Sometimes when a virus enters a cell, it becomes dormant for a while. Why might this make it difficult for a doctor to diagnose a viral infection?

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

genetic variation will increase because of a new habitat and food source.

explanation:

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.