Final answer:
Erythropoiesis may be triggered by hypoxia in erythropoietin (EPO)-producing cells, a circumstance that elicits EPO release to produce more red blood cells.
Step-by-step explanation:
The process that might trigger erythropoiesis is hypoxia in erythropoietin (EPO)-producing cells. Erythropoietin is a glycoprotein hormone secreted by the kidney in response to low oxygen levels. The bone marrow is stimulated by EPO to produce more red blood cells (RBCs), which are crucial for transporting oxygen throughout the body. Factors like moving to a lower altitude or a decreased tissue demand for oxygen would not typically trigger erythropoiesis, as they do not involve low oxygen levels. On the other hand, an increased number of erythrocytes would typically suppress erythropoiesis due to negative feedback mechanisms.