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What is the Six Kingdom Classification System?
It was introduced by Carl Woese, a Professor in the department of Microbiology, University of Illinois in 1990. This system is also named as three domain system as in it organisms are classified into three domains, i.e., Archaea, Bacteria and Eukarya. It mainly used basic principles of five kingdomRead more
It was introduced by Carl Woese, a Professor in the
department of Microbiology, University of Illinois in
1990. This system is also named as three domain system
as in it organisms are classified into three domains,
i.e., Archaea, Bacteria and Eukarya.
It mainly used basic principles of five kingdom system,
but divides Monera into two domains Archaebacteria,
Eubacteria and other eukaryotes in third kingdom.
i. Archaea
Archaea domain includes prokaryotic organisms. These
are characterised by a monolayer core of lipids in the cell
membrane and distinct nucleotides in their 16 S RNA.
It contains a single kingdom called Archaebacteria.
Kingdom—Archaebacteria
This kingdom includes early prokaryotes, which live in
extreme conditions of the environment. Include
methanogens, halophiles and thermoacidophiles.
ii. Bacteria
that
The bacteria domain consists of typical prokaryotes
lack membrane covered cell organelles. These do not have
microchambers for separating various metabolic activities
It also has a single kingdom—Eubacteria.
Kingdom—Eubacteria
The members of this kingdom have peptidoglycan cell wall,
naked DNA in coiled form and glycogen food reserves.
The sap vacuole is not present and 70 S ribosomes are present.
The members of this kingdom are bacteria, mycoplasma,
Actinomycetes, rickettsiae, spirochaetes, cyanobacteria.
iii. Eukarya
The domain eukarya contains all the eukaryotes.
The four kingdoms of this domain are
See less(a) Protista
(b) Fungi
(c) Plantae
(d) Animalia
What is the Five Kingdom Classification System?
This classification was proposed by RH Whittaker in 1969. Before 1969, the classification systems for the living organisms had undergone several changes over time. Whittaker created Fungi, as separate kingdom. The main criteria for classification used by Whittaker (i) Cell structure (ii) Mode of nutRead more
This classification was proposed by RH Whittaker in 1969.
Before 1969, the classification systems for the living
organisms had undergone several changes over time.
Whittaker created Fungi, as separate kingdom.
The main criteria for classification used by Whittaker
(i) Cell structure
(ii) Mode of nutrition
(iii) Thallus organisation
(iv) Reproduction
(v) Phylogenetic relationships
Merits of Five Kingdom
Classification System
Merits of five kingdom classification system are
(i) Euglena and other transition types which had been
included both amongst plants and animals are given
proper place under kingdom—Protista.
(ii) Fungi have their own biochemical, physiological and
structural organisation. They have never been related
to plants. In this system of classification, fungi are
separately placed.
(iii) A separate kingdom—Monera including prokaryotes
has been created. Monerans differ from all other
organisms in their cellular, reproductive and
physiological organisations.
(iv) The five kingdom classification system is based on
cellular organisation, the mode of nutrition and
complexity of structure. These were the basic factors
used in earliest two kingdom system of classification.
(v) The system shows the gradual evolution of early
organisms into plants and animals.
(vi ) The plant and animal kingdoms are more
homogenous than they were in the two kingdom
system of classification.
Demerits of Five Kingdom
Classification System
Demerits of five kingdom classification system are
(i) Animal protozoans have been included in
kingdom—Protista, which also includes unicellular
plants. They show different modes of nutrition.
(ii) Chlorella and Chlamydomonas, though unicellular
are included under the kingdom—Plantae.
They should be kept in Protista.
(iii) Euglena like organisms and slime moulds with
flexible life style may need the creation Of an
intermediate kingdom other than Protista.
(iv) Viruses and viroids are not kept in proper place in
this system.
(v) Lichens have also not been placed in this system.
See lessWhat is the Four Kingdom Classification System?
The four kingdom classification system included Monera in addition to Protista, Plantae and Animalia. Studies with electron microscope made it clear that bacteria and related organisms have a different nuclear structure as compared to others. They are prokaryotes, thus kingdom—Moneta was created byRead more
The four kingdom classification system included Monera in
See lessaddition to Protista, Plantae and Animalia. Studies with
electron microscope made it clear that bacteria and related
organisms have a different nuclear structure as compared to
others. They are prokaryotes, thus kingdom—Moneta was
created by Copeland (1956). Fungi continued to remain with
Plantae in this system.
What is the Three Kingdom Classification System?
Three Kingdonm Classification System Ernst Haeckel in 1866, classified living organisms into three kingdoms—Plantae, Protista and Animalia. The new kingdom—Protista included all those organisms which lack the capability of tissue differentiation. These are algae, fungi, and slime moulds. Later, bactRead more
Three Kingdonm Classification
See lessSystem
Ernst Haeckel in 1866, classified living organisms into three
kingdoms—Plantae, Protista and Animalia. The new
kingdom—Protista included all those organisms which lack
the capability of tissue differentiation. These are algae, fungi,
and slime moulds. Later,
bacteria
protozoans,
kingdom—Protista was reserved only for unicellular
organisms.
Limitations of Three Kingdom
Classification System
Limitations of three kingdom classification are
(i) Prokaryotes and eukaryotes were not separated.
(ii) Both unicellular and multicellular organisms were kept
in Protista.
What is the Two Kingdom Classification System?
Linnaeus (the father of taxonomy system) divided all the living organisms into two kingdoms in 1758. Features of Kingdom—Plantae The features of this kingdom are (i) Cell wall is present. (ii) A big central vacuole is present. (iii) Absorb inorganic nutrients from outside. (iv) Unlimited growth andRead more
Linnaeus (the father of taxonomy system) divided all the living organisms into
See lesstwo kingdoms in 1758.
Features of Kingdom—Plantae
The features of this kingdom are
(i) Cell wall is present.
(ii) A big central vacuole is present.
(iii) Absorb inorganic nutrients from outside.
(iv) Unlimited growth and well-defined growing
points.
(v) Autotrophic mode of nutrition, reserve food is
starch.
(vi) No locomotion (except in some lower algae).
(vii) Absence of excretory organs, nervous system, sense
organs and muscular system.
(viii) Slow response 😮 external stimuli.
Features of Kingdom—Animalia
The features of this kingdom are
(i) Absence of cell wall.
(ii) Inorganic crystals are not present in their cells.
(iii) Central vacuole is not present.
(iv) Heterotrophic mode of nutrition.
(v) Growth is limited and well-defined growing points
are not present.
(vi ) Reserve food as glycogen.
(vii) Excretory organs, nervous system and sense organs
are present.
(viii) Locomotion is present.
(ix ) Muscular system is present.
(x) Show quick response to external stimuli.
Shortcomings Of Two Kingdom
Classification System
The two kingdom system of classification was accepted
for a long time. However, some difficulties arised from
this classification as several new living organisms have
been discovered.
Some of these difficulties are mentioned below
(i) The first formed organisms (bacteria) were neither
plants nor animals. These were not given proper place
in the two kingdom classification system.
(ii ) Prokaryotes do not have an organised nucleus. They
have single envelope organisation, absence of spindle
, meiosis and sexual reproduction.
apparatus
Eukaryotes have a well-defined nucleus, a double
envelope organisation, spindle apparatus, meiosis and
sexual reproduction.
On the other hand, viruses have no protoplasm and
metabolic machinery of their own. Therefore, all of
these cannot be kept in a single group.
(iii) It is not easy to recognise the lower organisms as plants
or animals. For example, Euglena has chloroplast and
follows mixotrophic (dual) mode of nutrition, while
sponges are fixed, branched and irregular creatures like
plants that have holozoic mode of nutrition and
excrete nitrogenous waste like animals.
(iv) Fungi do not show structural, physiological and
reproductive similarity with other plants under
kingdom—Plantae. Fungi have heterotrophic mode of
nutrition with chitin in their walls while, other plants
are mostly autotrophic in nature with a cellulosic cell
wall.
(v) Slime moulds, a group of fungi, are wall-less in
vegetative phase. They develop cell wall in the
reproductive phase. Slime moulds can neither be
placed in animals, nor in plants.
(vi ) Lichens are formed by the symbiotic association of an
alga and a fungus. They neither resemble plants nor
animals.
(vii) This system does not distinguish multicellular and
unicellular organisms. For example, Chlamydomonas
and Spirogyra are placed together.
(viii) Unicellular algae like diatoms, euglenoids,
dinoflagellates and protozoans resemble each other.
But they are placed in different kingdoms.
What is the Need of Classification?
There have been many attempts to classify living organisms since ancient times. Aristotle was the earliest to attempt a scientific basis of classification. He used simple morphological characters to classify plants as trees, shrubs and herbs. He also classified animals into two groups, i.e., EnaimaRead more
There have been many attempts to classify living organisms since ancient times.
See lessAristotle was the earliest to attempt a scientific basis of classification. He used
simple morphological characters to classify plants as trees, shrubs and herbs. He
also classified animals into two groups, i.e., Enaima (with red blood) and
Anaima (without red A need for proper system Of classification was
always felt.
Living organisms need to be classified because of the following reasons
(i) The study of one or two organisms is not sufficient to know the essential
features of the group.
(ii) Classification helps in knowing the relationship amongst different groups
of organisms.
(iii) It helps in studying of the evolutionary relationship between organisms.
TYPES OF CLASSIFICATION SYSTEM
Depending upon the types of system of classification, organisms are classified
into following kingdoms
A student of taxonomy was puzzled when told by his professor to look for a key to identify a plant. He went to his friend to clarify what key the professor was referring to? What would the friend explain to him?
The key for identification of plants is a taxonomic key. It is an important taxonomic aid. Key can be defined as a set of alternate characters arranged in such a manner that by selection and elimination one can quickly find out the name of an organism. Depending upon the category, a key may be classRead more
The key for identification of plants is a taxonomic
See lesskey. It is an important taxonomic aid. Key can be
defined as a set of alternate characters arranged in
such a manner that by selection and elimination one
can quickly find out the name of an organism.
Depending upon the category, a key may be class
key, order key, family key, genus key and species
key.
Taxonomic keys can be of two types
(i) Indented or Yoked key
(ii) Bracketed key
Indented key provides a sequence of two or more
alternate characters from which selection and
elimination are carried out. In bracketed key, the
alternate characters are given numbers in
brackets. e.g., take three genera of family—
Ranunculaceae to explain this.
(i) Ranunculus Leaves alternate or radical,
flowers not subtended by involucre, carpels
ovuled, fruit achene.
(ii) Clematis Leaves opposite, compound petals
absent, sepals 4, carpels with one ovule and fruits
achenes.
(iii) Nigella Flowers regular, carpels united at base,
many ovules, fruit follicles.
A scientist came across a plant, which he feels is a new species. How will he proceed towards its identification, classification and nomenclature?
The scientist will first identify the family to which the plant belongs. He will further follow the given steps (i) Using genus key, the genus is identified. (ii) Using species key, identification is carried out. (iii) As the genus is known, the species is provided now with a latinised name as per gRead more
The scientist will first identify the family to which the plant
See lessbelongs.
He will further follow the given steps
(i) Using genus key, the genus is identified.
(ii) Using species key, identification is carried out.
(iii) As the genus is known, the species is provided now with a
latinised name as per guidelines.
(iv) Type specimen or holotype is placed in a recognised
herbarium or museum.
(v) Name, description and report of the discovery is published
in a reputed scientific journal.
Try to collect all the currently accepted meanings for the word 'species'. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand and bacteria on the other hand.
(i) Species is a basic unit of classification, where individuals share common characteristics. (ii) It is a natural population or group of natural population of individuals having similar morphology, anatomy, physiology and cytology. (iii) Species is an assemblage of structurally similar individualsRead more
(i) Species is a basic unit of classification, where individuals
See lessshare common characteristics.
(ii) It is a natural population or group of natural population
of individuals having similar morphology, anatomy,
physiology and cytology.
(iii) Species is an assemblage of structurally similar
individuals, which can interbreed freely. but are
reproductively isolated from members of other species.
Higher plants and animals Ihese are sexually
reproducing organisms. the third definition of species is
applicable in case of higher plants and animals.
Bacteria The second definition of the species can be
applied to bacteria. As bacteria do not reproduce sexually.
Therefore, the criterion of free interbreeding and
reproductive isolation cannot be applied to them.
Define the following terms
(i) Phylum It is a taxonomic category higher than clan and lower than kingdom, which consists of more than one class having some similar correlated characters. e.g., classes—Aves, Amphibia, Pisces, Reptilia and Mammalia belong to the phylum—Chordata. of this phylum have notochord in their body plan.Read more
(i) Phylum It is a taxonomic category higher than clan
See lessand lower than kingdom, which consists of more than
one class having some similar correlated characters.
e.g., classes—Aves, Amphibia, Pisces, Reptilia and
Mammalia belong to the phylum—Chordata.
of this phylum have notochord in their body plan.
(ii) Class The category class includes related orders. It is
higher than order and lower than phylum. e.g.,
class—Mammalia has orders—Carnivora, Primata, etc
(iii) Family It is the category higher than genus and lower
than order, which has one or more related genera
having some common features. e.g., Felidae, Canidae,
etc.
(iv) Order It is a taxonomic category lower than class and
higher than family. It consists of one or more related
families possessing some similar correlated characters
that differentiate them from families belonging to Other
orders. e.g., Carnivora, Primata, etc.
(v) Genus It comprises of a group of related species which
has more characters common in comparison to species
of other genera. In other words, genera are aggregates
closely related species. e.g., genus— Panthera has lion
(Panthera leo), leopard (P. pardus) and tiger (P. tigris).