Sometimes in Bio and ESS you'll need to Identify an organism. These apps are preferred for these courses:
iNaturalist - Worldwide database. Android. Works on iOS but not as well.
ObsIdentify - European focused. Android and iOS.
Anything based on Fiji. They take some work to understand and use, but they're good.
NOTE: New AI powered ones are popping up all the time, mostly paid. I haven't tried them.
Jmol: open-source Java viewer for chemical structures in 3D