Will it be challenging for a high school student that hadn't took any biology classes to major in ecology?

It shouldn't be all that hard, for three main reasons:

1. High school biology is very, very basic, and probably doesn't prepare you for a major in ecology anyway.

2. Most ecology majors require a series of bio classes anyway, so you will learn it whether you want to or not.

3. Ecology is much more than just biology. It encompasses biology, chemistry, botany, animal sciences, soil science, atmospheric science, etc., etc.

Biology is just one small part of Ecology, and although very important, you should have no problem completing the two or three pure Biology classes in college. If you find Ecology to be too boring or too difficult, also consider a major in Natural Resources. It's basically ecology (at least where I went to school) with a little of everything else thrown in.

I'm a psychology main in my 3rd yr already and that i suppose that AP Biology could be greater fitted to university prep. The motive for that is on the grounds that Psychology could require heavy workloads in particular in study and know-how as a substitute of memorization. So I could be extra positive with AP Biology however i can most likely NOT propose Chemistry of Living Systems.

Majoring in anything when you have no prior experience will be hard. How hard it is depends on the school you are taking it at and their specific program. A strong work ethic and some serious motivation should allow you to see it through, however. Best of luck!