Physics - The Most Fundamental Science
The principles and laws of physics underlie every other law of science. Every biological and chemical law is actually a result of some physical law.
All of chemistry is a result of the formation of chemical bonds between electrons in different atoms. The electrons tend to pair up so as to minimise the total energy – this is a physical law. This pairing up of the electrons in different atoms results in the atoms containing those electrons being attracted to each other. This can happen on a very large scale, resulting in the formation of complex molecules. Atoms tend to react with other atoms so that the total overall energy is minimised, but energy is constantly being supplied by the Sun. This can result in chemical reactions that would not otherwise happen. These chemical reactions run counter to the 'energy gradient''. Energy needs to be supplied to allow these reaction to proceed – they are endothermic. One such is photosynthesis.
The molecules that allow the photosynthesis reaction are biological molecules. They obey the laws of genetics and biology so that all the molecules involved are the result of gene expression, and the result is that plants are allowed to grow. Underlying thes laws of biology however are laws of chemistry which dictates that only certain chemical reactions are allowed, and that certain amounts of energy are needed for certain reactions to proceed, or released by certain other reactions.
There is more to physics than just this gradient of importance. Colour, density, hardness, energy requirements... are all purely physical properties, but they all have chemical and biological properties. Chemical reactions tend to increase in speed as the temperature increases, because chemical reactions require a certain amount of energy – activation energy – to break chemical bonds before new bonds can be formed. An increase in energy shows as an increase in temperature which promotes the breaking of those bonds, but if the temperature rises too high, new chemical bonds will never form, so total breaking down of substances will occur. The same sort of thing happens in biological systems. There is an optimal temperature for chemical reactions in biological systems. These are mediated by enzymes, which operate best at a temperature of about 37 degrees celsius. Any lower, and the reaction will slow down, but any higher and the enzyme which mediates the reaction will have it's own internal chemical bonds broken down, and will be unable to mediate the reaction. Again, biological laws are underlain by chemical laws which are underain by physical laws.
When scientists design new body parts – artificial joints, heart valves -chemistry is bypassed almost totally. All that is required is that these parts do not react with body tissue and are able to function reliably for long periods of time. An increasing number of body parts can now be replaced with totally artificial bits. Legs and arms can now be interfaced with nerve tissue to move in a semi natural way. It seems that the suitability of these pieces will only increases as time goes on.