Chapter no.2: Systematics of Living Organisms (Classification, Three domains of life , chemotaxonomy).
Ans: Whittaker proposed five kingdom system they are as follow:
1) Kingdom Monera ,
2) Kingdom Protista ,
3) Kingdom Fungi. ,
1) Artificial.
Phylogenetic classification is basedkaun common change coming down .
It is believed that the life originated on Earth is very simple form .After establish living beings it gave rise to more and more perfect forms of life.
4) Kingdom Plantae ,
5) Kingdom Animalia.
Our Earth contains huge diversity of organisms.since from many years human beings are using this for our own benefit.
By taking advantage humans differentiate organisms according to their cell structure ,
shape ,their properties like reproduction ,etc.by all these things we can easily identify organisms very easily .
This differentiation of species is a branch of Biology known as systematics or classification.The methodsof classification was used in past years later Indian Greek and Roman philosophers invent a new character or new name that is systematic science.
Systematics:"Systematics is the study of different kinds of diversity of organisms and their relative and gradually change relationship.".
Taxonomy:
Taxonomy means classification following certain rules or principles. Word Taxonomy comes from two Greek words ,
taxis- meaning arrangement and nomous -meaning law or rule .The term taxonomy was first introduced by A.P de Candolle (Swiss Botanist) .(1777-1841).
2.2) Classification:
Classification means the arrangement of organisms or group of organisms in different categories in accordance with the particular and well-established plan .
Gnerally classification is based on similarities and dissimilarities among the organism. Classification is of three types.
1) Artificial.
2) Natural.
3) Phylogenetic .
1) Artificial Classification:
Artificial classification is based on few easily observable and non evolutionary features such as habit ,colour, form ,etc.
of organisms often irrespective of their affinity ( relationship) with other organisms .example:Linneaus system of classification.
2) Natural Classification:
This classification is based on accurately important rather than being selected for availability like artificial system of classification. e.g: Bentham and Hooker's system of classification.
3) Phylogenetic Classification:
Phylogenetic classification is basedkaun common change coming down .
example: Engler and prantles classification. In the system of classification the terms like 'taxa' and categories are often used. Each category is referred to as a unit of classification. Infact
it represents a rank and is commonly termed as "Taxon".
2.3) Three domains of life:
It is believed that the life originated on Earth is very simple form .After establish living beings it gave rise to more and more perfect forms of life.
The struggle and progress is a change which lead to formation of different life forms. The three domains of life was proposed by Carl Woese in 1990 to classify life forms.
Domain: The unit larger than Kingdom in the system of classification is called as "Domain".
The three main types of domains are Archeae , Bacteria, and Eukarya.
Bacteria and Archeae both have prokaryotic cells (which do not have a well defined nucleus ) whereas Eukarya have eukaryotic cells (which have nucleus enclosed within a nuclear envelope ).
All three domains have very unique ribosomal RNA (rRNA ).Archeae live in very extreme conditions like high temperature , salinity, acidic conditions (pH less than 7 )etc.
Bacteria is also prokaryotes but differ from Archeae in structure of cell wall .Bacterial cell wall is made up of peptidoglycan ,
while Archeae cell wall is made up of polysaccharides and proteins and with no peptidoglycan.
2.4)Chemotaxonomy:
The word Chemo- Chemical ,and taxis - arrangement. Chemotaxonomy is one of the type of natural biological classification is based on similarities and differences in structure of certain compounds present among the organism being classified .
Chemotaxonomy means the classification based on chemical arrangement of organisms .example :Archeae cell wall is without peptidoglycan and that of prokaryo is with peptidoglycan .
While eukaryotic organisms like fungi have chitinous cell wall .This classification shows that organisms of same category have different chemical arrangements according to their properties and characteristics.
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