In any ecosystem, there is a wide variety of ecological niches. These are areas and/or ways of life that can be exploited by different types of animals. For example, in a rainforest, there are niches for animals that can climb to access fruit, but there are also niches for animals that will eat fruit that has fallen to the forest floor.
Evolution is a process that allows species to become differentiated. In this process, species gradually change in various ways. The changes that are useful will be passed on to future generations and may eventually lead to the rise of new species. It is in this way that evolution helps to explain the diversity of life. The process of evolution allows new species to arise. It allows species to come into existence and fill every niche in the ecosystem. Because there are so many niches, this means that there are also going to be a wide variety of types of life.
Evolution, then, allows species to arise that are successful at filling various niches. This leads to the existence of many diverse forms of life.
Evolution explains how new biological species arise. This happen when a change in the gene pool of a population has taken place. A population is a group of reproductively isolated organisms that interbreed or have the potential to interbreed. Evolution explains how certain conditions such as natural selection, choice of mate, , food preference, mutation, can cause a population not to be able to interbreed succesfully, and eventually become a separate species.
Recent studies claimed that a type of fruit fly called, Rhagoleitis pomonella might be currently undergoing sympatric speciation (new species arise from single population without geographical barrier). This type of fruit fly, originally feed on the fruits of hawthorn trees, but began to feed on apples. This apple maggot no longer feed on hawthorn fruits and its ancestor maggot does not feed on apples. Geneticist believed that is an example of sympatric speciation (new species arise from single population without geographical barrier).
Another example is the new plant species produced by Georgii Karpechenko after crossing a cabbage with a radish. The plant produced from these unrelated species could only breed with each other but not with either the cabbage and radish ancestors.