PUNJAB PUBLIC SERVICE COMMISSION
COMBINED COMPETITIVE EXAMINATION FOR
RECRUITMENT TO THE POSTS OF
PROVINCIAL MANAGEMENT SERVICE-2025
BOTANY (PAPER-II)
TIME ALLOWED: THREE HOURS
MAXIMUM MARKS: 100
NOTE:
1. All the parts (if any) of each Question must be attempted at one place instead of at different places.
2. Write Q. No. in the Answer Book in accordance with Q. No. in the Q. Paper.
3. No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.
4. Extra attempt of any question or any part of the question will not be considered.
NOTE: Attempt FIVE Questions. Attempt in Urdu or English.
Q. No. 1: a) What do you understand by crop rotation? How can it help maintain the balance of nitrogen in the soil?
b) Write down the role of gibberellins in plant growth.
c) Define nitrogen fixation. How does it take place in nature?
Q. No. 2: a) How is pyruvic acid converted into carbon dioxide? Explain with the help of the Krebs cycle.
b) Differentiate between alcoholic and lactic acid fermentation.
c) Briefly explain oxidative phosphorylation.
Q. No. 3: Define soil erosion. Discuss in brief the various biological and mechanical methods of soil conservation. Discuss in detail the effects of air pollution on the atmosphere, vegetation, and human health.
Q. No. 5: a) Name different types of models of the structure of biological membranes. Describe the fluid-mosaic model in detail.
b) Write a note on mitochondria.
Q. No. 6: Compare the following:
(i) Transcription and translation
(ii) Transduction and transformation
(iii) DNA and RNA
(iv) Monohybrid cross and dihybrid cross (5×4=20 Marks)
Q. No. 7: How did Meselson & Stahl prove the semi-conservative model of DNA replication?
Q. No. 8: a) What does the Hardy-Weinberg law state? Describe its main assumptions.
b) What are the main causes of changes in gene frequencies?
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