I’m just a little confused can someone explain ?

Basically, there is a presentation of types of food and the amount of those foods over 50 years in this graph. This means the graph is showing amounts of certain foods over the time period. I'm guessing that basing off of the the previous text you're just noting a change in the breaks of birds based off of the diet available to them at certain times. The adaptations and natural selection will explain the changes because due to certain limited and available foods the diet of the birds change.

It penetrates the skin and can cause mutations.

Explanation:

UV light is the most common source of radiation that affects DNA, but it is a weak radiation and it penetrates only the surface cells of your skin. However, UVA radiation is considered as a mutagen because it penetrates deep into the skin and can cause mutations.