i'm in year 11 doing units 1 and 2 this year. i would that say that it's pretty much memory based.
some area's we studied in unit 1 were energy; the sun, ecosystems, bio-geochemical cycles (nitrogen, water, phosphorus, carbon), the biosphere, negative and positive human impacts on the environment, and we touched lightly on sustainable living options. in this semester i think we focus on monitoring ecosystems.
the subject is really interesting and not at all difficult. we often have debates in class on environmental issues, excursions (!!) and our class even planted and are maintaining a garden in our school. if you're even slightly interested in environmental science i strongly recommend choosing it.
hope that helped and if you have any other questions feel free to ask