Daily Updated

Current Affairs Hub

Rozana naye current affairs MCQs — SSC, UPSC, Bank, Railway sab ke liye.

Daily
Auto Updated
National
India News
Free
Always Free
Current Affairs Quiz
Advertisement
Showing 51–60 of 96 questions
Q.51 Medium Physics
A lens has a focal length of 15 cm. What is its power?
A +6.67 D
B -6.67 D
C +2.25 D
D -2.25 D
Correct Answer:  A. +6.67 D
Explanation:

Power P = 1/f (in meters). P = 1/0.15 = 6.67 Diopters (positive for converging lens)

Take Test
Q.52 Medium Botany
The rate of photosynthesis increases with an increase in CO2 concentration until it reaches a plateau. This plateau is called:
A Compensation point
B Saturation point
C Optimum point
D Threshold point
Correct Answer:  B. Saturation point
Explanation:

The saturation point is the CO2 concentration beyond which photosynthesis rate does not increase further, limited by other factors like temperature or light.

Take Test
Q.53 Medium Botany
Which of the following is a chemosynthetic organism commonly found in soil?
A Cyanobacteria
B Nitrosomonas
C Chlorella
D Spirogyra
Correct Answer:  B. Nitrosomonas
Explanation:

Nitrosomonas is a chemosynthetic bacterium that oxidizes ammonia to nitrite, obtaining energy without requiring light (unlike photosynthetic organisms).

Take Test
Q.54 Medium Botany
The phenomenon of senescence in plants is primarily controlled by which hormone?
A Gibberellin
B Cytokinin
C Abscisic acid
D Ethylene
Correct Answer:  D. Ethylene
Explanation:

Ethylene is the major hormone controlling senescence (aging) in plants, promoting leaf yellowing, fruit ripening, and abscission.

Take Test
Q.55 Medium Botany
Which of the following transport mechanisms does NOT require energy in plant cells?
A Active transport of mineral ions
B Osmosis across the cell membrane
C Uptake of glucose by epidermal cells
D Loading of sugars in sieve tubes
Correct Answer:  B. Osmosis across the cell membrane
Explanation:

Osmosis is passive transport of water molecules across a semipermeable membrane in response to water potential differences.

Take Test
Advertisement
Q.56 Medium Botany
Which plant hormone is known to have antagonistic effects to gibberellins in seed germination?
A Cytokinin
B Abscisic acid
C Ethylene
D Auxin
Correct Answer:  B. Abscisic acid
Explanation:

Abscisic acid (ABA) promotes seed dormancy and inhibits germination, acting antagonistically to gibberellins which promote germination.

Take Test
Q.57 Medium Botany
The phenomenon where plants lose water as liquid droplets from leaf margins is called:
A Transpiration
B Exudation
C Imbibition
D Osmosis
Correct Answer:  B. Exudation
Explanation:

Exudation or guttation occurs when root pressure forces water out through specialized pores (hydathodes) as liquid water droplets, typically observed in early morning.

Take Test
Q.58 Medium Botany
C3 plants show a phenomenon of photorespiration. What is the primary substrate that reacts with RuBP when O2 concentration is high?
A Phosphoenolpyruvate
B Phosphoglycolate
C Oxygen (O2)
D Carbon monoxide
Correct Answer:  C. Oxygen (O2)
Explanation:

When O2 concentration is high, RuBisCO catalyzes oxygenase activity, causing O2 to react with RuBP instead of CO2, initiating photorespiration.

Take Test
Q.59 Medium Botany
The reduction phase of Calvin cycle produces which molecule as the final product?
A Pyruvate
B Glucose
C Glyceraldehyde-3-phosphate
D Oxaloacetate
Correct Answer:  C. Glyceraldehyde-3-phosphate
Explanation:

G3P (Glyceraldehyde-3-phosphate) is the final product of the reduction phase where 3-PG is reduced using ATP and NADPH from light reactions.

Take Test
Q.60 Medium Botany
The non-cyclic photophosphorylation in photosystem II produces:
A ATP only
B NADPH only
C Both ATP and NADPH, and releases O₂
D Glucose directly
Correct Answer:  C. Both ATP and NADPH, and releases O₂
Explanation:

Non-cyclic photophosphorylation involves PSII and PSI, producing ATP, NADPH, and O₂ from water photolysis.

Take Test
IGET
iget AI
Online · Ask anything about exams
Hi! 👋 I'm your iget AI assistant.

Ask me anything about exam prep, MCQ solutions, study tips, or strategies! 🎯
UPSC strategy SSC CGL syllabus Improve aptitude NEET Biology tips