Which statement about stomata is INCORRECT?
A Guard cells regulate stomatal opening through osmotic potential changes
B Stomata open during night to minimize water loss
C Abscisic acid causes stomatal closure in stress conditions
D Potassium ion accumulation in guard cells causes stomatal opening
Correct Answer:
B. Stomata open during night to minimize water loss Explanation:
Stomata open during the day (when light is available for photosynthesis) and close at night. This reduces water loss during low photosynthetic activity periods.
Which of the following is a C4 plant commonly found in tropical regions?
A Wheat
B Rice
C Sugarcane
D Potato
Correct Answer:
C. Sugarcane Explanation:
Sugarcane is a C4 plant adapted to high light and temperature conditions. C4 plants first fix CO2 into a 4-carbon compound (oxaloacetate).
Which organelle is responsible for the synthesis of ribosomal RNA in plant cells?
A Ribosome
B Nucleolus
C Rough endoplasmic reticulum
D Golgi apparatus
Correct Answer:
B. Nucleolus Explanation:
The nucleolus within the nucleus is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly in eukaryotic cells.
Which of the following statements about plasmolysis is TRUE?
A Plasmolysis is the separation of cell wall from cell membrane
B Plasmolysis occurs in hypertonic solutions
C Plasmolysis leads to cell death immediately
D Both A and B
Correct Answer:
D. Both A and B Explanation:
Plasmolysis is the shrinkage of protoplasm away from the cell wall when placed in hypertonic solution. It's reversible if not prolonged.
A body is thrown vertically upward with a velocity of 40 m/s. What is the maximum height reached? (Take g = 10 m/s²)
A 80 m
B 40 m
C 160 m
D 120 m
Explanation:
Using v² = u² - 2gh, where final velocity v = 0, u = 40 m/s, g = 10 m/s². We get h = 1600/20 = 80 m
Which of the following is NOT a SI base unit?
A Ampere
B Kelvin
C Newton
D Mole
Correct Answer:
C. Newton Explanation:
Newton is a derived unit (kg⋅m⋅s⁻²). Ampere, Kelvin, and Mole are SI base units
A car moving at 20 m/s suddenly applies brakes with deceleration of 5 m/s². How far does it travel before stopping?
Explanation:
Using v² = u² + 2as, where v = 0, u = 20 m/s, a = -5 m/s². We get s = 400/10 = 40 m
What is the SI unit of pressure?
Correct Answer:
B. Pascal Explanation:
Pascal (Pa) is the SI unit of pressure, equal to 1 N/m²
Which phenomenon explains the formation of a rainbow?
A Refraction and dispersion
B Reflection only
C Diffraction only
D Interference only
Correct Answer:
A. Refraction and dispersion Explanation:
Rainbows form due to refraction of sunlight entering water droplets and dispersion of different wavelengths
What is the angle of incidence when light ray falls on a plane mirror and the angle of reflection is 35°?
Explanation:
According to law of reflection, angle of incidence equals angle of reflection
