Hello friends, my name is Charles Darwin! I traveled the world, and one theory that I developed was Natural Selection. In order to understand this concept better, let's meet Percy and Jace the grasshoppers in a patch of grass outside Rye Country Day School. 
As you can see Percy is green, and blends in well with the grass. Jace on the other hand is yellow, and is seen easily. Let’s see what happens when the bird comes closer to the grass. 
As we can see, the bird has spotted Jace in the green grass, and eats him. Percy on the other hand is still alive!
This happened because of Natural Selection. This simply means that Percy is more fitted for his environment. Fitness describes how well an organism can survive and reproduce in it's environment. 
Percy later had kids with another green grasshopper and they had green grasshopper kids! Percys kids are now more adapted to their environments. Adapted means any heritable characteristic that increases an organisms ability to survive and reproduce in it's environment. 
It's the end for our lesson on Natural Selection, friends!