system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: different species can't breed, apart from some exceptions like lions and tigers, or donkeys and horses. What stops species from producing offspring and what's the biggest species separation that can produce offspring?
gpt
Picture the information that is given from the mommy tiger and the daddy donkeys like zippers.
Tiger zippers have really big teeth like a snowsuit.
Donkey zippers have really small teeth like those on a delicate piece of clothing. 

If you try to zipp the one side of the snowsuit to the other side of the delicate clothes it just won't go. 
If the two zippers were similar enough though - like a horse /donkey or lion / tiger... they may just fit. Not perfectly but they might fit..