Beacuse they died long time ago
Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor.
Cells within the body are properly arranged and their production uses up resources of the body. For example, red blood cells use iron while being produced. The body must dispose of cell properly to maintain the orderly arrangement of cells; for example, if dead skin cells were not removed, we would lose feeling in our skin due to the layer of dead cells. Moreover, the body must work to minimize wastage. This is why some of the iron from red blood cells is removed and reused.
A. Transport? i could be wrong
Proteins serve as antibodies.
