areas) that have been set for in-situ conservation of wild animals and plants include –

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(I) National parks

(II) Wild life sanctuaries

(III) Biosphere reserves

(IV) Several wetlands, mangroves and coral reefs

(V) Sacred grooves and lakes.

(ii) Ex-situ conservation: Ex-situ conservation includes the following:

(I) Sacred plants and home gardens.

(II) Seed banks, field gene banks, cryopreservation.

Botanical gardens, Arborata, Zoological gardens, Aquaria.

All these approaches help to conserve species and population diversityoutside the natural habitats.

In-situ Ex-situ1. It is the most appropriate

method to maintain species of wild animals and plants in their natural habitat.

2. No such technique can be used for In-situ conservation.

3. In this method organism alongwith its entire habitat is preserved. Chances of fertilization and propagation are higher.

4. Eg. National Park, Wild Life Sancturies.

1. In this approach, threatened animals and plants are not preserved in their natural habitat and placed in special setting, where they can be protected and special care.

2. Gametes of threatened species can be preserved in viable and fertile condition for long periods using cryopreservation techniques.

3. Reproduction in captivity often slows down and may not give desired results.

4. Eg. Seed banks.

(b) Association between the bumble bee and its favourite orchid ophrys is mutualism.

Orchids show a bewildering diversity of floral patterns many of which haveevolved to attract the right pollinator insect (bees and bumblebees) and ensureguaranteed pollination by it. If the female bee’s colour patterns change evenslightly for any reason during evolution, pollination success will be reducedunless the orchid flower co-evolves to maintain the resemblance of its petal tothe female bee.

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SECTION-A1. Mention the difference between spermiogenesis and spermiation. [1]

Ans. Spermiogenesis: Transformation of spermatids into spermatozoa.

Spermiation: The process of release of spermatozoa from Sertoli cells into the cavityof sperminiferous tubules.

3. What is an interaction called when an orchid grows on a mango plant? [1]

Ans. Commensalism.

4. Write the names of two semi-dwarf and high yiuelding rice varieties developed inIndia after 1966. [1]

Ans. Jaya/Ratna.

6. Mention the unique feature with respect to flowering and fruiting in bamboo species.[1]

Ans. Bamboo species flower only once in their lifetime.

8. State the significance of biochemical similarities amongst diverse organism inevolution. [1]

Ans. Biochemical similarities point to the same shared ancestory as structural similaritiesamong diverse organisms.

SECTION-B15. Mention the importance of Lactic acid bacteria to humans other than setting milk

into curd. [2]

OR

How do methanagens help in producing biogas? [2]

Ans. (a) Lactic acid bacteria play a very beneficial role in checking disease causingmicrobes.

(b) Methanogens such as Methanobacterium act on excreta of cattle and growanaerobically, producing large amount of methane along with CO

2 and H

2.

Methane is the main predominant gas of bio gas.

Code No. 57/1/3

Studymate Solutions to CBSE Board Examination 2011-2012

UNCOMMON QUESTIONS ONLY

Series : SMA/1

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SECTION-C19. (a) Construct a complete transcription unit with promotor and terminator on the

basis of the hypothetical template strand given below:

ATGCATGCATAC

(b) Write the RNA strand transcribed from the above transcription unit along withits polarity. [3]

OR

How are the structural genes inactivated in lac operon in E. Coli? Explain. [3]Ans. (a)

Promoter Terminator

A T G C A T G C A T A C

T A C G T A C G T A T G

3

5

5

3

(b) RNA strand transcribed from above transcription unit.

U A C GU A C G U A U G

5 3

(c) In the absence of lactose, no inactivation of repressor occurs and hence therepressor (which is constitutively produced from i gene) binds to the operatorregion of the operon; thus preventing RNA polymerase from transcribing theoperon thus inactivating of the production of structural genes in E.coli occurs.

20. Write the function of each of the following: [3]

(a) Seminal vesicle (b) Scutellum

(c) Acrosome of human sperm

Ans. (a) Seminal vesicle: Constitute seminal plasma which is rich in fructose calciumand enzymes.

(b) Scutellum: Is the papery cotyledon of the monocot seed and acts as a passagefor movement of nutrients from the endosperm to the developing embryo.

(c) Acrosome of human sperm: Contains hydrolytic enzymes that help inpenetration of egg during fertilization.

25. (a) Why are the colourful polysterene and plastic packagings used for protectingthe food, considered an environmental menace?

(b) Write about the remedy found for the efficient use of plastic waste by AhmedKhan of Bangalore. [3]

Ans. (a) Colourful polysterene and plastic packaging used for protecting the food areconsidered to be environmental menace as plastic is non-biodegradable and itsrecycling process is very costly and includes manual participation thus exposingworkers to toxic substances produced during recycling process.

(b) The remedy found for efficient use of plastic waste by Ahmed Khan of Bangalorewas making of Polyblend, a fine powder of recycled modified plastic. This mixtureis mixed with the bitumen, and is used to lay roads.

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In collaboration with R.V. College of Engineering and Banglore city Corporation,Ahmed Khan proved that blends of Polyblend and Bitumen, when used to layroads enhanced the bitumen’s water repellant properties and helped to increaseroad life by a factor of three.

SECTION-D30. Name the scientists who proved experimentally that DNA is the genetic material.

Describe their experiment. [5]

OR

(a) List the three different allelic forms of gene ‘I’ in humans. Explain the differentphenotypic expressions, controlled by these three forms.

(b) A woman with blood group ‘A’ marries a man with blood group ‘O’. Discuss thepossibilities of the inheritance of the blood groups in the folllowing startingwith ‘yes’ or ‘no’ for each:

(i) They produce children with blood group ‘A’ only.

(ii) They produce children some with ‘O’ blood group and some with ‘A’ bloodgroup. [5]

Ans. The two scientists that proove DNA is the genetic material are:

(i) Griffith Transformation Experiment

(a) In 1928, Frederick Griffith, in a series of experiments with Streptococcus

pneumoniae (bacterium responsible for pneumonia), witnessed a miraculoustransformation in the bacteria.

(b) When Streptococcus pneumoniae (pneumococcus) bacteria are grown on aculture plate, some produce smooth shiny colonies (S) while others producerough colonies (R). This is because the S strain bacteria have a mucous(polysaccharide) coat, while R strain does not. Mice infected with the Sstrain (virulent) die from pneumonia infection but mice infected with the Rstrain do not develop pneumonia.

S strain Inject into mice Mice die

R strain Inject into mice 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) Inject into mice Mice live

When he injected a mixture of heat-killed S and live R bacteria, the micedied.

S strain (heat-killed) + R strain (live) Inject into mice Mice die

Moreover, he recovered living S bacteria from the dead mice.

(c) He concluded that the R strain bacteria had somehow been transformedby the heat-killed S strain bacteria. Some ‘transforming principle’,transferred from the heat-killed S strain, had enabled the R strain tosynthesise a smooth polysaccharide coat and become virulent. This mustbe due to the transfer of the genetic material.

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(d) Prior to the work of Oswald Avery, Colin MacLeod and Maclyn McCarty(1933-44), the genetic material was thought to be a protein. They workedto determine the biochemical nature of ‘transforming principle’ in Griffith’sexperiment.

(e) They purified biochemicals (proteins, DNA, RNA, etc.) from the heat-killedS cells to see which ones could transform live R cells into S cells. Theydiscovered that DNA alone from S bacteria caused R bacteria to becometransformed.

(f) They also discovered that protein-digesting enzymes (proteases) and RNA-digesting enzymes (RNases) did not affect transformation, so thetransforming substance was not a protein or RNA. Digestion with DNasedid inhibit transformation, suggesting that the DNA caused thetransformation. They concluded that DNA is the hereditary material.

(ii) Hershey and Chase Experiment

(a) DNA is the genetic material came from the experiments of Alfred Hersheyand Martha Chase (1952). They worked with viruses that infect bacteriacalled bacteriophages.

(b) The bacteriophage attaches to the bacteria and its genetic material thenenters the bacterial cell. The bacterial cell treats the viral genetic materialas if it was its own and subsequently manufactures more virus particles.Hershey and Chase worked to discover whether it was protein or DNAfrom the viruses that entered the bacteria.

(c) They grew some viruses on a medium that contained radioactivephosphorus and some others on medium that contained radioactive sulfur.Viruses grown in the presence of radioactive phosphorus containedradioactive DNA but not radioactive protein because DNA containsphosphorus but protein does not. Similarly, viruses grown on radioactivesulfur contained radioactive protein but not radioactive DNA because DNAdoes not contain sulfur.

(d) Radioactive phages were allowed to attach to E. coli bacteria. Then, as theinfection proceeded, the viral coats were removed from the bacteria byagitating them in a blender. The virus particles were separated from thebacteria by spinning them in a centrifuge.

(e) Bacteria which was infected with viruses that had radioactive DNA wereradioactive, indicating that DNA was the material that passed from thevirus to the bacteria. Bacteria that were infected with viruses that hadradioactive proteins were not radioactive. This indicates that proteins didnot enter the bacteria from the viruses. DNA is therefore the genetic materialthat is passed from virus to bacteria.

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OR

(a) Three different allelic forms of ‘I’ gene are

(i) i (ii) IA

(iii) IB

Genotype Blood Group

ii O

IA IA; IA i A

IB IB; IB i B

IA IB AB

(b) Possibility I

IA IA ii

(woman) (man)

i

i

I A i

I A i

I A i

I A i

IA IA

Yes. A Blood group only

Possibility II

IA i ii

(woman) (man)

i

i

I A i

I A i

ii

ii

IA i

Yes. 50% A Blood Group

50% O Blood Group

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