Final answer:
Leukocytes come in different sizes, with monocytes being the largest and lymphocytes having the widest size range. These cells form an integral part of the body's immune system and are produced in the bone marrow.
Step-by-step explanation:
Leukocytes, also known as white blood cells, vary in size and are classified into different types based on their physical and functional characteristics. These cells are important components of the immune system and are produced in the bone marrow. According to size range, the largest leukocytes are typically monocytes which are around 12 to 20 micrometers (µm) in diameter. Followed by, in decreasing size, neutrophils (10-12 µm), eosinophils and basophils (both approximately 10-14 µm in diameter). Lastly, lymphocytes vary widely in size, with the smaller cells being approximately 6-9 µm and the larger ones 10-14 µm, and sometimes extending up to 17 µm.
It's important to also consider that leukocytes have a much shorter lifespan than erythrocytes, with some living only hours to days. They are far less numerous in the blood compared to red blood cells, and unlike erythrocytes, leukocytes are complete cells, consisting of both a nucleus and organelles.