All life, and subsequently all organisms, evolve according to the dictates of their surrounding environment; that is of course, if the surrounding environment changes over a time period sufficient to allow the organism to evolve. An immediate catastrophe, and by immediate I mean something happening in hundreds instead of millions of years according to the universal clock, may regress or destroy the organism.
Evolving, or evolution as we prefer to call it, only takes place through necessity. If there is no change to an environment then, it follows there is no change to the species living in that environment. A simple oraganism may have a greater chance of survival, simply because its environmental requirements may be simpler. It may however also be a catalyst from which more complex organisms are formed. If we take a single celled organism; a good example being the amoeba, its evolutionary path seems to have made little progress since its arrival on the planet so many millions of years ago. Its presence however, has been the building block for many creatures. This argument can also be made for many species of lichen and algae.
It is important to realise, that an organism's exposure to other organisms also plays a part in the evolutionary process. With the advance of genetic engineering, man is unfortunately reaching the state where manipulated interaction between variants of human and animal genes results in a set of intriguing circumstances. This could be changing the natural order as laid down by nature and, subsequently see an accelerated form of evolution. This accelerated evolutionary process may in itself have short term advantages, but regrettably can only have long term disadvantages. Common sense tells us that we as humans, have very little understanding of the long term effects of what we do.
What seems right at this moment, may have disastrous effects in the future.
Organisms evolve into more complex forms because nature either requires their development in a changing environment, or humanity manipulates the process to stimulate the satisfaction of its own needs. Nothing in nature happens without purpose. Balance is essential for survival, and organisms change to cater for this balance.
Orgasms that have evolved, but have failed to meet the requirements of the natural world seemed to have died out. Darwin called this process 'natural selection'. As I write I ponder the evolutionary development of an organism called human. Does nature see this organism as part of its balanced process, or does this organism fall outside the natural order, a species fast becoming unimportant in the evolutionary process of organic balance?