Night blindness is caused by the deficiency of which vitamin? MCQ with Answer and Explanation

Explanation:
Collenchyma is a simple permanent tissue with living cells, unevenly thickened primary cell walls (cellulose and pectin), providing mechanical support and flexibility, especially in young stems and leaf petioles. Parenchyma is for storage and metabolism, sclerenchyma is dead, rigid with lignified walls, xylem conducts water.

Explanation:
Vitamin D (calcitriol) stimulates the production of calcium-binding proteins in the intestinal lining, enhancing calcium absorption. Deficiency leads to rickets/osteomalacia. Vitamin A is for vision, C for collagen, B₁₂ for nerve function.

Explanation:
Reptiles generally have a three-chambered heart with two atria and one partially divided ventricle; crocodiles are an exception with a four-chambered heart. Amphibians have a three-chambered heart with two atria and one undivided ventricle. Mammals and birds have four-chambered hearts. This adaptation reflects their metabolic demands and evolutionary advancement.