The evolution of new species

The theory of evolution by natural selection suggests that all modern species evolved from earlier species. Natural selection causes each generation of a species to become better adapted to its environment. Natural selection can cause common features of a population to change so much that we classify them as a new species. Populations of the same species living in different conditions can evolve to become separate species. An example of speciation of populations living in different conditions (e.g. Galápagos tortoises).