I've just had a look at the tags you mentioned and can't seem to reproduce your problem:
conservation-biology shows 4 questions in the tag list and has 4 questions on the tag page.
entomology shows 59 questions in the tag list and has 59 questions on the tag page.
ecology shows 43 questions in the tag list and has 43 questions on the tag page.
Are you definitely on one of the regular tabs for the tag page? I.e. are you on the newest, votes or active tabs (which show all questions) rather than the frequent or unanswered tabs (which do not show all questions, only a subset).
Also check that you are not filtering between multiple tags, a search for
[conservation-biology][botany] would only produce one result, for example.
I wont put this as status-norepro until you've got back to us because I can't reproduce the numbers you mention (5 and 1) for the conservation biology tag in any arrangement and can't see that any questions have been active recently for it to be a caching issue. Perhaps you could try and see if the problem persists in incognito/private browsing mode or on a different computer.