Mutations

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as hypermutation. In multicellular organisms, mutations can be subdivided into germ line mutations, which can be passed on to descendants, and somatic mutations, which cannot be transmitted to descendants in animals. Plants sometimes can transmit somatic mutations to their descendants asexually or sexually (in case when flower buds develop in somatically mutated part of plant). A new mutation that was not inherited from either parent is called a de novo mutation.
Mutations create variations in the gene pool, and the less favorable (or deleterious) mutations are reduced in frequency in the gene pool by natural selection, while more favorable (beneficial or advantageous) mutations tend to accumulate, resulting in evolutionary change. For example, a butterfly may produce offspring with a new mutation. Many times new mutations are harmful; a new mutation might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to see. If this color change is an advantage, the chances of this butterfly surviving and producing its own offspring are a little better, and over time the number of butterflies with this mutation may form a larger percentage of the population.
Neutral mutations are defined as mutations whose effects do not influence the fitness of either the species or the individuals who make up the species. These can accumulate over time due to genetic drift. The overwhelming majority of mutations have no significant effect, since DNA repair is able to mend most changes before they become permanent mutations, and many organisms have mechanisms for eliminating otherwise permanently mutated somatic cells.