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Thursday, 8 October 2015


CLASSIFICATION: - Classification of organisms may be defined as a system of
arrangement of organisms into different groups and sub-groups on the basis of their
similarities, differences and relationship.
Classification of organisms is also known as taxonomy. It has the following
1. Classification makes the study of a wide variety of organisms convenient and
2. It is not possible for man to know about all the organisms but the study of a
few representatives from each taxonomic group gives a general idea of all life
forms at a glance.
3. Classification also reveals the interrelationship among different gr4oups of
4. Correct identification of an organism and its placement in a definite taxonomic
group is the basic requirement of various branches of biological sciences.
Thus, classification of organisms provides a base for the development of other
biological sciences.
Classification can be done on the following basis.
1. Cells are prokaryotic or eukaryotic. Organisms may be grouped into two
broad categories on the basis whether they possess prokaryotic cells or
eukaryotic cells. In case of prokaryotic cells the nuclei and other organelles
are not clearly demarcated. The eukaryotic cells, on the other hand, have
membrane-bound organelles, including a nucleus.
2. Cells occur singly or in clusters. Many organisms are unicellular, i.e. made
up of only one cell, e.g. Amoeba. Others are multicellular, i.e., cells group
together to form single organism (e.g., insect). In case of multicellular
organisms the different groups of cells carry out specialized functions
3. Organism is photosynthetic or takes food from outside. Green plants
perform photosynthesis an synthesis their own food. Animals cannot perform
photosynthesis. They get food from outside.

4. Organization of different body parts. Grouping of organisms may be done
on the basis of body organization. For example, plants possess stem, root and
leaves. Similarly, the animals possess specialized organs to perform different
function. The characteristic based on body design used for classification of
plants is quite different when used for classifying animals.
Systems of classification:-
R H whittaker in 1969, suggested five kingdom classification on the basis ofr
(i) preence or absence of a nucleus (ii) unicells or multicells and (iii) mode of
He proposed five kingdoms:
1. Monera, 2. Protista, 3. Fungi, 4. Plantae and 5. Animalia.
Monera: - these organisms do not have a defined nucleus or organelles, nor do any
of them show multi-cellullar body designs. They show diversity based on many other
characteristics. Some of organisms of this group are either autotrophic or
heterotrophic. This group includes bacteria, blue-green algae or cynobacteria and
Protista:- This group includes many kinds of unicellular eukaryotic organisms.
Some of these organisms use cilia or flagella for moving around. Their mode of
nutrition can be autotrophic or heterotrophic. Examples are unicellular algae,
diatoms and protozoans.
Fungi:- these are heterotrophic eukaryotic organisms. They are saprophytes and
thrive on decaying organic material. They have cell-walls made of chitin. Examples
are yeast and mushrooms.
Plantae:- these are multi-cellular eukaryotes with cell walls. They are autotrophs
and used chlorophyll for photosynthesis. All plants are included in this group.
Animalia:- these includes all multi-cellular organisms. They are heterotrophs.
Naming a correct scientific name to an organism or a taxon is called nomenclature.
It involves the principals governed by set rules formulated by internationals bodies
so that a particular organism or taxon is known by its specific name throughout the
According to the binomial system of nomenclature, the scientific name of an
organism consist of two separate components – first on designates the genus
(generic name) and the second one designates the species (specific name). For
example, the scientific binomial name of human species is Homo sapiens, where first
name Homo is generic and the second name sapiens is a specific. Homo sapiens are
understood to mean humans all over the world. Since this system of naming
organisms gives two names to an organism, it is known as a binomial
Various ranks used in classification (Hierarchy of classification).
In classification, the organisms that closely resemble one another are placed in a
group. These groups are further placed in large groups on the basis of close
similarities. The larger groups are again placed in still larger grouping levels or
ranks in classification are known as categories. Each category has its specific name.
There are seven major categories:
1. Species 2. Genus 3. Family 4. Order
5. Class 6. Phylum (for animals)/division (for plants) 7.Kingdom.
1. Species. Species is the lowest category regarded as basic unit classification. Itis a group of similar individuals which resembles with each other in
morphology, breed among themselves but not with others and probably
descended from a common ancestor.
2. Genus. A genus is a group of closely resembling species having a common
ancestry. A;; the species in a genus show similarities in broad features of their
organization but differ in minor details.
3. Family. A family represents a larger group of closely related genera. It is
composed of one or more genera.
4. Order. An order is a group of closely related families.
5. Class. A class is a group of related orders.
6. Phylum/Division. Phylum (in case of animals) or Division (in case of plants) is
a group of related classes.
7. Kingdom. Kingdom is the highest category in biological classification. It is
group of phyla (in case of animals) or divisions (in case of plants).
Mainly, the following rules apply to scientific names:
They were initially framed by Linnzeus. And were revised in 9th and 20th century
through international code of Botinical Nomenclature (ICBN) and international code
of Zoological nomenclature (ICZN). They are as followes:1. Each organisms has a distinct scientific name having a words, generic and
2. The generic and specific words should not have less then three letters or more
than 12(twelve) letters.
3. The generic name is written first. It is like a noun . Is first letter is always
4. The specific word is written after the generic name, It starts with small letter.
5. The name of the discoverer is appended to the two-word scientific name either
In full or abbreviate form e.g., mangifera indic . L(L stands for Linnaeus).
6. Scientific name is printed in italics hand written name is underlined.
7. When an organism has been given different scientific names by different
workers the “law of priority” is followed that is old valid name is accepted and
others rejected.
Characteristics features of kingdom plantae.
i) They are made of eukaryotic cells.
ii) They are multicellular.
iii) The cells have wall made of cellulose.
iv) They store carbohydrates such as starch.
v) Some cells (except in some parasites) contain chloroplast.
vi) The organisms feed by photosynthesis.

According to the classification proposed by eicher, plant kingdom is divided in to two
subkingdoms i.e crypotogamae and phanerogamae.
CRYTOGAMAE:- These are known as lower plants. The flower/seed are
absent and hence these are considered to have hidden reproductive organs. It
is categorized into 3 divisions.
1).THALLOPHYTA:- Thallophytes have a body which is not differentiated into stem,
root and leaves. This kind of undifferentiated body is called thallus, hence the name
It has the following characteristics.
(1) The plant body is thalloid i.e., cannot be differentiated into stem, root and leaves.
(2) The vascular system is absent in such plants.
(3) The reproductive organs are single called and there is no embryo formationThallophyta is further subdivided into:
(A) Algae
(B) Fungi
(C) Lichens
(A) ALGAE : They generally include aquatic plants. Some 20,000species of algae
are known. The main characteristics are as under :
1. They are generally chorophyllous thallophytes in which vascular tissues are absent.
2. The plant body is thalloid i.e., cannot be differentiated into root, stem and leaves.
3. They are found in fresh water resources as well as in sea water.
4. They are autotrophic because of the presence of chlorophyll in leaves. The
reserve food is generally a carbohydrate.
5. The cell wall is double layered. The outer layer is made of pectin and inner
layer is made cellulose.
6. They may be unicellular as well as multicellular.
7. A few members such as chlamydomonas are motile.
8. They reproduce by vegetative, asexual as well as sexual methods. The sex
organs are unicelled and lack a sterile covering around them.
Example : oedogonium, Chara, Sargassum, Ectocarpus, Chlamydomonas, Ulothrix
(B) FUNGI : it is a large group of over 90,000 species. They show the following
characteristics :
1. They are achlorophyllous and nonvascular plants.
2. The plant body may be unicelled or vthalloid, made of branched or unbranched filamentous structures, the hyphae.
3. The network of hypae is called mycelium.
4. The hyphae may be aseptate or sepate and each cell may be uni-or multinucleale.
5. The cell wall is made of chitin or fungal cellulose.
6. They show heterotrophic mode of nutrition.
7. The reserved food is in the form of glycogen and oil globules.
8. They reproduce by asexual or sexual methods.
9. The sex organs are unicelled and lack a sterile covering around them. The
higher forms lack distinct sex organs.
Example : Rhizopus, Yeast, Agaricus (Mushroom) etc.
(C) LICHENS : They represent a symbiotic association of a fungus and a alga in
which two organisms are so closely associated with each other as to form a single
plant. They are show growing long lived plants. The commonly grow on leaves, tree
trunks, old logs, soils and rocks. Some lichens occur in extreme conditions of cold,
humidity and drought.
In these plants the algal part prepares the food and the fungal part showsreproduction. Thus, their association is mutualistic.
2). BRYOPHYTA:- Bryophytes are simple terrestrial plants.
They have over 25,000 species. They show the following characteristics:-
1. They lice in damp and sandy habitates hence they are called amphibians of
the plant kingdom. They are aften found to grow during rainy season forming
green carpets or mats on damp soil, rocks, walls, tree trunks etc.
2. The vascular tissues are absent.
3. The roots are absent and instead rhizoids are present. They may be
unicellular or multicellular.4. The reproduction takes place by vegetative or sexual methods.
5. The vegetative reproduction is quite common through fragmentation tubes,
gemmae, buds, adventitions branches etc.
6. They show distinct alternation of generation.
Example: Riccia, Marchantia, Funaria (Moss).
(iii). PTERIODOPHYTA: - These are the oldest vascular plants this includes the
forms. The important characteristics are.
1. The plant body is differentiated into roots, stem, and leaves.
2. The dominant phase or plant body is a sporophyte.
3. They are seedless vascular plants and hence called vascular cryptogams.
4. The gymetophyte is small or inconspious.
5. The sex organs are multicellular.
6. The fertilization requires water medium results in the formation of zygote.
7. They show distinct alternation of generation.
Example : Selaginella, Adiantum, Dryopteris.
PHANEROGAMAE: - They are seed bearing plants. The plants body is differentiated
into ture stem, leaves and root. A well developed vascular system is presents in
phanerogames. Sex organs are multicellular.
On the basis of fruit formation, they are classified into two subdivisions.
(a) Gymnosperme and (b) Angiosperme
(a). GYMNOSPERME:- the term is made from two Greek words : gymo – means
naked and sperme means seed. The plants of this group bear naked seeds and are
usually pereneal, evergreen and woody. It has nearly 650 living species. They chief
characteristics are:-
1. They have well developed vascular tissues but lack vessels. The ‘flowers’
compose two types of sporophylls i.e., microsporophylls and megas[orohylls.
2. The pollination is anemophilous and the fertilization does not require water
medium. There is formation of pollen tube. (Siphonogamous)
3. The zygote develops into an embryo.
4. Since the ovules are not covered by a cattel there is no fruit formation. They
are naked.
Example : Cycas, Pinus and Emphedra etc.
(b). ANGIOSPERMAE:- The word is made from two Greek words: anger means
covered and sperma means seed. The seeds develop inside an organ which is
modified to become a fruit. These are also called flowering plants. They are most
abundant and conspicuous plants with about 2,00,000 species. The general
characteristics are.
1. They are usually terrestrial plants. The plant body is sporophytic.
2. The plants may be herbaceous or woody. They may be annual,biennial or
3. A well developed vascular system is present in them. The xylem has vessels.
4. The angiosperms are characterized by the presence of the double fertilization
forming a zygote and the primary endosperm, the nutritive tissue.
5. During fertilization the nonflagellate male gametes are carried by a pollen tube
(siphon gamous).
6. Fertilized ovules ripens into seed thus the ovary is converted into a fruit.
Example : Brassica campestris (Mustard), Pisum santivum (pea) etc.
Angiosperms are divided into Monocots and Dicots.
i. Monocot:- monocots bear seeds which have a single cotyledon or seed leaf . the
veins on their leave are parallel to each other. Their vascular bundles are arranged
in a complex manner.Example : Palms, Bamboos, Sugar – can, rice etc.
ii. Dicot:- the seeds of dicot have two cotyledons. The veins on their leaves are like a
network. Their vascular bundles are arranged in a ring. Their root system consists of
a man tap root with smaller branches.
Characteristics features of kingdom Animalae are:-
I. The organisms are made up of eukaryotic cells.
II. The body of animals is multicellular.
III. The cells do not contain cell wall, but contain only cell membrane.
IV. They do not perform photosynthesis but have heterotrophic nutrition.
V. They have the power of locomotion.
VI. They show increased sensitivity through the nervous system.
Basis of animal classification:- They are many features used for distinguishing
broad categories of animals. These features include organization, symmetry, body
cavity, number of embryonic cell layers and presence of absence of notochord.
Animals are multicellular. But their body cells may or may not be recognized
into tissues and organ systems. For example, animals such as sponges are
aggregate of cells. They are at a cellular level of organization. Human beings have
organs and systems for performing body functions and are at the organ-system level
of organization.
Symmetry means dividing the body into equal and identical parts. Sponges
are symmetrical. Cnidaria are radially symmetrical and all other animals are
bilaterally symmetrical.
Body Cavity
Body cavity or coelom is a cavity between the body wall and the food canal. It
is absent in Acoelomates and present in Euoelomates. The body cavity of
roundworms is not true and is known as Pseudocoelom.
Embryonic layers
There are three layers of cells-ecotoderm (outer layer), mesoderm (middle
layer), and endoderm (inner layer) in the embryo which give rise to parts of the body
of animals. Sponges and Cnidaria do not have mesoderm in their embryos and are
called diploblastic. Others animals have three layers of cells and are called
The notochord is a stiff rod running along the body, close to the dorsal
surface. The notochord helps to provide support to the animal. All chordates possess
a notochord at some stage of their development. The notochord is absent invertebrate animals, also termed as non-chordates.
The word means organisms with hopes. These are non-motile animals attached to
some solid support. They have holes all over the body. These animals are covered
with a hard outside layer or skelton. They are commonly called sponges and are
mainly found in marine habitats. Example: Euplectelia; sycon etc.
These are aquatic animals. They show body. The body is made of two layer of cells;
one makes up cells on the outside and the other makes the inner living body of the
body. They have a gut cavity with a single opening for food and waste material.
Example: hydra, Jellyfish.
These are generally called flatnorms they do not have a body cavity. The body isbilaterally symmetrical. Some of them are free, living in water and soil, but most are
parasites. There are three layers of cells in them and thus are called triploblastic.
They range from a few millimeters to a few centimeters in size. Reproduction is
mostly sexual. Example: Planarians, Liverflukes.
The organisms belonging to this group are mostly parasites having selender,
elongated bodies. Tapering at each end. There body is bilaterally symmetrical and
triploblastic. These cause diseases such as elephantiasis etc. Example: Ascaris,
.(5) ANNELIDA:- ‘Annelid’ means ringed. The annelids are worms with body
appearing as if made up of series of rings. Annnelids are a coelomates, triploblastic
animals. There is extensive organ differentiation. There body is segmented. Each
segment posseses a similar pattern of organs. These may be equatic or terristerials
and some live in tubes. Example: Earthworms, leaches.
(6) ARTHROPODA:- ‘Artho’ means joined and ‘pod’ means legs. Thus,
arthopropoda means jointed legs. These are triploblastic coelomates. They
metamerically segmented. These have an open circulatory system. The coelomic
cavity is blood-filled. They possess a hard exoskeleton. Sexes are usually separate.
Example : Prawns, Butterflies, Hies, Crabs.
(7) Mollusca:- the mollusca are animals with a coelomate triploblastic
body. There is bilateral symmetry. They have an open circulatory system and kidney
like organs for excretion. The body is often protected by a shell. They a muscular
foot to move. Sexes are separate or united. Example: Snails, Mussels.
(8) ECHINODERMATA:- ‘Echinos’ means hedgehog, and ‘derma’ means
skin. These are spiny skilled organisms. They are exclusively free-living marine
animals. They are triploblastic and have a coelomic cavity. They have peculiar
features of regeneration of lost parts. Sexes are separate.
Example: Starfish and sea urching.
(9) PROTOCHORDATA:- these are bilaterally symmetrical, triploblastic coelomate
animals. Notochord is present at some stage at some stage of their life history. These
are marine animals they have a closed blood system, they have a post-anal tail.
Example: Herdemania, Amphioxus.
(10) VERTEBRATA:- these animals have a true vertebral column and internal
skelton vertebrates are bilaterally symmetrical, triploblastic, Coelomic and
segmented, with complex differentiated of body tissues and organs.
(1). PISCES:- These are fish and live exclusively in water. Their skin is covered with
scales. They use oxygen dissolved in water by gills. They are cold – blooded and their
health have only two chambers. They lay eggs. The two important classes of fishes
are cartilaginous fishes and osteichthyes fishes. Example: sharks, Tuna, Rohu etc.
(2). AMPHIBIANS:-Amphibians means ‘Amphi’ ‘double’ and bias ‘life’. They are
partly adapted to live on land, and partly in water. Most amphibians lay their eggs in
water. These have three chambered hearts. Example: Frogs, Toads and salamanders
(3). REPTILES:- these animals can lively solely on land and are very less dependent
on water. These are cold blooded, have scales and breathe through lungs. These
have three chambered heart (except crocodiles). They lay eggs covered with
waterproof shells. Their skin is water proof and is covered with waterproof horny
scales. Example: Lizards, Snakes, Crocodiles, and Dinosaurs.
(4). AVES:- ‘AVIS’ means birds, evolved from reptiles and have many similarities
with them. These are warm-blooded and have a four chambered heart. They lay
eggs. Birds are distinguished because their bodies are covered with feathers, and
two forelimbs modified for flight. They breathe through lungs. Examples: Cuckoo,
crow, Sparrow etc.
(5). MAMMALIA:- Mammals are warm-blooded animals with four-chambered hearts.
They have mammary glands for the production of milk to nourish their young. Their
skin has hairs as well as sweet and oil glands. Most mammals give birth to theiryoung their ones. Sexes are separate. Example: Man, Tiger, At etc.

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