Biological Classification: Class 11 Biology NCERT Chapter 2

Key Features of NCERT Material for Class 11 Biology Chapter 2 – Biological Classification

In the previous chapter: The living world, you must have learned about how cells are the building blocks of the living world and the structural and functional unit of life. In Chapter 2 of NCERT Class 11 Biology textbook: Biological Classification, you will know how biological classification is done to put the immense number of animals and plants into categories that can be easily named and recalled without ambiguity.

Notes on natural grouping for class 11. There have consistently been endeavors to arrange living life forms in mankind’s history. In prior occasions, individuals have done arrangements intuitively with no logical measures. Aristotle was the principal individual to endeavor order. Moreover, Aristotle utilized basic morphological characters to empower the grouping of plants into bushes, spices, and trees. Moreover, Aristotle separated creatures into two gatherings dependent on whether they had red blood or not. 

Thusly, Linnaeus approached with a significant arrangement of living life forms into two realms Animalia and Plantae. Whittaker approached with a detailed five-realm characterization Protista, Monera, Fungi, Plantae, and Animalia. Generally imperative, the five-realm rating’s fundamental standards were the structure of a cell, method of sustenance and generation, and the phylogenetic connections. Along these lines, this class 11 notes of organic characterization will jump profound into this point. 

 Quick revision notes

Natural characterization is known as a particular strategy of putting and masterminding living beings into gatherings and subgroups relying upon their likenesses and dissimilarities and gathering them in a progressive system of classes. 

Importance of classification

  • The living being of the past can’t be concentrated without a legitimate arrangement of characterization. 
  • Arrangement 
  •  Artificial arrangement of grouping 
  • The common arrangement of grouping 
  • The phylogenetic arrangement of grouping 

Counterfeit arrangement of order Only a couple of morphological characters for gathering of a life form is utilized. Blossoming and non-blooming plants, weakness, and pallor.

The characteristic arrangement of order Takes into thought practically identical investigation of a few characters to bring out natural similitudes and dissimilarities and furthermore intelligent connections among the life forms—Bentham and Hooker characterization, and so forth. 

Phylogenetic System of Classification–It depends on the developmental relationship of life forms. In this framework, orgIt is beyond the realm of imagination to expect to concentrate each creature. 

  • The investigation of a couple of living beings of a gathering gives adequate data about the basic highlights of the gathering. 
  • It helps in the distinguishing proof of another living being. 

Arrangement helps in knowing the connection between various gatherings of organisms.anisms are grouped dependent on their development on earth from crude to exceptionally advanced—Engler and Prantl order and Hutchinson characterization, and so forth.

Contingent on the kind of arrangement of grouping, life forms are ordered into following realm frameworks. 

Realm arrangement of grouping 

  1. Two realms: Plantae Animalia 
  2. Three realms: Plantae Protista Animalia 
  3. Five realms: Monera Protista Fungi Plantae Animalia 
  • Two realms: Plantae Animalia 

In two-realm frameworks of arrangement, living beings are gathered dependent on the nearness and nonappearance of a cell divider proposed by Linnaeus( father of scientific categorization). 

  • Three realms: Plantae Protista Animalia 

Three realm frameworks Haeckel isolated unicellular creatures, green growth, and parasites dependent on absence of tissue separation, and the new realm Protista was presented. 

  • Five realm: Monera Protista Fungi Plantae Animalia 

Five kingdom systems:

R.H.Whittaker isolated all the living beings in five-realm to create phylogenetic grouping. 

Classification of Monera

  1. The realm of Monera incorporates all prokaryotes-mycoplasma, microbes, actinomycetes, and cyanobacteria. 
  2. Contain the most crude of living structures and are unicellular, prokaryotes. 
  3. The cells are tiny, and the cell divider is commonly present. 
  4. Genetic materials are not composed into the core and contain stripped DNA. 
  5. Membrane limited organelles are missing. 
  6. Reproduction is abiogenetic with the exception of quality recombination. 
  7. Flagella might be available and are of single-abandoned. 

Classification of Monera

Example- Blue-green algae, Bacteria, etc.

Microscopic organisms are the most plentiful microorganism that can make due in a wide range of climate.The atmosphere incorporates conditions like extraordinary pungent zones (halophiles), natural aquifers (thermoacidophiles), and mucky territories (methanogens). Different microbes have diverse cell divider structures (nonappearance of peptidoglycan). 

Methanogens are answerable for creating biogas (methane) from the compost of these creatures. They are available in the gut of a few ruminant creatures like dairy animals and bison. 

Biological Classification: Class 11

Eubacteria – They are called real microscopic organisms. They contain an inflexible cell divider if the motile contains flagellum. Cyanobacteria or blue green growth are gram-positive photosynthetic microorganisms. They contain chlorophyll and carotenoids. They might be unicellular, provincial or filamentous, freshwater, marine, or earthly. The nearness of certain has specific heterocyst cells to perform nitrogen obsession (Nostoc and Anabaena). 

Chemosynthetic microbes oxidize inorganic substances like nitrate, nitrite, alkali, and so on to deliver vitality and help in reusing nitrogen, phosphorus, sulfur, and so forth. 

Heterotrophic microorganisms are the most bountiful and go about as decomposers. They are useful in the creation of curd, anti-toxin, and fixing nitrogen in leguminous plants. Some of them are pathogenic and cause sicknesses like cholera, typhoid, lockjaw, and citrus infection. 


Mycoplasma – they are the least difficult free-living prokaryotes. They are otherwise called PPLO (Pleuropneumonia like life forms). They do not have a cell divider, can get by without oxygen, and can likewise cause ailments in plants and creatures. 


Kingdom Protista incorporates Chrysophytes, Dinoflagellates, Euglenoids, ooze form, and Protozoans. 

  1. It incorporates all the unicellular and frontier eukaryotes. 
  2. Most of them are sea-going framing tiny fish. 
  3. Their methods of sustenance are photosynthetic, saprophytic, parasitic, or holozoic. 
  4. Flagella, if present, is 11 abandoned with a 9+2 game plan of microtubules and made out of tubulin. 
  5. Genetic material contains at least 2 DNA atoms. 
  • They incorporate brilliant green growth (desmids) and diatoms found in freshwater just as marine water. 
  • In diatoms, the cell divider structures two meager covering cells that fit together in the soapbox. 
  • The siliceous indestructible cell divider accumulates at the base of water repositories and makes huge stacks called diatomaceous earth. It might stretch out for a hundred meters and be utilized for cleaning, filtration of oil, and syrups. They are boss makers in seas. 
  • They are unicellular, motile, biflagellate, and photosynthetic protists. 
  • Predominate shading is brilliant earthy colored, however yellow, green, red, and even blue additionally exists. 
  • Some Dinoflagellates like Gymnodinium and Gonyaulax develop in enormous numbers in the ocean and make the water look red and cause the alleged “red tide.” 
  • They are Euglena like unicellular lashes which have pellicle which make their body adaptable. 
  • They have two flagella, one short and another long. 
  • They are photosynthetic within the sight of daylight and go about as predators without the sun. 
  • Example-Euglena, Peranema. 

Ooze Molds 

  • Slime Molds are saprophytic protists. They feed on rotting twigs and leaves. 
  • Under positive conditions, they structure a total called plasmodium, that produce fruiting bodies that bear spores. 
  • Cellulose is available in the cell mass of spores. 
  • Air flows scatter the spores. 
  • Example-Physarum, Fuligo. 


  • They are known as crude family members of creatures. 
  • Being heterotrophs, all protozoans live as either predators or parasites. 
  • Amoeboids move and catch food by pseudopodia, some being parasitic. 
  • Flagellated protozoans have flagella and they are free-living or parasitic. 
  • Ciliated protozoans are sea-going creatures and they have cilia all over their body for development. 
  • Sporozoans incorporate a living being that has an irresistible spore-like stage in its life cycle. 

Protozoan: Biological Classification

 Kingdom Fungi

  • Organisms from this realm are spore-shaping, heterotrophic, achlorophyllous non-vesicular eukaryotic life forms.
  • Chitin or contagious cellulose makes cell dividers.
  • They have their held food as glycogen.
  • Saprophytic, parasitic, or harmonious is a method of sustenance.
  • Reproduction may be vegetative (fracture, splitting or sprouting), sexual generation, by oospores, ascospore and basidiospores or agamic (conidia, sporangiospores or zoospores). 

Sexual cycles include 

  1. Combination of male and female gametes, plasmogamy.
  2. Combination of two cores, karyogamy.
  3. Meiosis in zygote for delivering haploid spores. 


  • These are found in sea-going natural surroundings and on rotting wood in sodden and soggy spots. 
  • The mycelium is coenocytic and aseptate. 
  • Asexual multiplication is finished by aplanospores (non-motile) or zoospores( motile).
  • Examples are Mucus, Rhizopus, Albugo and so forth.

Fungi: Biological Classification

Ascomycetes (The sac fungi)

  • They are coprophilous (developing on fertilizer) or saprophytic, decomposers, parasitic. 
  • Conidia are stretched, mycelium, septate and agamic spores. 
  • Sexual spores are otherwise called ascospores which are delivered inside the fruiting body known as ascocarps.

Examples are Neurospora, Aspergillus, Claviceps, etc.

Basidiomycetes (The club fungi)

  • The mycelium is septate and branched.
  • Vegetative reproduction is done by fragmentation. Sexual reproduction is done by somatic cells or two vegetative cells that form basidium. Asexual spores are not found.
  •     Examples are Agaricus, Ustilago, Puccinia.

Deuteromycetes (The fungi imperfect)

The mycelium is septate and fanned. 

  • Vegetative propagation is finished by fracture. Sexual propagation is finished by substantial cells or two vegetative cells that structure basidium. Abiogenetic spores are not found. 
  • Examples are Agaricus, Ustilago, Puccinia

Kingdom Plantae

 They are coprophilous (developing on fertilizer) or saprophytic, decomposers, parasitic. 

  • Conidia are stretched, mycelium, septate and agamic spores. 
  • Sexual spores are otherwise called ascospores which are delivered inside the fruiting body known as ascocarps. 

Kingdom Animalia

  1.   Heterotrophic, eukaryotic organisms that are multicellular and cell wall are absent in the cell.
  2.   Holozoic is the mode of nutrition and reserve food is fats or glycogen.
  3. Sexual reproduction is done by copulation between males and females followed by embryological development.

Virus, Viroids and Lichens

Five kingdom system of classification which  do not include Virus,Lichens and Viroids.

  • Non-cellular organisms are also known as Viruses. When they insert in crystalline structure outside the living.And when they enter the living cell, they take over the machinery of the living cell to replicate themselves.
  •  D.J.Ivanowsky who recognized certain microbes as causal organisms of mosaic disease of tobacco.
  •  In addition to proteins, viruses also contain genetic material that could be DNA or RNA. In general, viruses that infect plants have single stranded RNA and viruses that infect animals have double stranded DNA.
  • Some common diseases caused by viruses are the common cold, influenza. 
  • Smallpox, AIDS are leaf rolling and curling.
  • Bacteria feeding virus are also called Bacteriophage.They are usually double stranded of DNA viruses.
  • The protein coat is called capsid which is made of small subunits called capsomeres, which protects the nucleic acid. These capsomeres are arranged in  polyhedral geometric forms or helical.
  • T.O.Diener discovered viroids as a new infectious agent smaller than virus causing potato spindle tuber disease. They are free RNA without any protein coat.

Also, Lichens are known as a symbiotic association amidst the algae and fungi. Phycobiont is known as the algal part and fungal parts are called Mycobiont. They are good pollution indicators as they do not grow in polluted areas.





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