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BIOLOGICAL CLASSIFICATION
BIOLOGICAL CLASSIFICATION
Prerequisites
Learning Objectives
• Kingdom Monera
• Kingdom Protista
• Kingdom Fungi
• Kingdom Plantae
• Kingdom Animalia
• Viruses, Viroids and Lichens
Prerequisites
Before studying this chapter, you are required to know the following concepts as pre-requisites for better
understanding of this chapter:
1) Clear understanding of diversity in the living world.
2) Basic understanding of biology and biological concepts.
3) What is classification and why it is required in any field.
4) What is the meaning of a ‘kingdom’ and
5) Different taxonomic categories and the position of taxonomic category “Kingdom”.
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BIOLOGICAL CLASSIFICATION
Learning Objectives
After completing this chapter you will be able to know and answer the following concepts:
1) Why classification is required
2) Two kingdom classification
3) Five kingdom classification
4) Merits of five kingdom classification
5) Kingdom Monera
6) Kingdom Protista
7) Kingdom Fungi
8) Kingdom Plantae
9) Kingdom Animalia and
10) Viruses, Viroids and Lichens.
Let us study the above concepts in brief with some examples.
Introduction
In the last chapter, we studied “Diversity in the living world”. As we knew that life on earth is famous for its
diversity. There are millions of different types of organisms living in this world. Hence, they need to be classified
into different groups to help identify them. The biggest groups into which living organisms are classified into are
called “kingdoms”. Aristotle was the earliest to attempt a more scientific basis for classification.
Two Kingdom Classification:
Two kingdom system of classification was developed during Linnaeus’ time. These two kingdoms are Plantae and
Animalia which include all plants and animals respectively.
This system did not differentiate prokaryotes and eukaryotes, unicellular and multicellular organisms and
photosynthetic (green algae) and non-photosynthetic (fungi) organisms. This system included a large number of
organisms which does not fit into either category. Hence it was found to be inadequate.
Aristotle two kingdom Classification
kingdom
kingdom
Plantae
Animalia
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BIOLOGICAL CLASSIFICATION
Five Kingdom Classification:
It was proposed by R.H. Whittakar (1969).
The five kingdoms defined by him are: Kingdom Monera, Protista, Fungi, Plantae and Animalia. The main criteria
for his classification are cell structure, mode of nutrition, reproduction, thallus organization and phylogenetic
relationships. See the table for comparative understanding of different characteristics of the five kingdoms.
Monera
R.H. Whittakar
Five Kingdom
Classification
Animalia
Protista
Plantae
Fungi
Characters
Cell type
Cell wall
Five Kingdoms
Monera
Procariotic
Protista
Fungi
Eucariotic
Eucariotic
Non cellular
Present
(Polysaccharide) Present in some (without cellulose)
+ amino acid
Plantae
Eucariotic
Eucariotic
Present
(cellulose)
Absent
Nuclear
membrane
Absent
Present
Present
Present
Body
organisation
Cellular
Cellular
Multicellular/
loose tissue
Tissue/
organ
Autotrophic
(chemosynthetic
and
Photosynthetic)
and Heterotrophic
(saprophyte/
parasite)
Autotrophic
(Photosynthetic
and
Heterotrophic
Mode of
nutrition
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Heterotrophic
(Saprophytic/
Parasitic)
Animalia
Autotrophic
(Photosynthetic)
Present
Tissue/organ/
organ system
Heterotrophic
(Holozoic/
Saprophytic
etc)
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BIOLOGICAL CLASSIFICATION
Benefits of Five Kingdom Classification:
1) Earlier classifications placed prokaryotic bacteria and the blue green algae with other groups which are eukaryotic. This classification separated prokaryotes from eukaryotes.
2) All unicellular eukaryotic organisms are kept in one group.
3) Differentiated heterotrophic fungi from autotrophic green plants.
4) It is based on evolutionary relationships.
In this chapter, we shall study the characteristics of kingdom Monera, Protista and Fungi of five kingdom
classification.
KINGDOM MONERA
Kingdom Monera includes Bacteria which most abundant micro-organisms. Bacteria live in extreme habitats like
hot springs, deserts, snow and deep oceans. Prokaryotes are bacteria which are unicellular and have no distinct
nucleus. They have a naked DNA. Structure is simple but behaviour is complex. They show the most extensive
metabolic diversity. Some of the bacteria are autotrophic i.e. they prepare their own food material from inorganic
substances.
Vast majority of bacteria are heterotrophic i.e. they do not synthesize their own food but depend on other organisms
or on dead organic matter for food.
Bacteria
Categories of Bacteria:
Bacteria are grouped into 4 categories based on their shape. They are
1. The Spherical Coccus (plural: cocci)
2. The Rod-shaped Bacillus (plural: bacilli)
3. The comma-shaped Vibrium (plural: vibrio) and
4. The Spiral-shaped Spirillum (plural: spirilla).
Bacteria
Coccus
Bacillus
Vibrium
Spirillum
Categories of Bacteria
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BIOLOGICAL CLASSIFICATION
Archaebacteria:
These are special type of bacteria live in most harsh
habitats such as extreme salty areas (halophiles),
hot springs (thermoacidophiles) and marshy areas
(methanogens). The reason for living in most harsh
habitats is because of having a different cell wall structure.
The production of methane (biogas) from the dung of
ruminant animals such as cows and buffaloes is because
of the presence of methanogens kind of bacteria in their
gut.
Archaebacteria
Eubacteria:
These are true bacteria characterized by the presence
of a rigid cell wall and a flagellum, if motile. These are
either autotrophs or heterotrophs based on how they
synthesize their food.
Cyanobacteria (or) blue-green algae have chlorophyll
similar to green plants called photosynthetic autotrophs.
Eubacteria
Cyanobacteria:
These are true bacteria characterized by the presence of a rigid cell wall and a flagellum, if motile. These are either
autotrophs or heterotrophs based on how they synthesize their food.
Cyanobacteria (or) blue-green algae have chlorophyll similar to green plants called photosynthetic autotrophs.
The cyanobacteria are unicellular, colonial or filamentous, marine or terrestrial algae. The colonies are surrounded
by gelatinous sheath.
Some of these bacteria can fix atmospheric nitrogen inspecialized cells called heterocysts. Examples: Nostoc
and Anabaena.
Hetirosysts
Cyanobacteria
Nostoc
Anabaena
Some bacteria which oxidize various inorganic
substances like nitrates, nitrites and ammonia for their
ATP production are called chemosynthetic autotrophic
bacteria. They play major role in recycling nutrients like
nitrogen, phosphorous, iron and sulphur.
Chemosynthetic autotrophic bacteria
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BIOLOGICAL CLASSIFICATION
Heterotrophic bacteria are the most abundant in nature. These act as decomposers and helpful in making curd
from milk, production of antibiotics, fixing nitrogen in legume roots etc.
Some heterotrophic bacteria are pathogens causing diseases in human beings, crops, farm animals and pets.
The method of reproduction in bacteria is fission. The smallest living cells without a call wall and survive without
oxygen called mycoplasmas. These are pathogenic in animals and plants.
Heterotrophic bacteria
Mycoplasmas
Binary Fission in Bacteria
KINGDOM PROTISTA
These are single-celled eukaryotes. They contain a well defined nucleus and other membrane bound organelles.
Algae and Protozoa are included in this kingdom. Mostly unicellular or simple multi-cellular. These members live
in water i.e. aquatic in nature.
This kingdom forms a link with other kingdoms dealing with plants, animals and fungi.
Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation.
In this module, we include the following groups under kingdom Protista:
1. Chrysophytes
2. Dinoflagellates
3. Euglenoids
4. Slime moulds and
5. Protozoans.
We shall see some characteristics with examples for the above groups.
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BIOLOGICAL CLASSIFICATION
Kingdom Protista
Chrysophytes
Dianoflagellates
Euglenoids
Slime moulds
Protozoans
Kingdom Protista
1. Chrysophytes:
It includes diatoms and golden algae (desmids) found in fresh water as well as marine water. They are microscopic
and float passively in water currents (plankton). In diatoms, the cell walls form two thin overlapping shells. The
walls are embedded with silica and thus the walls are indestructible and left behind in large quantities. This
accumulation over billions of years is referred to as ‘diatomaceous earth’.Diatoms are chief producers in the
oceans.
Diatomacious Earth
Examples of Diatoms
2. Dinoflagellates:
These are mostly marine and photosynthetic appear in
different colors like yellow, green, brown, blue or red
depending on the main pigments present in their cells.
The presence of stiff cellulose plates on the outer surface
of cell wall and two flagella is a characteristic feature of
dinoflagellates. One flagella lies longitudinally and the
other transversely in a furrow between the wall plates.
Example: Gonyaulax (Red dianoflagellate) – These
multiply very rapidly and make the sea appear red (red
tides).
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Dinoflagellates
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BIOLOGICAL CLASSIFICATION
Gonyaulax (Rad dinoflagellate)
3. Euglenoids:
These are fresh water protists found in stagnant water.
No cell wall but pellicle is present which makes their body
flexible. Two flagella are present – a short and a long one.
In the presence of sunlight they are photosynthetic in
nature, otherwise they act as heterotrophs.The pigments
present in euglenoids are similar to those present in
higher plants.
Example: Euglena.
4. Slime Moulds:
These are saprophytic protists. The body moves along
decaying twigs and leaves engulfing organic material.
They form an aggregation called plasmodium under
suitable conditions and spread over several feet. During
unfavourable conditions, the plasmodium differentiates
and forms fruiting bodies bearing spores at their tips.
The spores are highly resistant and dispersed by air
currents.
long flagella
short flagella
Pellicle
Euglena
fruiting body
Smile Moulds
5. Protozoans:
All protozoans are heterotrophs and live as predators or
parasites.
There are four major groups of protozoans:
1. Amoeboid protozoans – Example: Amoeba and
Entamoeba
2. Flagellated protozoans – Example: Trypanosoma
3. Ciliated protozoans – Example: Paramoecium and
4. Sporozoans – Example: Plasmodium (Malaria
parasite).
Trypanosoma
Paramecium
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Amoeba
Entamoeba
Plasmodium
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BIOLOGICAL CLASSIFICATION
KINGDOM FUNGI
We commonly observe rotten oranges, moulds on the bread in our daily life. These are all because of fungi. The
common mushroom we eat and toadstools are also fungi. White spots on the mustard leaves are due to a parasitic
fungus.
Oranges
Leaf
Bread
Yeast, unicellular fungi, is used to make bread and beer. Some fungi cause diseases in plants and animals. For
example; Puccinia causes rust disease in the wheat.
Fungi are cosmopolitan but they prefer to grow in warm and humid places.
Fungi have filaments. Fungi bodies have long, slender thread like structures called hyphae. The network of hyphae
is known as mycelium. Coenocytic hyphae are continuous tubes filled with multinucleated cytoplasm.
Fungi
Mycelium
The cell walls of fungi are composed of chitin and polysaccharides.
Moulds, yeasts and mushrooms are included in the kingdom fungi. These are heterotrophic eukaryotes with a
chitin cell wall. They are also saprotrophs, meaning they get their food from the decomposing matter. Some fungi
depend on plants and animals for their food are called parasites.
They also live as symbionts – in association with algae as lichens and with roots of higher plants as mycorrhiza.
Reproduction in fungi is by both sexual and asexual methods. Fragmentation, fission and budding are the
vegetative means of reproduction.
Above figures in association with algae as lichens and with roots of higher plants as mycorrhiza
Asexual reproduction is by spores called conidia or sporangiospores or zoospores whereas sexual spores are
oospores, ascospores and basidiospores. These spores are produced in specialized structures called fruiting
bodies.
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BIOLOGICAL CLASSIFICATION
Reproduction in fungi
vegetative reproduction
Asexual reproduction
sexual reproduction
Fragmentation
Conidia
oospores
Fission
sporangiospores
ascospores
budding
zoospores
basidiospores
The sexual cycle involves three steps as follows:
1. PLASMOGAMY: Fusion of protoplasms between two
motile or non-motile gametes.
2. KARYOGAMY: Fusion of two nuclei.
3. SPORES FORMATION: Meiosis in zygote resulting in
haploid spores.
Examples of Sexual cycle in Fungi
Classification of the Kingdom FUNGI:
Kingdom Fungi classified into the following classes based on the morphology of mycelium, mode of spore formation
and fruiting bodies.
Fungi
Phycomycetes
Basidiomycetes
Ascomycetes
Deuteromycetes
Classification of the Kingdom Fungi
Phycomycetes:
Members belong to phycomycetes live in aquatic habitats and decaying wood in moist places. They also live as
obligate parasites on plants.
The mycelium is aseptate and coenocytic.
Asexual reproduction is by zoospores (motile) or by aplanospores (non-motile). These are produced endogenously
in sporangium.
Zygospores are formed by fusion of two gametes. These gametes are isogamous or anisogamous.
Examples: Mucor, Rhizopus (Bread mould) and Albugo (Parasitic fungi on mustard)
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BIOLOGICAL CLASSIFICATION
Mucor
Rhizopuses
Albugo
Ascomycetes:
These are also known as sac-fungi.
These are unicellular or multicellular in nature. Example for
unicellular ascomycetes is yeast (Sacharomyces).
Example for multicellular ascomycetes is Pencillium.These
are saprophytic, decomposers, parasitic or coprophilous
(growing on dung). Mycelium is branched and septate.
Yeast
Pencillium
The asexual spores are conidia which are produced on conidiophores. Conidia on germination produce mycelium.
Ascospores are sexual spores produced in a sac like asci (singular ascus) which are arranged in fruiting bodies
called Ascocarps.
Examples: Aspergillus, Claviceps and Neurospora.
Neurospora is extensively used in biochemical and genetic work.
Aspergillus
Claviceps
Neurospora
Basidiomycetes:
Mushrooms, bracket fungi or puff balls are common members of basidiomycetes.
These fungi cause plant diseases called rusts and smuts.
Asexual spores absent. Vegetative reproduction by fragmentation is common. Special sex organs are absent.
The fusion of two vegetative cells of different strains results in plasmogamy which results in dikaryotic basidium
(plural basidia).
Karyogamy and meiosis takes place inside basidium resulting
in four basidiospores.
Basidia are arranged in fruiting bodies called Basidiocarps.
Examples: Agaricus (Mushroom), Ustilago (Smut), Puccinia
(Rust fungus).
Agaricus
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Ustilago
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BIOLOGICAL CLASSIFICATION
Deuteromycetes:
These are commonly known as imperfect fungi because only the asexual or vegetative phases are known. Once
perfect (sexual) stages were known, they often moved to ascomycetes and basidiomycetes. Mycelium is branched
and septate. The asexual spores are conidia.
A large number of members are decomposers on litter and help in mineral cycling.
Examples: Alternaria, Colletotrichum and Trichoderma.
Alternaria
Colletotrichum
Trichoderma
KINGDOM PLANTAE
It includes chlorophyll containing multi-cellular eukaryotes called plants. Cell wall is present and made up of
cellulose. Most of the members are autotrophic means that they prepare their own food material. A few members
are partially heterotrophic such as the insectivorous plants or parasites.
Insectivorous plants or Parasites
Examples for insectivorous plants are – Bladderwort and
Venus fly trap.
Example for a parasitic plant – Cuscuta.
Life cycle shows alternation of generation by having
haploid gametophytic and diploid saprophytic phases.
You will study further details in the next chapters.
Dionaea
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Cuscuta
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BIOLOGICAL CLASSIFICATION
KINGDOM ANIMALIA
It includes heterotrophic multi cellular eukaryotes called animals. Cell wall is absent. Depend on plants directly or
indirectly for food. Stores food reserves as fat or glycogen. The mode of nutrition is holozoic. These are capable
of locomotion. Reproduction is sexual. Further details can be studied in the coming chapters.
Multi cellular Eucaryotes
VIRUSES, VIROIDS AND LICHENS
Viruses:
Viruses are not placed in a proper kingdom as they are not truly ‘living’.
Viruses are non-cellular organisms and they have an inert crystalline structure outside the living cell.
TMV
Vaccinia virus
Adeno virus
Polio virus
Rabies virus
The name ‘virus’ means venom or poisonous fluid was given by Pasteur. D.J. Ivanowsky (1892) when he
recognized certain microbes as casual organism of the mosaic disease of tobacco.
M.W.Beijerinek (1898) extracted a fluid called Contagium vivum fluidum (infectious living fluid) which cause
infection in healthy plants.
W.M. Stanley (1935) crystallized the viruses and shown that crystals consist largely of proteins. Viruses are
obligate parasites as they are inert outside their specific host cell.
Pasteur. D.J. Ivanowsky
(1892)
M.W. Beijerinek
(1898)
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W.M. Stanley
(1935)
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BIOLOGICAL CLASSIFICATION
Body has protein coat called capsid and genetic material is DNA or RNA. No virus contains both RNA and DNA.
Plant viruses have single stranded RNA. Animal viruses have double stranded DNA or RNA. Animal diseases like
mumps, herpes, small pox, influenza and AIDS are caused by viruses. Plant diseases like mosaic, leaf rolling,
curling and yellowing of leaves is caused by viruses.
Rabies virus
RNA
TMV
Bacteriophage
Viroids:
Discovered by T.O.Diener in 1971.
Smaller than virus and lack protein coat, hence called
viroids.
It has a free RNA of low molecular weight. It caused
potato spindle tuber disease.
T.O.Diener
(1971)
Lichens:
The mutually beneficial symbiotic association between algae and fungi is known as lichens.
The algal component is known as phycobiont and fungal component as mycobiont which are autotrophic and
heterotrophic respectively.
Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its algal
component. Lichens do not grow in polluted areas and hence they are very good pollution indicators.
Lichens
algal component
(Phycobiont)
fungal component
(Mycobiont)
Autotrophic
Heterotrophic
Lichens
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BIOLOGICAL CLASSIFICATION
SUMMARY
•
•
•
•
•
•
Aristotle was the earliest to attempt a more scientific basis for classification based on morphological characters.
Two kingdom classification was proposed by Linnaeus. He divided all the living organisms into two kingdoms
namely Plantae and Animalia.
Five kingdom classification was proposed by Whittakar. They are Monera, Protista, Fungi, Plantae and Animalia.
The main criteria for five kingdom classification were cell structure, body organization, mode of nutrition ,
reproduction and phylogenetic relationships.
Kingdom Monera includes bacteria which are prokaryotic in nature. Bacteria are unicellular without distinct
nucleus. Bacteria may be autotrophic or heterotrophic in their mode of nutrition.
Kingdom Protista includes single-celled eukaryotes. Algae and Protozoa are included in this kingdom. These
are aquatic in nature.
Kingdom fungi include moulds, yeasts and mushrooms. Fungi are heterotrophic eukaryotes with a chitin in
their cell wall. Most fungi are saprophytic in their mode of nutrition.
Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes are the four classes included in the
kingdom fungi.
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