Why does food go mouldy?

As I was photographing Jelly so much I forgot to chuck it out, when reaching for this in the fridge I discovered a nasty surprise but also a good one, as I could document the mould spreading around the Jelly. It looks quite surreal, so I think I will used this for the text to go on top.

I wanted to show a before and after shot of the fruit disintegrating into nothing. The studio again sets up this question like a forensic still life, where we can see every detail as the mould takes over the fruit. 

I really like the differences here, however apples take ages to mould! So I should of investigated more to find out what fruit goes off quickly.