Here is a summary of the episode:

1. Cephalopods biologically are closely related to gastropods where open and closed circulatory systems are the main driver of the difference but ecologically cephalopods are closer to fish.


2. Through evolution, the protective shell of cephalopods has been reduced and so did its function. 


3. Cephalopods display complex behaviours and can solve complex problems using the tools in the surrounding environment.