As more and more life’s building blocks were formed, they inevitably mingled and reacted with each other to form new compounds. Eventually, a chance combination gave rise to a molecule of DNA, a self replicating material that is the basis of all living matter. Here, perhaps, was the “spark of life” and the scene was then set for the appearance of the first cells and the subsequent evolution of all life on Earth. Since the beginning of life, millions of different kinds of organisms have come and gone. It is estimated that there are about 300,000 different kinds of plants in the world at the present time, and there may be over five million kinds of animals- or some estimates, nearer ten million – although only a little over a million of these have so far been described.