Evolution, as defined in biology, the continual process by which one form of life changes, or evolves, into another form. Some religious groups deny that evolution exists, but most scientists accept it as fact. The theory of evolution suggests that all living things descended from one or several kinds of simple organisms. It also explains why there are so many different kinds of organisms. The inherited characteristics of nearly all living things change from generation to generation. Eventually the accumulated changes may become so great that the descendant bears little likeness to its remote ancestor and may belong to a different species. Evolution is of two types: anagenesis and cladogenesis. Anagenesis is gradual change in a single species. Cladogenesis involves the branching of the species into two or more species over generations. It took a single species more than 3 million years to evolve into the current 10 million species on Earth today. This implies that all species on the planet today had a common ancestor.
During evolution, natural selection works in a way that ensures that species that are more capable of adapting to their environment live and evolve further, while species that are unsuited to their environment die out.
