Final answer:
Red blood cells do not contain a nucleus at maturity. Shedding their nucleus allows more space for hemoglobin, enabling the efficient delivery of oxygen to tissues.
Step-by-step explanation:
Red blood cells, also known as erythrocytes, do not contain a nucleus at maturity. As erythrocytes mature in the red bone marrow, they shed their nucleus and most of their other organelles. This allows them to have more space for hemoglobin, which is responsible for carrying and delivering oxygen to the tissues. Without a nucleus, erythrocytes can change shape to squeeze through capillaries and deliver oxygen efficiently.