discuss the structure of flagellum and cillia with suitable diagram

They are fine hair like movable protoplasmic processes of the cells which are capable of producing a current in the fluid medium for locomotion and passage of substances.

Flagella are longer (100-200 µm) but fewer. Only 1-4 flagella occur per cell, e.g., many protists, motile algae, spermatozoa of animals, bryophytes and pteridophytes, choanocytes of sponges, gastro dermal cells of coelenterates, zoospores and gametes of thallophytes. Cilia are smaller (5-20 µm) but are numerous.

They occur in group ciliata of protista, flame cells of worms, larval bodies of many invertebrates, epithelium of respiratory tract, renal tubules, oviducal funnel, etc. Cilia present on the tracheal and bronchial epithelial cells are specialised to send back dust particles into the pharynx so that the lungs remain unharmed.

However, cigarette smoking reduces/stops ciliary activity so that air borne dust particles pass into the lungs of smokers causing irreparable harm. Both cilia and flagella are structurally similar and possess similar parts— basal body, rootlets, basal plate and shaft.