Excretion

Step 1: Understanding inheritance patterns.
Different genetic phenomena show characteristic phenotypic ratios depending on the number of genes involved and their interaction.
Step 2: Correct matching.
Pleiotropy in sickle cell anaemia shows a 2:1 ratio due to lethality in homozygous condition.
Polygenic inheritance in wheat kernel colour shows a 1:4:6:4:1 ratio.
Polygenic inheritance in human skin colour involves multiple genes producing a 16:15:20:15:6:1 ratio.
Co-dominance in cattle coat colour produces a 1:2:1 ratio.
Step 3: Verification.
Only option (A) correctly matches all inheritance patterns with their respective ratios.
Step 4: Conclusion.
Hence, option (A) is the correct answer.

Step 1: Understanding serum bilirubin levels.
Bilirubin is a product of the breakdown of red blood cells and is measured in the blood. The normal range for serum bilirubin is typically between 3 to 13 μmol/L in healthy individuals.
Step 2: Analyzing the options.
(A) 19 to 29: Incorrect, this value is higher than the normal range for serum bilirubin.
(B) 3 to 13: Correct, this is the typical normal range for serum bilirubin levels.
(C) 15 to 25: Incorrect, this is slightly higher than the normal range.
(D) 33 to 37: Incorrect, this range is significantly higher than normal, indicating possible liver dysfunction.
Step 3: Conclusion.
The correct answer is (B) 3 to 13, which is the normal range for serum bilirubin.

Step 1: Understanding tubular secretion.
Tubular secretion is the process by which substances are added to the renal fluid from the blood, typically in the distal tubules of the kidneys. This process includes the secretion of hydrogen ions, creatinine, and potassium ions, which are vital in regulating the body's fluid and electrolyte balance.
Step 2: Analyzing the options.
(A) hydrogen ions: Correct. Hydrogen ions are secreted into the renal fluid to help maintain pH balance in the body.
(B) creatinine: Correct. Creatinine is a waste product excreted by the kidneys and is secreted into the renal fluid.
(C) potassium ions: Correct. Potassium ions are also secreted during tubular secretion to regulate electrolyte balance.
(D) sodium ions: Incorrect. Sodium ions are reabsorbed, not secreted, during the tubular secretion process.
Step 3: Conclusion.
The correct answer is (D) sodium ions, as sodium ions are reabsorbed rather than secreted in the kidneys.

Step 1: Understanding the endocrine function of kidneys.
Kidneys are involved in hormone production, including the secretion of calcitriol, which is important for calcium homeostasis. Calcitriol is the active form of vitamin D.
Step 2: Analyzing the options.
(A) calcitriol: Correct. The kidneys secrete calcitriol, which is essential for regulating calcium levels.
(B) aldosterone: Incorrect. Aldosterone is secreted by the adrenal glands, not the kidneys.
(C) glucagon: Incorrect. Glucagon is produced by the pancreas, not the kidneys.
(D) vasopressin: Incorrect. Vasopressin (antidiuretic hormone) is produced by the pituitary gland, not the kidneys.
Step 3: Conclusion.
The correct answer is (A) calcitriol, as it is the hormone secreted by the kidneys that demonstrates their endocrine function.

Step 1: Understanding chlorophyll structure.
Chlorophyll–a is the primary photosynthetic pigment present in green plants and contains magnesium at its centre.

Step 2: Identifying correct formula.
The accepted empirical formula of chlorophyll–a is C H O N Mg.

Step 3: Conclusion.
Therefore, the correct answer is C H O N Mg}.