What is essential for all life forms, according to biological principles?

Water is essential for all life forms as it is crucial for various biological processes. It serves as a solvent for biochemical reactions, which allows nutrients, gases, and waste products to dissolve and circulate within organisms. Water is also critical for maintaining cell turgor and facilitating thermoregulation in many organisms, ensuring proper body temperature and homeostasis.

Additionally, water plays a key role in photosynthesis for plants, which ultimately supports the entire food web by providing energy through the production of glucose and oxygen. Without water, cellular functions would be impaired, and most life forms could not survive, underscoring its fundamental importance in biology.

While air, soil, and sunlight are also important for certain life forms, they are not universally essential across all species as water is. For instance, some organisms exist in extreme environments where sunlight is scarce, and not all life forms depend on soil for nutrients, especially aquatic organisms.