An Ecologist Is Studying a Rocky Intertidal Zone

An ecologist is studying a rocky intertidal zone.She maps the area and takes samples to calculate the species diversity.She determines the tidal variations and figures out how long each dominant organism is covered by tides and then analyzes the population density of each dominant species over a year.This ecologist is working at what level(s) of organization?

A) Ecosystem level only
B) Population level only
C) Community level only
D) Population and community levels
E) Population, community, and ecosystem levels