Quadrat - 

A small rectangular plot laid off, as in a forestAn area with many trees., rangeIn biology, the total area in which an individual or species can be found., pasture, or cultivated field, for the study of vegetation or animals. Also called a quadrant.

Quarantine - 

To isolate for the purpose of preventing the spread of contagious diseases.

Quill - 

A hollow, sharp spineA stiff, sharp projection on an animal; another word for quill., made of modified hair, found on the backs of animals such as porcupines, hedgehogs, and echidnas. The hollow shaft of a feather, or a type of feather.