Protista was divided into two new kingdoms, Monera containing all prokaryotes and Protoctista containing all simple, microscopic eukaryotic organisms like algae, protozoa and fungi.
The kingdoms Monera includes all the bacteria and the protoctista which includes the protozoa, the diatoms and some algae are in a way the lowest among the living world. Since only bacteria are prokaryotic (lacking a true nucleus), that is without nuclear membrane, monera is the only prokaryotic kingdom.
Hundreds of bacteria are present in a handful of soil. They also live in extreme habitats such as hot springs, deserts, snow and deep oceans where very few other life forms can survive. Many of them live in or on other organisms as parasites. Bacteria were the first organisms to evolve on planet earth after life originated around 3.5 billion years ago and were the only organisms on earth for almost the next two billion years.
They lack true nuclei and other membrane bound organelles such as mitochondrion, chloroplast, Golgi bodies, lysosomes etc. and DNA, which is the genetic material and is called nucleoid, is not found associated with histone proteins; cell wall is often present but chemically made up material other than cellulose.
The Kingdom Monera can be divided into 2 divisions
*Division Schizophyta
A. Includes close to 2,000 different kinds of bacteria
B. Occur in nearly all types of environments on earth
*Division Cyanophyta
A. Includes the cyanobacteria or blue-green algae
B. Cyanobacteria are normally larger than bacteria of Division Schizophyta
C. They possess chlorophyll and carry on photosynthesis
Kingdom Monera
