Is it generally considered acceptable from a search engine optimization perspective to have one domain with multiple different areas of content within it (ie: domain.com/category1/ & domain.com/category2/). For example if I wanted to create a site about animals and have all different types of animals on it would i still have a chance to rank high on different animal keywords?
Search engines typically take into consideration the content of all the pages on the website when ranking even just one page... but, the more content and pages on the site the better also it seems. You might have better luck putting the different areas of content in subdomains if your going to have a descent amount of content and pages for each. Otherwise (like if it's 1 page for each animal) then I'd just use subfolders. Basically, if the subdomain isn't large and informative enough to be an actual site of it's own, then stick with subfolders. That's my opinion, but you may find others.