Life, the universe, football!
This clip explains what selective breeding (artificial selection) is and why it is important for animal breeders. You need to know how this differs from natural selection by evolution.
It will also be useful to have a good understanding of how natural selection can bring about evolutionary changes in the colour of peppered moths. see here
here are the groundbreaking pictures first seen in the 1960′s of a developing embryo in its mothers uterus. Truly marvellous!