Final answer:
Cilia serve as extensions of the cell membrane that can perform various functions, including clearing mucus in the respiratory tract and moving food particles in protozoans, as well as aiding in the movement of egg cells in the fallopian tubes.
Step-by-step explanation:
Cilia are microscopic extensions of the apical cell membrane that play various roles in organisms. Cilia in human lung cells, for instance, function to sweep foreign particles and mucus toward the mouth and nose, assisting in keeping the respiratory tract clear of debris and pathogens.
Another key function of cilia is in the female reproductive system. Cilia lining the fallopian tubes aid in moving the ovum, or egg cell, from the ovary toward the uterus, which is critical for fertilization to occur. These diverse functions of cilia showcase their importance in both single-celled organisms for feeding and locomotion, and in multicellular organisms for maintaining health and facilitating reproduction.