Detailed study of various Kingdoms I. Kingdom Monera

 The kingdom Monera includes bacteria, cyanobacteria (Blue–green-algae), Archaebacteria, and some smaller groups like Mycoplasmas, Ricketsias, Actinomycetes, etc.

Bacteria

Bacteria were first discovered by a Dutch (Holland), Antony Von Leeuwenhoek in 1676. He observed them in a raindrop with the help of a simple microscope designed by him. The name bacteria (Greek= small stick) was given to these organisms by a German Biologist Christian G. Ehrenberg (1828). Louis Pasteur laid the scientific foundation of Bacteriology.

General Characters:

The following are some of the major characters of bacteria.

1. Bacteria are the simplest and the most primitive organisms. They are cosmopolitan and found in all places where life is possible.

2. Bacteria are considered to be plants because they have a rigid cell wall.

3. Bacteria are Prokaryotes.

4. Bacteria are unicellular and generally occur singly. Some of them are found in groups.

5. Bacteria lack a nuclear membrane and therefore, distinct nucleus and nucleoli are absent.

6. Bacteria also lack membrane-bound organelles, like Endoplasmic reticulum, Golgi bodies, Mitochondria, Plastids, etc.

7. Most of the bacteria lack chlorophyll, hence, they are heterotrophic. However, few bacteria possess chlorophyll and are autotrophic. The chlorophyll remains scattered in the cytoplasm.

8. Genetic material is represented by histone-free DNA.

9. The commonly reproduce vegetatively by fission.

10. Variation in the genetic characters is due to genetic recombination brought about by conjugation, transformation, and transduction. Flagellated gametes are, however, not produced.

Distribution:

Bacteria are found in all the habitable places. They are widely distributed in air, water, and land. A large number of bacteria also occurs in animal and human bodies. Bacteria can live both aerobically as well as anaerobically. They can survive in extreme cold (-1900c) and can also tolerate very high temperatures (800c) and drought. 

The presence of bacteria in a variety of habitats is due to i. Their resistant nature; ii. Characteristic mode of nutrition; iii. Formation of resistant endospores.