Procaryotic Structure and Diversity
The first organisms which did not have well defined nucleus, called procaryotes, (pro = earlier, caryon = nucleus) were probably anaerobic and heterotrophic. It is believed that at that time there was no free oxygen available in the atmosphere, and the autotrophs had a complex metabolism to prepare their own food. You can observe the difference between autotrophism and heterotrophism in Figure shown below.
We will now discuss different types of procaryotes and their evolutionary relationship to draw an outline of orgahic evolution.The 'group of procaryotes' is known as Monera. This group includes eubacteria, archaebacteria, green bacteria, purple bacteria, virus, prochlorophyta, cyanophyta and mycoplasma. Here we will describe the structure of two procaryotes viz. bacteria and virus.