In taxonomic, the organism is classified based on some similarities. In upper division, the similarities should be more general and in the lower division, the similarities will be more specific. It was mostly based on an organ, example: vertebrate.
An organism with the same phylum could be put in different order.
But the organism with the same order should have the same phylum and class too since order is located below the phylum. That means the organism with the same order should have more similarities than the organism with the same phylum. Those similarities are tightly correlated with the evolutionary relationship.
The image is not really helping since it was showing kingdom division, not the sequence of the taxonomic division.
A molecule.
Have a nice day, hope this helps.
Cheers~
Answer:
One easy way to measure the "size" of a ball is how far it is from side to side. Your tennis ball example is a good one: a typical tennis ball is about 2.5 inches form side to side.
