2.5 Water As Medium of Life

Introduction

Water is one of the main constituents on earth. Origin, sustainability, and continuity of life depend on water. More than two-thirds of the earth is covered by water. Distribution of life on earth is directly proportional to the availability of water — for example, deserts have few living organisms whereas rivers and oceans are full of life. Approximately 70 percent of any organism is formed of water.

Definition

Water as Medium of Life: Water is the most abundant component in any organism and is the medium in which all life processes occur.

In simple words: Water is essential for life and is the liquid in which all life activities take place.

Core Concept

• Water is the most abundant component in any organism.
• The lowest water content is 20% in seeds and bones.
• The highest water content is 85–90% in brain cells.
• Jellyfish has an exceptionally large amount of water — 99% — making the body of jellyfish transparent.
• Water is essential for all life processes.

Detailed Explanation

Distribution of Water

• More than two-thirds of the earth is covered by water.
• Distribution of life on earth is directly proportional to the availability of water.
• Deserts have few living organisms.
• Rivers and oceans are full of life.

Water Content in Organisms

Science Tidbits (from textbook)

Important Note: Involvement of water in hydrolysis reactions should not be confused with making a solution. Water does not act as a solvent in hydrolysis — it takes part in a chemical reaction. Also, do not assume that this breakdown releases energy, as produced when simpler substances are oxidized in respiration. Hydration is yet another completely different process, involving the addition of water, but not breaking of bonds.