Biology
SECTION – A
(Q. Nos. 1 – 5 are of one marks each)
Q.1. Name the type of cross that would help to find the genotype of a pea plant bearing violet flowers.
Answer: Test cross
Q.2. State two postulates of Oparin and Haldane with reference to the origin of life.
Answer: (i) First form of life could have come from pre-existing non-living organic molecules / RNA & Protein
(ii) Formation of life was preceded by chemical evolution / formation of diverse organic molecules from inorganic constituents.
Q.2. Bt -toxins are released as inactive crystals in the bacterial body. What happens to it in
the cotton boll worm body that it kills the boll worm.(SET-III)
Ans: It is converted into an active protein (due to alkaline pH of the gut of the boll worm) , the toxin binds to midgut cells / create pores / causes cell swelling and lysis that kills the bollworm.
Q.3. A herd of cattle is showing reduced fertility and productivity. Provide one reason and one suggestion to overcome this problem.
Answer: Reason: Inbreeding depression / continuous inbreeding.
Suggestion: Should be mated with unrelated superior cattle of the same breed / out – breeding / out – crossing.
Q.3. Name the specific type of gene that is incorporated in a cotton plant to protect the plant against cotton bollworm infestation. (SET-II)
Answer: cry I Ac / cry II Ab
Q.4. What are Cry genes ? In which organisms are they present ?
Ans. The genes which code for Bt toxin / Cry proteins / toxic proteins , Bacillus thuringiensis.
Q.5. An electrostatic precipitator in a thermal power plant is not able to generate high voltage of several thousands. Write the ecological implication because of it.
Answer: Air Pollution // particulate matter / dust particles released in the air.
SECTION – B
(Q Nos. 6-10 are of two marks each)
Q.6. A pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage ?
Answer: • In 2-celled stage the mature pollen grain contains a generative and vegetative cell, whereas in 3- celled stage one vegetative cell and two male gametes are present.
• The generative cell floats in the cytoplasm of vegetative cell
Q.7. Differentiate between the genetic codes given below :
(a) Unambiguous and Universal
(b) Degenerate and Initiator
Answer:
| (a) Unambiguous: One codon codes for only one amino acid. | Universal: Genetic code/codons are (nearly) the same for all organisms from bacteria to humans. |
| (b)Degenerate: More than one codon coding for the same amino acid. | Initiator: Start codon / AUG. |
Q.8. Mention one application for each of the following :
(a) Passive immunization
(b) Antihistamine
(c) Colostrum
(d) Cytokinin-barrier
Answer: (a) Provide preformed antibodies / antitoxins for quick response in case of infection by deadly microbes(tetanus) or snake bite.
(b) Reduces symptoms of allergy
(c) Provides passive immunity / antibodies / Ig A to new born.
(d) Protection of non-infected cells from further viral infection.
Q.9. Name the microbes that help production of the following products commercially:
(a) Statin
(b) Citric acid
(c) Penicillin
(d) Butyric acid
Answer: (a) Monascus purpureus
(b) Aspergillus niger
(c) Penicillium notatum
(d) Clostridium butylicum
Q.10. List four benefits to human life by eliminating the use of CFCs.
Answer: (i) Delay in aging of skin
(ii) Prevent damage to skin cells
(iii) Prevent skin cancer
(iv) Prevent snow blindness / inflammation of cornea
(v) Prevent cataract (a) Unambiguous:
(vi) Prevents ozone depletion
(vii) Prevents global warming
(viii) Reduces greenhouse effect
(ix) Reduces odd climatic changes or El Nino effect
OR
Q.10. Suggest two practices giving one example of each, that help protect rare or threatened species.
Ans: (1) In situ conservation , biodiversity hotspot / biosphere reserve / national parks /sanctuaries / Ramsar sites / sacred groves (Any one).
(2) Ex situ conservation , Zoological parks / botanical garden / wildlife safari parks /
cryopreservation techniques / Tissue culture / seed bank / pollen banks.
Q.6. Name the type of immunity the colostrum provides to a newborn baby. Write giving an example where this type of immunity should be provided to a person.
Answer: Passive Immunity.
In case of infection by deadly microbes(tetanus) / snake bite where quick immune response is required =1
Q.8. Write the binomials of two fungi and mention the products/bioactive molecules they help to produce.
Answer: Trichoderma polysporum , cyclosporin A
Aspergillus niger,citric acid
Monascus purpureus , statin
Saccharomyces cerevisiae, ethanol / alcohol
Penicillium notatum , Penicillin
Q.7. Give the binomials of two types of yeast and the commercial bioactive products they help to produce.
Ans: Saccharomyces cerevisiae- ethanol / alcohol Monascus purpureus- statin
Q.9. How many cells are present in the pollen grains at the time of their release from another ? Name the cells.
Ans. Pollen grain may be released at
2-celled stage , one vegetative and one generative cell ,
3-celled stage , one vegetative cell and two male gametes
Q.10. Name the group of cells the HIV enters after getting into the human body. What happens in these cells and what are these cells subsequently referred to as ? Name the next group of cells the HIV attacks from here.
Ans. Macrophages , Reverse transcription , HIV Factory , helper T-lymphocytes (TH)
SECTION – C
(Q Nos. 11-22 are of three marks each)
Q.11. (a) Can a plant flowering in Mumbai be pollinated by pollen grains of the same species growing in New Delhi ? Provide explanations to your answer.
(b) Draw the diagram of a pistil where pollination has successfully occurred. Label the parts involved in reaching the male gametes to its desired destination.
Answer: (a) Yes, By artificial means ( any relevant explanation).
(b) Diagram with following labellings Stigma , Pollen tube , Synergid / Filiform Apparatus , Micropyle.
Q.12. Both Haemophilia and Thalassemia are blood related disorders in humans. Write their causes and the difference between the two. Name the category of genetic disorder they both come under.
Answer:
| Haemophilia | Thalassemia |
| Single protein involved in the clotting of blood is affected | Defects in the synthesis of globin leading to formation of abnormal haemoglobin. |
| Sex linked reccessive disorder. | Autosomal recessive disorder. |
| Blood does not clot. | Results in anaemia. |
Q.13. (a) List the two methodologies which were involved in human genome project. Mention how they were used.
(b) Expand ‘YAC’ and mention what was it used for.
Answer: (a) Expressed Sequence Tags , Identifying all the genes that are expressed as RNA Sequence Annotation , sequencing the whole set of genome coding or non coding sequences and later assigning different region with functions.
(b) Yeast Artificial Chromosome , used as cloning vectors (cloning / amplification ).
Q.14. Write the characteristics of Ramapithecus , Dryopithecus and Neanderthal man.
Answer: Ramapithecus: hairy/ walked like gorillas and chimpanzees , more man like.
Dryopithecus: hairy/ walked like gorillas and chimpanzees , more ape- like.
Neanderthal man: brain size is 1400cc , used hides to protect their body / buried their dead.
Q.15. Name a human disease, its causal organism, symptoms (any three) and vector, spread by intake of water and food contaminated by human faecal- matter.
Answer: Amoebiasis (Amoebic dysentery) , Entamoeba histolytica , constipation / abdominal pain / cramps / stools with excess mucus / blood clots (Any three symptoms) , Housefly.
Ascariasis, Ascaris , internal bleeding / muscular pain / fever / anaemia / blockage of intestinal passage (Any three symptoms), Housefly.
Typhoid, Salmonella typhi, high fever / weakness / stomach pain / constipation / headache / loss of appetite (Any three symptoms), Housefly.
OR
Q.15. (a) Why is there a fear amongst the guardians that their adolescent wards may get
trapped in drug/alcohol abuse ?
(b) Explain ‘addiction’ and ‘dependence’ in respect of drug/alcohol abuse in youth.
Defects in the synthesis of globin leading to formation of abnormal haemeoglobin Sex linked recessive disorder.
Autosomal recessive disorder Blood does not clot Results in anaemia
Answer: (a) Adolescents are easily affected by ( vulnerable to) peer pressure /adventure /curiosity / excitement / experimentation / media .
(b) Addiction -Psychological attachment to certain effects such as Euphoria / temporary feeling of well-being. Dependence-Tendency of the body to show withdrawal syndrome / symptoms if regular doses of drug / alcohol is abruptly discontinued.
Q.16. (a) Write the desirable characters a farmer looks for in his sugarcane crop.
(b) How did plant breeding techniques help north Indian farmers to develop cane with
desired characters ?
Answer: (a) High yield , thick stem,high sugar content , ability to grow in their areas.
(b) By crossing Saccharum officinarum / south Indian variety having desired characteristics with Saccharum barberi / north Indian low yield variety.
Q.17. Secondary treatment of the sewage is also called Biological treatment. Justify this statement and explain the process.
Answer: Involves biological organism such as aerobic and anaerobic microbes / bacteria and fungi to digest / consume organic waste.
Primary effluent is passed into aeration tank where vigorous growth of aerobic microbes (flocs) take place, BOD reduced (microbes consume major part of organic matter), effluent is passed to settling tank where flocs sediment to produce activated sludge , sludge is pumped to anaerobic sludge digester to digest bacteria and fungi.
Q.18. (a) Explain the significance of ‘palindromic nucleotide sequence’ in the formation of recombinant DNA.
(b) Write the use of restriction endonuclease in the above process.
Answer: (a) Palindromic nucleotide sequence is the recognition (specific) sequence present both on the vector and on a desired / alien DNA for the action of the same(specific) restriction endonuclease to act upon.
(b) Same restriction endonuclease binds to both the vector and the foreign DNA , cut each of the two strands of the double helix at specific points in their sugar phosphate backbone of recognition sequence for restriction endonucleases / palindromic sequence of vector and foreign DNA , to cut strand a little away from the centre of the palindrome sites, creates overhanging stretches /sticky ends .
(b) If depict diagrammatically showing the above mentioned value points it can be accepted.
Q.19. Describe the roles of heat, primers and the bacterium Thermus aquaticus in the process of PCR.
Answer: Heat – Denaturation / separation of DNA into two strands.
Primer- Enzyme DNA Polymerase extend the primers using the nucleotides provided in the reaction and the genomic DNA as template.
Thermus aquaticus – source of thermostable DNA polymerase / Taq polymerase.
Q.20. Explain the various steps involved in the production of artificial insulin.
Answer: Two DNA sequences corresponding to A and B polypeptide chains of human insulin were prepared , these were introduced into E.coli to produce A and B chains separately , these chains were extracted and combined by creating disulphide bonds.
Q.21. (a) “Organisms may be conformers or regulators.” Explain this statement and give one example of each.
(b) Why are there more conformers than regulators in the animal world ?
Answer: (a) Conformers- organisms which cannot maintain a constant internal environment under varying external environmental conditions / change body temperature and osmotic concentration with change in external environment eg. all plants / fishes / amphibians / reptiles.
Regulators – organisms which can maintain homeostasis (by physiological means or behavioural means ) // maintain constant body temperature and osmotic concentration eg. birds /mammals.
(b) Thermoregulation is energetically expensive for animals.
Q.22. Describe the inter-relationship between productivity, gross primary productivity and net productivity.
Answer: Productivity is the rate of biomass production per unit area over a period of time ,
Gross primary productivity is the rate of production of organic matter during photosynthesis in an ecosystem , Net productivity is the gross primary productivity minus respiration losses ®.
Q.13. Explain the process of pollination in Vallisneria. How is it different in water-lily, which is also an aquatic plant ?
Answe: In Vallisneria pollination takes place through water , the female flower reach the surface of water by long stalk , male flowers / pollen grain released on to the surface of water , carried passively by water current reaching the female flowers / stigma.
In Water lily pollination takes place through wind or insect , female flower emerges above the surface of water and gets pollinated
Q.15. What is disturbance in Hardy-Weinberg genetic equilibrium indicative of ? Explain how it is caused.
Answer: Disturbance in Hardy-Weinberg equilibrium is an indicator of change of frequency of alleles in a population , resulting in evolution.
It is caused by genetic drift / gene flow or gene migration / mutation / genetic recombination /natural selection.
Q.18. Different animals respond to changes in their surroundings in different ways. Taking one example each, explain “some animals undergo aestivation while some others hiberna
tion”. How do fungi respond to adverse climatic conditions ?
Answer: Some animals go into aestivation to avoid summer related problems ( heat and desiccation) , eg. snails / fish ( any other suitable eg.)
Some animals go into hibernation to avoid winter related problem ( extreme cold) eg. bear ( any other suitable eg.).
Fungi form thick walled spores and suspend their activities to respond to adverse climatic condition.
Q.11. Rearrange Ramapithecus, Australopithecus and Homo habilis in the order of thein evolution on the Earth. Comment on their evolutionary characteristics.
Answer: Ramapithecus Australopithecus Homo habilis.
Ramapithecus – hairy / walked like gorilla and chimpanzees / more man like.
Australopithecus – Hunted with stone weapons / ate fruit.
Homo habilis -Brain capacity 650- 800 cc / probably did not eat meat.
Q.16. (a) Trace the development of an endosperm after fertilisation with reference to coconut. Mention the importance of endosperm development.
(b) Write the importance of ‘pollen bank’.
Answer: (a) In coconut Primary Endosperm Nucleus (PEN-3n) undergoes successive nuclear divisions , give rise to free- nuclear endosperm known as coconut water , white kernel is the cellular endosperm , provides nourishment to the growing embryo.
(b) Storage / cryopreservation ( storage in liquid nitrogen at – 196 o C) , to use in crop breeding programmes.
Q.20. Describe the inter-relationship , between productivity, gross primary productivity and net productivity.
Answer: Productivity is the rate of biomass production per unit area over a period of time ,
Gross primary productivity is the rate of production of organic matter during photosynthesis in an ecosystem ,Net productivity is the gross primary productivity minus respiration losses ®.
Q.22. How do kangaroo rats and desert plants adapt themselves to survive in their extreme habitat ? Explain.
Answer: Kangaroo rats- internal fat oxidation where water is a byproduct , excretes concentrated urine.
Desert Plants -thick cuticle / sunken stomata / leaves reduced to spines / deep roots /
Special photosynthetic pathway / CAM.
SECTION – D
(Q No. 23 is of four mark)
Q.23 . It is commonly observed that parents feel embarrassed to discuss freely with their adoles- cent children about sexuality and reproduction. The result of this parental inhibition is that the children go astray sometimes.
(a) Explain the reasons that you feel are behind such embarrassment amongst some
parents to freely discuss such issues with their growing children.
(b) By taking one example of a local plant and animal, how would you help these parents
to overcome such inhibitions about reproduction and sexuality ?
Ans: (a) Illiteracy / conservative attitude / misconceptions / social myths / any other relevant point (Any two).
(b) If a student gives the clarity of the concept of reproduction and sexuality by taking any example of a plant and an animal with respect to reproductive organs, gamete formation, fertilization, sexual behaviour etc.
SECTION – E
(Q Nos. 24-26 are of five marks each)
Q.24. (a) When a seed of an orange is squeezed, many embryos, instead of one are observed.
Explain how it is possible.
(b) Are these embryos genetically similar or different ? Comment.
Ans: (a) Polyembryony , nucellar cells surrounding embryo sac start dividing , protrude into the embryo
sac and develop into many embryos.
(b) These embryos are genetically similar, as produced from nucellar cells by mitotic division / formed without fertilisation (but different from the embryo formed by fertilization).
OR
Q.24. (a) Explain the following phases in the menstrual cycle of a human female:
(i) Menstrual phase
(ii) Follicular phase
(iii) Luteal phase
(b) A proper understanding of menstrual cycle can help immensely in family planning.
Do you agree with the statement ? Provide reasons for your answer.
Ans: (a) (i) Menstrual phase – first 3-5 days of the cycle where menstrual flow occurs due to break down of endometrial lining of the uterus, if the released ovum is not fertilised.
(ii) Follicular phase – from 5th to 14th day of the cycle where the primary follicles grow to become a fully mature Graafian follicle , endometrium of uterus regenerates , Graafian follicle ruptures to release ova (ovulation on 14th day).
(iii) Luteal Phase – During 15th to 28th day remaining parts of graafian follicle transforms into the corpus luteum , secretion of progesterone (essential for maintenance of endometrium).
All these phases are under the influence of varying concentrations of pituitary and ovarian Hormone.
(b) Yes , can take appropriate precautions between 10th to 17th day of the menstrual cycle when the chances of fertilisation are high.
Q.25. (a) Compare, giving reasons, the J-shaped and S-shaped models of population growth of a species.
(b) Explain “fitness of a species” as mentioned by Darwin.
Answer:
| J shaped – growth curve | S shaped- growth curve |
| Resources are unlimited | Resources are limited |
| Growth is exponential | Logistic Growth |
| As resources are unlimited all individuals survive and reproduce | Fittest individual will survive and reproduce |
| Growth Equation dN/dt=Rn (If explained) | Growth Equation dN/dt=rN (k-N/K) (If explained) |
Note – Marks to be awarded only if the corresponding difference is written.
(b) When resources are limited , Competition occurs between individuals , the fittest will survive,
who reproduce to leave more progeny.
OR
Q.25. (a) What is an ecological pyramid ? Compare the pyramids of energy, biomass and numbers.
(b) Write any two limitations of ecological pyramids.
Ans: (a) Graphical representation of the relationships among organisms at different trophic levels.
(b) It does not accommodate the food web / does not take into account the same species belonging to two or more trophic levels , Saprophytes are not given any place.
Q.26. (a) Describe the structure and function of a t-RNA molecule. Why is it referred to as an adapter molecule?
(b) Explain the process of splicing of hn-RNA in a eukaryotic cell.
Ans: (a) Clover-leaf shaped / inverted L shaped molecules has an anticodon loop with bases complementary to specific codon , has an amino acid acceptor end = 1+1
As it reads the code on one hand and binds with the specific amino acid on the other hand.
(b) Introns are removed and exons are joined in a definite order.
Process of splicing shown diagramatically.
OR
Q.26. Growth Equation dN/dt=rN (k-N/K) (If explained) Pyramid of Energy Pyramid of BioMass Pyramid of Numbers Pyramid of Numbers Shows transfer of Energy from shows numbers of one trophic level to another
organisms at each trophic level. Always upright Mostly upright but can be inverted Mostly upright can be
inverted Shows transfer of amount of food/ biomass from one trophic level to another. Write the different components of a lac-operon in E.coli. Explain its expression while in an ‘open’ state.
Ans: It consists of one regulatory gene(i) , promoter gene , operator gene , and three structural genes(z,y,a).
Lactose/ inducer binds to the repressor protein , makes it inactive so it cannot bind with operator, allows RNA Polymerase access to the promoter and transcription proceeds ,β -galactosidase , permease , transacetylase formed (by translation process for Lactose metabolism).
Q.25. (a) Explain Polygenic inheritance and Multiple allelism with the help of suitable examples.
(b) “Phenylketonuria is a good example that explains Pleiotropy.” Justify.
Answer: (a) Traits that are generally controlled by three or more genes , the phenotype reflects the contribution of each allele / effect of each allele is additive.
eg. Human skin colour , controlled by three genes (A , B, C).
In multiple allelism more than two alleles , govern the same character / phenotype.
eg . Human blood group (ABO system) , controlled by three different alleles (IA, IB, i).
(b) In pleiotropy a single gene can exhibit multiple phenotypic expressions , in phenylketonuria single mutated gene express mental retardation and reduction in hair and skin pigmentation
OR
Q.25. (a) What is an operon ?
(b) Explain how a polycistronic structural gene is regulated by a common promoter and a
combination of regulatory genes in a lac-operon.
Answer: (a) An operon is a polycistronic structural gene which is regulated by a common promoter and regulator
gene / transcriptionally regulated system in which polycistronic structural gene is controlled by a common promoter and regulator gene.
(b)
- Lac operon consist of one regulatory gene i which codes for the repressor protein , promoter (P) and operator (o) are adjacent to gene i.
- Structural genes z, y, a code for enzymes (â-galactosidase , permease and transacetylase respectively).
- The regulator gene i synthesizes the repressor protein (all the time) , in the absence of inducer , the repressor protein binds to the operator region of the operon , prevents transcription (by RNA polymerase).
- The repressor is inactivated in the presence of an inducer (lactose) that binds with it , this allows RNA polymerase access to promoter and transcription proceeds.
Q.24. (a) A pea plant bearing axial flowers is crossed with a pea plant bearing terminal flowers. The cross is carried out to find the genotype of the pea plant bearing axial flowers. Work out the cross to show the conclusions you arrive at.
(b) State the Mendel’s law of inheritance that is universally acceptable.
Answer: (i) If the plants is homozygous for the dominant trait
(ii) If the plants is heterozygous for the dominant trait A A a a (All plants with Axial Flower) A a a (50 % plants are with Axial ?ower and 50% plants with terminal ?ower) a
Conclusion : If all progeny show axial flowers ( dominant) the plant is homozygous (AA) ,
If 50 % of Progeny show Axial flower ( Dominant) and 50% Terminal flower ( Recessive) the plant is heterozygous.
(b) Law of Segregation , allelic pair segregate (separates) during gamete formation ( do not loose their identity ).
OR
Q.24. (a) Absence of lactose in the culture medium affects the expression of a Lac-operon in E. coli. Why and how ? Explain.
(b) Write any two ways in which the gene expression is regulated in eukaryotes.
Answer: (a) • Lactose acts as inducer thus absence of lactose switches off the operon.
• Repressor protein produced by regulatory gene ( i-gene ) is free ( in the absence of inducer ) ,
• Repressor protein binds with the operator gene ( o-gene ) ,
• Preventing RNA polymerase to transcribe the structural gene and operon is switched off.
If the above mentioned points are properly represented with help of schematic diagram.
(b) • Transcriptional level ( formation of primary transcripts )
• Processing level ( regulation of splicing )
• Transport of messengar RNA from nucleus to the cytoplasm
• Translational level
Q.25. (a) When a seed of an orange is squeezed, many embryos, instead of one are observed. Explain how it is possible.
(b) Are these embryos genetically similar or different ? Comment.
Ans: (a) Polyembryony , nucellar cells surrounding embryosac start dividing , protrude into the embryosac and develop into many embryos = 1+ 1+ 1
(b) These embryos are genetically similar, as produced from nucellar cells by mitotic division / formed without fertilisation (but different from the embryo formed by fertilization)
OR
Q.25. (a) Explain the following phases in the menstrual cycle of” a human female:
(i) Menstrual phase
(ii) Follicular phase
(iii) Luteal phase
(b) A proper understanding of menstrual cycle can help immensely in family planning.
Do you agree with the statement ? Provide reasons for your answer.
Ans: (a) (i) Menstrual phase – first 3-5 days of the cycle where menstrual flow occurs due to break down of endometrial lining of uterus, if the released ovum is not fertilised.
(ii) Follicular phase – from 5th to 14th day of the cycle where the primary follicles grow to become a fully mature Graafian follicle , endometrium of uterus regenerates , Graafian follicle ruptures to release ova (ovulation on 14th day)
(iii) Luteal Phase – During 15th to 28th day remaining parts of graafian follicle transform into corpus luteum , secretion of progesterone (essential for maintenance of endometrium)
All these phases are under the influence of varying concentrations of pituitary and ovarian hormone.
(b) Yes , can take appropriate precautions between 10th to 17th day of the menstrual cycle when the chances of fertilisation are high.