Scientific name of wheat.

The complete name of a plant in binomial nomenclature has

The common name of pea is simpler than its botanical (scientific) name $Pisum$ $sativum$. Why then is the simpler common name not used instead of the complex scientific/botanical name in biology?

Into how many groups did Theophrastus classify plants?

Who is known as the '$20^{th}$ century Darwin'?

The study of the kind and diversity of organisms and the existing relationship among them is called