Answer:
I think it is the excretory system
Eukaryotes occurs in the nucleus while porkaryotes transcription occurs in the cytoplasm <span />
New moon, quarter moon, full moon are what we call the lunar phases. These are consequences of the motions of the Sun, Earth and moon. Three dimensional models are useful because the face of the moon that catches the light of the Sun depending on their position at any given time could be depicted well. Circular models would be the best visuals for the lunar phases.
