This a great Biology lab to use when you are teaching about cellular transport. Students will see that some substances can pass across the membrane and other substances cannot. This is one of my favorite labs, and my students always enjoy it.
Big Guns: The Muscular System - CrashCourse Biology This guy is funny and enjoyable to watch. Just watching up to about 5 minutes with explain the understanding level 3 students need for muscle structure and how muscles expand and contract.