Biology

Step 1: Understand the role of aldosterone.
Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex. It plays a critical role in maintaining sodium and potassium levels in the body, thereby helping to regulate blood pressure and fluid balance.
Step 2: Mechanism of action.
Aldosterone acts mainly on the distal convoluted tubules and collecting ducts of the nephrons in the kidneys. Its effects include:
Increasing reabsorption of sodium ions (Na⁺) into the blood.
Promoting reabsorption of water (H₂O) indirectly, because water follows sodium osmotically.
Enhancing excretion of potassium ions (K⁺) into the urine.
Promoting excretion of phosphate ions (PO₄^3-) as a part of maintaining electrolyte balance.
Step 3: Evaluate the options.
Option (1): Correct — This matches the physiological role of aldosterone.
Option (2): Incorrect — Aldosterone does not stimulate K⁺ reabsorption.
Option (3): Incorrect — Aldosterone promotes Na⁺ reabsorption, not its excretion.
Option (4): Incorrect — Aldosterone promotes K⁺ excretion, but not PO₄^3- reabsorption.

Step 1: Understand the metabolic classification
The prefix "chemo" means it obtains energy from chemical compounds (not light).
"litho" indicates the electron donor is inorganic.
"heterotroph" indicates it depends on organic carbon for its carbon source.
Step 2: Apply this to Beggiatoa
Beggiatoa uses inorganic chemicals as an electron donor litho
It depends on organic carbon heterotroph
Its energy is derived from chemical reactions chemo
Conclusion: Therefore, Beggiatoa is correctly classified as a Chemolithoheterotroph.

Step 1: Prophase (A - III)
During prophase, the chromatin condenses into visible chromosomes. Therefore, condensation of DNA into chromatids (III) occurs in prophase.
Step 2: Metaphase (B - IV)
In metaphase, the chromosomes align themselves along the metaphase plate (equatorial axis). Thus, chromatids line up along an axis (IV).
Step 3: Anaphase (C - II)
During anaphase, the centromeres split and sister chromatids are pulled toward opposite poles. Hence, separation of daughter chromosomes (II) occurs.
Step 4: Telophase (D - I)
In telophase, the nuclear envelope reforms around the chromosomes at each pole, so reformation of the nuclear envelope (I) is correct.

Step 1: Understanding types of metabolic pathways.
Metabolic pathways can be categorized as:
Catabolic (breakdown of molecules to release energy),
Anabolic (synthesis of complex molecules), and
Amphibolic (functioning both as anabolic and catabolic).
Step 2: Nature of respiratory pathway.
The respiratory pathway (like glycolysis, Krebs cycle) primarily breaks down glucose to release energy, making it catabolic. However, intermediates of the pathway are also used for biosynthetic (anabolic) processes such as synthesis of amino acids and nucleotides.
Step 3: Conclusion.
Since it serves both anabolic and catabolic functions, the respiratory pathway is termed amphibolic.