Evolution does not involve the conscious will of the organism. Nor does it happen through any adaptation that is forced on it by its surroundings, or any strategy learned by the organism during its lifetime being passed on by it to its offspring. It happens, simply, because certain characteristics in an organism's genetic make-up are either selected for or selected against by the particular characteristics of environment in which it finds itself. The environment, in this context, is the physical surroundings of the organism, such as the topography, the temperature or the rainfall, and the other organisms that coexist with it, both those that it feeds on and those that feed on it.
The rate of evolution has little to do with the rate at which genetic mutation occurs - the important factor is the environment's rate of change; the speed at which new pathways open up into which new forms may evolve and develop.
As well as being responsible for structural and morphological traits in an animal the genetic make-up of a cell also gives rise to behavioural traits that allow an animal to interact with its neighbours and with its environment in a way that ensures its survival.
It can be argued that the function of an organism is merely to pass on its genes to the next generation. Evidence to support this view can be drawn from patterns of behaviour seen in animals. Behaviour is, simply, an animal's active response to its environment, and along with growth and reproduction is one of the factors that defines a living thing.