UPSC Civil Services Mains Exam: Botany Optional 2018 Paper-II
Baljit Dhaka

UPSC Civil Services Mains Exam: Botany Optional 2018 Paper-II

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UPSC Civil Services Mains Exam: Botany Optional 2018 Paper-II

Marks-250                                                                                                                                   Time: Three Hours

Question Paper Specific Instructions:

Please read each of the following instructions carefully before attempting questions.

  • There are EIGHT questions divided into two sections.
  • A candidate has to attempt FIVE questions in all.
  • Questions no 1 and 5 are compulsory and out of the remaining, THREE are to be attempted choosing at least ONE from each section.
  • The number of marks carried by a question /part is indicated against it.
  • Word limit in questions, wherever specified should be adhered to.
  • Attempts of questions shall be counted in chronological order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the answer book must be clearly struck off.


Q1 Answer the following questions: 10x5=50 marks

(a) "Organelles bound by membranes in eukaryotic cells have originated from endosymbiosis of prokaryotic cells." Explain

this statement with the help of some suitable diagrams. 10 marks

(b) Gray seed colour in peas is dominant over the white. In the following experiments, parents with known phenotypes but unknown genotypes produced the following progeny:
Parents Progeny
Gray White
Gray x Gray 82 78

(ii) Gray x Gray 118 39

(iii) White x White 0 50

(iv) Gray x White 74 0

(v) Gray x Gray 90 0
Using the letter G for gray and g for white, give the genotype of each parent. 10 marks

(c) Explain the concept of multiple alleles with one example. 10 marks

(d) Why is RNA considered as the first living molecule ? Discuss its role in the origin of life. 10 marks

(e) Briefly describe the different methods of gene transfer in plants. 10 marks

Q2.(a) Briefly discuss the cellular function of mitochondria and endoplasmic reticulum with required diagrams. 20 marks

(b) How are insect resistant transgenic plants developed ? Which gene is used in this technology ? Briefly explain the rationale of the technology. 20 marks

(c) Which statistical test is used to determine whether the observed progeny of a cross fits or differs from the expected values ? Name the test and briefly describe the steps involved. 10 marks

Q3.(a) Discuss the role of cyclin-dependent protein kinases in controlling the cell cycle. Explain with the help of a diagram. 20 marks
(b) (i) Explain the synthetic theory of organic evolution, 10 marks

(ii) Enumerate the different causes of heterosis. 10 marks

(c) Explain the importance of the following techniques : 10 marks

(i) FISH

(ii) Molecular probe

Q4.(a) Briefly describe the following terms and emphasize their applications: 15 marks
(i) Restriction endonucleases

(ii) Mutation breeding

(iii) Gene mapping

(b) Describe with suitable diagram, the lac operon of bacterium E. Coli. Discuss the control mechanism of the operon which produces the enzymes necessary for catabolizing the lactose. 20 marks

(c) Describe the structure and function of Plasmodesmata. 15 marks

5. Describe the following in about 150 words each:
Q5. Explain each of the following:

(a) Water potential 10 marks

(b) Glycolysis 10 marks

(c) Phloem loading 10 marks

(d) Phytogeographical regions of India 10 marks

(e) Components of an ecosystem 10 marks

Q6. (a) What is Phosphorylation ? Differentiate between photophosphorylation and oxidative phosphorylation. 20 marks

(b) What is red data book ? Describe it. Discuss the various IUCN threat categories. 20 marks

(c) How do plants monitor day length ? Discuss the various categories of plants based on their photoperiodic responses. What happens when the dark period is interrupted by night break and why? 20 marks

Q7. (a) What is ecological succession ? Discuss the various models describing the mechanism of succession. 15 marks

(b) Define plant community. Discuss the various analytical characters of plant community. 15 marks

(c) Define enzyme, prosthetic groups, coenzymes and isoenzymes, Discuss the mechanism of enzyme action. 20 marks

Q8. (a) Describe C4 pathway of CO, fixation. Discuss the advantages that the C4 plants have over C3 plants. 20 marks

(b) What is biodiversity ? Discuss the major strategies for the conservation of biodiversity. 15 marks

(c) Define natural forests and mention the name of the forest type covering the maximum area in India. Discuss the major forest types in India as described by Champion and Seth. 15 marks