In California, Pacific Northern rattlesnakes prey on California ground squirrels. Their relationship is a great example of co-evolution. Read the article about their relationship found at https://news.osu.edu/how-is-rattlesnake-venom-like-fine-wine-both-have-regional-varieties/, and then address the following questions:

Explain why the relationship between these two species is considered an example of co-evolution.
What did you find most interesting or significant about how the rattlesnake population adapts to the squirrels defenses against its venom?