Biological classification – In India so far 81000 species of animals and 49000 species of plants have been described by zoological survey of India and botanical survey of India, respectively. Many of these organisms have become extinct and others are continuously changing to accommodate themselves in the changed environment.  To study such enormous diversity and abundance of plants and animals, one would naturally feel the the necessity of arranging these innumerable forms in group according to their similarities and dissimilarities. This is known as classification.

Need of classification

Living organisms need to be classified because of the following reasons: –

  1. The study of one or two organism is not sufficient to know the essential of life group.
  2. Classification help in knowing the relationship among different group of organisms.
  3. it helps in studying in revolutionary or phylogenetic relationship between organisms.

Type of classification system

Depending upon the type of system of classification, organisms are classified into following kingdoms which are as follows: -1.Two kingdom classification system: – Linnaeus divided all the living organisms into two kingdoms in 1758. They are –



Three kingdom classification: – Hackle classified living organisms into three kingdom




Five kingdom classification system: –  This classification was proposed by R.H whitkar in 1969. it is the most accepted type of classification and he classified all the organisms on the basis of cellular organisms, mode of nutrition, life cycle of an organisms etc. Into five kingdoms:-






1.Kingdom Monera

The kingdom monera (also called kingdom prokaryotes) consist of all prokaryotic organisms viz. eubacteria (true bacteria) cyanobacteria and the archaebacterial. They are unicellular: they lack true nuclei. Other membrane enclosed organelles such as mitochondria, chloroplast, lysosomes etc. Are also absent. Thylakoids are, however, present in phototrophs.  

It includes all the microscopic prokaryotic and unicellular organisms like bacteria microplasma (PPLO), cyanoplasma (Blue green algae). They have rigid cell wall made up of murein, also called peptidoglycan. Bacteria possess a cell wall but do not have a nucleus and mitochondria.

They reproduce simply by dividing into two separate cells asexually by binary fission.

Modes of nutrition are autotrophic (chemosynthetic and photosynthetic) and heterotrophic (saprophytic and parasitic).

Note: – Microplasma /PPLO is considered among a smallest member of bacteria that completely lack of cell wall (made up of peptidoglycan) and can survive without oxygen.

Types of bacteria:-

Based on shape: –

  1. Spherical shape – coccus (Cocci-plural)
  2. Cylindrical /rod shapes- Bacillus (Bacilli-plu)
  3. Spiral shape – spirillum
  4. Common shape- Vibrio

Based on presence or absence of flagella – The bacillus and spirillum forms may possess flagella. On the basis of the number and position of flagella, they have been classified as –

1.Atrichous: – Bacteria without flagella

2. Monotrichous: – bacteria with single flagellum

3. Lophotrichous: – Bacteria with more than one flagellum arising from one single end.

4. Amphitrichous: – Bacteria with flagella arising from two opposite ends.

5. Cepotrichous: – Bacteria with group of flagella arising from two opposite ends.

6.  Peritrichous: – Bacteria with flagella all around the body.

Based on straining property

  1. Gram +ve bacteria – Retain strain even after washing with acetone. e.g. Diplococcus, Pneumonia 
  2. Gram –ve bacteria – Do not retain stain even after washing with acetone. E.g. E. coli, Cyanobacteria  

Based on different modes of nutrition: –

  1. Archaebacteria-  Having a different cell wall structure and survival in extreme conditions. It represents earliest /oldest forms of bacteria.

e.g. a. Methanogens- present in the gut of ruminant animals (cows, buffaloes) and are responsible for the production of methane (biogas) from the of these animals.

b. Thermoacidophiles – can survive in hot temperature condition.

c. Thelophiles- can survive in saline condition.

Note: – Cell wall of Archebacteria is made up of cellulose.

2.Eubacteria – Having rigid cell wall and is made up of peptidoglycan. This type of bacteria shows autotrophic and heterotrophic modes of nutrition.

e.g.- cyanobacteria

3.Autotrophic bacteria – They are phototrophic bacteria and have chlorophyll similar to small plants.They oxidise various inorganic substances such as ammonium, nitrates, nitrides,etc and use the released energy for their energy production .They have specialized cell called heterocyst that fix atmospheric nitrogen.

4. Hetrotrophic bacteria: – They are most abundant in nature and collectively called decomposers /saprotrops because they are feeding on dead and decaying matters of living organisms. some of them are useful/beneficial and some are also harmful for the living organisms.

Note: – 

  1. Useful bacteria –   a. lactobacillus (helpful in making curd.) b. streptomycin (Used in the production of antibiotics)
  2. Harmful bacteria – Vibrio cholera – (These bacteria causes a disease called cholera).

Kingdom Protista –

1. It is a large and variable group containing organisms with both plant itself and animal characteristics. e.g. Euglena, Diatoms etc.

2. They are found almost everywhere but generally in water.

3. This kingdom include eukaryotic and unicellular organisms except bacteria and blue-green algae.

4.  They reproduce asexually and sexually by process involving cell fusion and zygote formation.

5.Mode of nutrition is autotrophic (Photosynthetic) and Heterotrophic. 

Note: – Kingdom Protista includes following classes which are as follows –

Class dristophyta – characteristics: – They are found in fresh water as well as in marine water. e.g.- The diatoms and golden algae.

They are microscopic and float passively in water current. e.g. – The diatoms and golden algae(dismites).

Note: – in diatoms the cell walls forms two thin – overlapping cell and are embedded with silica. Diatoms are the chief producers in ocean.

Dinoflagellates – They are mostly marine and photosynthetic in nature. 

They appear yellow, green, brown, red, blue, depending on the main pigments present in their cell.

The cell wall has stiff cellulose plates on the outer surface.e.g.-  Gonyaulatates (red dinoflagettes)

Euglenoids –

They are mostly fresh water organisms and found in stagnant water.

They lack cell wall but have protein rich layer called pellicle which makes their body flexible.

They have two flagella, short and a long one.

Their mode of nutrition is an autotrophic as well as e.g.- Euglena

Slime molds: – They are saprophytic protists.  

Under favorable conditions, they form an aggregation called plasmodium which, may grow a spread over several feet.

During unfavorable condition, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips.

Notes: – The spores possess true walls called cysts and are displaced by electric current.

Protozoa: – They are heterotrophs and live as predator or parasites.  They are primitive forms of lives on the earth. Them are four major groups of protozoan.

Amoeboid protozoans – lives in fresh water sea water or moist soil. They move and captures their food by giving out fingers like projections called pseudopodia (false feet). e.g.- amoeba, Entamoeba and some parasites.

Flagellated protozoans: – They are free living or parasitic and have flagella. The parasitic forms of disease such as sleeping sickness. e.g.-  Tripanosoma

Ciliated protozoans: – They are aquatic and actively moving organisms due to presence of cilia in their body surface. They have a cavity (gullet)that opens to the outside of the cell surface. e.g.- paramecium (commonly called slipper animals cell).

Sporozoans: – They are diverse organisms because they have an infectious spore like stage in their life cycle.e.g.-  Plasmodium (malarial parasitic) which cause malaria.

Kingdom fungi

Characteristics: – It includes eukaryotic and multicellular organisms such as molds, yeasts and mushrooms. Fungi looks like plant but are without chlorophyll. Cell wall is made of chitin .Mode of nutrition is of absorptive and heterotrophic type. The study of fungi is celled mycology. Structurally most fungi grow in the form of a cylindrical thread like structure called hyphae. Numerous hyphae twinned together to form mycelium (network of hyphae).

 Note: – Fungi are used in the production of cheese beer and wine. some are also useful in the production antibiotics (penicillin, notata) that help urine fatal disease like cancer. 

Reproduction in fungi: –

Vegetative reproduction: – By mission of fragmentation fission and budding.

Asexual budding: – By the formation of spores called conidia.

Sexual budding: – By formation of two spores.

Note: – The sexual cycle involves the following three steps

Fusion of protoplasm between two motile or non-motile gametes called plasmogeny.

Fusion of two nuclei called karyogamy.

Meiosis of zygote resulting in haploid spores.

Classes of Fungi

Ascomycetes: – ascomycetes (sac fungi) –Dung

Basidiomycetes: – (Club fungi)- soil, plants

Deutromycetes: – (Fungi imperfection)-mostly terrestrial

Phycomycetous: – (Lower or Algae fungi) –water and decaying water

They are commonly sac fungiThey are commonly called club fungiThey are common called fungi imperfectThey are common called lower /algal fungi.
Mycelium is branchedMycelium is branchedMycelium is unbranchedMycelium is unbranched .
Generally grow in dung .Generally grows in soil and plants .Generally grows on land .Generally grows in water and decayed plants.
E.g.- penicilium, aspergillus ,neurosporese.g.- Agaricus(common mushroom)ustilago(smult)paccinia (rust fungus )e.g.- Alternaria, trichoderma,colletotrichum  e.g.- Rhizopus,bread mould albugo,
Fig -1 Different types of fungi and their characteristics.

Kingdom plantae

1.It is a kingdom of macroscopic autotrophic plants (called metaphytes ) .All of them are multicellular and eukaryotic .

2.Except for some filamentous algae (e.g ulothrix, spirogyra) they show differentiation of tissues.

3.They have rigid cell wall made up of cellulose. It is present outside the memebrane. The cell possess plastid and a large central vacuole but centrosome is generally absent from plant cell.

4.The kingdom includes sea weeds like green, red and brown algae, all thalloids and foliase bryophytes, ferns, conifers and flowering plant. (angiosperms).

5.They are primary producers on land and algae sea shores. They also occur in all other type of aquatic habitats (lakes, ponds and streams).

6.Plants usually show very slow and poor response to to stimulus.

7. Food is mainly stored in the form of starch or fats.

8.Some plants are insectivorous: they fulfill their nitrogen requirement by digesting insects.

9. Reproduction takes place by sexual and asexual methods. In higher plants multicellular embryo is formed as fertilization. In lower plants (algae and bryophytes) the gametophytes forms the dominant phase of the life cycle whereas in higher plants (pteridophytes, gymnosperms and angiosperms) the sporophytic  phase is dominant and the gametophytes are inconspicuous.

Kingdom Animalia

1.The kingdom Animalia includes all multicellular heterotrophic organisms.

2.Most of the animals show organ system organization i.e. the cells form tissue (e.g.- epithelial tissue, glandular tissue) various type of tissue form organ (e.g.-  stomach, intestine, liver) and different organ co-ordinate to form system (e.g. Digestive system, reproductive system).

3. Animal cells are without cell wall, central vacuole and plastids but possess centrosome.

4.They generally reproduced by sexual method. gametes are formed in gonads. Haploids phase is represented only by gametes.

5. Animals show quick response to stimulus. They possess nerve cell which conduct the impulse.

6. Animals can move physically from one place to another and thus are capable of locomotion.

7. Ecological animals are consumer. They form link in different food chain and complex food webs.

Salient featureMoneraProtistaFungiPlantaeAnimalia
Cell typeProkaryoticEukaryoticEukaryoticEukaryoticEukaryotic
Cell wallNon- cellularPresent in somePresentPresentAbsent
Body orgnisationCellularCellularMulticellular TissueTissue organTissue Organ Organ system
Mode of nutritionAutotrophic HeterotrophicAutotrophic HeterotrophicAutotrophicAutotrophicheterotrophic
Fig 2: Five kingdom classification

Virusses, viroids and lichens

 In the five kingdom classification of whitecker, there is no mansion of some organisms like viruses, viroid and, lichens    

Virusses – The name virus means venome /poisonous fluid,was given by D.J Ivanwsky in 1892 They are categorized by having an inert crystalline structure outside the living surface. Insert virus outside the cell is called virion. They show the characteristics of both living and non-living organisms.Viruses are smaller than bacteria pox virus is the largest and polio virus is the smallest. D.J Ivanowsky (1892) discovered the first virus from extract of tobacco plant suffering from TMV (Tobacco mosaic virus). Viruses are simple, non-cellular initiates consisting of one or more molecule of either DNA or RNA enclose in a coat of protein they can reproductive only within living cells and are obligate intracellular parasites.

Note: –  A fully assembled infectious virus is called virion .

Type of virus

 A. on the basis of their cell

Helical shape. e.g. – TMV

Cuboidal shape e.g.- Polio virus

Binal shape e.g.-  Bacterio-phage(T2-T4)

B. on the basis of host

Plant virus (TMV)

Animals Virus (Chicken pox)

Bacteria Virus or Bacteriophage

Phycophage (Virus parasite or Algae)

Mycophage (Virus parasite on fungi)

1.Plant virus

They cause disease in plants.e.g.- TMV, PMV (Potato mosaic virus) tomato leaf curl virus

Biological classification

Note: – Majority of plants viruses have RNA as genetic material but many possess DNA

e.g- (Cauliflower mosaic viruses)

2. Animal Virus: – They cause disease in animal including human beings. Polio virus, influenza virus, Small pox virus, mumps virus, Rhinovirus, common cold viruses.

Note: – Majority of animal virus DNA as genetic material but several possess RNA as genetic material Rabies virus, Polio virus etc.) 

Bacteriophage: – These are also called bacterial virus.e.g.-  T2, T4,

Biological classification

Structure of virus: – A complete virus particle or a virion consist of following structural components.

1.Nucleoids: – It represents the viral chromosomes .it is made up of a single molecule of nucleic acid. It may be linear of circular with various degree of coiling. Nucleoid is the infective part of viruses. The nucleic acid is either DNA or RNA but never both DNA containing viruses are called Deoxyribose while RNA containing virus are termed as riboviruses .

2.Capsid – it is the protein covering around the virus with protect the nucleoid from damage to genetic material from chemical, Physical agent. The capsid consist of a number of sub units called copsomers or capsomeres.

3.Envelop – it is a loose membrane covering that occurs in some animal viruses rarely plants and bacterial viruses. The viruses without an envelope are called nacked. Envelop consist of proteins from viruses, lipids and carbohydrate (From host). It has sub-unit called peplomers or peplomers common envelop virus’s HIV.

Viriods – In 1971 T.O dineal discovered a new infections agent that was smaller than viruses and causes potato splinders tuber disease. It was found to be a free RNA as a genetic material and it locked the protein capsid i.e found in viruses , Hence the name viriods .The RNA of the Viriods .The RNA of the viriods was law of molecular weight . Licheans – Licheans are symbiotic association i.e mutually useful association between algae and fungi . The algal component is known as phycobioant and fungal component is known as micopoint. With are autotrophic and heterotrophic respectively. Algae prepares food for fungi and fungi provides shelter and absorbed mineral nutrients and water for its partners. Licheans are very good pollutions indicators because they do not grow in polluted areas hence these are used in controlling the environment pollutions.

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Tapoj class 11 notes and solutions.

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