yes because it is only found in the human body : )
i guess so, its commonly known to be in a animal all over the body but very rarely in a plant it can be found in a plant called a cycad which is a plant on Madagascar
go on youtube and you well find your answer http://www.youtube.com/watch?v=1Fz5HiL0cgA copy an past this
yes, they do, if you search one up you can see a diagram of it and it says they have one.