There are fewer universal constraints that we know of from biology, but one seems to be very likely and quite general the need for water. Water provides a solvent in which life s chemical processes can take place, and there are not many other fluids that would work comparably. Such liquids as ammonia or methyl alcohol are possibilities but water has some advantages. Water stays liquid at higher temperatures, which means that chemical reactions can proceed more quickly. Water has a large heat of vaporization, making it ideal as a cooling mechanism by enabling a bit of water to evaporate from its surface an organism can cool itself off very efficiently.
Water has a high surface tension, allowing it to form droplets.
The surface tension may play a role in concentrating organic molecules. Finally, water is an excellent solvent, dissolving a wide variety of common compounds and having a high capability for keeping other compounds in solution. On most of these points of comparison, water is two or three times as effective as the other liquids. So we may conclude that while sometimes life could occur in a different solvent, it will form most easily and most often if there is water present. There are other biological constraints that relate to the possible forms of highly evolved plants and animals.