(Original post by Gwilym101)
Mutation is a source of random change in the DNA structure, it can be harmful, or beneficial but most of the time doesn't have any phenotypic effect. If it has an effect on the body it is then acted on by other forces, most notably selection. If it is useful the organism with it is more successful and passes it on to it's offspring who will also possess the mutation, gradually over time this mutation is passed on to an increasing number of offspring to subsequent generations. Eventually those that don't possess it are outcompeted and driven to extinction and the species has evolved into a new species entirely.
A good example of a beneficial and a harmful mutation is Sickle cell anemia, if you possess both recessive mutations you have the disease, but if you only possess one and are therefore a carrier, you possess resistance to Malaria (that's an enhancement in my book).
Yes new species can emerge through evolution, you want evidence? Birds. They evolved from dinosaurs, we know this as we've found fossils that possess lizard traits and bird traits in varying ratios.
Examples include Archeopteryx, a dinosaur with clawed fingers on it's forelimbs and teeth like a lizard but possessed feathers. Another example Gigantoraptor, a large, feathered, beaked dinosaur that exhibited nesting behaviour. A third is Microraptor a dinosaur with feathers on every limb (including hind limbs or legs) that potentially enabled it to glide.
There are too many examples to go into of how evolution has created the species that are alive today, but mutation is one of the key drivers in how it happened.
Species go extinct all the time, we are currently in the SIXTH MASS EXTINCTION EVENT. There have been five previous ones, that's how evolution works some species go extinct as they were out competed by more suitably adapted species.
Initially I thought you were just playing devils advocate to get a discussion going, but now I realise you're one of those idiotic creationists that ignore any evidence that doesn't fit in your world view.