DIVAKARAN T,

PGT BIOLOGY,

JNV DAVANAGERE,KARNATAKA

BIOLOGICAL CLASSIFICATION

BIOLOGICAL CLASSIFICATION

Students will be able to:

• Understand the process of classification of organism
• Identify the different categories of bacteria,phycobiont and mycobiont,RNA and DNA virus
• Define dikaryon,alternation of generation
• Describe the features of different protozons,virus
• Apply the gained knowledge
• Appreciate the role of bacteria in human progress

Learning Outcomes:-

BIOLOGICAL CLASSIFICATION

INTRODUCTION:-

Bewildering variety of life around us has evolved on the earth over millions of years. However, we do not have more than a tiny fraction of this time to try and understand all these living organisms, so we cannot look at them one by one. Instead, we look for similarities among the organisms, which will allow us to put them into different classes and then study different classes or groups as a whole. In order to make relevant groups to study the variety of life forms, we need to decide which characteristics decide more fundamental differences among organisms. This would create the main broad groups of organisms. Within these groups, smaller subgroups will be decided by less important characteristics.

Aristotle was the earliest to attempt a more scientific basis for classification.

Non-motile-Plants:

• morphological characters to classify

plants into trees, shrubs and herbs.

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Motile-Animals:

• Classified based on habitat
• those which had red blood and

those that did not.

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Biological System of Classification

TWO KINGDOM

THREE KINGDOM

FOUR KINGDOM

SIX KINGDOM

Five Kingdom Classification -R.H. Whittaker (1969)-

The kingdoms defined by him were named

1. Monera, Protista, Fungi, Plantae and Animalia.

The main criteria for classification include:-

• cell structure,
• thallus organisation,
• mode of nutrition,
• reproduction and
• phylogenetic relationships.

KINGDOM MONERA

Bacteria are grouped under four categories based on their shape:

1. Coccus -spherical
2. Bacillus -rod-shaped
3. Vibrium - comma-shaped
4. Spirillum - spiral

• Bacteria - members of the Kingdom Monera.
• They are the most abundant micro-organisms.
• Bacteria occur almost everywhere and also live in extreme habitats such as hot springs, deserts, snow and deep oceans .
• Many of them live as parasites

ARCHAEBACTERIA

EUBACTERIA

MYCOPLASAM

KINGDOM MONERA

ARCHAEBACTERIA:

• Live in some of the most harsh habitats
• Archaebacteria in having a different cell wall help them to survive in extreme conditions.
• Methanogens are present in the gut of several ruminant animals which produce methane (biogas) from the dung of these animals.

1.HALOPHILES-Extreme salt area

2.THERMOACIDOPHILIES-Hot springs

3.MEHANOGENS-marshy area

ARCHAEBACTERIA

• Presence of a rigid cell wall, and if motile, a flagellum.
• The cyanobacteria - unicellular, colonial or filamentous, freshwater/marine or terrestrial algae.
• The colonies are generally surrounded by gelatinous sheath. They often form blooms in polluted water bodies.
• The cyanobacteria or blue-green algae have chlorophyll a similar to green plants and are photosynthetic autotrophs
• They can fix atmospheric nitrogen in specialised cells called heterocysts, e.g., Nostoc and Anabaena.

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EUBACTERIA OR ‘TRUE BACTERIA’.

EUBACTERIA OR ‘TRUE BACTERIA’.

• Chemosynthetic autotrophic bacteria-
• oxidise various inorganic substances such as nitrates, nitrites and ammonia.
• They play a great role in recycling nutrients like nitrogen, phosphorous, iron and sulphur.

HETEROTROPHIC BACTERIA-

• Important decomposers.
• They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc.
• Some are pathogens causing damage to human beings, crops, farm animals and pets..

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• Bacteria reproduce mainly by fission and produce spores during unfavorable condition.

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• They also reproduce by a sort of sexual reproduction, conjugation.

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• Organisms that completely lack a cell wall.
• They are the smallest living cells,PPLO-Pleuro Pneumonia Like Organism.
• They can survive without oxygen.
• Many mycoplasma are pathogenic in animals and plants.

MYCOPLASMA

KINGDOM PROTISTA

• Members of Protista are primarily aquatic.
• Includes Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds and Protozoans.

1.CHRYSOPHYTES

• Includes diatoms and golden algae, desmids.
• Found in fresh water as well as in marine environments, are microscopic as planktons.
• Most of them are photosynthetic.
• Cell walls form two thin overlapping shells.
• The walls are embedded with silica
• Diatomaceous earth-accumulation of large amount of cell wall deposits in their habitat.
• Used in polishing, filtration of oils and syrups.
• Diatoms are the chief ‘producers’ in the oceans.

2. DINOFLAGELLATES

• Mostly marine and photosynthetic.
• Appear yellow, green, brown, blue or red depending

on the main pigments present in their cells.

• The cell wall has stiff cellulose plates on the outer surface.
• Most of them have two flagella; one lies longitudinally and the

other transversely in a furrow between the wall plates.

• Red tide-Very often, red dinoflagellates ,Gonyaulax,

undergo such rapid multiplication that they make the sea appear red .

3.EUGLENOIDS

• Fresh water organisms found in stagnant water.
• With a protein rich layer called pellicle which makes their body flexible instead of cell wall
• They have two flagella, a short and a long one.
• Generally photosynthetic , when deprived of sunlight they behave like heterotrophs
• Interestingly, the pigments of euglenoids are identical to those present in higher plants. Example: Euglena.

4. SLIME MOULDS

• Are saprophytic protists.
• The body moves along decaying twigs and leaves engulfing organic material.
• Plasmodium-an aggregation during during suitable conditions which may grow and spread over several feet.
• During unfavorable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips.
• The spores possess true walls, dispersed by air currents.

5.PROTOZOANS

• Heterotrophs -live as predators or parasites.
• Believed to be primitive relatives of animals.
• There are four major groups of protozoans.

Amoeboid protozoans: live in fresh water, sea water or moist soil. Move and capture their prey by pseudopodia Eg.. Amoeba.

• Marine forms have silica shells on their surface. Entamoeba are parasites.

Flagellated protozoans: either free-living or parasitic. They have flagella. The parasitic forms cause diaseases such as sleeping sickness. Example: Trypanosoma.

Ciliated protozoans: aquatic, presence of thousands of cilia.

• With a cavity (gullet) that opens to the outside of the cell surface.
• Movement of rows of cilia causes the water laden with food to be steered into the gullet. Example: Paramoecium.

Sporozoans: organisms that have an infectious spore-like stage in their life cycle.

• Plasmodium (malarial parasite) which causes malaria.

KINGDOM FUNGI

• Kingdom of heterotrophic organisms.
• Unicellular and multicellular.
• Hyphea-long, slender thread-like structures which form bodies of fungi.
• Mycelium-The network of hyphae .
• Some hyphae are continuous tubes filled with multinucleated cytoplasm – these are called coenocytic hyphae.
• Others have septae or cross walls in their hyphae.
• The cell walls of fungi are composed of chitin and polysaccharides.
• Fungi- saprophytes, parasites,symbionts – in association with algae as lichens and with roots of higher plants as mycorrhiza.

• Reproduction-by vegetative means – fragmentation, fission and budding.
• Asexual reproduction – spores like conidia or sporangiospores or zoospores,
• Sexual reproduction- oospores, ascospores and basidiospores.
• The sexual cycle involves the following three steps:

(i) Plasmogamy -fusion of protoplasms between two motile or non-motile gametes

(ii) Karyogamy -Fusion of two nuclei .

(iii) Meiosis in zygote resulting in haploid spores.

• Dikaryon-fungi like ascomycetes and basidiomycetes an intervening

dikaryotic stage (n + n, i.e., two nuclei per cell) occurs after fusion.

• They are found in aquatic habitat and on decaying wood in moist and damp places, as obligate parasites.
• The mycelium is aseptate and coenocytic.
• Asexual reproduction by zoospores( motile) or aplanospores (non-motile).
• A zygospore is formed by fusion of two gametes.

Example- Mucus, Rhizopus, Albugo etc.

PHYCOMYCETES

ASCOMYCETES (THE SAC FUNGI)

• They are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
• Mostly multicellular or rarely unicellular.
• Mycelium and branched and septate and asexual spores are conidia on conidiophores
• Sexual spores are called ascospores produced inside the fruiting body called ascocarps.

Example- Neurospora, Asperigillus, Claviceps etc.

BASIDIOMYCETES (THE CLUB FUNGI)

• They grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts
• The mycelium is branched and septate.
• Vegetative reproduction is by fragmentation. Asexual spores are not found.
• Sexual reproduction is by two vegetative or somatic cells forming basidium.
• Basidiospores are produced in basidium by developing a fruiting body called

basidiocarps.

• Example- Agaricus, Ustilago, Puccinia.

DEUTEROMYCETES ( THE FUNGI IMPERFECT)

• Only vegetative and asexual phase is known, hence fungi imperfect
• Mycelium is septate and branched.
• Some members are saprophytes or parasites and mainly decomposers
• Reproduce only by asexual spores known as conidia.
• Example- Alternaria, Trichoderma, Colletotrichu.

KINGDOM PLANTAE

• Eukaryotic, chlorophyll bearing organism.
• A few members are partially heterotrophic such as the insectivorous plants or parasites.
• Insectivorous-Bladderwort and Venus fly trap.
• Parasite- Cuscuta .
• Life cycle is divided into diploid saprophytic and haploid gametophytic, which alternate with each other,hence alternation of generation
• Includes Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.

KINGDOM ANIMALIA

• Heterotrophic, eukaryotic organisms that are multicellular and cell wall is absent in the cell.
• Capable of locomotion.
• Show elaborate sensory and neuromotor mechanism.
• Mode of nutrition is holozoic and reserve food is glycogen or fats.
• Sexual reproduction is by copulation between male and female followed by embryological development.

VIRUS

• L.Pasteur-named virus that means venom or poisonous fluid
• D.J. Ivanowsky (1892) -recognised certain microbes as causal

organism of the mosaic disease of tobacco .

• M.W. Beijerinek (1898)- demonstrated that the extract of the infected

plants of tobacco could cause infection in healthy plants and called the

fluid as Contagium vivum fluidum (infectious living fluid).

• W.M. Stanley(1935)- showed that viruses could be crystallised and crystals consist largely of proteins. .

VIRUS

• Viruses are non-cellular organisms having inert crystalline structure outside the living.
• Viruses are obligate parasites.
• When they enter the living cell, they take over the machinery of living cell to replicate themselves.
• In addition to proteins, viruses also contain genetic material that could be DNA or RNA.
• Virus that infect plants have single stranded RNA and virus that infect

animals have either single or double stranded RNA or double stranded DNA.

• Bacterial viruses or Bacteriophage (viruses that infect the bacteria) are

usually double stranded DNA viruses

• Causes diseases like common cold, influenza, AIDS, small pox,

leaf rolling and curling.

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VIRUS

• The protein coat called capsid made of small subunits called capsomeres, protects the nucleic acid.
• These capsomeres are arranged in helical or polyhedral geometric forms.

LICHENS

• Lichens are symbiotic association between algae and fungi. The algal part is called
• Phycobiont and fungal parts are called Mycobiont.
• They are good pollution indicator as they do not grow in polluted area.