Which of the following is a characteristic feature of mammals?
A. Presence of feathers
B. Cold-blooded metabolism
C. Presence of mammary glands
D. Lay eggs only
Answer: Option C
Solution (By JKExamLibrary)
Mammals are distinguished by the presence of mammary glands in females that secrete milk for nourishing young. They are warm-blooded, have hair/fur, and most give birth to live young (viviparous), though monotremes like platypus lay eggs. Feathers are characteristic of birds. Cold-blooded refers to ectotherms (reptiles, amphibians, fish). Mammals are endotherms.
The hormone aldosterone, which acts on the distal convoluted tubule and collecting duct to increase sodium reabsorption and potassium excretion, is secreted by the:
Explanation:
Aldosterone is a mineralocorticoid hormone secreted by the zona glomerulosa, the outermost layer of the adrenal cortex. Its primary function is to regulate electrolyte balance by promoting the active reabsorption of sodium (Na+) and the excretion of potassium (K+) and hydrogen ions (H+) in the distal tubules and collecting ducts of the kidneys. The zona fasciculata secretes glucocorticoids (cortisol).
Explanation:
Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in synthesis of lipids, steroid hormones, and detoxification of drugs and toxins via cytochrome P450 enzymes. Rough ER is for protein synthesis, Golgi for packaging, lysosomes for digestion. SER is abundant in liver and gonadal cells.
Explanation:
Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis, spreading through airborne droplets. Cancer, diabetes, and hypertension are non-communicable.
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