The scientist who discovered the bacterium that causes plague (Yersinia pestis) was: MCQ with Answer and Explanation

Explanation:
Platelets (thrombocytes) are small, anucleate cell fragments that adhere to the site of injury, release clotting factors, and aggregate to form a platelet plug, initiating the coagulation cascade. RBCs transport oxygen, WBCs defend against infection, and plasma proteins like albumin maintain osmotic balance. Clotting factors are also present in plasma, but platelets are the primary cellular component.

Explanation:
Zinc is a micronutrient that acts as a cofactor for tryptophan synthetase, an enzyme involved in the biosynthesis of the auxin indole-3-acetic acid (IAA) from tryptophan. Zinc deficiency causes stunted growth and 'little leaf' disease. Iron is for chlorophyll synthesis, copper for enzymes, manganese for photosystem II.

Explanation:
Habitat refers to the physical environment where an organism lives (address), whereas niche refers to its functional role in the ecosystem (profession), including interactions and resource use. Ecosystem is the community plus abiotic factors, biome is a large ecological area with similar climate and vegetation. A pond habitat can have various niches.