ABSTRACT
Planet Earth is unique in our solar system, its size and the distance from the
sun allowing a crucial signiicant range of temperature and the existence
of both liquid water and water vapor. Solid water, as ice, also exists in cold
conditions, mainly near the poles and at altitudes, but Earth is dominated
by land masses between oceans and water vapor above them. Water, as we
already saw before in previous chapters of this book, is actually the key
molecule for the living. Life appeared and developed in water. Living beings
are constituted of water. Without water, a land rapidly becomes a desert with
very poor and specialized life, or without life. Water is life: take a look at
the periphery of a Chilean desert, which receives rainfall only every 10-12
years. In a matter of days it is covered by lowers (with the requisite cortege
of insects!) that last for a few weeks, the temporary ecosystem returning to
its extreme arid state for the next years. This is a natural phenomenon, but
humans can also cause an explosion of life by irrigating the desert. So, life
emerged from water and is constituted by water! We propose to successively
present here the relationships between water and life origin and emergence
from the ocean, water in biodiversity, and the major facts in terms of water
and ion metabolism before concluding.
