Final answer:
Anemia is the condition that exists when the oxygen-carrying capacity of the blood is reduced, typically due to insufficient levels of hemoglobin in red blood cells. Conditions like sickle cell anemia and thalassemia are specific examples that negatively impact the blood's oxygen-delivery capability.
Step-by-step explanation:
Anemia exists when the oxygen-carrying capacity of the blood is reduced. This condition is characterized by insufficient levels of hemoglobin, the protein in red blood cells (RBCs) that is responsible for delivering oxygen to the body's tissues. Anemia can result from blood loss, the destruction of red blood cells, or a lack of red blood cell production. Diseases such as sickle cell anemia and thalassemia also reduce the blood's ability to carry oxygen. In sickle cell anemia, the red blood cells are abnormally shaped, impairing their journey through capillaries and reducing oxygen delivery. Thalassemia, a genetic disease, leads to a high quantity of RBCs but with lower-than-normal levels of hemoglobin, thus diminishing the oxygen-carrying capacity of the blood.