Removal and microscopic examination of a tissue sample to determine if cancer is present is a(n)

Biopsy

A biopsy is a medical test, which involves the removal or extraction of sample cells or tissues from the patient in order to examine the samples for the presence or extent of a disease. The cells or tissues are usually examined under a microscope and sometimes by chemical means as well. Biopsies are commonly performed in the diagnosis or examination of possible cancerous or inflammatory conditions. 

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.