Final answer:
The presence of partially digested membranes of other organelles and cellular debris in a secondary lysosome provides evidence of phagocytosis in the cell.
Step-by-step explanation:
The presence of partially digested membranes of other organelles and cellular debris in a secondary lysosome provides evidence that phagocytosis is occurring in the cell.
Phagocytosis is the process in which a section of the plasma membrane invaginates and engulfs a pathogen or cellular debris. The invaginated section, along with the engulfed material, forms a vesicle that fuses with a lysosome. The lysosome's hydrolytic enzymes then break down and digest the engulfed material.