The opening and closing of stomata is regulated by the:
A. Epidermal hairs
B. Xylem vessels
C. Phloem cells
D. Guard cells
Answer: Option D
Solution (By JKExamLibrary)
Stomata are surrounded by two kidney-shaped guard cells in dicots (dumb-bell-shaped in grasses) that control pore opening/closing via turgor pressure changes. When guard cells absorb water and become turgid, the stomatal pore opens; when flaccid, it closes. This process is influenced by light, CO₂ concentration, and abscisic acid (ABA). Stomata are critical for gas exchange and transpiration.
Consider the following statements about the blood:
1. Plasma is about 55% of blood volume.
2. Albumin is the most abundant plasma protein.
3. Red blood cells have nuclei in humans.
Which of the above is/are correct?
Explanation:
Fossils are direct evidence showing transitional forms. Lamarck proposed use and disuse, not natural selection. Analogous organs do not indicate common ancestry; homologous do. Appendix is vestigial.
Consider the following statements regarding photosynthesis:
1. Light reactions occur in the thylakoid membranes.
2. Oxygen is released from carbon dioxide.
3. ATP and NADPH are produced in the light reactions.
Which of the above is/are correct?
Explanation:
Light reactions occur in thylakoid membranes, producing ATP, NADPH, and oxygen. Oxygen comes from water (photolysis), not CO₂. So statement 2 is incorrect. 1 and 3 are correct.
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