How can you tell if the human population as passd through the demographic transition

: The historical shift of birth and death rates from high to low levels in a population. The decline of mortality usually precedes the decline in fertility, thus producing rapid population growth during the transition period.

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.