How do the potential energy and the kinetic energy change when the skateboarder is at the top or the bottom of the hill? Why do you think this change occurs?

Potential at the top. Kinetic when going down the hill.

Explanation:

Its basically mechanical energy! While at the top you have the potential to go down and race down using kinetic energy.

The potential energy (P.E) and the kinetic energy (K.E) are two types of distinct energy that is commonly observed in our day-today's life.

Usually, K.E is defined as a type of energy that is produced when an object is in motion. Where, as P.E is a type of energy that is stored in an object when that object is placed at a certain height.  

In the given condition, when the skateboarder is at the top of the hill, then at that position, it is comprised of maximum P.E. As the he slowly comes down the hill, then the P.E gradually decreases, and the K.E gradually increases. This shows the P.E is slowly changing into the K.E. And as it comes down, the K.E increases, and eventually when he stops, then both the K.E and P.E becomes zero.

This changes occurs because energy can never be created nor destroyed, and it changes from one form to another.

Explanation:

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.