Figure 1. Terrestrial species evolved from creatures that originated in the ocean.

A. As life invaded land, it carried with it some of the ocean water. The drawing was taken from the Delpire laboratory website at Vanderbilt University Medical center: https://www.vumc.org/delpire-lab/. B. In humans, and most terrestrial species, water is constantly lost through perspiration/evaporation from the skin, exhalation from the lungs, urination from the bladder, and feces from the colon. To maintain water homeostasis (in = out), an equivalent amount of water needs to be consumed through drinking and food.