Find a video lesson on this sub-topic at Dan Rott videos.
The Speciation Song – a song and an animation to introduce Speciation.
Crash Course Biology #15 – Speciation: Of Ligers & Men, in which Hank explains speciation in terms of finches, ligers, mules and dogs.
Paul Andersen (from Bozeman High) explains Reproductive Isolation and Speciation, then details the processes of Speciation & Extinction and finally describes Genetic Drift (this is more detail than is required for IB).
Here’s a presentation that explains the origin of species (speciation) very clearly: