Final answer:
Water is crucial for life because it constitutes a major portion of living organisms and is involved in essential processes such as nutrient transport and temperature regulation. Freshwater is scarce, yet vital for human use and ecosystems. The search for water on other planets may indicate potential for life.
Step-by-step explanation:
Water is essential to all life on Earth because it plays a critical role in numerous biological and chemical processes. Water makes up approximately 60-70 percent of the human body and is involved in cellular processes such as nutrient transport, chemical reactions, and temperature regulation. Beyond its importance in organisms, water is a key ingredient for creating an environment where life can thrive, indicated by the fact that scientists actively search for water on other planets as a sign of potential life.
On our planet, the majority of water is found in the oceans, constituting over 97% of Earth's water, making it saline and unsuitable for direct human consumption or use in agriculture. Freshwater resources, which humans and many terrestrial ecosystems rely on, account for only a small fraction of the global water supply.
The unique properties of water, such as its ability to dissolve a wide variety of substances and its solid form (ice) floating on its liquid form, contribute to its special role on our planet. Without the presence of liquid water on Earth's surface, the remarkable complexity and diversity of life we observe would likely be impossible.