CBSE Sample Papers for Class 12 Biology Paper 7 are part of CBSE Sample Papers for Class 12 Biology. Here we have given CBSE Sample Papers for Class 12 Biology Paper 7.
CBSE Sample Papers for Class 12 Biology Paper 7
Board | CBSE |
Class | XII |
Subject | Biology |
Sample Paper Set | Paper 7 |
Category | CBSE Sample Papers |
Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 7 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.
Time: 3 Hours
Maximum Marks: 100
General Instructions:
- There are total 26 questions and five sections in the question paper. All questions are compulsory.
- Section A contains question number 1 to 5, Very Short Answer Type Questions of one mark each.
- Section B contains question number 6 to 10, Short Answer Type Questions of two marks each.
- Section C contains question number 11 to 22, Short Answer Type Questions of three marks each.
- Section D contains question number 23, Value Based Question of four mark.
- Section E contains question number 24 to 26, Long Answer Type Questions of five marks each.
- There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examiner is to attempt any one of the question out of the two given in the question paper with the same question number.
- No. of printed pages are three.
SECTION-A
Question 1.
Name the type of cross that would help to find the genotype of a pea plant bearing violet these questions, an examinee is to attempt any one question out of the two given alternatives. flowers.
Question 2.
State two postulates of Oparin and Haldane with reference to origin of life.
Question 3.
A herd of cattle is showing reduced fertility and productivity. Provide one reason and one suggestion to overcome this problem.
Question 4.
What are Cry genes? In which organism are they present?
Question 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.
SECTION-B
Question 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?
Question 7.
Differentiate between the genetic codes given below:
(1) Unambiguous and Universal
(2) Degenerate and Initiator
Question 8.
Mention one application for each of the following:
(a) Passive immunization
(b) Antihistamine
(c) Colostrum
(d) Cytokinin-barrier
Question 9.
Name the microbes that help production of the following products commercially:
(a) Statin
(b) Citric acid
(c) Penicillin
(d) Butyric acid
Question 10.
List four benefits to human life by eliminating the use of CFCs.
OR
Suggest two practices giving one example of each, that help protect rare or threatened species.
SECTION-C
Question 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.
Question 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.
Question 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.
Question 14.
Write the characteristics of Ramapithecus, Dryopithecus and Neanderthal man.
Question 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.
OR
(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.
Question 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?
Question 17.
Secondary treatment of the sewage is also called Biological treatment. Justify this statement and explain the process.
Question 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.
Question 19.
Describe the roles of heat, primers and the bacterium Thermus aquaticus in the process of PCR.
Question 20.
Explain the various steps involved in the production of artificial insulin.
Question 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?
Question 22.
Describe the inter-relationship between productivity, gross primary productivity and net productivity.
SECTION-D
Question 23.
It is commonly observed that parents feel embarrassed to discuss freely with their adolescent 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 ?
SECTION-E
Question 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.
OR
(a) Explain the following phases in the menstrual cycle of a human female:
(1) Menstrual phase
(2) Follicular phase
(3) 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.
Question 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.
OR
(a) What is an ecological pyramid ? Compare the pyramids of energy, biomass and numbers.
(b) Write any two limitations of ecological pyramids.
Question 26.
(a) Describe the structure and function of a 7-RNA molecule. Why is it referred to as an adapter molecule?
(b) Explain the process of splicing of hn-RNA in a eukaryotic cell.
OR
Write the different components of a lac-operon in E. coli. Explain its expression while in an ‘open’ state.
Answers
SECTION-A
Answer 1.
Test cross = 1
Answer 2.
(1) First form of life could have come from pre-existing non-living organic molecules / RNA & Protein (2) Formation of life was preceded by chemical evolution / formation of diverse organic molecules from inorganic constituents
Answer 3.
Reason: Inbreeding depression / continuous inbreeding
Suggestion: Should be mated with unrelated superior cattle of the same breed / out-breeding / out-crossing
Answer 4.
The genes which code for Bt toxin / Cry proteins / toxic proteins, Bacillus thuringiensis
Answer 5.
Air Pollution
OR
particulate matter / dust particles released in the air.
SECTION-B
Answer 6.
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
Answer 7.
(a) Unambiguous: One codon codes for only one amino acid. | Universal: Genetic code/codons are (nearly) same for all organism/from bacteria to human |
(b) Degenerate: More than one codon coding for the same amino acid | Initiator: Start codon AUG |
Answer 8.
(a) Provide preformed antibodies / anti-toxins 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
Answer 9.
(a) Monascus purpureus
(b) Aspergillus niger
(c) Penicillium notatum
(d) Clostridium butylicum
Answer 10.
(1) Delay in aging of skin
(2) Prevent damage to skin cells
(3) Prevent skin cancer
(4) Prevent snow blindness / inflammation of cornea
(5) Prevent cataract
(6) Prevents ozone depletion
(7) Prevents global warming
(8) Prevents global warming
(9) Reduces odd climatic changes or El Nino effect
OR
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 / wild life safari parks / cryopreservation techniques / Tissue culture / seed bank / pollen banks (Any one)
SECTION-C
Answer 11.
(a) Yes, By artificial means (any relevant explanation)
(b) Diagram with following labellings
Stigma, Pollen tube, Synergid / Filiform Apparatus, Micropyle
Answer 12.
Haemophilia | Thalassemia |
Single protein involved in the clotting of blood is affected | 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 |
Mendelian disorder.
Answer 13.
(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)
Answer 14.
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
Answer 15.
Amoebiasis (Amoebic dysentery), Entamoeba histolytica, constipation/abdominal pain/cramps/stools with excess mucus / blood clots (Any three symptoms), Housefly
OR
Ascariasis, Ascaris, internal bleeding / muscular pain / fever / anaemia / blockage of intestinal passage (Any three symptoms), Housefly
OR
Typhoid, Salmonella typhi, high fever / weakness / stomach pain / constipation / headache / loss of appetite (Any three symptoms), Housefly
OR
(a) Adolescents are easily affected by ( vulnerable to) peer pressure /adventure /curiosity / excitement / experimentation / media (Any two)
(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
Answer 16.
(a) High yield, thick stem,high sugar content, ability to grow in their areas
(b) By crossing Saccharum officinamm / south Indian variety having desired characteristics with Saccharum barberi / north Indian low yield variety
Answer 17.
Involves biological organism such as aerobic and anerobic microbes / bacteria and fungi to digest / consume organic waste Primary effluent is passed into aeration tank where vigorous growth of aerobic microbes (floes) take place, BOD reduced (microbes consume major part of organic matter), effluent is passed to settling tank where floes sediment to produce activated sludge, sludge is pumped to anerobic sludge digester to digest bacteria and fungi
Answer 18.
(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
OR
(b) If depicted diagramatically showing the above mentioned value points it can be accepted
Answer 19.
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
Answer 20.
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
Answer 21.
(a) Conformers- organisms which cannot maintain a constant internal environment under varying external environmental conditions
OR
change body temperature and osmotic concentration with change in external enviomment eg. all plants / fishes / amphibians / reptiles (Any one)
Regulators – organisms which can maintain homeostasis (by physiological means or behavioural meins ) OR
maintain constant body temperature and osmotic concentration eg. birds /mammals
(b) Thermoregulation is energetically expensive for animals
Answer 22.
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 (R)
SECTION-D
Answer 23.
(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
Answer 24.
(a) Polyembryony, nucellar cells surrounding embryosac 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
(a)
(1) 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
(2) 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)
(3) 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
Answer 25.
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, fittest will survive, who reproduce to leave more progeny
OR
(a) Graphical representation of the relationship among the organisms at different trophic
Pyramid of Energy | Pyramid of Bio Mass | Pyramid of Numbers |
Shows transfer of energy from one tropic level to other | Shows transfer of amount of food/biomass from one tropic level to other | Pyramid of numbers shows numbers of organism at each tropic level. |
Always upright. | Mostly upright but can be inverted. | Mostly upright can be inverted. |
(b) It does not accomodate the food web / does not take into account the same species belonging to two or more tropic levels, Saprophytes are not given any place
Answer 26.
(a) Clover-leaf shaped / inverted L shaped molecules has an anti codon loop with bases complementary to specific codon, has an amino acid acceptor end
As it reads the code on one hand and binds with the specific amino acid on the other hand.
(b) Introns are removed, exons are joined in a definite order
OR
Process of splicing shown diagramatically.
OR
It consists of one regulatory gene
(1), promotor 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 promotor and transcription proceeds, [l-galactosidasc, permease, transacetylase formed (by translation process for Lactose metabolism)
OR
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