GCSE Bitesize more-or-less covers all of Variation, Inheritance & Evolution in 15m.
For self-assessment questions, with exercises and discussions, just click on the correct topic at Biology GCSE & IGCSE Question Bank. A powerpoint can be downloaded from the same site here. The s-cool revision site lets you revise the topic, summarizes the topic & tests you on it. GCSE Bitesize has revision pages (that take you through the topic), a test and an activity.
Here’s Penguins in peril: Inheritance – know your genetic jargon & ratios:
This is a great power-point that covers most of this topic, although we don’t need to know about co-dominance or pedigree charts: