How does evolution work?
Variation in a species usually occurs due to mutations.
Usually mutation can be bad, however sometimes they can offer the animal an advantage. Such as a giraffe having a longer neck. This advantage means it may be able to survive for longer and therefore pass on these advantageous genes. After generations, this mutation will be seen within the species.
Evolution into another species can occur if a species is split and separated from another in a different habitat. The animal will have to adapt to suit the new climate, this occurs once again through mutations. Species A could evolve so much they are no longer able to mate with species B- consequently making them a new species.