Hello Elaina,

We've made significant enhancements to our Science domain and, for high school biology, high school physics, and AP physics 1, we completely replaced the old content for the new one. If you had progress saved in the older versions of these courses, however, it doesn't mean you lost access to your work. You can still access the old versions of these courses through the direct links:

• https://www.khanacademy.org/science/high-school-biology
• https://www.khanacademy.org/science/high-school-physics
• https://www.khanacademy.org/science/ap-physics-1

We make these kinds of updates in service of providing free, world-class education, and we truly appreciate your understanding. You can see exactly what content items we’ve added in the new courses below. Happy learning!