Final answer:
In anemia, the oxygen affinity of hemoglobin decreases, despite the oxygen pressure remaining unchanged, due to altered hemoglobin or reduced red blood cell count.
Step-by-step explanation:
Individuals with anemia exhibit decreased affinity for O₂ with the same oxygen pressure. Anemia affects the oxygen-carrying capacity of the blood due to either a decreased number of red blood cells or a reduced amount of hemoglobin within those cells. In conditions such as sickle cell anemia or thalassemia, the shape or amount of hemoglobin is altered, impairing the blood's ability to deliver and carry oxygen. As oxygen pressure remains unchanged in an anemic individual, the affinity of hemoglobin for oxygen decreases, causing a right shift in the oxygen dissociation curve.