With the final date announced for the CBSE class 12 Biology paper that is 5th April, 2017, students appearing for the exam must have geared up for the final revisions. Now it’s important for the students to utilize this mean time more cautiously by following the best strategic study plan. The best practice would be solving the previous years’question papers which will not only help you to track your performance but also to understand the exam pattern and marking trends. Moreover, it will give a clear overview of the types of questions asked in the board exam.
Jagranjosh here brings a collection of Class 12 Biology Last 5+1 years’ long answer type questions to help the students get a firm grip over the type of questions that are probably going to be asked in the upcoming board exam. At the there are also given the value based questions that asked in previous years’ CBSE Class 12 Biology question papers.
As per the latest exam pattern in CBSE Class 12 Biology paper which comprises of four sections, Sectior D contains question number 23, value based question carrying 4 marks and Section E contains questions number 24 to 26, long-answer type questions of 5 marks each.
1. (a) Draw a diagram of an enlarged view of T.S. of one microsporangium of an angiosperm and label the following parts:
(ii) Middle layer
(iv) Microspore mother cells
(b) Mention the characteristic features and function of tapetum.
(c) Explain the following giving reasons:
(i) Pollen grains are well preserved as fossils.
(ii) Pollen tablets are in use by people these days.
(a) Why is the process of fertilisation in angiosperms termed as double fertilisation ? Explain.
(b) Draw a diagram of an angiospermic embryo-sac where fertilisation is just completed. Label the following parts :
(i) Micropylar end of the embryo-sac
(ii) The part that develops into an embryo
(iii) The part that develops into an endosperm
(iv)The degenerating cells at the chalazal end
(c) Draw a labelled diagram of globular embryonic stage of an angiosperm.
2. Name the process involved in the production of nematode-resistanttobacco plants, using genetic engineering. Explain the strategy adopted to develop such plants.
Describe the various stages involved in gene transfer for the commercial production of human insulin by Eli Lilly.
3. Trace the life-cycle of malaria parasite in the human body when bitten by an infected female Anopheles.
4. List the salient features of double helix structure of DNA.
How are the structural genes activated in the lac operon in C. coil?
5. Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples.
6. (a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.
(b) Name the vector used for introducing the nematode specific gene in tobacco plant.
7. (a) Taking one example each of habitat loss and fragmentation, explain how are the two responsible for biodiversity loss.
(b) Explain two different ways of biodiversity conservation.
(a) What depletes ozone in the stratosphere? How does this affect human life?
(b) Explain biomagnification or DDT in an aquatic food chain. How does it affect the bird population?
(a) Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.
(b) Specify the endocrine function of corpus luteum. How does it influence the uterus Why is it essential?
(c) What is the difference between “d” and “e”?
(d) Draw a neat labelled sketch of Graafian follicle.
(a) Why is Fertilisation in an angiosperm referred to as double fertilisation? Mention
the ploidy of the cells involved.
(b) Draw a neat labelled sketch of L.S. of an endospermous monocot seed.
9. Describe Frederick Griffith's experiment on Streptococcus pneunnoniae. Discuss the conclusion he arrived at.
(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross.
10. (a) Draw a diagrammatic sectional view of a human seminiferous tubule and label sertoli cells, primary spematocyte, spermatogonium and spermatozoa in it.
(b) Explain the hormonal regulation of the process of spermatogenesis in human
11. (a) Draw a L.S of a pistil showing pollen tube entering the embryo sac in and angiosperm and label any six part other than stigma, style and ovary
(b) Write the changes a fertilized ovule undergoes within the ovary in an angiosperm plant.
12. (a) What is the conclusion drawn by Griffith at the end of his experiment with Streptococcus pneumonia.
(b) How did Oswald Avery, Colin MacLeod and Maclyn McCarty prove that DNA was the genetic material, Explain?
(a) Explain the mechanism of sex determination in human
(b) Differentiate between male heterogamety and female heterogamety with the help of an example.
13. Describe the Hershey and Chase experiment. Write the conclusion drawnby the scientists after their experiment.
Work out on a typical Mendelian dihybrid cross and state the law that he derived from it.
14. With advancements in genetics, molecular biology and tissue culture,new traits have been incorporated into crop plants.Explain the main steps in breeding a new genetic variety of a crop.
(a) State the objective of animal breeding.
(b) List the importance and limitations of inbreeding. How can thelimitations be overcome?
(c) Give an example of a new breed each of cattle and poultry.
15. (a) Where does fertilization occur in humans? Explain the events that occur during this process.
(b) A couple where both husband and wife are producing functional gametes, but the wife is still unable to conceive, is seeking medical aid. Describe any one method that you can suggest to this couple to become happy parents.
(a) Explain the different ways apomictic seeds can develop. Give an example of each.
(b) Mention one advantage of apomictic seeds to farmers.
(c) Draw a labelled mature stage of a dicotyledonous embryo.
16. (a) List the different attributes that a population has and not an individual organism.
(b) What is population density? Explain any three different ways by which the population density can be measured, with the help of an example for each.
It is often said that the pyramid of energy is always upright On the other hand, the pyramid of biomass can be both upright and inverted. Explain with the help of examples and sketches.
17. (a) Plan an experiment and prepare a flow chart of the steps that you would follow to ensure that the seeds are formed only from the desired sets of pollen grains. Name the type of experiment that you carried out.
(b) Write the importance of such experiment
Describe the roles of pituitary and ovarian hormones during the menstrual cycle in a human female.
18. (a) Why are colour blindness and thalassemia categorised as mendelina disorders ? Write the symptoms of these diseases seen in people suffering from them.
(b) About 8% of human male population suffers from colour blindness whereas only about 04% of human female population suffers from this disease. Write an explanation to show how it is possible.
Explain the process of transcription in prokaryotes.How is the process different in eukaryotes?
19. (a) Explain the menstrual phase in a human female. State the levels of ovarian and pituitary hormones during this phase.
(b)Why is follicular phase in the menstrual cycle also referred as proliferative phase? Explain.
(c) Explain the events that occur in a graafian follicle at the time of ovulation and thereafter.
(d) Draw a graafian follicle and label antrum and secondary oocyte.
(a) As a senior biology student you have been asked to demonstrate to the students of secondary level in your school, the procedure(s) that shall ensure cross-pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each one of them.
(b) Draw a diagram of a section of a megasporangium of an angiosperm and label funiculus, micropyle, embryosac and nucellus.
20. Describe Meselson and Stahl’s experiment that was carried in 1958 on E. Coli. Write the conclusion they arrived at after the experiment.
(a) Describe the process of transcription in bacteria.
(b) Explain the processing the hnRNA needs to undergo before becoming functional mRNA in eukaryotes.
21. (a) Name the two growth models that represent population growth and draw the respective growth curves they represent.
(b) State the basis for the difference in the shape of these curves.
(c) Which one of the curves represent the human population growth at present? Do you think such a curve is sustainable? Give reason in support of your answer.
(a) Taking an example of a small pond, explain how the four components of an ecosystem function as a unit.
(b) Name the type of food chain that exists in a pond.
Value based questions carrying 4 marks each:
1. Person in your colony has recently been diagnosed with AIDS. People/residents in the colony want him to leave the colony for the fear of spread of AIDS.
(a) Write your views on the situation giving reasons.
(b) List the possible preventive measures that you would suggest to the residents of your locality in a meeting organised by you so that they understand the situation.
(c) Write the symptom and causative agent of AIDS
2. Community Service department of your school plans a visit to a slumarea near the school with an objective to educate the slum dwellers withrespect to health and hygiene.
(a) Why is there a need to organise such visits?
(b) Write the steps you will highlight, as a member of this department, in your interaction with them to enable them to lead a healthy life.
3. Your school has been selected by the Department of Education to organize and host an inter school seminar on “Reproductive Health - Problems and Practices”. However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is “too
embarrassing”. Put forth four arguments with appropriate reasons and explanation to justify the topic to be very essential and timely.
4. A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being child less.
(a) Why in your opinion the female partner is often blamed for such situations in India? Mention any two values that you as a biology student can promote to check this social evil.
(b) State any two reasons responsible for the cause of infertility.
(c) Suggest a technique that can help the couple to have a child where the problem is with the male partner.