Final answer:
Leukocytes indeed move through the circulatory system and tissues by amoeboid motion, exiting the capillaries via emigration or diapedesis and following chemical signals through positive chemotaxis.
Step-by-step explanation:
To answer your question about leukocytes and their movement, it is true that leukocytes move through the circulatory system by amoeboid motion. While erythrocytes, or red blood cells, remain within the blood vessels to transport oxygen, leukocytes have a different set of tasks that often require them to leave the bloodstream. These white blood cells exit the smallest blood vessels, known as capillaries, through a process called emigration or diapedesis. Once outside the capillaries, they move through tissue spaces in a manner similar to amoebas, which involves extending their plasma membranes and creeping along tissues. This movement is oriented and can be influenced by chemical signals - a process known as positive chemotaxis - where they respond to distress signals from infected or damaged cells, moving toward the source to provide a defense response. This detailed explanation includes the key terms amoeboid motion, emigration or diapedesis, and positive chemotaxis.