Water is essential to human beings because it is needed to carry out cell activity, and plants need water to carry out photosynthesis. Water is also required for the replenishing and transportation of nutrients. Water can either be consumed by living things, or serve as a habitat for them.
Animals that live in water are known as aquatic animals. Water covers 66 percent of the entire planet, and about 75 percent of the human body is composed of water.
Water is also important for the metabolic process. It facilitates the chemical reactions that break down larger substances into smaller ones for use as energy. Energy produced from metabolism is essential to growth and the maintenance of daily processes.
The chemical reactions that take place within the human body are mostly catalyzed by enzymes. Water helps to regulate the temperature within the human body allowing these enzymes to reach peak performance.
Water plays a key role in respiration and photosynthesis. Photosynthesis is the process through which plants produce food in the form of starch. Aside from water, the process also requires chlorophyll and sunlight. Oxygen is a byproduct of photosynthesis, and is the basis of all life on earth. Water also plays a role in weather.