Land, Water and Air are the three sub-groups of animals in Aristotle's classification system. He also classified on basis of red blood cells and without red blood cells.
<h3><u>Explanation:</u></h3>
Aristotle is very popular in ancient Greece and he is very popular in the field of biology and mathematics. He divided the living organisms into two classes called the Plants and the Animals. He divided the animals into two classes – one which contains red blood cells and the other which didn’t contain any red blood cells.
He also noticed that most of the organisms which contained red blood cells are vertebrates i.e they contained a body vertebral column in their back. So they were called as vertebrates and the others were called as invertebrates.
The first thing that the etiologist can do is try and culture bacteria from the tissue samples in the lab. And then study about the bacterium's properties and characterstics that are leading to causing diseases in the humans.
