EVERYDAY SCIENCE

Detailed explanation-1: -Platelets and megakaryocytes are found in all three clades of mammals but not in reptiles. Therians, i.e. eutherians and marsupials, share viviparity. In reptiles, the mode of reproduction is variable.

Detailed explanation-2: -Platelets are found only in the blood of mammals. Platelets are formed when cytoplasmic fragments of megakaryocytes, which are very large cells in the bone marrow, pinch off into the circulation as they age. They are stored in the spleen. Hence, option C is the correct answer.

Detailed explanation-3: -A tiny, disc-shaped piece of cell that is found in the blood and spleen. Platelets are pieces of very large cells in the bone marrow called megakaryocytes. They help form blood clots to slow or stop bleeding and to help wounds heal.

Detailed explanation-4: -Birds have high-pressure cardiovascular systems like mammals but generate nucleated thrombocytes rather than platelets.

Detailed explanation-5: -Platelets are formed and released into the bloodstream by precursor cells called megakaryocytes that reside within the bone marrow. The production of platelets by megakaryocytes requires an intricate series of remodeling events that result in the release of thousands of platelets from a single megakaryocyte.