DIVERSITY IN LIVING ORGANISMS
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 advantages. 1.
Classification makes the study of a wide variety of organisms convenient and
easy. 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 organisms. 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.
BASIS OF CLASSIFICATION:- 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 of
(i)
preence or absence of a nucleus
(ii)
unicells
or multicells and
(iii)
mode of
nutrition.
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 mycoplasma.
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.
NOMENCLATURE:- 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 world.
BINOMIAL NOMENCLATURE:- 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
nomenclature. 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. It is 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. Oder. 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 scientific.
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 capital.
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.
KINGDOM PLANTAE:- 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.
PLANT KINGDOM 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 thallophytes. 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 formation. Crypotogama Phanerogama Thalloph Bryophy Pteridoph Gymnosper
Angiosper Algae Fungi Lichens Monoco Dicot
Thallophyta 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 etc.
(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
shows reproduction. 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 perennial.
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.
KINGDOM ANIMALIA Characteristics features of
kingdom Animalia 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. Organization 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- 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 triploblastic.
Notochord -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 in vertebrate animals, also termed as
non-chordates.
ANIMALS Cellular Tissue Porifera Codenterata
Plathyhelminthes Nematoda Coelomate Annelida Arthropoda Mollusca Echinodermate
Henichrodata Chordata Protochordata Vertebrata Pisces Amphibia Reptilia Aves
Mammalia
(1) PORIFERA:- 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.
(2) COELENTERATA:-
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.
(3) PLATHELMINTHES:- These are generally called flatnorms
they do not have a body cavity. The body is bilaterally 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.
(4) NEMATODA:- 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, Lumbricoides.
(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 etc.
(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 their young their ones. Sexes
are separate. Example: Man, Tiger, At etc.
