Given a scientific question, generate a correct answer to it.

Ex Input:
When different types of tissues work together to perform a unique function, what do they form?

Ex Output:
organ

Ex Input:
What is a sac-like organ that stores urine?

Ex Output:
the urinary bladder

Ex Input:
What functions like a flexible coat of armor, preventing the protist from being torn or pierced without compromising its range of motion?

Ex Output:
pellicle