Slader.com offers moderated user-generated answers to the questions in the "Modern Biology" textbook. As of December 2015, printed copies of the "Modern Biology Study Guide Answer Key" are available from third-party sellers on Amazon.com.
Slader.com provides user-generated textbook solutions, question-and-answer forums, and tutoring for high school and college students. Users may access the website at no cost with ads or upgrade to an ad-free version for $1.99 a month. It also uses an on-site currency called Gold which can be used to encourage answers for questions or to pay for a session with a professional tutor. Gold can be earned by writing solutions that are viewed by other users or solving problems or purchased with PayPal or a credit card. Gold earnings over 10,000 can also be paid out to users.