Similarities: Natural Selection and Artificial Selection both result in the alteration of the gene pool. It can also change phenotypes of different species'.
Differences: Artificial Selection is when a specific trait is not wanted, and so it is not bred.
For example, humans did not like how yellow peas looked. They liked the healthy looking green better. So, they killed the yellow peas, and bred the green peas with other green pea plants, and right now it is almost completely out of our gene pool.
Natural Selection is when something naturally occurs, such as a natural disaster, famine, plague, invasive species introduction.
For example, if 10 camels lived in a desert, but one of them didn't have as good of a metabolism and stayed full longer, then that one would survive, while the others might not.
