Yeah, exactly, not people, but they are persons, they are conscious.
Let me put it this way: if you open https://en.wikipedia.org/wiki/Human - can you substitute "human" with "person"? Does "Persons are the only extant members of the subtribe Hominina." or "The closest living relatives of persons are chimpanzees (genus Pan) and gorillas (genus Gorilla)" make sense? Do we speak about "global person population"? I don't think so.
We accept "person" in most sentences, if the word "człowiek" refers to a specific person (exactly) and not the species, like in "He is a nice man/person". But not here.
what part you don't understand ? rz? ę? ę sounds like e (polish one) at the and of word. nouns in Nominative end with ę - and you hear that ę in other cases zwierzęcia....zwierzęta rz sounds exactly like ż and while there are sometimes rules for which is when I don't recall any that applies to zwierzę