The definition of evolution is basically the descent of an organism changes/ modifies over time. Evolution helps us to understand the history of our lives and how we came to be what we are today and why. There are two forms of evolution, small (microevolution) and large scale (macroevolution). Microevolution occurs overtime within a population, an example of which is when bacteria become resistant to an antibiotic. Macroevolution is the changes within a species or population which happens over a different time scale to microevolution, an example of macroevolution is the appearance of feathers during the evolution of birds from theropod dinosaurs. This evolution by the theropod helped the survival of its species, making it a macroevolution.
The cause for evolution is all based around genetic mutation. The mutation usually occurs during the gametes production or when cells are divided. Mutation is random (according to most people’s opinions) and most of the cells die quickly. However sometimes the mutation survives and becomes helpful to its species. Most of the time the mutation neither helps nor hinders the organism. Mutations that survive do not always help the organism, however.
When a group of the population of a species have acquired significant mutations so they cannot have offspring with the rest of its none mutated species, they have effectively turned into another species. In the larger organisms, this could take thousands of generations, as it did with humans.
Every human has individual pieces of DNA from each other. This can appear in many forms, for example unusually shaped ears. These may appear in families where the trait has been passed down through generations. This is evolution in progress, in small scale. The majority of mutations are internal. Evolutionary changes occur in very small steps. For a new major organ to form in a large mammal, a great many small changes are required over many millions of years. This...