Assertion (A): The genetic code is universal. Reason (R): The same codon codes for the same amino acid in all organisms. MCQ with Answer and Explanation

Explanation:
Vitamin A (Retinol) is essential for the formation of rhodopsin (visual purple), a pigment in the rod cells of the retina necessary for vision in low light conditions. Deficiency of Vitamin A leads to night blindness (nyctalopia), where a person has difficulty seeing in dim light. Severe deficiency can also cause xerophthalmia and complete blindness.

Explanation:
Antonie van Leeuwenhoek, a Dutch linen merchant and amateur scientist, is known as the 'father of microbiology'. Using his own handcrafted, high-quality single-lens microscopes, he was the first person to observe and describe living, single-celled organisms, which he called 'animalcules' (little animals). These included bacteria, protozoa, and sperm cells, in the late 17th century.

Explanation:
Osmosis is the special case of diffusion of water across a semipermeable membrane down its concentration gradient (from high to low water potential). It does not require energy. Diffusion refers to solute movement, active transport requires energy against a gradient, and plasmolysis is the shrinking of protoplasm due to water loss.