Biological Classification

Full text

Biological Classification
Institute of Lifelong Learning, University of Delhi
Discipline Courses-I
Semester-I
Paper: Phycology and Microbiology
Unit-I
Lesson: Biological Classification
Lesson Developer: Ishwar Singh
College/Department: Hansraj College, University of Delhi

Biological Classification
Institute of Lifelong Learning, University of Delhi
1
Table of Contents
Chapter: Biological Classification
 Introduction
 Nomenclature and Taxonomic Hierarchy
 Five kingdom classification
 Kingdom Monera
 Kingdom Protista
 Kingdom Plantae
 Kingdom Fungi
 Kingdom Animalia
 Three domain classification
 Summary
 Glossary
 Exercise/ Practice
 References/ Bibliography/ Further Reading

Biological Classification
Institute of Lifelong Learning, University of Delhi
2
Introduction
In our daily life we come across several animals, plants and microbes, which have been
named in order to understand their importance and to communicate about them. However,
this communication about organisms becomes difficult in an area or a region where they do
not occur or if they occur but are recognized by some other name. Further, organic
evolution has caused great number of biodiversity adding another problem to biologists to
remember, and to identify new ones. All these factors contribute to a need of developing a
system, called taxonomy.
Taxonomy is the branch of science dealing with naming, grouping of organisms on the basis
of the degree of similarity and arranging them in an order on the basis of their evolutionary
relationship. Therefore in other words, taxonomy is related to nomenclature,
classification and phylogeny of organisms. Taxonomy unlike natural sciences such as
Botany, Zoology, Physics, Chemistry, etc. is considered as a synthetic (man made) and
multidisciplinary science. It owes its progress on the advancement made in other branches
of sciences like morphology, histology, physiology, cell biology, biochemistry, genetics,
molecular biology, computational biology etc.
Nomenclature and Taxonomic Hierarchy
Figure: Carolus Linnaeus (1707-78)

Biological Classification
Institute of Lifelong Learning, University of Delhi
3
Source:http://commons.wikimedia.org/wiki/File:Carolus_Linnaeus_%28cleaned_up_version
%29.jpg
Carolus Linnaeus (1707-78) a Swedish botanist known as father of taxonomy is credited for
establishment of taxonomy as a separate science. He was instrumental in framing the rules
for naming the organisms, which he applied uniformly while giving his classification. It was
he who popularized the binomial nomenclature that is the modern scientific way of
naming organisms.
 In binomial nomenclature name of every organism is composed of two parts: first is
called generic name representing the taxon – Genus to which it belongs and second
is called specific epithet- Species.
 The generic name always starts with capital letter and specific name always with
small letter.
 These scientific names are used uniformly regardless of regions/countries or
languages, and two different organisms cannot posses same scientific name.
 The names of different organisms used in binomial nomenclature system must be
derived from Latin or if names to be used are from different languages they must be
treated as Latin.
The nomenclature of organisms is governed by a set of rules framed by International Codes
of Nomenclature. There are different codes of nomenclature for different groups of
organisms for example, naming of bacteria, animals and plants is governed by International
Code for Nomenclature for Bacteria (ICNB), International Code of Zoological Nomenclature
(ICZN) and International Code of Botanical Nomenclature (ICBN) respectively. The scientific
name of an organism, when cited in any text, is always mentioned as in italics or underlined
font style. The name of the author who first gave the correct name as per rules is written in
abbreviated form after the specific name and is written in Roman.
Another aspect of taxonomy is classification, which is the grouping of different organisms on
the basis of shared features into different categories called taxa. Different taxa are then
arranged in a hierarchical manner starting from lower to higher ranks that is:
Species
Genus

Biological Classification
Institute of Lifelong Learning, University of Delhi
4
Family
Order
Class
Phylum/Division
Kingdom
Domain
This ordered arrangement of various taxa is called taxonomic hierarchy.
Figure: An organism is placed in different groups (ranks) on basis degree of similarity. All
related groups are arranged in a hierarchical fashion starting from lowest, Species to
highest. Dissimilarity among different related groups increases of hierarchical order.
Example- as shown in the figure classification of rolling alga- Volvox aureus.
Source: Author
In this taxonomic hierarchy each organism is assigned a species name and species of very
similar organisms are grouped into a genus. The genera having very similar characteristics
are grouped together into a family and similarly several families form an order, several
orders into a class and ultimately on the top all similar classes are grouped into a kingdom.

Biological Classification
Institute of Lifelong Learning, University of Delhi
5
In recently proposed classifications, a new higher rank- domain/empire has been added on
the top of rank, kingdom.
Classification is done in order to make the process of identification of known organisms
simpler. While classifying the organisms it is presumed that all the organisms have been
diverged through organic evolution from one common ancestor. This is called concept of
unity amongst diversity. Another important point to remember about classification is that
members of higher level of ranks share fewer characteristics than those in lower level ranks.
One of the objectives of taxonomy is to classify organisms according to their evolutionary
(ancestral) relationship (phylogeny), which is not an easy task especially in absence of
connecting fossils links. Creating a universally accepted system of classification has always
remained a problem in the field of taxonomy. This is because being synthetic branch,
taxonomy is very subjective, and there is no consensus among biologists over the
uniformity of importance given to different characters in relation to evolution. Moreover, our
knowledge about living organisms is still incomplete; therefore any change or addition in
this knowledge-database always reflects in the field of taxonomy.
Earlier taxonomists divided the living organisms on the basis of morphological characters, as
there was no any sophisticated tool available to study living world. So, whatever information
was available it was about visible macro-organisms. Therefore organisms were arranged
into two groups- plants and animals based on easily observable (phenotypic)
characteristics.
Table: Different characteristics of two kingdoms, Plantae and Animalia.
Source: Author

Biological Classification
Institute of Lifelong Learning, University of Delhi
6
This system of classification was called two-kingdom classification and it was followed for a
very long period in history of biological sciences. However, invention of microscope in 16th
century made it possible to explore the living world, which was not earlier possible to
explore through human-naked-eyes. This exploration revealed an altogether new world of
microorganisms sharing features of both plants and animals. For example, Euglena, a
green, autotrophic, motile organism having definite shape and size, and obtains food by
ingestion process in absence of light. Similarly Chlamydomonas, a photoautotrohic
organism but also has animal-like feature such as motility and definite shape and growth.
Further, fungi although have plant-like features such as immobility, irregular shape and
indefinite growth but also posses heterotrophic mode of nutrition, a characteristic feature
of animals. Therefore such microorganisms could not have appropriate placement in two-
kingdom classification. In order to classify these microorganisms, Ernst H. Haeckel in 1866
proposed a three-kingdom classification in which he added a new kingdom – Protista.
Character
Kingdom
Plantae
Animalia
Body organization
Simple, Organ systems
like excretory, sensory,
nervous etc. absent
Well developed and organ
systems like excretory,
sensory, nervous etc.
present
Mobility
Absent as organs of
locomotion are not
present
Present due to
occurrence of organs of
locomotion
Growth and
development
Indefinite
Definite as body grows to
certain size and then
stop.
Nutrition
Autotrophic through
ether photosynthesis or
absorption
Heterotrophic through
ingestion

Biological Classification
Institute of Lifelong Learning, University of Delhi
7
Figure: Tree of life based on three-kingdom classification.
Source: http://commons.wikimedia.org/wiki/File:Haeckel_arbol_bn.png
In this new kingdom he included all simple microscopic living organisms such as bacteria,
microalgae, protozoa, fungi and sponges. Further advancement in the techniques of
microscopy and their application to biology generated new information that added to the
scientific knowledge. Studies of various organisms at cellular and subcellular level in 19 th
and 20th centuries proved that all organisms are made up of a basic unit called cell, which
could be structurally simple (prokaryotic cell) or complex (eukaryotic cell). All the

Biological Classification
Institute of Lifelong Learning, University of Delhi
8
known organisms posses either prokaryotic or eukaryotic cell organization and therefore
they can be accordingly called as ether prokaryotes or eukaryotes, respectively. Several
taxonomists insisted on inclusion of this fact (cell type) in classification of organisms. In
1956, Lynn Margulis and H. F. Copeland adapted this criterion in their classification and
proposed a four-kingdom classification system in which kingdom- Protista was divided into
two new kingdoms, Monera containing all prokaryotes and Protoctista containing all
simple, microscopic eukaryotic organisms like algae, protozoa and fungi.
In 1969, R. H. Whittaker proposed a five-kingdom classification in which kingdom –
Protoctista was split into kingdoms- Protista and Fungi. Carl Woese (1990) suggested
further rectification in system of classification. Relying on the information gathered with the
help of various techniques of molecular biology about different prokaryotes he proposed
revision of kingdom- Monera. In this classification kingdom- Monera was abolished and a
new category- domain on the top of category, Kingdom was introduced. This taxonomic
system is known as a three-domain classification that includes domains – Bacteria, Archaea
and Eukarya.
Thus, in conclusion, taxonomy is still a growing discipline, and system of classification and
status of evolutionary relationship amongst various groups will remain unsettled until we
have complete information about all the organisms present on this earth. Till then we have
to revisit our taxonomic system again and again in light of new information and knowledge
as we have been doing so since past .

Biological Classification
Institute of Lifelong Learning, University of Delhi
9
Figure: Progress taken place in classification system as a result of incorporation of new
information.
Source:Author
Five Kingdom Classification
This is one of the most widely accepted systems of classification proposed by an American
taxonomist, R. H. Whittaker in 1969. After Whittaker, this system is also called Whittaker’s
system of classification. In this classification, cellular organisms have been divided into five
kingdoms namely, Monera, Protista, Fungi, Plantae and Animalia. This classification is an
improvement of earlier proposed four-kingdom classification as in this system a new
kingdom- Fungi has been erected.

Biological Classification
Institute of Lifelong Learning, University of Delhi
10
Figure: Whittaker’s five-kingdom classification based on complexity of cell, cellular
organization, mode of nutrition and ecological role played
Source: adapted from Dr S.K. Aggarwal,2010. Foundation course in Biology.
Whittaker delimited the five kingdoms on the basis of three main criteria viz. cell structure
type, degree of cellular organization and mode of nutrition. Besides these major
characteristics he has also given importance to characters of ecological role-played and
mode of reproduction.
Table: Major criteria on which five-kingdom classification is based
Criterion
Kingdom
Monera
Protista
Plantae
Fungi
Animalia
Cell type
Prokaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Cellular
organization
Unicellular
Unicellular
Multicellular
Multicelluar
Multicellular
Nutrition mode
Variable-
Phtotrophic/
heterotrophic/
chaemoautotrophic
Phototrophic/
heterotrophic
Autotrophic
(photosynthesis)
Heterotrophic
(absorption)
Heterotrophic
(ingestion)
Reproduction
Asexual
Asexual or
sexual without
embryo stage
Asexual or
sexual with
embryo stage
Asexual or
sexual with
spore
Sexual with
embryo stage
Ecological role
Variable
Variable
Producer
Decomposer
Consumer
He also attempted to establish phylogentic relationship amongst various groups of different
kingdoms.

Biological Classification
Institute of Lifelong Learning, University of Delhi
11
Figure: Phylogenetic relationship among different groups in five-kingdom classification
Source: http://evolution-
textbook.org/content/free/figures/05_EVOW_Art/15_EVOW_CH05.jpg
According to him the earliest living forms (progenote) produced prokaryotic organisms or
monerans. Monera gave rise to protists probably through association of several types of
primitive and advanced monerans. Protists in tern gave rise to fungi, plants and animals.
The characteristic features and members of each of five kingdoms are briefly discussed:
Kingdom – Monera

Biological Classification
Institute of Lifelong Learning, University of Delhi
12
1. It is the kingdom of all the prokaryotes and includes eubacteria, cyanobacteria (blue-
green algae) and archebacteria.
2. The organisms are unicellular, colonial, mycelial and filamentous in form.
3. They lack true nuclei and other membrane bound organelles such as mitochondrion,
chloroplast, Golgi bodies, lysosomes etc. and DNA, which is the genetic material and
is called nucleoid, is not found associated with histone proteins; cell wall is often
present but chemically made up material other than cellulose.
4. Mode of nutrition varies from autotrophy to heterotrophy.
5. Sexual reproduction is absent and asexual reproduction may take place through
fission, fragmentation, budding and sporulation.
Kingdom – Protista
1. It is a group of organisms differing widely with one another except that they all are
simple and minute eukaryotes. It includes microalgae, protozoa and slime moulds.
2. Majority of them are unicellular but some may be colonial in form.
3. They contain true nuclei and membrane bound organelles; cell wall may or may not
be present.
4. Nutrition is very diversified and may be autotrophic (via photosynthesis) or
heterotrophic (ingestion/absorption).
5. Asexual means of reproduction is common but when organisms reproduce sexually,
embryo is not formed.
Kingdom – Fungi
1. It is the group of mostly multicellular or multinucleate achlorophyllous and spore-
producing eukaryotic organisms and includes mildews, moulds, yeasts, morals,
truffles, mushrooms, rusts etc.
2. The body of organisms is mycelial in form; cell wall is present and made up of chitin
or cellulose.
3. Nutrition is absorptive heterotrophy where organism secretes digestive enzymes into
the substrate and then absorbs the digested food.

Biological Classification
Institute of Lifelong Learning, University of Delhi
13
4. Asexual reproduction is primary mode of reduction and sexual reproduction causes
formation of specialized spores.
5. They play the ecological role of decomposer.
Kingdom – Plantae
1. It includes all coloured multicellular photosynthetic eukaryotic organisms commonly
called as plants. The important constituents are macroalgae, bryophytes,
pteridophytes, gymnosperms and angiosperms.
2. Plant body is either thalloid (algae and some of bryophytes) or differentiated into
root, stem and leaves; nonmotile; Cell wall is present and it is chemically made up of
cellulose.
3. Nutrition by: autotrophy (photosynthetic)
4. Both asexual and sexual reproductions occur. An embryo stage is present except in
algal group.
5. They play the ecological role of producers.
Kingdom – Animalia
1. It is a group of all macroscopic animals derived from zygote and includes sponges,
coelentrates, worms, annelids, arthopodes, mollusces, star fishes, fishes,
amphibians, reptiles, birds and mammals.
2. Organisms are multicellular with higher degree of body organization where tissue
differentiation usually leads to specialized organ formation. Eukaryotic cell is without
cell wall and chlorophyll pigments.
3. They exhibit mobility, sensitivity to different stimuli and definite growth.
4. They reproduce primarily by sexual reproduction and embryo stage is usually
present.
5. They play ecological role of consumer.
Demerits of five- kingdom Classification: Although this system is considered to be an
advanced system but still objections have been raised against this, which are following.

Biological Classification
Institute of Lifelong Learning, University of Delhi
14
1. It fails to distinguish between archaebacteria and eubacteria.
2. The kingdom- Protista is highly heterogeneous group of organisms, which seems to
be having polyphylatic evolution.
3. Placement of algae on the basis of degree of cellular organization into different
kingdoms appears to be unrealistic.
4. Red and brown algae placed in kingdom – Plantae are not related to other members.
5. Viruses an important form of life has not been considered in this system of
classification.
Three Domain Classification
Progress done in molecular biology especially in biochemistry and molecular genetics in later
decades of 20th century provided new techniques to study and compare organisms. The
study of chemical structure and sequence of macromolecules such as proteins and nucleic
acid can give insights in understanding the functions and evolutionary relationship of
different organisms. For example, cytochrome c protein, a component of electron transport
chain occurring in mitochondria; rbcl gene, encoding rubisco enzyme present in chloroplast
and small subunit ribosomal RNAs (SSUrRNAs) are very useful in such studies.
Among various probable contender macromolecules that can help in determining the
relationship amongst entire living world, rRNA fits the requirement the most as this form of
ribonucleic acid is (a) found uniformly distributed in all the self-replicating cells as one of
the basic components of ribosomes; (b) easy to isolate; (c) structurally stable due to its
very low mutation rate therefore making it an ideal molecule for detecting the relatedness
amongst distant species. Carl Woese and George Fox (1977) compared 16s/18s rRNA
present in different species and concluded that rather than two different basic cell types
(prokaryotic and eukaryotic cells) as suggested by cytological data, molecularly, there are,
in actual, three basic types of cells –
 one, present in eubacteria
 second, present in archaebacteria and
 third, present in eukaryotes.
If organisms are grouped on the basis of three basic cells, the molecular dissimilarity among
different cell type based groups appears so prominent that these groups cannot be

Biological Classification
Institute of Lifelong Learning, University of Delhi
15
considered equivalent to the taxon, kingdom. Therefore, Carl Woese et al. introduced a new
taxon – domain above the level of kingdom in their new system of classification, which they
proposed in 1990. Under this system, life has been divided into three domains, the Bacteria,
the Archaea and the Eukarya.
Figure: Three domains of life showing phylogenetic relationship among groups on the basis
of rRNA data.
Source: http://commons.wikimedia.org/wiki/File:Tree_of_life.svg
Just beneath domain is the rank of kingdom. The question of exact number of kingdoms in
each domain has been left unaddressed for future settlement, as new emerging molecular
data will soon throw more light on such natural groupings. However, in domain- Bacteria
the elevation of different phyla, proposed in earlier contemporary systems, to the ranks of
kingdoms has been suggested. Similarly, in domain- Eukarya three kingdoms: Plantae,
Animalia and Fungi; and division of protists (kingdom-Protista) into various kingdoms on the
basis of molecular characterization have been suggested. Domain, Archaea contains two
kingdoms- Euryarchaeota (group of methanogens) and Crenarchaeota (group of extreme
thermophiles).
Table : Characteristic features of three domains.
Character
Bacteria
Archaea
Eukarya
Cell type
Prokaryotic
Prokaryotic
Eukaryotic
Cell wall
Present; contain
peptidoglycan
Present; peptidoglycan
absent
Present/absent;
peptidoglycan absent

Biological Classification
Institute of Lifelong Learning, University of Delhi
16
Membrane lipids
Diacyl glycerol
diesters
isoprenoid glycerol
diethers or
diglycerol tetraethers
Glycerol fattyacyl
diesters
Genetic material
Small circular DNA
not associated with
histones
Small circular DNA
associated with histones
like proteins
Large linear DNA
associated with
histones
Translation (first
amino acid)
Formylmethionine
Methionine
Methionine
RNA polymerase
One; simple
One; complex
Three; complex
tRNA (TψC arm)
Thymine present
Thymine absent
Thymine present
Intron
Absent
Present rarely
Present
Antibiotic
sensitivity
Yes
No
No
Diphtheria toxin
sensitivity
No
Yes
Yes
Reproduction
Spore formation
present
Spore formation absent
Spore formation
present or absent
Habit
Variable
Extremophile
Variable
The distinguishing features of these domains :
Domain – Bacteria
1. It is a group of organisms having prokaryotic cell organization.
2. Lipids present in plasma membrane are predominantly diacyl glycerol diesters; cell
wall contains peptidoglycan.
3. Ribosomes present in these organisms contain bacterial type of rRNA where between
position 500 and 545 occurs a hairpin loop possessing a side bulge made up of six
nucleotides.
Domain – Archaea
1. Cellular organization is prokaryotic.

Biological Classification
Institute of Lifelong Learning, University of Delhi
17
2. Membrane lipids present are predominantly isoprenoid glycerol diethers or diglycerol
tetraethers; cell wall lacks peptidoglycan.
3. Ribosomes contain an archaeal type of rRNA where corresponding side bulge is made
up of seven nucleotides and exhibit unique structure between positions 180-197 or
405 and 498.
Domain – Eukarya
1. Organisms posses eukaryotic cell organization.
2. Membrane lipids are predominantly glycerol fattyacyl diesters; cell wall when present
contains chemicals other than peptidoglycan.
3. Ribosomes contain eukaryotic type of rRNA.
Merits of Carl Woese’s system: Since this is most advance system of classification, it
has attempted to address various demerits of five-kingdom classification. This system
recognizes the independent lineages of archaebacteria and bacteria and provides their
natural classification. By introduction of the rank of domain, this system has become natural
up to highest level.
Summary
Taxonomy is a synthetic and multidisciplinary branch of science dealing with nomenclature,
classification and phylogeny of organisms. The progress of this science is directly related to
the advancement made in other sciences from which it owes its principles. Carolus Linnaeus
established taxonomy as a separate science. Binomial nomenclature is used for assigning
scientific names to different organisms in which each name is composed of two names, first,
generic name and second, specific name. Each organism has a unique scientific name in
Latin language. Classification is the grouping of different organisms in different taxa and
then their arrangement in hierarchical manner starting from species to kingdom. Initially
organisms were classified on the basis of phenotypic characters into plants and animals.
This system is called two-kingdom classification. Revelation of microbial word created
problem of distribution of these microorganisms into existing two kingdoms. So a new
kingdom, Protista was erected to adjust these and this system is known as three-kingdom
classification. Further cytological studies showed that all organisms are basically made up of
either prokaryotic cell or eukaryotic cell. Therefore, system of classification was modified to

Biological Classification
Institute of Lifelong Learning, University of Delhi
18
four-kingdom classification in which fourth kingdom, Monera was added. The most widely
accepted system of classification, known as five-kingdom classification, was proposed by R.
H. Whittaker in 1969. In this classification living organisms have been divded into
kingdoms, Monera, Protista, Fungi, Plantae and Animalia on the basis of certai n criteria.
However, this also needs revision as some valid objections have been raised against this.
The most advance classification is three-domain classification that based on molecular
characterization of different organisms. In this system life has been divided into domains,
Bacteria, Archaea and Eukarya.
Glossary
Autotrophic: Ability to prepare own food using ether solar light (phtoautotrophy) or
chemical energy (chemoautotrophy).
Binomial nomenclature: Giving two names to an organism.
Cell: The basic structural and functional unit of life.
Classification: Formation and arrangement of groups in an order.
Heterotrophic: Dependence for food on others.
Nomenclature: System of assigning names to organisms as per set rules.
Nutrition: Process of acquiring nutrients.
Phylogeny: Evolutionary history of any group.
Species: The basic unit of taxonomy; according to typological –morphological concept it is
a group of individuals, which are morphologically distinct from other such groups.
Taxon: Any taxonomic group.
Exercise/ Practice
Q1. Define the following.
(i) Taxonomy
(ii) Binomial nomenclature
(iii) Classification
(iv) Taxon

Biological Classification
Institute of Lifelong Learning, University of Delhi
19
(v) Domain
(vi) Phylogeny
Q2. Fill in the blanks.
(i) The basic unit of biological classification is ………………..
(ii) ………………… is a group of related genera.
(iii) ……………….. is the top most rank in most advance system of classification.
(iv) Carolus Linnaeus is called as ………………………….. of taxonomy.
(v) Specific epithet is …………. .name in binomial nomenclature and this always starts
with a ……………. .letter.
(vi) Major criteria used in two-kingdom classification are ……………………. characters in
number.
(vii) Whittaker proposed a new kingdom,………………….. in his classification in 1969.
(viii) Three domain classification was given by ……………………
(ix) Three domain classification is mainly based on criterion of …………………….
Q3. Taxonomy is a multidisciplinary science. How does development taken place in other
branches change the course of taxonomy? Elaborate with examples.
Q4. What is a hierarchical order? What is the importance of this in classification?
Q5. Why is it considered difficult to propose a phylogenetic classification?
Q6. What are the major criteria of Whittaker’s classification?
Q7. Name all the kingdoms along with characteristic features in Whittaker’s classification.
Q8. Distribute given organisms - E. coli (bacterium), Chlamydomonas sp. (microalga),
Amoeba sp. (protozoan), brown alga, bread mould, pea plant and horse at the level of
kingdom as per following systems of classification.
(i) Two-kingdom classification
(ii) Three-kingdom classification
(iii) Four-kingdom classification
(iv) Five-kingdom classification
Q9. Why is the study of rRNA considered useful in determining the evolutionary relationship
among organisms?
Q10. What are the distinguishing features of three domains?

Biological Classification
Institute of Lifelong Learning, University of Delhi
20
Q11. Write the major differences among eubacteria, archaebacteria and eukaryotes.
References/ Bibliography/ Further Reading
1. Black JG (2002). Microbiology – Principles and Explorations. 5th ed. John Wiley &
Sons Inc. USA.
2. Raven PH, Johnson GB, Losos JB and Singe SR (2005). Biology. 7th ed. Tata
McGraw-Hill
3. Willey JM, Sherwood LM and Woolverton CJ (2008). Prescott, Harley, and
Kleinth’s Microbiology. 7th ed. McGraw-Hill.
4. Woese C R and Fox GE (1977). Phylogenetic structure of the prokaryotic domain:
The primary kingdoms. Proc. Nati. Acad. Sci., 74(11): 5088-5090.
5. Woese C R, Kandlert O and Wheelis ML (1990). Towards a natural system of
organisms: Proposal for the domains Archaea, Bacteria, and Eukarya. Proc. Nati.
Acad. Sci., 87: 4576-4579.
Links
1. http://www.youtube.com/watch?v=g9AQbkQgVeU
2.http://books.google.co.in/books?id=Vs5V3cAzOMsC&pg=PR3&lpg=PR3&dq=S+K+aggarw
al+deshbandhu+college&source=bl&ots=BLmLNS6M67&sig=4TTSNnwJeZK3O2TumifEyAvn
me0&hl=en&sa=X&ei=2xAfUtDvKoHjrAfFxoDYAQ&ved=0CGAQ6AEwCQ#v=onepage&q=S%
20K%20aggarwal%20deshbandhu%20college&f=false

Biological Classification
Institute of Lifelong Learning, University of Delhi
21