The disease caused by the bacterium Corynebacterium diphtheriae is: MCQ with Answer and Explanation

Explanation:
A food chain is a linear, simplified sequence showing the transfer of energy and matter from one organism to another through consumption. A food web is a more realistic, complex network of interconnected food chains, illustrating the multiple feeding relationships and pathways of energy flow in an ecosystem. While nutrients (matter) are continuously recycled in an ecosystem through biogeochemical cycles, energy flows unidirectionally and is eventually lost as heat; it is not recycled. Thus, statements 1 and 2 are correct.

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:
The proximal convoluted tubule (PCT) reabsorbs about 70-80% of electrolytes and water, and almost 100% of glucose, amino acids, and vitamins back into the blood via active transport and facilitated diffusion. The loop of Henle concentrates urine, the DCT reabsorbs sodium and water under hormonal control, and the collecting duct reabsorbs water (ADH-dependent). PCT cells have microvilli for increased surface area.