Answer:
Erythrocytes are not considered true cells, because of their lack of a nucleus. The effect of having no nucleus makes their self-reproduction impossible, and the absence of mitochondria is a disadvantage because they have to obtain energy by alternative reactions.
Step-by-step explanation:
Erythrocytes, or red blood cells, are the structure in charge of transporting gases in the blood. When these cells are mature, they have already lost their nucleus —in order to have space to house the hemoglobin molecule— which prevents mature red blood cells from being able to reproduce.
Additionally, red blood cells do not have mitochondria —the main energy generator in eukaryotic cells— so in order to obtain energy they need to perform lactic fermentation, with a lower enegetic yield, which may be a disadvantage, but sufficient for this structure to perform its function.