**Why Organisms Need Water**

Water is essential for the survival of all living organisms. It plays a crucial role in various biological processes and is involved in maintaining homeostasis within the body. Here are the reasons why organisms need water:

**1. Cellular processes and reactions:**
- All cellular processes take place in a water-based medium. Water acts as a solvent and facilitates the transportation of molecules within cells.
- Many biochemical reactions occur in an aqueous environment, as water provides a medium for chemical reactions to take place.

**2. Solvent for nutrients and waste products:**
- Water acts as a universal solvent, meaning it can dissolve a wide range of substances. This property allows nutrients, such as glucose and amino acids, to dissolve in water and be transported to cells for metabolism.
- Waste products, such as carbon dioxide and urea, can dissolve in water and be eliminated from the body through various excretory systems.

**3. Temperature regulation:**
- Water has a high specific heat capacity, meaning it can absorb and store a large amount of heat energy without a significant increase in temperature. This property helps organisms regulate their body temperature, preventing drastic fluctuations.
- Sweat, a water-based secretion, helps in cooling down the body through evaporation.

**4. Lubrication and cushioning:**
- Water acts as a lubricant in various physiological processes. For example, it reduces friction between joints, allowing smooth movement.
- Water also provides cushioning to protect vital organs, such as the brain and spinal cord, by surrounding them with cerebrospinal fluid.

**5. Transport medium:**
- Blood, the primary fluid in the circulatory system, is mostly composed of water. It transports oxygen, nutrients, hormones, and immune cells throughout the body.
- Water also facilitates the movement of substances across cell membranes through processes like osmosis and diffusion.

**Importance of Maintaining Water Balance:**
Organisms must maintain water balance within their cells and bodies to stay alive. Here's why it is crucial:

- Water is essential for maintaining cell shape and structure. A lack of water can lead to cellular shrinkage and, ultimately, cell death.
- Adequate water balance is necessary for proper functioning of organs and tissues. Dehydration can affect the efficiency of physiological processes.
- Water is involved in the regulation of blood pressure, pH balance, and electrolyte concentrations within the body.
- Maintaining water balance helps optimize metabolic reactions, enzymatic activity, and overall cellular function.

In conclusion, water is vital for the survival of organisms as it serves as a medium for cellular processes, solvent for nutrients and waste products, temperature regulation, lubrication, and transportation. Maintaining water balance is crucial for proper cellular function and overall wellbeing.

Water is the single most abundant chemical found in living things.Virtually all chemical reactions in life processes take place in solution in water. Some organisms can live in a dormant and desiccated state for long periods of time but require water to become active. Water is present both inside and outside cells. In the body of a mammal for example although it is about 70% water by weight, about 46% (approximately 2/3) is inside cells, and about 23% (approx. 1/3) is present outside cells in blood plasma and other body fluids.