The cellular life forms have been divided into three domains; such as Archaea, Bacteria, and Eukarya. The three domain system represents a biological classification introduced by Carl Woese in 1990, Professor, Department of Microbiology, University of Illinois, Urbana-Champaign. Theprokaryotes have been divided into Bacteria (originally Eubacteria), and Archaea (originally Archaebacteria). Woese opined that both of them evolved separately from one ancestor called Progenote (having poorly developed genetic system).The third domain is Eukarya
Three Doman System is actually based on six kingdom classification
1. Archaea domain. These early prokaryotes have a monoplayer core of lipids in their cell membrane and distinct nucleotide in their 16 S RNA. It has only one kingdom. Kingdom-Archaebacteria. These primitive prokaryotes live in extreme environment. Ex. - Halophiles, live in seas, Thermoacidophiles - live in acid and at high temperature (upto 110 degree Celsius), Methanogens - converts hydrogen and Co2 into methane.
2. Bacteria domain. These are typical prokaryotes which lack membrane covered cell organelle. It contains some micro chambers for separate activities. It has only one kingdom . Kingdom-Eubacteria. This kingdom contains various types of typical bacteria. It has peptidoglycan cell wall, nucleoid (a coiled naked DNA), food reserve in shape of glycogen, 705 Ribosome and absence of sap vacuoles. Common groups are - Ex. - Mycoplasma, Actinomycetes, Cyanobacteria, Firmicutes, Spirochaetes, Rickettsiae.
3. Eukarya domain. This domain contains eukaryotes. These are evolved by endosymbiotic association between archaebacteria and eubacteria. The four kingdoms present in this are:Kingdom-Protista. It contains Protophyta (photosynthetic autotrophs), Gymnomycota saprophytes), Protozoans (animal like heterotrophs).
Kingdom-Fungi. It contains fungi, mouids, mushrooms etc. Kingdom-Plantae. It includes all multicellular plants. Kingdom-Animalia. It includes all multicellular consumers (metazoa).
0 Comments
إرسال تعليق