Taxonomy (Taxis - arrangement, nomous = law / rule) is the branch of biology for the study of classification of organisms following certain rules or principals.
Systematics (systema - order) - The camparative study of organisms on the basis of morphology, anatomy, ecology, physiology, biochemistry etc. is known as systematics.
Systematics have three fields (i) Nomenclature (ii) Classification (iii) Taxonomy
Classification - grouping of organisms, (plants or animals) in different ranks on the basis of their characters is known as classification.
History of systematics
Father of taxonomy - Carolus Linnaeus. (Books - Species plantarum & systema naturae) and Philosophica Botanique
Taxonomy term - de Candolle
Systematics term - C. Linnaeus
Father of Botany - Theophrastus. He had written the book Historia plantarum and Enquiry into the plants.
Father of Indian Taxonomy - Santapau
New Systematics - Or Biosystematics - Classification of organisms on the basis of evolution, genetical & morphological traits. It is the another field of
New systematics-term by - Julian Huxley
Biosystematics-term by - Camp & Gilly
Types of Taxonomy
(i) Chemotaxonomy - (Biochemical Systematics) - Classification based on chemicals present in organisms
(ii) Numerical Taxonomy - (or phenetics or Adansonian classification)
Classification based on number of shared characters of various organisms.
(iii) Cytotaxonomy (Alston & Turner) - Classification based on nuclear & chromosomal studies,
Nomenclature- (Nomen - name, Calare - to call). Naming of an organism.
(1) Polynomial nomenclature : It is consist of many words., Discarded later on :
(2) Binomial nomenclature : This system was proposed by C. Linnaeus in his book Species plantarum, Philosphica botanica & Systema nature
- Each organism has two word name, first word generic & second word specific name.
- Generic name started with capital letter & specific name started with small letter.
- The names are printed in italics, when hand written, both names are underlined separately.
- The same scientific name of any plant is applied in all countries of the world.
- Scientific names have been standarised through - the codes of biological nomenclature
(i) ICBN - International codes for botanical nomenclature, London. (For naming plants)
(ii) ICZN - International codes for zoological nomenclature, London. (For naming animals)
(iii) ICVN - Virological
(iv) ICNCP - International code of nomenclature for cultivated plants
(3)Trinomial nomenclature -
Proposed by Lamark.
Ist name - Generic, 2nd name - Specific, 3rd name Variety
China rose -Hibiscusrosa sinensis.
Holotype - Nomenclature type
Isotype - Duplicate of Holotype
Syntype - When there is no holotype any of two or more specimens cited by author.
Lectotype - When there is no holotype specimens selected from original matter serve as nomenclature type
Neotype - New nomenclature type when the original material is missing.
Taxon - Any rank (hierarchy) of Classification is called a taxon.
- Kingdom, class, family Species etc.
Systems of Classification
There are three main system of classification
Artificial system of classification
This system is based on few morphological characters. First introduced by Pliny. Later on given by Aristotle, Theophrastus, Linnaeus, Bauhin, etc. This system has several lacunae.
Natural system of classification
It is based on a number of characters of organisms that are classified on the basis of Morphology, Anatomy, Cytology, Physiology, Ontogeny, Phylogeny, Biochemistry etc.eg.
Given by Schimper, Eichler, Bentham & Hooker.Phylogenetic System of Classification
This Classification is based on evolutionary interrelationships of organisms.
Phylogenetic system is also calledcladistics
A Cladogram is based on Phenetic is calledDendrogram
Proposed by Engler & Prantl. Hutchinson, Takhtajan, Dobzhansky & Mayr are modern phylogenetist.
System of classification
Different workers have classified living organisms as follows.
I. Two kingdom system
By Linnaeus (1758)
1 Euglena and other similar unicellular organisms have characters of both animals and plants.
2 Blue green algae (now called Cyanobactria) and bacteria having some cytological differences from other organisms also present as difficulty.
3. Fungi, which are usually included in plants, have some characters not common to plants.
4. Instead of two modes of feeding (ingestion in animals and primarily photosynthesis in plants), now 3 modes are recognized photosynthetic, ingestion & bsorption.
II.Five kingdom system
By Whittaker (1969)
1. Kingdom monera:
Prokaryotic cells lack Nuclear membrane, Plastids, Mitochondria and advanced (9+2) strand flagella.
(b) Reproduction is asexual by fission or budding.
Ex. Blue green algae, Bacteria etc.
2. Kingdom Protista:
(a) They are unicellular or colonial eukaryotic cells.
(b) Reproduction is asexual and sexual.
Ex.Unicellular Algae, Diatoms etc.
3. Kingdom plantae:
(a) Multicellular organisms with cellulose wall and frequently vacuolated, eukaryotic cells.
(b) Nutritive mode is photosynthetic but absorptive.
(c) Reproduction is sexual.
Ex. Rhodophyta, Phaeophyta, Chlorophyta, Bryophyta, Tracheophyta, Pteridophyta, Gymnosperms, Angiosperms.)
4. Kingdom Fungi:
(a) Multinucleate organisms with eukaryotic nuclei.
(b) Plastids and photosynthetic pigments lacking.
(c) Reproduction asexual
and sexual both.
5. Kingdom Animalia:
( a) Multicellular organisms, eukaryotic cell devoid of cell wall.
(b) Lack plastids and photosynthetic pigments.
(c) Organization and tissue differentiation complex
(d) Reproduction is sexual.
Seeds remain naked (exposed) in cones.
Seeds enclosed in fruit.
developed inside the fruits
Includes most ancient, prokaryotic, microscopic and simplest form of life present in this universe. This kingdom comprises of various types ofbacteria
. Monerans are found everywhere on this earth-in water, air and soil. They are also found within and upon the bodies of other life forms.Monerans
consists of two main groups-the Eubacteria (true bacteria) and theArchae-bacteria
or blue-green algae form a distinct subgroup of eubacteria.
Cyanobacteria (Blue-green algae)
These are gram negative, photosynthetic, one-celled, colonial or filamentous (Oscillatoria
) bacteria. They have an exceptionally wide distribution. They are found in soil, fresh water and oceans throughout the world. Cyanobacteria are thermophilic, therefore, inhabit hot-springs. They can perform the process of photosynthesis with the evolution of oxygen and are called as photo-autotrophs. They can fix atmospheric nitrogen for fulfilling their nitrogen requirements.
Thalli of most of the members are surrounded by gelatinous envelope. Branching is either false or absent.
Cyanobacteria show characteristic blue-green colour due to the predominance of pigments,c-phycocyanin
. They have incipient nucleus and cytoplasm differentiated into an outer colouredchromatoplasm
The chromatophores and pyrenoids are absent. Reserve food product is in the form ofcyanophycean starch.
Asexual reproduction takes place by means of cell division, endospores, hormogones, akinites etc.
Some of the members possess the ability to fix atmospheric nitrogen and are widely used asbiofertilizers
in the paddy fields etc. Other uses include reclamation of user soils, in fisheries etc.
They form a small groups ofchemoheterotrophic bacteria.
They are found in mud and water as free-living organisms. Many of the spirochaetes are parasites of an and animals. Spirochaetes are unicellular and helicoid in shape. The protoplasm is enclosed by a flexible cell wall and the cell is having two overlapping sets of fibrils. Asexual reproduction takes place by binary fission.
Spirochactes cause many human diseases, e.g.,syphilis
is caused byTreponema pollidium
and a type of infectious jaundice byLeptospira
Mycoplasmas were discovered byNocard
in 1898. They are known as“Pleuropneumonia like organisms” (PPLO).
They are the smallest known prokaryotes. They arePleomorphic
i.e. their body can change shape. The cells of mycoplasma are non-motile and very delicate. They have a cell membrane but lack a rigid cell wall. The diameter of the pleuropneumonia type agent is estimated to be 125 to 175 nm.
They cause diseases of man and animals, e.g.Mycoplasma pneumoniae
cause primary and typicalpneumonia; Mycoplasma salivarium
cause infection in the upperrespiratory tract.
They are most simple andancient
group of bacteria living in extreme environmental conditions. Their cell wall consists ofpolysaccharides
The cell membrane contains special type of branched chain lipids which enables them to withstand extreme conditions of temperature and activity. Archaebacteria can be grouped into following types -
forms of bacteria found in marshy areas and in the rumen (stomach) of cattle. They producemethane gas
(CH4) from carbon dioxide or formic acid. They are used in biogas plant to produce methane gas.
-These are also anaerobic forms of bacteria found in extremely strong salt solutions. In sunlight they develop purple colour pigmented membrane which can utilise light energy to carry out their metabolic activities by producing ATP. But this process is different from photosynthesis.
forms of bacteria found in hot, acidic sulphur springs. They oxidise sulphur to sulphuric acid at a temperature of about 80°C. Some of their forms can reduce sulphur to hydrogen sulphide under anaerobic conditions.
(1909) for the first observed them butRocha-Lima
(1916) properly described them and named them asRickettsia.
These are very small, obligate, intracellular parasites found in blood sucking insects like tics, lices, mites etc. They may be circular or rod shaped. Cell wal is of mucopeptide and their genetic material is DNA. They also contain RNA. They multiply by fission. They cause diseases in human beings like typhus, Q-fever, rickettsial pox etc. They are sensitive to antibiotics.