That dolphins are mammals and so are porposes (sp). We learned about blubber also. My girls are watching a documentary on the artic ocean and got in a fight about whether dolphins and whales where mammals.
When I said my dd6 was right my 5 year old started pouting because she thought I was just agreeing with her sister.
So onto the trusty internet we went and look up mammals and what they had to have and compared it to dolphins and whales. Then we looked up porposes and found they are mammals also.