The answer is All of the above
Organisms used to be classified in the earliest times according to their size. As science progressed, they started getting organized by their physical traits and now they're organized by traits found in their species that are not found in others based on the theory of evolution. They are classified according to how they developed from a starting organism.
This is happening because of tides which happen in the opposite places on Earth at the same time
Structurally, plant and animal cells are very similar because they are both eukaryotic cells. Beyond size, the main structural differences between plant and animal cells lie in a few additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles.