•In Linnaeus’ time a Two Kingdom system of classification with Plantae and Animalia kingdoms was developed.
•Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) have tried to classify all living organisms into broad categories, called kingdoms.
•The classification Whittaker proposed has five kingdoms and is widely used:
1. Monera,
2. Protista,
3. Fungi,
4. Plantae and
5. Animalia
•At present the biological classification includes:
1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi
4. Kingdom Plantae
5. Kingdom Animalia
6. Viruses, Viroids and Lichens.
Kingdom Monera
■The Monerans are unicellular organisms.
They contain 70S ribosomes.
■ The DNA is naked and is not bound by a nuclear membrane.
■ It lacks organelles like mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome, etc.
■They reproduce asexually by binary fission or budding.
■The cell wall is rigid and made up of peptidoglycan.
■ Flagellum serves as the locomotory organ.
■ These are environmental decomposers.
■ They show different modes of nutrition such as autotrophic, parasitic, heterotrophic, or saprophytic.
■ Bacteria comes under the Monera Kingdom
Bacteria
■ Bacteria are microscopic organisms that can survive in diverse environments.
Beneficial as well as harmful.
■ Simple structure without a nucleus and a few cell organelles.
■ Surrounded by two protective coverings- the outer cell wall and the inner cell membrane.
■ Some covered by a capsule.
■ Mycoplasma do not have a cell wall.
■ Pili surround the surface of the bacteria.
■ Long whip-like structures are known as flagella.
■ Autotrophic and heterotrophic modes of nutritions.
■ Heterotrophic bacteria are saprotrophs, parasites and symbionts.
Bacterial Shape and Size :
Cocci Shape– Bacteria are spherical or oval in shape. These can be micrococcus (single), diplococcus (in pairs), tetracoccus (in fours), streptococcus (in chains), and staphylococcus (in clusters like grapes)
Bacilli Shape– These are rod-shaped bacteria with or without flagella.
Vibrios Shape– These are comma or kidney-shaped small bacteria with flagella at one end.
Spirillum Shape– These are spiral or coiled shaped. They are rigid forms due to the spiral structure and bear flagella at one or both the ends.
Filament Shape– The body consists of small filaments like fungal mycelia.
Stalked- The bacterium possesses a stalk.
Budded Shape– The body of the bacterium is swollen at places.
Classification of Monera
■ Kingdom Monera is classified into three sub-kingdoms-
⦿ Archaebacteria
⦿ Eubacteria
⦿ Cyanobacteria.