What is evolution? What is it when we say the theory of evolution? What does the theory of evolution say about the diversity of life on earth? What is evolution? What is it when we say the theory of evolution? What does the theory of evolution say about the diversity of life on earth? Solution Evolution is defined as the process by which different kinds of living organisms are believed to have developed from earlier forms during the history of the earth. Biological evolution refers to cumulative changes that occur in a population over time. Theory of evolution: The theory of evolution proposed by Charles Darwin, entails the evolution by natural selection of life on earth. It states that new generations are born with different inheritable traits, and that the traits superior for the survival will be passed on to new generation. This means that given enough time an organism can change and evolve to create a new speices. Using the theory of evolution, scientists predicted the ancestors of modern life forms, paleontologists found fossils that backed up the initial predictions..