Answer:
Evolution is the gradual change of characteristics and traits, that occurs within a species, over many generations.
Explanation:
Due to natural selection, some genes of a species can be passed on to their offspring, to increase chances of survival. This is because these new traits are enabling, the organisms who have them, to survive longer then the ones who don't, thus allowing them to procreate and have more offspring, who share that same trait.
This process can occur over several generations, and in turn, can really change a species.
Hope this helps. :)
