All cells of the body age and are replaced in a natural order. when rbcs age, they are destroyed in the spleen. during this process, the iron from their hemoglobin is released into the circulation and returned?

Bone marrow.

Explanation:

Hematopiesis may be defined as the formation of the blood cells by the precursor stem cells. This process occurs in the bone marrow, thymus and liver.

The red blood cells are enucleated cells with the minimum span of around 120 days. These cells are processed and destroyed in the spleen. The iron is recovered from the red blood cells and sent again into the bone marrow for the production of new blood cells.

Thus, the answer is bone marrow.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

and after water is usually warmed by the sun the water temperature raises and then evaporates .