This illustration shows a species of giraffes. One of the giraffes is very tall while the other is short. This demonstrates variation
hows the weather up there?
The tall giraffe has an advantage, he has an adaption that helps them get food easily. He has adapted to the tall trees, so this makes it easy to get food from their tall branches
I'm so hungry :(
Soon, the shorter giraffe will starve from not eating, and there will be an overproduction (when an organism is produced more than the environment is suited for) of the tall giraffes
As time goes on, giraffes with longer necks will gradually (gradualism) become more common. Later on, selection (when a certain organism thrives more than the other in the environment provided) will cause the tall giraffes to become more dominant
Now, giraffes with short necks are very hard to find as through natural selecton and its four principles, giraffes have become more suitable to their environment due to their tall necks passed on through genes from ancestors