UNIT I

Diversity of Living Organisms

The Living World

(IN THIS CHAPTER
1
.What is living Characteristics of living organisms. Biodiversity (Diversity in the living world)
Classification of
living organisms History classification Need
of biological for classification
Thre domains of life Domain archaea orarchaebacteria Domain bacteria or eubacteria
Domain eukarya oreukaryota Archaebacteria or Archaea Mycoplasma Ricketsia
Taonomy and systematics Taxonomy Systematics Phylogeny Concept ofspecies
Taxonomicalhierarchies . Taxon Category Revision of categories Intermediate categories
Subspecies categories Nomenclature Common or vernacular names
Binomial nomenclature (Scientific names)
Herbaria
Trinomial nomenclature Aids
Botanical gardens Zoological parks (Zoo) Zoological museums
forstudy of taxonomy
Taxonomic keys Systems of biological classification

WHAT IS LIVING
All diverse things on this planet are divided into living (animate) and nonliving (inanimate).
Living beings are called organisms and are defined as a complex unit of physico-chemical
materials that are capable of growth, reproduction, metabolism, ability to sense environment and
mount a suitable response.
Characteristics of Living Organisms
Let us try to understand each characteristic of living organisms one by one:
1All Living Organisms Grow: Increase in mass and increase in number of individuals are
two characteristics of growth. All organisms are able to grow. A multicellular organism grows
Dy cell division. In plants growth occurs throughout their life. In animals growth occurs up to
a certain age, and after that cell division occurs in certain tissues to replace the lost cells. Growth
in unicellular organisms is the increase in cell mass. In living organisms, this growth is from inside.

Nonliving objects such as mountains, boulders and sand dunes also grow but the growth is
due to accumulation of material on the surface. Thus, growth cannot be taken as a defining
product of living systems. Growth is just a characteristic of living systems.
2Beproduction is a Characteristic of Living Organisms: All multicellular and unicellular
rganisms produce new individuals similar to them. Organisms reproduce sexually as well as
sexual means. Fungi multiply and spread by producing millions of asexual spores.
at-worms (Planaria) regenerate from fragmented part of their body. Fungi, filamentous algae
and
protonema of Moss multiply by fragmentation.
In unicellular organisms like bacteria, Amoeba or unicellular algae, reproduction and growth
are
synonymous, i.e., increase in number of cells.
 1.2 19CBIOLOQY 11

Many organisms like mules, sterile worker bee, warblers, infertile human couples, etc., do not
eprodue, Thus reproduc tion alone also cannot he takern as a defining characteristic of living
Organiss. As a malter of fact, no nonliving object can reproduce or replicate by itself.
Metabolism is a Characteristic of Life: All living organisms are madeof chemicals. These
hemicaln belong to various classen and are called biomolecules. These are constantly being
made in the body by biochemieal reactions, called metabolic reactions. Thousands of such
etabolie reaetions are oceurring simultaneously inside the iving organisms. All plants,
a l s , fungi and microorg.anisms carry out these reactions. The sum total of all chemical
reactions occurring in our body is metabolism
Metabolic reactioms can be performed outside the body in cell-free systens. But an isolated
metabolic reaction performed outside the body of an organism is neither living nor nonliving
he isolated metabolic reactions in vito are just living reactions. Hence, metabolism is a defining
feature ot all living organisms.
iving Beings havea Cellular Organisation: All living organisms, starting from simple
to
highly oomplex,
are
of one or more cells, similar in basic structure and
made
cellular ofganisation of the body is a defining feature of the living forms.
functions. Hence,
.
A Living Organisms have
Consciousness: The most complicated feature living
oTganisms is the ability to sense their surroundings or environment and then respond to
of all
environmentalstimuli which could be physical, chemical or biological. This is called
consciousness. Wesense our environment with the help of our sense organs. Photoperiod, ie.
duration of light affects reproduction in seasonal breeders, both in plants and animals. Plants
respond to external factors like light, water, temperature, pollutants and other organisms. All
organisms handle chemicals entering their bodies. Human being is the only organism who is
aware of himself also and has self consciousness.
Therefore, consciousness is the defining
property of living organisms.
It is difficult to define living state in human beings. For example, a patient lying in coma has
n o self-consciousness and is not
likely to come back to normal life. Is he or living nonliving?
Thus, Living Organisms are Interacting Biological System. All living phenomena in living
beingsare due to underlying interactions. Properties of tissues are not present in the constituent
cells. These arise as a result of interactions among the constituent cells. In the same way,
properties of cell organelles are not present in the molecular constituents but are due to
interactions among the molecular components that constitute the organelle. These interactions
esult in emergent properties at a higher level of organisation. Therefore, it can be said that living
organisms are self-replicating, evolving and self-regulating interactive systems that can
respond to external stimuli. All iving organisms of present and past are linked to one another
by sharing, ot common genetic material, but to varying degrees. Samne sharing ot common genetic
material will be found in future.

BIODIVERSITY (DIVERSITY IN THE LIVING WORLD)

Diversity in the living workl, ie.,Biodiversity reters to staggering diversity and enormous variety
found in living organisms ientists have identified and named 1.7-L.8 million species of living
organisms. Of these, about J.2 million are animal species and 0.5 million plant species. The »ingle
group ot insects, howeverfoutnumber all the plants and other animals. This group contains about
1.025 million species. Every year, more than 15,000 new organisms are discovered.
According to biologists, sone 5 to 30 million species of organisms exist on the earth. Majority
of them are thought to ocrur in the unexplored tropical rainforests and underwater coral rees
of tropcal seas. Destruction of these forests and reets may make many speciesextinct before b e g
identified. In l n d i a , Silent Valley R a i n t o r e s t (Kerala) h a s b e e n s a v e d from s u b m e r g e n c e d u e to

proposed dam across river Kuntizha.

4/Isc BIOLOaY-11
yeedfor Classification
The purpose of classification of living organisms is to organise the vast number of known plants
and animals into groups and categories that could be named, remembered and studied easily
Arranging and grouping the plants and animals in a definite plan, makes the study of living
organisms easy. Just by selecting a few representatives from each group, a broad idea of life in
this world can be achieved.
Without a particular method of classification of living beings, it would be like dealing with
a large library where books have not been classified and arranged according to title, subject or
author. Grouping of organisms according to a definite plan is useful in following respects:
1. It makes the study of different organisms very convenient.
2. It facilitates identification of organisms.
3. It shows relationship among various groups of organisms.
4. Biological classification shows evolutionary trends in various groups of organisms by
revealing gradual increase in the complexity of their structure.
5. It helps in interpreting the poorly developed structures of the fossil organisms.
6. Study of a few representatives of a group gives the general characteristics of that group
as a whole.

THREE DOMAINS OF LIFE

Concept of three domains of life was proposed
by Woese and others (1969). It presents an DOMAIN
EUKARYAA
evolutionary model of classification, based on:
Animals
1. Difference in the sequence of nucleotides Plants
Fungi
in the cell's ribosomal RNAs (rRNA) Protists
2. Lipid structure of cell membrane and its
sensitivity to antibiotics.
Modern concept of biological classification DOMAIN
has evolutionary basis. Since ribosomal RNA EUBACTERIA
DOMAIN
molecules have most conserved structure Gram-positive Gram-negative ARCHAEA
bacteria
bacteria
throughout the nature and perform the same Methanogens
function, similarities and differences in rRNA Cyanobacteria Halophiles
Green
nucleotide sequences are a good indication of
relationship in different living groups. It is now
Mycoplasmas non-sulphur
baçteria Thermoacido-
accepted that three distinct domains of phles

organisation evolved in nature from a common

archaeal-prokaryotic ancestor cell. These
domains are Archaea (Archaebacteria), Bacteria
(Eubacteria) and Eukarya (Eukaryota).

UNKNOWN ANCESTOR
1.Domain Archaea or Archaebacteria Fig. 1.1 Three-Domain system of classification of
1. These are the most primitive forms.
organisms as proposed by Carl Woese (1978)
2 Their cell menbrane is composed of
branched hydrocarbon chains attached to glycerol.
3. Their cell membrane has no
peptidoglycans.
4 Archaea are not influenced by antibiotics that destroy bacteria.
5 Their rRNA is unique and much different from bacterial rRNA.
6. Archaea live in extreme environment.
Examples: Methanogens, halophiles and hyperthermophiles.
 THE LIVING WORLD 1.5

2. Domain Bacteria or Eubacteria

1.Their cell membrane is composed of unbranched fatty acid chains attached to glycerol.
2. Their cell wall is formed of
peptidoglycans.
3. Bacteria are sensitive to antibiotics.
4. Naked DNA molecule lies in the cell
cytoplasm.
5. Bacterial rRNA is unique and distinctly different from rRNA of Archaea and Eukarya.
6. Bacterial ribosomes are 70S
type.
Examples: Eubacteria include Mycoplasma, Cyanobacteria (Blue-green algae), Gram
positive bacteria and Gram negative bacteria.

3. Domain Eukarya or Eukaryota

1. Cells have
eukaryotic organisation.
2. Cell membrane is composed of trilaminer protein-lipid-protein layer as in bacteria.
3.Cell wall is absent in animal cells but present in plant cells. Peptidoglycans are not found.
4.Eukarya are resistant to traditional antibiotics.
5. Hereditary material is formed of nucleoprotein fibres composed of DNA + basic proteins
(histones).
6.
Eukaryotic rRNA is unique to Eukarya.
7. Eukarya ribosomes are 80S type.
Eukarya is divided into the following four kingdoms:
(a)
Kingdom Protista: It includes slime molds, euglenoids, algae and protozoans.
(b) Kingdom Mycota: It includes phycomycetes, zygomycetes, ascomycetes, basidiomycetes,
deuteromycetesS.
() Kingdom Plantae: It includes bryophytes, pteridophytes, gymnosperms and angiosperms.
(d) Kingdom Animalia: It includes all animals.

ARCHAEBACTERIA OR ARCHAEA
Archaebacteria form a primitive group of bacteria. They are the most ancient bacteria and are
believed to have evolved on primitive earth, billions of years ago, when conditions on earth were
hostile. Since then they have survived unchanged and still live in extreme environments like
Great Salt Lake, Dead Sea, Sulphur springs and Volcanic wells. Archaebacteria are known as
evolutionary relics or living fossils.

General Characters of Archaebacteria

1. The cell wall is noncellulosic but is formed of polysaccharides or proteins. It is without
peptidoglycans.
2. Cell membrane lipids are arranged in a monolayer. The lipids have long, branched
hydrocarbon chains linked to glycerol which enables these forms to tolerate extremes of
heat and acidity.
3. Archaebacterial ribosomal RNA has different sequence of nucleotides a_s compared to true
bacteria.
Classification of Archaebacteria
Based on the habitat and metabolic activities archaebacteria are divided into three groups:
Methanogens, Halophiles and Thermoacidophiles.
1. Methenogens or Methanogenic Archaebacteria (Methane Producers)
a ) They are obligate anaerobic autotrophs.
 1.6 IsC BIOLOGY-11
(b) They produce methane gas from carbon dioxide and acetic acid from sewage in marshy
conditions.
hy
CO +4H CH +2H,0
CH,COOH CHA+ CO2
Methane is a greenhouse gas that leads to global warming.
(c) They are found in marshes, bogs, swamps and in the rumen of cattle like cows and buffaloes
(d) Methanogens help in fermentation of cellulose. They do not decompose the organic matter
but utilise the end products of decomposition.
2. Halophiles or Halophilic Archaebacteria (Salt Lovers)
a) They are aerobic or facultative anaerobic heterotrophs.
(b) They live in saline environment in salt lakes, marshes, brine (salt solution) and salt-rich
soil where salt concentration varies from 2.5M - 5.0 M.

(c) They have high intracellular salt concentration. Their enzymes and ribosomes function
efficiently only at high salt concentration.
(d) They have special photoreceptor pigment - bacteriorhodopsin. Due to the presence of
bacteriorhodopsin, halophiles become purple to harness solar energy in strong sunlight.
This serves three purposes:
i) protects halophiles from strong solar radiation, and
(ii) It helps in the synthesis of ATP.
(ii) ATP synthesised during this period is used under conditions of oxygen stress.
(e) Nutrition is chemoautotrophic.
Examples: Halococcus, Halobacterium.
3. Jhermoacidophiles or Thermoacidophilic Archaebacteria (Heat/Cold Lovers)
(a) They are aerobic or facultative anaerobic chemoautotrophs.
b) They are adapted to live in hot and acidic medium. Some are adapted to live at very low
temperature even below freezing temperature. They can tolerate temperature up to 80°C or
above and a pH up to 2 (i.e., highly acidic).
(c) They are found in hot sulphur springs (Sulfolobus), in refuse piles of coal mines
(Thermoplasma) or in geothermal areas of Iceland (Thermoproteus).
(d) They are chemoautotrophs, i.e., they synthesise their food by using chemical energy.
(i) Under aerobic conditions, they oxidise sulphur to sulphuric acid, e.g., Sulfolobus.

2S+2H,0+302 2H,SO+Energy
(ii) Under anaerobic condition, sulphur is reduced to hydrogen sulphide (HS).

Economic Importance of Archaebacteria

1. Methanogen archaebacteria are used in the generation of gobar gas from cow dung and
sewage to be used as cooking gas.
2. Heat resistant thermophilic enzymes and restriction enzymes are used in biotechnology.
3. Halophiles are used in bioleaching of poor mines.
4. Archaebacteria are used as biosensfs.

VMYCOPLASMA
Mycoplasmas are the simplest known aerobic prokaryotes without a cell wall. They are
pleuropneumonia-like organisms (PPLO), discovered by Nocard and Roux (1898). Nowak
(1929) placed them in genus Mycoplasma. They were first isolated from Bovine sheep suffering
 THE LIVING wORLD 1.7

trom pleuropneunmonia. Mycoplasma are LIPOPROTEIN

MEMBRANE
considered to be intermediate between (3 LAYER)
bacteria and viruses.
REPLICATING
DISC
Occurrence
RIBOSOMES
Mvcoplasmas occur in soil, sewage water,
ditterent types otf substrates, humans, L UBLE
animals and plants. They are also found in PROTEIN

hot water springs and other warm

DNA
environnments.

ANA
Structure
iycoplasmas show marked pleomorphism
(showing several shapes of cell). Their size Fig. 1.2 An electron micrograph of a
varies trom 0.1 um-0.15 um. They lack cell Mycoplasma cell
wall. Due to the absence of cell wall, they
occur in variable shapes. They are pleomorphic.
Mvcoplasma cells are covered by a unit lipoprotein membrane, the cell membrane or plasma
membrane. They lack a well organised nucleus, endoplasmic reticulum, mitochondria, plastids,
Golgi bodies, centrioles and flagella. Genetic material is present in the form of a nucleoid. It
consists of a single, circular, double-stranded DNA molecule without a nuclear membrane. It
remains coiled in the cytoplasm. Ribosomes are 70S and lie scattered in the cytoplasm.
Mycoplasmas are Gram negative. They represent the lowest limit essential for a cellular
organism.
Locomotion, Nutrition and Reproduction
Mycoplasmas are usually nonmotile, some show gliding movements. They are heterotrophic.
Some of them are saprotrophs but most are parasitic on plants and animals. They reproduce by
budding and binary fission.

EConomic Importance of Mycoplasma

Mycoplasmas cause serious diseases in humans, animals and plants.
and mycoplasmal
In Humans and Animals: They mostly produce Atypical pneumonia
urethrities in humans and pleuropneumonia in animals.
In Plants: Mycoplasmas cause diseases, like Big bud in tomato, bunchy top of papaya, Stripe
disease in sugarcane, Little leaf in brinjal, Witches broom in legumes, etc.

RICKETTSIA
Rickettsia are smaller than bacteria but larger than viruses. They may be spherical or rod-shaped.
They vary in length from 30 Å - 200 A.
Rickettsiasare similar to bacteria in structure. But, like viruses, they multiply only within the
ving systems. They are obligate intracellular parasites.
There are about 50 different kinds of rickettsia living as harmless parasites in the intestinal
tract and salivary glands of lice, bed bugs and ticks. But, when transmitted into man by the

insect bite, they multiply within human cells and produce disease symptoms. The main diseases
in man caused
by rickettsia are Rocky Mountain spotted fever and typhus fever.
on the chick
embryo inside the egg shel
vaccine for rickettsia is produced by growing thenm in 1910 due to
Rickettsia were first observed by Howard Ricketts. Unfortunately, he died
typhus fever while studying the same organisms that cause this disease.
 1.8 ISC BIOLOGY-11

TAXONOMYAND SYSTEMATICS
Taxonomy
The process of classification of
living organisms into different categories or taxa is called taxonomy.
Modern taxonomy includes identification and study of various characteristics,
identification.
classification and nomenclature of living organisms. It collects informations about the external
and
internál structure, cell structure, biochemistry, physiological characteristics,
developmental processes
and ecological features of the organisms to trace the similarities and differences.

Systematics
Systematics is the branch of Biology that deals with the diversity of organisms and their
comparative and evolutionary relationships based on comparative anatomy, comparative
biochemistry, comparative physiology and comparative ecology. Generally, the terms taxonomy,
systematics and classification are used interchangeably, but they carry different meanings.
According to Simpson, these three have separate fields of study and should not be confused with
each other.
Classical or Old and Modern or New Systematics
Systematics, from the earliest times tothe time of Linnaeus is known the
as classical systematics
and that of
post-Linnaean period as the
systematics. new
Classical Old Systematics: During the era
to be an
or
of classical systematics, species was considered
independent and immutable (changeless) entity and the work of the creator. But this is
contrary to the evolutionary process which is still going on in the organisms. In classical
systematics, emphasis was given to morphological features only, whereas no emphasis was laid
on
evolutionary relationships among species.the
New Systematics: The term new
systematics was coined by Julian Huxley in 1940. New
systematics takes into consideration all types of characters available from classical morphology,
cytology, physiology, biochemistry, ecology, genetics, etc.
Differences between New Systematics and Classical
New
Systematics
Systematics differs from classical systematics in the following respects:
1. Species no longer occupies the central position. In its place, emphasis is given to
subspecies and populations.
2. Biological definition has replaced
morphological definition. It takes into consideration
cytology, physiology, biochemistry, genetics, etc., in addition to morphology.
3. The material used for consists of several hundreds
4. To measure various
specimens.
parameters, experimental variability has been introduced.
5. Statistical data is
compiled
to know the of degree primitiveness, advancement and
inter-relationships.
6. According to new
systematics, species is not fixed or static but highly dynamic.
Requisites of Systematics
The requisites of systematics are:
1. Characterisation: The organism to be studied is described for all its morphological and
other characteristics.
2. Identification: Based on characteristics, identification of the organism is carried out to
establish whether it is similar to any of the known
group of taxa.
3. Classification: It is the
arrangement of organisms into groups based on their relationships.
4. Taxonomy: It is the
framing of rules for classification.
 THE LIVING wORLD 1.9
Utility of Systematics
The utility of systematics can be discussed under the
following
heads:
1. In the Study of Other Disciplines ofBiology:
studying other branches of Knowledge of systematics is helpful in
biology such as morphology,
genetics, evolution, population biology and plants and animals physiology, anatomy, pathology,
2. Applied breeding.
Biology: Proper knowledge of systematics is essential for the
plants and animal varieties of economic improvement of
importance.
(a) We obtain several useful products from wild
of plant pests, pollinators and plants. To protect these plants, knowledge
(b) The identification of various
organisms biological control is essential.
for
pathogens causing diseases of plants, animals and human
beings and their control measures need proper
the knowledge of identification. This is possible only with
systematics.
(c) Systematics helps in establishing
animals with their wild relatives.relationships amongst various domesticated plants and
3. Study ofOrganisms: A vast number of organisms are present on the earth. It is not
possible study all of them individually. With the help of
to
representatives from each group and can acquire the knowledge systematics, one can study a few
of other
is also essential to
identify new organisms being discovered day by day.organisms. Systematics
4. Evaluation of
Crops: Systematics is helpful in evaluating different crops, medicinal
ornamental and fod plants to increase their
yield.
plants,
5. Indicators:
Many organisms are indicators of pollution, fossil fuels and types of minerals
present in the soil. This can be achieved with the help of systematics.
Phylogeny
The evolutionary history of a particular species is called phylogeny. Classification of
based on their organisms
phylogenetic relationship or on the basis of evolution is called evolutionary or
phylogenetic classification.
Even according to Linnaeus the
Baptiste de Lamarck (1744-1829) introduced the concept thatspecies
were fixed entities.
species gradually change Jean
and
give rise to new species.

CONCEPT OF SPECIES
According to recent concept, a species includes all those organisms, that
1. resemble one another more than with individuals
of any other species.
2. have a broad
similarity in morphological characters.
3. are able to interbreed and
produce fertile offsprings.
4. have descended from a common ancestor even if located in remote
areas of the world.
5. show anatomical
complete similarity.
6.7. have similar karyotype and genetic material and
have similarity in their biochemistry.

TAXONOMICAL HIERARCHIES
Classification is a multi-step process. It involves hierarchy of steps and each step represents a
rank or a category. Each taxonomic category is a unit of classification and is termed as taxon
(PI. taxa).
Taxonomic hierarchy is the arrangement of taxonomic groups or taxons in a definite order
from higher to lower categories. The categories used in classification of animals are Kingdom,
hylum, Class, Order, Family, Genus and Species. In case of plants phylum is replaced by
Division. Thus in taxonomic hierarchy, there are minimum seven categories, called taxa. The
species is the lowest taxonomic category and kingdom the highest category. Linnaeus introduced
this
hierarchical system of classification.
 1.10 Isc BIOLOGY-11
Taxon
Various taxonomic categories-like
species, genus, family, order and class
are abstract terms and represent a rank
or level in taxonomic hierarchy. The SPECIES
tigris
term taxon is used to represent the
actual biological objects included in a
category. For example, tigers are real GENUS:
animals belonging to the species Panthera
category Panthera tigris. All cat-like
species of animals constitute the family
taxon Felidae and all mammals in the FAMILY:
Felidae
class taxon Mammalia.
Similarly, al
plants having barry-like fruits belong
to Family Solonaceae. ORDER:
Camivora
CategoryY
In classification, the organisms that
closely resemble one another are CLASS:
placed in a group, the groups having Mammalia
similarities are combined together into
larger groups, and these into still
larger ones. The various grouping
PHYLUM:
levels or ranks in classification are Chordata
known as categories. There are seven

major categories: Kingdom, Phyla,

Classes, Orders, Families, Genera and
DOMAIN:
Species. Bacteria
KINGDOM
Animalia
DOMAIN
Species Archaea
Species is the lowest basic and natural
unit in the classification. In sexually
DOMAIN:
reproducing organisms, interbreeding Eukarya
is the basic criterion for delimiting a
species. It means a species is defined Flg. 1.3 Linnaean classification: At each level or rank
species are placed in groups within more inclusive groups
as a group of organisms (animals or
plants) that closely resemble,freely interbreed and produce fertile offspring. They descend
from the common ancestor and because of common
ancestry, the members ot a species possess
similar hereditary material.
For example, Lion, Leopard and Tiger (Panther leo, P. pardas and P. tigris) belong to three
different species leo, pardas and tigris and can easily be identified. All thethree species belong
to the same genus Panthera. Similarly in plants Tomato, Potato and Brinjal, etc. belong to three
diferent species lycopersicum, tuberosum and melongena respectively. But all these three species
belong to same genera Solanum.
Genus
The genus is the next category higher to the species. It comprises a group of related species which
havemore characters in common than the species of other genera. For example, Potato, Tomato
and Brinjal are three different species but they belong to the same genus Solanum. Similarly, Lion,
Tiger and Panther belong to the same genus but are different species. Genus Panthera is different
from other genera of cats.
 THE LIVING WORLD 1.11
Pamily
Family is a group of related genera with still less number of similarities as
species. For example, Leopard, Tiger and Lion are placed in the cat compared to genus and
differentiated from the family of Dogs and Foxes Canidae. family Felidae. This family is
In
case of plants, Wheat, Rice and Maize are included in the same
Pea and Sòyabean in the
family Leguminosae
family,
Gramineae,
and genera Solanum, Petunia and Datura Gram,
in the family Solanaceae. are
placed
Order
The next higher category is the order which
includes related families. For
Carnivora includes families like Felidae and Canidae.
In
example, order
Leguminosae and Rosaceae. plants, order Rosales includes families
Since order is a higher taxonomic
characters. The similarities are lesscategory,
the families of order exhibit
in number
an
only a few similar
beBonging to a family. as
compared to similarities seen in genera
Class
The related orders are included in a
class. The similarities in the orders of a
than the families of an order. For
in class are still less
and Primata. The order Carnivora has example, class Mammalia has both the orders Carnivora
carnivorous mammals like Lion,
while order Primata contains
Man, Monkey, Chimpanzee, Gorilla, Gibbons, Tiger, Leopard, etc.,
plants with well etc. Similarly, all
developed vascular bundle are placed in class Tracheophyta.
Phylum
Phylum includes different classes of animals or
plants having very few similarities. For example,
classes like Pisces (fishes),
Amphibia (frogs and toads), Reptilia (snakes and
lizards), Aves
(birds) and Mammalia (mammals) are all
Division is used for Phylum. All grouped into a single phylum. In case of
plants, term
flowering
and fruit bearing plants are
placed in Division
Angiosperms.
Kingdom
All animals belonging to various phyla are placed together in the
Kingdom Animalia and all
plant divisions are put
together in Kingdom Plantae.
Suffixes used for Naming the Categories
Family: A plant family ends in a suffix.. aceae and subfamily in oideae. An animal family has
..

a suffix...
idae, a subfamily.. inae and superfamily has the suffix... oidea.
Order: In plants the order ends in a suffix... ales. Different suffixes
are used in animals,
Lagomorpha, Artiodactyla, Primata, Carnivora (all orders of class Mammalia). e.g..
Class: In plants the suffix used for class is..
case of animals,
phyceae, opisda 0r... ae. The suffix is not fixed in
...

e.g., Amphibia, Aves, Mammalia, Cyclostomata.

Phylum or Division: In plants, a division ends in suffix... phyta, a subdivision in... phytina while
there is no fixed suffix for animals, e.g., Porifera, Annelida, Cnidaria.
enus occupies a special position in the classification because
species cannot be named without
assigning the genus. The genus may or may not have more than one species. Genera with
one
species are called monotypic while those with more than two are only
polytypic.
Revision of Categories
(Classifying a
Group of Species)
Kevision of categories is associated
with establishing between defferent species and
grouping them into higher taxonomic categories onrelationship,
the basis of similarity in characters and
evolutionary relationship. These relationships are traced from sources of morphology, anatomy,
Subspecies, Varieties and Races
Subspecies, varieties and races are categories inferior in rank to species.
The term 'subspecies' is used by zoologists and
variety by the botanists. Subspecies or variety
is a distinct subgroup of species. It consists of one or more
populations which have certain
characteristics which distinguish its members from other members of the
The examples of subspecies and varieties are:
species.
Corvus splendens splendens: Indian crow
Corvus splendens protegatus: Sri Lankan crow
(subspecies)
Corvus splendens insolens: Burmese crow
(subspecies)
Brassica oleracea var. capitata: Cabbage
(subspecies)
Brassica oleracea var. botrytis: Cauliflower
(variety)
(variety)
Race is agroup of individuals within a species. Some taxonomists consider this term as
with subspecies while other consider synonym
race to be subordinate to
beings belong to genus Homo, species sapiens and subspeciesspecies. There
For example, human
human races. These are sapiens. are six main
All these races differ in
Negroid, Mongoloid, Caucasoid, Polynesian, Australoid and Bushman.
pigmentation of skin and hair, shape of nose and other physical features.
But members of all these races
though separated by geographical or spatial barriers, can freely
interbreed.
 1.14 ISc BIOLOGY-11

Binomial Nomenclature (Scientific Names)

In 1753, Carolus Linnaeus proposed the Binomial System of Nomenclature for the
animals. He is called The father of taxonomy. According to thie
scientific names of plants and
or animal, bears two names: the first is generic name and
system, each organism, whether plant
second is the specific epithet. He explained this system in his famous book, Systema Naturae
a name with two components is called Binomial
published in 1758. This system of providing
Nomenclature. For example, the scientific name of modern man is Homo sapiens sapiens, where
Homo is the generic name and sapiens is the species name. Second sapiens denotes the name of
subspeciesSimilarly, the scientific name of onion is Allium cepa, of mango is Mangifera indica,
tha dómestic cat is Felis domesticus and of honeybee is Apis mellfera.

Rles for Binomial Nomenciature

The organisms are given scientific name on the basis of universal rules, framed and
standardised by International Code of Botanical Nomenclature (1CBN) and International Code
of Zoological Nomenclature (ICZN). These help in avoiding error, duplication, confusion and
ambiguity in scientific names. The names of bacteria and viruses are decided by International
Code of Bacterial Nomenclature (ICBacN). Similarly, there is a separate International Code of
Nomenclature of Cultivated Plants (ICNCP),.
1. The scientific name of each animal or plant has a generic name followed by the name of
species (binomial nomenclature). Species having a subspecies, varieties or races are given
trinomial name.
2. The generic name begins with a capital letter and species name with a small letter.
3. Both the generic and the species name should be written in italics.
4. The taxonomist's name who first assigned the species name is added at the end. For
example, Homo sapiens Linnaeus (or L) is scientific name for modern human species. In this
case Linnaeus was the first scientist who named human beings as Homo sapiens.
5. To avoid confusion, no two generic names in any kingdom can be the same.
6. Scientific names are usually taken from Latin language. When words in a language other
than Greek or Latin are used, they are Latinised with suitable endings. For example,
Banyan is Ficus benghalensis. Here benghalensis means from Bengal, where banyan tree is
commonly found.
7. Generic and common names can be same as Gorilla is the generic name of Gorilla, and Ape.
Generic and species name can also be the same as Catla catla, a freshwater fish, and
Eucalyptus is the generic name of the plant Eucalyptus.

TABLE 1.3 Scientific Names of Some Common Organisms

ANIMALS PLANTS
Common Name Scientific Name Common Name Scientific Name
1. Cobra Naja naja 1. Mango Mangifera indica
2. Cockroach Periplaneta americana 2. Onion Allium cepa
3. Dog Canis familiaris 3. Potato Solanum tuberosum
4. Tiger Panthera tigris 4. Wheat Triticum aestivum
5. Man Homo sapiens 5. Mustard Brassica compastris
6. Frog Rana tigrina 6. Maize Zea mayss
7. Tapeworm Taenia solium 7. Neem Azadiracta indica

8. Earthworm Pheretima posthuma 8. Cabbage Brassica oleracea

9. Rat Rattus rattus 9. Pea Pisum sativum

10. Elephant Elephas maximus 10. Carrot Daucus caro

 THE LIVING wORLD 1.15
Trinomial Nomenclature

With the introduct of population systemati modern taxonomists found that it is essential
vnise even the subspecies within the species. Therefore, an organism is given a third name
Forexample, the common lion is Panthera leo. But lions of this species from different
r i s show minor differences from the original form. Therefore, a third subspecies name is
rbduced. The scientitic name of the Indian lion is
designated as Panthera leo persica
Adyantagés of Using Scientific Names
he ddvantages of giving scientific names to the organisms are given below:
1. Scientific name is universal, i.e., an organism has the same name throughout the
world.

2. All known animals and plants irrespective of their utility have been provided with
scientitic names. This facilitates systematic study of plants and
animals
3. Scientific name eliminates confusion of multiple naming of an organism in different regions.
4. It indicated a relationship between different varieties of a species in a genus. The Dog, Wolf
and Jackal have the same generic name, Canis. It implies that all these animals have certain
common characters.
5. It facilitates recognition identification of a newly discovered organism
or

An incorrect or misleading name can be

6.
easily corrected.
7. Scientific names often indicate certain important characteristic of the
organisms.
8. Scientific names are derived from Latin or Greek language. There is less possibility in the
change of meaning of their words because both these languages are dead.

AIDS FOR STUDY OF IAXONOMY

Techniques, procedures and stored informations that are useful in the identification and
classitfication of organisms are called taxonomic aids. Their nomenclature and placement in
taxonomical hierarchy are useful in agriculture, forestry and industry. Such studies are also
required for knowing our bioresources and their biodiversity. Identification of species and their
axonomical details are obtained by laboratory as well as field studies. The information so
gathered is stored and in many cases, the specimen is preserved for future studies.
Herbaria, botanical gardens, zoological parks, museums, etc., are several kinds of taxonomic
aidsthat help in taxonomic studies.

Herbaria
herbarium is a collection of well-pressed, dried and preserved plants mounted og herbarium
ts,properly labelled and systematically arranged and available for reference.
lants parts or plants such as succulents, fruits, seeds, corns, etc., which cannotbe mounted,
ther preserved in 2.5% formalin or FAA, or dried and stored in large containers. These dried
apreserved specimens kept in herbarium are then readily available for reference in
dxOnomical comparative and morphological studies.
Historical Account Herbaria
of
Mos
the o the herbaria have originated from the botanical gardens. It was Luca Ghini who set up
themerbarium at Pisa in Italy. He mounted plant specimens on paper sheets and then bound
Lin book volumes. Soon this art of making herbarium became popular al over Europe.
Worlasstarted storing the plants mounted on sheets in piles, a practice followed all over the
Tesently herbaria have grown into large national and international institutions.
 THE LIVING wORLD 1.17
s Only one specimen should be mounted on one herbarium sheet. While mounting, care
d be taken so that the
specimen is well spread and the specimen is
sh
of herbarium sheet. preferably in the centre

Labelling (7 cm 12 the
x
cm) of specimen
is done by entering the field information on right
hand side lower corner of herbarium sheet. It bears:
(a) Scientific name of the plant
(b) Common vernacular name
(c) Family
(d) Date of collection
(e) Habitat
( Locality
(g) Name of the collector
(h) Name of the institution
5. Storing of
Herbarium Sheets: The herbarium sheets are stored in
steel almirahs to protect
them from fire and insects. Herbarium sheets are
kept in a
specific order according to the approved
svstem of classification. Mostly, Bentham and Hooker's
system of classification is followed.
6. Fragment Packets: Small paper envelopes, called fragment packets, having seeds or extra
flowers are attached to the paper sheet.
7. index Register: An index register is maintained to locate desired specimen in alphabetical
order
8. Type of
Specimens: These are usually kept separately.
TABLE 1.4 Major Herbaria and their Locations

Name of Herbaria
Location Approx. number
of Specimens
A. In India
1. Herbarium of Forest Research
Institute, Dehradun Uttarakhand 3,00,000
2. Central National Herbarium of
Botanical Survey of India, Kolkata West Bengal
3. Madras 2,00,000
Herbarium, Coimbator Tamil Nadu 1,50,000
4.
Regional Herbarium, Shillong Meghalaya 86,000
5. Herbarium of NBRI, Lucknow Uttar Pradesh 80,000
6.
Regional Herbarium of BSI, Pune Maharashtra 12,000
B. In Other Countries
7. British Museum of Natural
8.
History, London Britain 65,00,000
Royal Botanic Garden, Kew Britain
9. Museum of Natural History, Paris 60,00,000o
France 60,00,000o
10.
11.
Conservatory & Botanical Garden, Geneva Switzerland 50,00,00o
New York Botanical Garden, New York USA
12. US 50,00,000
Nationl Museum, Washington USA 41,00,000
. Herbaridm of Komorov Botanical Institute, Leningrad Russia 40,00,000
Role of Herbaria
Herbaria play different roles:
are
re kept in Type Specimens: The type specimens of which the species names are established,
in safe
safe places with limited access.
ect
insects. They are protected from the attack of pests and
e Spepilation of Flora, Manuals and Monographs: The compilation work is mainly based on
pecimens in herbaria. The herbarium provides knowledge of plant taxonomy and distribution.
 1.18 19c BIOLOGY-11
&tdentification: Herbaria offer facility for identification of plants.
Research and Training: Herbaria have become centres for research in Plant Taxonomy
Opholo8Y, Plant Distribution, etc. These days they impart information on endangered species
SO. Many herbaria provide training in Herbarium Practices like plants collection, pressing,
drying, mounting, labelling, storing, etc.
reservation of Voucher Specimens: The specimens on which specialised studies such
as chromosomal, phytochemical or ultrastructural are conducted, are called voucher specimens.
These specimens are preserved in herbaria with all due precautions. On getting some
contradictory report, the voucher specimens are re-examined to confirm earlier findings.

Botanical Gardens
A botanical garden is a place with an assemblage of living plants maintained for scientific
teaching, research, conservation and public education. It also houses a laboratory, a library, a
herbarium and a museum. It also offers teaching and training facilities. The botanical gardens
are
mainly maintained by government and semigovernment agencies and private organisations
Historical Account of Botanical Gardens
The ancient history shows the existence of gardens in ancient India, Egypt, China, Mesopotamia
and some other countries. But they were not botanical gardens. They were simply used for
growing food plants, herbs, ornamental plants and for religious purposes.
The famous Hanging Gardens of Babylon, Mesopotamia is a typical example of Botanical Gardens.
It was during 1543-45, that the first Botanical Garden was established at Pisa in Italy by Luca Ghini.
But, this garden does not exist today.

TABLE 1.5 Some Major Botanical Gardens in the World

Name of Botanical Gardens Year of

Locations Establishment
1. Pisa Botanical Garden
Pisa, Italy 1543
2. Padua Botanical Garden
Padua, Italy 1545
3. Leyden Botanical Garden
4. Oxford Botanic Garden
Leyden, Netherlands 1590
5. Royal Botanic Garden
Oxford, England 1621
6. Botanical Garden of the Edinburgh, Scotland 1670
University of Vienna
Vienna, Austria 1754
7. Royal Botanic Garden
Kew, England 1759
8. Cambridge University
Botanic Garden
9. New York Botanical Garden Cambridge, England 1831
10. Botanic Garden New York, USA 1891
11. Main Botanic Garden Montreal, Canada 1931
Moscow, Russia 1945
TABLE 1.6 Some Major Botanical Gardens in India
Name of Botanical Gardens Year of
Locations Establishment
1. Acharya Jagadish Chandra Bose Indian Botanic Garden
2. Agri Horticultural Society Kolkata 1787
3. Government Botanical Gardens Kolkata 1820
4. Lalbagh Botanical Garden Udagamandalam 1847
5. Darjeeling Botanical Garden or
Lloyd Botanic Garden
Bengaluru 1856
6. Garden of the lndian Agricultural Research Darjeeling 1878
Institute New Delhi
7. Garden of the Forest Research institute 1905
Dehradun 1906
8. National Botanical Research Institute
Lucknow 1953
 THE LIVING woRLD 1.19
Piants Grown in Botenical Gardens
ln most of the botanical gardens, only those
plant species are grown which are found suitable
to the climatic conditions of that area In well known botanical
gardens, special enclosures with
ontrolled environmental conditions are maintained for the growth of some specific plants. Green
houses for cacti and other succulents and Screen
houses for foliage plants are the examples of
such enelosures Botanical Gardens also maintain
plants) and insectivorous plants
rare plants, bonsai (potted tree or shrub

Significence of Botenical Gardens

Herharium and
ibrary: A large number of botanical gardens have well maintained
herbaria and libraries to facilitate research
2onserv ation Botanical gardens play a key role in the conservation of endangered plant
specier and genetic diversity

Research. Since
materal tor biosystematic studies.
a wide range of
plants are found in botanical gardens, these provide ready
4Icological Role: Botanical gardens help in
improving the environment. purify the air and
serve as a habitat for a
large number of animals
5Aesthetic Appeal: A large number of people visit the botanical gardens to enjoy their
aesthet appeal
6. Exchange: Botanical gardens also act as acclimatisation centres for the introduction
Seed

ofeconomically useful plants. Many botanical

botanical studies.
gardens supply seeds and plant material for

Zoological Parks (Zoo)

An enclosed
place where wild animals are kept without any human control and in the
surroundings akin to their natural habitat is called a zoological park or a zoological garden or
Simply a zoo

Historical Account of Zoological Parks

Keeping wild animals for recreation is an old practice. But the history
of zoo is just 200 years
old when the first
public zoos were created. Since then, a large number of zoos have come up
all over the world. Now, zoos also include
birds aquaria, sanctuaries, and satari
serpentaria
parks, etc
According to World Zoo Conservation Strategy (WZCS), the zo0s are recreation centres for
the public and also conservation centres for wild animals. Some of the leading zoos have
adopted the programmes of conservation of endangered species and their natural ecosystems.

Aims 6f Zoological Parks

Zoos are involved in the conservation of
many endangered species of wild animals through
captive breeding. To conserve the wild life, special attention is being given to the protection of
natural habitats and ecosystems and the captive breeding of wild animals.
The Captive Breeding Specialist Group, (CBSG) of the
of International Union of Conservation of Nature and Natural
Species Survival Commission (SSC)
Resources (IUCN), is closely
associated with this programme. Ong other aim of zoological parks is to develop interest about
wild animals in the
public.
Care of Animals in Zoological Parks
Proper food and scientific humane treatment tends to increase the lifespan of zoo animals.
The health of animals
depends on four factors: enough food, fresh air, sunlight and enough
space for their movements.
1.20 180 BIOLOQY 11

Central Zoo Authority

A Central Zoo Authority has been set-up in our country to look after the management of
70ologi al parks. It coordinatles and supervises the activities of the zo0s and exchange of animalk
on Neientific basis. Each zoo is looked after by a director, supported by wardens, officestaff
Velerinary doctors, zoologists, supervisors, animal keepers and security persons.

Animals and their Habitats in Zoological Parks

Animals like lions, tiger, leopards, elephants, wolves, foxes, giraffe, zebras, deer, mountain goat,
to retreat in sun, rain
Kangaroos, kept
etc., in the open. But they are provided with a shelter
are
and at night. Certain animals like apes, monkeys, rodents, birds, reptiles (snakes, lizards),
etc., are kept in
amphibians (frogs, toads, salamanders) and arthropods like scorpions, spiders,
cages or glass showcases. Bats are kept in rooms with very dim light.
water fowls, ducks, geese, etc., are
Aquatic animals like otters, beavers, crocodiles, tortoises,
kept in artificial ponds or water courses. In foreign countries dolphins and seals are kept in big
enclosures. Fishes show an astonishing
tanks.Many zoological parks display fishes in glass
variety of form and colour patterns.
Actiíties in Zoological Parks
pological parks run many activities to amuse the visitors and for some specific purpose. Some
of these are:
Shows and Rides: For the amusement of visitors, zoological parks offer animal
1.such
rides
Animal
as camel ride, pony ride and elephant ride. Many zoological parks screen short
duration films depicting life and behaviour of animals.
Training Centres: In large zoological parks, there are centres of research
on
2. Research and
the lot of
requirements and breeding habits of animals. This is aimed improving
nutritional at
zo0 animals.
3. Recreation Centres: Thereare children's parks and restaurants in the zoological gardens
where visitors can relax and have their meals or refreshments.
animals of the
4. Gift Shop: Zoological parks have gift shop where souvenirs depicting
a
zoo

are available for purchase. Souvenirs keep us reminding of the visit to a zoo.

TABLE 1.7 Some Major Zoological Parks in India

Year of
Name of Zoological Parks Locations Establishment

1. Arignar Anna Zoological Park Chennai, Tamil Nadu 1855

2. Thiruvananthapuram Zoo Thiruvananthapuram, Kerala 1857
3. Sakkarbaug Zoological Garden Junagarh, Gujarat 1863
4. Alipore Zoological Gardens Kolkata, West Bengal 1876
5. Jaipur Zoo Jaipur, Rajasthan 1876
6. Sri Chamarajendra Zoological Gardens Mysore, Karnataka 1892
7. Lucknow Zoo Lucknow, Uttar Pradesh 1921

8. Assam State Zoo Guwahati, Assam 1957

9. Padmaja Naidu Himalayan Zoological Park Darjeeling. West Bengal 1958
10. National Zoological Park New Delhi 1959
11. Nehru Zoological Park Hyderabad, Andhra Pradesh 1959
12. Nandankanan Zoo Bhubaneswar, Odisha 1960
13. Sanjay Gandhi Jaivik Udyan Patna, Bihar 1969
Kanpur, Uttar Pradesh 1971
14. Kanpur Zoo
15. Indira Gandhi Zoological Park Visakhapatnam, Andhra Pradesh 1977
Nainital, Uttarakhand 1984
Altitude Zoo
16. Pt GB Pant High
 THE LIVING wORLD 1.21

ZoologicalMuseums
A2ological museum is a place which is used for the preservation, storage and exhibition of
arumate objects pertaining to the animal life.
History of Indian Museum
The indsan Museum was founded by the Asiatic Society of Bengal which was founded in 174.
t started storage and preservation of antiques in 1796 and the museum was established in 1814.
tally it had two sections (a) archaeological, ethnological and technical, and (b) geological
and zoologIcal.
Now. the zoological museum has following six sections:
1 Archaeology
Art
Zoolog
Industry and Botany
Anthropology
Geoiogy
Aims and Categories of Zoological Museum
The zoological museunms give more information about the animals than the zoological parks do.
Trese educate people about the animal life and create interest and love for animals. The museums
ve us a hidden message that animals share the earth with us, and we should learn to coexist
wih them Since extinction of animals would disturb the balance of nature, we should not
oserexploit the animal life.

TABLE 1.8 Some Important Museums of Natural History

Year of
Museums of Natural History Locations Estabiishment
Pars Museum of Natural History Paris, France 1793
2 kcatemy of Natural Sciences Phitadelphia, USA 1912
1 indan Museum Kolkata, india 1814
4. Museum Scienc Boston, USA 1830
Nanural Hisory Museum of Basel Basel, Switzerland 1840
Amercan Museum of Natural History New York, USA 1869
7. Natural Hisory Museum London, England 1881
&Mumoai Natural History Society (Hornbil House) Mumbal, India 1883
Musum of Natural History of Vienna Vienna, Austria 1889
6. Smtscnian iational Museum of Natural History Washington DC, USA 1910
11. aticnai Museum of Natural History Niew Deihi, tndia 1978

New Messo Museum of Natural History and Science

13.
New Mexico, USA 1986
Finnin Museum of Naturai History Helsinki, Finland 1988
14 Regonal Museum of Natural History Mysore, india 1995
Harvard Museum of Naturai Higtory Cambridge. USA 1998

t e zoological museuns may be small, mediun or large.

m a l l Museums: Every school and college where biology is taught has a small museum
e d to the biology or zoology department. It contains a limited number of specimens more
rticularly that figure in the syilabus or curriculum.
1.22 ISC BIOLOGY 11
2. Medium Museums: These museums are located in the zoology departments of
the
universities. These museums have relatively a large number of preserved specimens and of vivid
variety. These museums are looked after by curators
3. Large Museums: These museums are located in very big cities
only. These museums
maintain a large collection of preserved animals, their parts and products. These museums are
maintained by a large statf including a director, office staft, curators, etc.
These museums are entirely funded by the government or natural history societies.
Objects, Exhibits and Activities in Zoological Museums
1. Preserved Animals: Amphibians, fishes and nonchordates like sponges, cnidarians,
worms, mollusks and arthropods are kept in glass jars dipped in 25% formalin and 70% ethyl
alcohol. To avoid desiccations, the specimens and mounting of insects require a special

technique.
2. Stuffing: Birds, reptiles and beasts are stuffed and displayed. A stuffed specimen looks
like an original living animal. The stuffed animal is supported on a stand which itself is
mounted on a board.
The art of preparing and mounting of animal skin in its natural form is called taxidermy and

the person skilled in this field is called taxidermist.

3. Stuffed Heads: Heads of large mammals like walls.tiger, leopard, deer, bison, etc., are stuffed
and mounted on wooden plates to be hung o n the
4. Beaks, Feet, Eggs, Feathers and Nests of Birds: Beaks
and feet show different modes of
of different birds vary in colour patterns, feathers
feeding and perching respectively. The eggsnests
vary in and brilliance of colours and
design complexity of architecture. All these structures
are exhibited in glass showcases.
a r e called fossils. These are
Fossils: The remains of extinct birds, animals and plants
5.
m u s e u m s and give glimpses of past
life.
displayed in the natural history in glass
6. Elephant Tusks and
Molluscan Shells: The molluscan shells are displayed

showcases. These show a great variety of form

and colour. The elephant tusks a r e upper incisors
which make interesting exhibits in museums.

displayed in the museums.

7. Animal Products: Several types of animal products are

mud nests of wasps, pearls, lac, musk,

These include honeycombs, bee-swax, honey, silk,
ivory, etc.
world exhibited in the form of
8. Models and Charts: A number of events in the living are

other mammals a r e depicted with the help of models

models and charts. Human evolution and
and charts.
film shows to create interest in the
9. Film Museums also have arrangement for
Shows:
visitors about animal life.

Parks and Zoological Museums

TABLE1.9 Differences between Zoological
Zoological Museums
Zoological Parks
in the open or large enclosures. 1. Dead animals are well protected in rooms.
1. Animals are kept
here.
Whole stuffed animali their parts
2. Live animals are kept
(skeleton, feathers, etc.) and products (eggs.
etc.) are preserved.
3. Fossils are also displayed
3. Fossitls are not displayed are shown.
4. Animals from almost all the groups
4. Only certain groups of animals are shown.
 THE LIVING WORLD 1.25

Questions Option
1. Wings present Go to 2
Wings absent Go to 4
2. Feet webbed Duck
Feet unwebbed Go to 3
3. Upper beak movable Parrot
Upper beak not movable Hen
Skin covered with wool
Skin not covered with wool
Sheep
Goat
5. Teats four in number Go to 6
6. Horns coiled Buffalo
Horns straight Cow
Teats two in number Goat
5. Teats several in number (canines present) Go to 7
7. Capable of climbing Cat
7. Not capable of climbing
Dog

SYSTEMS OF BIOLOGICAL CLASSIFICATION

There are four main systems of biological classification. These are:

Artificial System of Classification

The artificial scheme of classification was based on superficial similarities. Pliny in first century
AD adopted thismethod and classified animals on the basis of habits, e.g., land, air and water.
On the basis of flying ability, animals were divided into two categories: (a) animals which can
fly (b) animals which cannot fly. But it could not differentiate birds, insects or bats.
Similarly, on the basis of habit, plants were classified into herbs, shrubs and trees. On the
basis of life-span, plants were classified as annuals, biennials and perennials, and on the basis
of nutrition they were classified as epiphytes, saprophytes and parasites.

Natural System of Classification

Natural system of classification is based on natural affinities among the organisms. It includes
not only the external, but also internal features like ultrastructure, anatomy, morphology and
cytochemistry. Natural system of classification was proposed by John Ray (1627-1705). This
system avoids the grouping of heterogeneous and unrelated organisms.
Phylogenetic System of Classification
he evolutionary history of a particular species is called phylogeny. Classificatiorn of organisms
based on the basis of evolution is called evolutionary or phylogenetic classification. According
to Jean Baptiste de Lamarck (1744 -1829) species gradually change and give rise to new species.
le
arranged all living creatures of past (fossils) and present (living ones) in an evolutionary
Sequence. Charles Darwin (1859) proposed theory of Origin of Species by Natural Selection
and established dynamic nature.
its

TABLE 1.10 Differences between Natural and Phylogenetic Systems

Natural System Phylogenetic System
his system is based on resemblances and 1. It is based on possible evolutionary sequences
aifferences amongst organisms. taken place.
2.
Fossils have a littie significance. 2. Fossils have a vital role in providing evolutionary
relationship.
3. It
has 3. It has lesser practical utility because organisms
more
practical utility have both primitive and advanced characters
and in many cases, fossil record is not available.
 THE LIVINGwORLD 1.23

TAXONOMICKEYS t
ta taNonomic studies, key is a set of alternate characters that helps in the identification of plants
d animals. This is achieved by selecting and eliminating the characters according to their
and
aresence or absence in the organisation under study. There is a species key for the identification
f species in a genus, key for the identification
a genus
of a genus in a family, and a family
key
for the identification of a family in an order and so on.
The taxonomic keys are of two types: Yorked or Indented key and Bracketed key.
1.Yorked or Indented key: It provides a sequence of choices between different statements
of characters made for a species. For example, in the family Ranunculaceae (belonging to
angiosperms) identification is made on the basis of the characters of the carpel and fruit of
different genera. First of all carpel with single ovule and achene type of fruit is considered over
to many-ovuled carpels and follicle type of fruits as shown below.

Identification Characters of Different Genera of

Family Ranunculaceae with Yorked Key
Identification Characters
Genus
1. Carpel single ovuled, achene type of fruit
(a) Leaves opposite and compound
Clematis
(b) Petals absent

(c) Leaves without tendril

(d) Petals present
(e) Third or terminal leaflet modified into tendril
Naravelia
(t) Leaves radical or alternate.
Anemone
2. Carpel many ovuled, follicle type of fruit

(a) Carpels united at base; flowers regular

Nigella
(b) Carpels free at the base; flowers irregular Aconitum

2. Bracketed Key:In this case, the key usescontrasting characters like the indented one but
they are not separated by intervening subdividing characters. Instead each character is given a
number in bracket. This can be explained by taking seven genera of family Ranunculaceae.
(a) Anemone: Leaves alternate or radial, flowers subtended by involucre, carpels - ovuled,
fruit achene.
b) Ranunculus: Leaves alternate or radical, flowers not subtended by involucre, carpels
ovuled, fruit achene.
c) Clematis: Leaves opposite, compound, petals absent, sepals 4, carpels 1-ovuled and fruit
achene.
(d) Naravelia: Leaves opposites, compound, terminal leaflets modified into tendrils, sepals and
petals present, carpels 1-ovuled, fruit achene.
e) Nigella: Flowers regular, carpels united at base, many ovuled, fruit a follicle.
Aconitum: Flowers irregular, posterior sepal enlarged to form hood, carpels free, many
ovuled, fruit follicle.
g) Delphinium: Flowers irregular, posterior sepal enlarged to form spur, carpel free, many
ovuled, fruit a follicle.