Final answer:
Erythropoietin (EPO), a hormone released by the kidneys, stimulates the production of red blood cells in the bone marrow in response to low oxygen levels in the blood.
Step-by-step explanation:
Erythropoietin (EPO), a glycoprotein hormone secreted by the kidneys, stimulates the production of red blood cells (erythrocytes) in the bone marrow. EPO is released in response to low oxygen levels in the blood. When there is an oxygen deficiency, the kidneys release EPO, which then triggers erythropoiesis, the production of new red blood cells. This helps to increase the oxygen-carrying capacity of the blood and ensure that enough oxygen is delivered to tissues throughout the body.