What is considered the most relied upon chemical compound by both plants and animals?

Water is considered the most relied upon chemical compound by both plants and animals due to its essential roles in biological processes. For plants, water is crucial for photosynthesis, the process by which they convert sunlight into energy. Water acts as a solvent in which nutrients are dissolved and transported throughout the plant, and it also helps in maintaining turgor pressure, which is essential for structural support.

For animals, water is vital for various physiological functions including digestion, circulation, temperature regulation, and waste excretion. Given that animals are largely composed of water, it plays a critical role in maintaining homeostasis, allowing chemical reactions necessary for life to occur efficiently.

In contrast, while nitrogen is important as a nutrient for plants, it is not directly utilized by animals in the same way as water. Oxygen is essential for respiration but is not a chemical compound in the same sense as water, which consists of hydrogen and oxygen in a specific molecular arrangement. Carbon dioxide is a byproduct of respiration in animals and a key reactant in photosynthesis for plants, but it is not as universally required across both kingdoms as water. Thus, water stands out as the most essential and relied-upon compound for both plants and animals.