SCHOOL
A GLOBAL
FIELD
THE LEARNING
Name:
Class : 11 medical
Subject: biology
Session: 2024-25
BIOLOGY Biological classification bacteria
W H AT I S B I O L O G I C A L
C L A S S I F I C AT I O N
Biological classification is the scientific procedure of
arranging organisms in a hierarchical series of
groups and sub-groups on the basis of their
similarities and dissimilarities.
N E E D O F C L A S S I F I C AT I O N
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„ enaima (with red blood) and anaima
(without red blood). A need or 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) All
kinds of organisms do not occur in one locality.(iii)
Classification helps in knowing the relationship
among-est different groups of organisms.(iv) It helps
in knowing the evolutionary relationship between
organisms.
T Y P E S O F C L A S S I F I C AT I O N
Depending upon the types of system of classification,
organisms are classified into following Kingdom
TWO KINGDOM
C L A S S I F I C AT I O N S Y S T E M
Linnaeus (the father of taxonomy system) divided all
the living organisms into two kingdoms in
1758.These are Plantae and Animaelia
THREE KINGDOM
C L A S S I F I C AT I O N S Y S T E M
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 Protozoa. Later,
kingdom-Protista was reserved only for unicellular
organism.
FOUR KINGDOM
C L A S S I F I C AT I O N S Y S T E M
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-Monera was
created by Copeland (1956). Fungi continued to
remain with Plantae in this system.
FIVE KINGDOM
C L A S S I F I C AT I O N S Y S T E M
This classification was proposed by RH Whittaker, in
1969. Before 1969, the classification systems for the
living organisms have undergone several changes
overtime.He created fungi, as separate kingdom.The
main criteria for classification used by Whittaker(i)
Cell structure (ii) Modes of nutrition(iii) Thallus
organisation (iv) Reproduction(v) Phylogenetic
relationships.
SIX KINGDOM
C L A S S I F I C AT I O N S Y S T E M
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 the Monera into two domains Archaebacteria,
Eubacteria and other eukaryotes in third kingdom.
BACTERIA
The term Bacteria was proposed by Ehrenberg in 1829.
They have widespread distribution be it air, water or
soil. They can survive in extreme range of
temperatures like up to 78°C and -190°C.
I M P O R TA N T C H A R A C T E R I S T I C S
OF BACTERIA ARE
(i) Bacteria are found in all kinds of habitats.(ii) They are
prokaryotic microorganisms.(iii) They are unicellular.
(iv) Cell wall contains peptidoglycan.(v) An organised
nucleus in absent.(vi) Extrachromosomal self
replicating DNA segments called plasmids occur in
most of the bacteria.(vii) Mitochondria, plastids, Golgi
apparatus,endoplasmic reticulum and other membrane
covered cell organelles are absent
SHAPETHE BACTERIA POSSESS
THE FOLLOWING FORMS
(i) Coccus (PI. Cocci) bacteria are oval or spherical cells without flagella. The
spheres occur as single cells (Monococcus), a pair of cells (Diplococcus),
in groups of four cells (Tetracoccus), as chain of cells (Streptococcus) or in
sheets (Staphylococcus).A few cocci may also occur in cube-like
arrangements of 8 or more cells (Sarcina).(ii) Bacillus (PI. Bacilli) bacteria
are rod-shaped cells which many occur singly (Monobacillus), in pairs
(Diplobacillus), in chains (Streptobacillus) or as a layer (suck) with many
cells called Palisade bacillus.(iii) Spirillum (PI. Spirilla) bacteria are cells,
which are twisted, like a screw. They occur as free single cells, e.g.,
Spirillum, Spirochaete, etc.(iv) Vibrio are cells which are curved, C-shaped
or comma-shaped, e.g., Vibrio cholerae.
