Can we write the wave function of the living things? If yes then how? In quantum mechanics we studied that everything has a wave function associated with it.My question is can we write down the wave functions of things. Then how we can write down the wave functions of the things like animals, human eye, motion of snake etc.
 A: There are 37.2 trillion cells in a typical human body, (probably a good few more in mine ;), then in each cell there are 20 trillion atoms, then you have to obtain the wave function for each of the electrons....... 
Actually, it may well be that you cannot describe a wavefunction for a macroscopic object, like a human body.  In the study of quantum mechanics, we are usually presented with the exercise of writing a wave equation for a single microscopic particle, an electron, proton and so on.
But a macroscopic object is "joined" to it's surroundings by entanglement, rather than the single electron wavefunctions we are used to deal with,  which does not need to take account of this.
If two (or more) systems  are entangled, such as the parts of our body and their surroundings, as in this case, then  we cannot describe the wave function directly as a product of separate wavefunctions, as I implied incorrectly in my first line. 
However, by the use of Reduced Density Matrices, as pointed out by Mitchell Porter below, we can describe entangled states. With the number of wave functions involved, this would theorically possible, but in practice, not a feasible option.
Incidentally, this may be  one reason why the STAR TREK, "beam me aboard" transporter system may be rather difficult to achieve, but that is probably covered elsewhere on this site.
A: My answer will be very non-technical, but hopefully will convey some basic ideas about what the quantum state (or wavefunction) is about.
One intuitive way to picture the nature of the quantum state of a system is to see it as the interference (hence the "wave" idea) of every different changes it could possibly undergo while it is not being messed with. 
In other words, when a system is not observed, its dynamics takes into account absolutely all the behaviors it could have and somehow mixes them together in constructive and destructive ways (this is known as the "path integral").
There are two aspects here that make it impossible in practice to formulate the wavefunction of a living being: 
First, if the system is not isolated one must take into account all interactions it has with its environment (which is made of other systems themselves subject to the same description). Living beings are obviously not isolated, they are very open systems continuously exchanging matter and energy with their environment.
Second, for anything else than simple systems there is no way to build the interference of all possible behaviors, because they can be very complex and there is an infinity of them. 
