Which of the following statements about the ozone layer is correct?
A. Ozone is composed of three oxygen atoms and is harmless at ground level.
B. It is depleted by increased CO₂ levels.
C. It absorbs harmful UV radiation.
D. It is located in the troposphere.
Answer: Option C
Solution (By JKSSB Mock Tests)
The ozone layer in the stratosphere absorbs most of the Sun's harmful UV radiation. CFCs, not CO₂, cause its depletion. Ozone at ground level is a pollutant. So B is correct.
Explanation:
Monocot stems have numerous vascular bundles scattered in the ground tissue. They are closed (lack cambium), collateral, and hence do not undergo secondary growth. Dicot stems have vascular bundles arranged in a ring, open (with cambium) allowing secondary growth. Radial vascular bundles are characteristic of roots. Scattered bundles are a key identifying feature of monocots.
Consider statements about cell biology: 1. The cell membrane is selectively permeable. 2. The nucleus contains genetic material. 3. Mitochondria are the site of photosynthesis. Which are correct?
Explanation:
The cell membrane (plasma membrane) is selectively permeable, regulating the passage of substances in and out of the cell to maintain internal homeostasis. The nucleus is the membrane-bound organelle that houses the cell's genetic material (DNA) organized into chromosomes, directing cellular activities. Mitochondria are the site of aerobic cellular respiration and ATP production; chloroplasts are the organelles where photosynthesis occurs in plant cells. Thus, statements 1 and 2 are correct.
Explanation:
The bacterial cell wall is a rigid structure that provides shape and protection. It is primarily composed of peptidoglycan (also known as murein), a polymer consisting of sugars and amino acids. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane. Cellulose is in plant walls, and chitin is in fungal walls.
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