Question about classifying content and breadcrumb

Hello,

I can't understand how to classify my content on Drupal 6.
For example, when I want to create a page about a dog, the Golden Retriver, and I want it to be in the vocabulary & terms :
Animals
-Domestic
--Dogs

My questions :
1- When creating the page, do I have to select both Domestic AND dogs or Drupal will understand, if I only select Dogs, that this page is relative de Dogs in the Domestic category ?
2- How to create a breadcrumb like : Home > Animals > Domestic > Dogs > Title of the page ?

Thanks