Study Material and Notes of Ch 2 Biological Classification Class 11th Biology
Topics in the Chapter
System of Classification
• Earliest classification was given by Aristotle. He divided plants into herbs, shrubs and trees.
Animals into those with red blood and those who do not have it.
• Two kingdom classification: Given by Carolous Linneaeus. They are:
(i) Kingdom plantae
(ii) Kingdom Animalia
• Five kingdom classification: Given by R.H. Whittaker. They are:
(i) Monera
(ii) Protista
(iii) Fungi
(iv) Plantae
(v) Animalia
• The main criteria for classiÆcation of organisms into Æve kingdoms include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.
Kingdom Monera
• Has bacteria as sole members.
• Bacteria can have shapes like : Coccus (spherical), Bacillus (rod-shaped), Vibrium (comma shaped) and spirillum (spiral shaped).
• Bacteria found almost everywhere and can be Photosynthetic autotrophs, Chemosyn thetic autotrophs or Heterotrophs.
• Bacteria are divides in two parts:
(i) Archaebacteria
(ii) Eubacteria
• Halophiles (salt-loving)
• Thermoacidophiles (in hot springs)
• Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)
• Photosynthetic autotrophs like Cyanobacteria (Blue-green algae-BGA). Some like Anabaena and Nostoc have specialized cells called heterocysts for nitrogen fixation.
• Algae bloom is rich growth of blue green algae over the surface of polluted water bodies.
• Algae bloom releases neurotoxins, deplete oxygen and water unfit for use.
• Chemosynthetic autotrophs : Oxidise various inorganic substances like nitrates/nitrites, ammonia and use released energy for their ATP proudction. They helps in nutrients recycling of N, P, Fe and S.
• Heterotophic bacteria: Decomposers, help in making curd, production of antibiotic, N2 fixation, casuse disesaes like cholera, typhoid, tetanus and citrus canker.
• Mycoplasmas: Completely lack cell wall. Smallest living cells. Can survive without oxygen. Pathogenic in aniamls and plants.
Kingdom Protista
• It comprises of all single celled eukaryotes.
• Forms a link between plants, animals and fungi.
(i) Chrysophytes (Has diatoms and golden algae/desmids)
→ Fresh water/marine, photosynthetic, microscopic plankton.
→ Cell walls have silica which makes it indestructible and cell walls overlap to fit together like a soap box.
→ Their accumulation forms 'Diagomaceous Earth' (gritty soil)
→ Used in polishing, filtration of oils and syrups.
(ii) Dinoflagellates
→ Marine, photosynthetic cell wall has stiff cellulose plates.
→Two flagella, one longitudinal and other trnasverse in a furrow between wall plates.
→ Example : Gonyaulax multiples rapdily, make sea appear red (red tides) and produce toxins to kill marine animals.
(iii) Euglenoids
→ Found in stagnant fresh water.
→ Have protein rich layer ëpellicleà which makes body flexible.
→ Photosynthetic in presence of sunlight but become heterotrophs if they do not get sunlight. (Mixotrophic nutrition)
→ Example : Euglena
(iv) Slime Moulds
• Saprophytic protists
• Under suitable conditions form an aggregates called plasmodium, grows on decaying twigs and leaves.
• During unfavourable conditions, plasmodium differentiates and forms fruting bodies bearing spores at their tips.
• Spores have true walls which are exrtremely resistant and survive for many years and dispersed by air currents.
(v) Protozoans: Are heterotrops and live as predators or parasites. Have four major groups.
• Amoeboid: Catch prey using pseudopodia. Example: Amoeba. Entamoeba are parasite.
• Flagellated : Have one or more flagella. Cause disease like Sleeping
• Sickness e.g., trypanosoma.
• Ciliated : Have clilia to move food into gullet and help in locomotion. e.g., Paramoecium.
• Sporozoans : Have infective spore like stage in life cycle, e.g., Plasmodium which causes malaria.
Kingdom Fungi
• Heterotrophic organisms
• Non chlorpohyllous hyphae
• Network of hyphae called mycelium
• Hyphae which have multinucleate cytoplasm are called coenocytic hyphae
• Cell wall of chitin and polysaccharides
• Cosmopolitan. Grow in warm and humid places.
• Saprophytic, parasitic, symbiotic (Lichen and Mycorrhiza) e.g., Puccinia, (wheat rust disesae), Penicillium, Yeast is a unicellular fungus.
• Reprouction can take place by vegetative means fragmentation, fission and budding. Asexual reproduction by spores-conidia, sporangiospores or zoospores. Sexual reproduction by Oospores, ascospores and basidiospores produced in fruiting bodies.
• Sexual cycle involves 3 steps:
(i) Plasmogamy (fusion of Protoplasms.)
(ii) Karyagamy (fusion of two nuclei.)
(iii) Meiosis in zygote resulting in haploid spores.
• Dikaryophase is a condition of having dikaryon in an intervening dikaryotic stage (n + n i.e., two nuclei per cell) between plasmogamy and karyogamy in fungi like ascomycetes and basidiomycetes.
Classes of Fungi
(i) Phycomycetes:
→ grow on decaying wood or as obligate parasites on plants.
→ Mycelium aseptate and coenocytic.
→ Spores produced endogenously in sporangium.
→ Asexual repdouction by Zoospores or Aplanospores
→ Zygospores are formed by the fusion of gametes. Example: Rhizopus, Albugo, Mucor
(ii) Ascomycetes:
→ also known as ‘sac fungi’.
→ Are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
→ Mycelium branched and septate.
→ Asexual spores are called conidia produced exogenously on the conidiophores.
→ Sexual spores are called ascospores produced endogenously in ascus, produced inside fruiting body called Ascocarp.
→ Example: Aspergillus, Neurospora, Sacharomyces (Unicellular fungi), Claviceps, morels, trufles.
(iii) Basidiomycetes:
→ Mycelium septate and branched.
→ Generally asexual sprors are not found.
→ Vegetative reproduction by fragmentation.
→ Sexual reproduction by fusion of vegetative or somatic cells to form basidium produced in basidiocarp.
→ Basidium produces four basidiospores exogenously after meiosis.
Example: Agaricus, Ustilago, Puccinia.
(iv) Deuteromycetes:
→ Called as ‘Fungi Imperfecti’ as sexual form (perfect stage) is not known for them.
→ Once sexual form is discovered the member is moved t o Ascomycetes or Basidiomycetes.
→ Mycelium is septate and branched.
→ They are saprophytic parasitic or decomposers.
→ Example: Alternaria, Colletotrichum, Trichoderma.
Viruses:
→ They did not find a place in classification.
→ Not truly living.
→ non-cellular organisms which take over the machinery of host cell on entering it and become living but as such they have inert crystalline structure appear non-living. So, difficult to call them living or non-living.
→ Virus means venom of poisonous fluid. Pastuer gave the term virus.
→ D.J. Ivanowsky found out that certain microbes caused Tobacco Mosaic Disease in tobacco plant.
→ M.W. Beijerinek called fluid as ‘Contagium vivum fluidum’ as extracts of infected plants of tobacco could cause infection in healthy plants.
→ W.M. Stanely showed viruses could be crystallized to form crystatls of protein which are inert outside their specific host.
→ Viruses are obligate parasites.
Structure of Virus:
→ It is a nucleoprotein made up of protein coat called Capsid. Capsid is made up of capsomeres arranged in helical or polyhedral-geometric forms. Have either DNA or RNA as genetic material which may be single or double stranded.
→ Usually plant viruses have single stranded RNA; bacteriophages have double stranded DNA and animal viruses have single or double stranded RNA or double stranded DNA.
Diseases caused in humans:
→ Mumps, Small pox, herpes, influenza and AIDS etc. In plants, symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.
Viroids:
→ Infectious agent, free RNA (lack protein coat)
→ RNA has low molecular weight.
→ Causes potato spindle tuber disease.
→ Discovered by T.O. Diener.
Lichens:
→ Symbiotic association between algal component (Phycobiont) and fungal component (mycobiont). Algae provides food. Fungi provides shelter and absorb nutrients and water for alga.
→ Good pollution indicators as they do not grow in polluted areas.
NCERT Solutions of Class 12 Biological Classification
- Systems of Classification
- Kingdom Monera
- Kingdom Protista
- Kingdom Fungi
- Classes of Fungi
- Viruses
- Structure of Virus
- Diseases caused in humans
- Viroids
- Lichens
System of Classification
• Earliest classification was given by Aristotle. He divided plants into herbs, shrubs and trees.
Animals into those with red blood and those who do not have it.
• Two kingdom classification: Given by Carolous Linneaeus. They are:
(i) Kingdom plantae
(ii) Kingdom Animalia
• Five kingdom classification: Given by R.H. Whittaker. They are:
(i) Monera
(ii) Protista
(iii) Fungi
(iv) Plantae
(v) Animalia
• The main criteria for classiÆcation of organisms into Æve kingdoms include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.
Kingdom Monera
• Has bacteria as sole members.
• Bacteria can have shapes like : Coccus (spherical), Bacillus (rod-shaped), Vibrium (comma shaped) and spirillum (spiral shaped).
• Bacteria found almost everywhere and can be Photosynthetic autotrophs, Chemosyn thetic autotrophs or Heterotrophs.
• Bacteria are divides in two parts:
(i) Archaebacteria
(ii) Eubacteria
• Halophiles (salt-loving)
• Thermoacidophiles (in hot springs)
• Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)
• Photosynthetic autotrophs like Cyanobacteria (Blue-green algae-BGA). Some like Anabaena and Nostoc have specialized cells called heterocysts for nitrogen fixation.
• Algae bloom is rich growth of blue green algae over the surface of polluted water bodies.
• Algae bloom releases neurotoxins, deplete oxygen and water unfit for use.
• Chemosynthetic autotrophs : Oxidise various inorganic substances like nitrates/nitrites, ammonia and use released energy for their ATP proudction. They helps in nutrients recycling of N, P, Fe and S.
• Heterotophic bacteria: Decomposers, help in making curd, production of antibiotic, N2 fixation, casuse disesaes like cholera, typhoid, tetanus and citrus canker.
• Mycoplasmas: Completely lack cell wall. Smallest living cells. Can survive without oxygen. Pathogenic in aniamls and plants.
Kingdom Protista
• It comprises of all single celled eukaryotes.
• Forms a link between plants, animals and fungi.
(i) Chrysophytes (Has diatoms and golden algae/desmids)
→ Fresh water/marine, photosynthetic, microscopic plankton.
→ Cell walls have silica which makes it indestructible and cell walls overlap to fit together like a soap box.
→ Their accumulation forms 'Diagomaceous Earth' (gritty soil)
→ Used in polishing, filtration of oils and syrups.
(ii) Dinoflagellates
→ Marine, photosynthetic cell wall has stiff cellulose plates.
→Two flagella, one longitudinal and other trnasverse in a furrow between wall plates.
→ Example : Gonyaulax multiples rapdily, make sea appear red (red tides) and produce toxins to kill marine animals.
(iii) Euglenoids
→ Found in stagnant fresh water.
→ Have protein rich layer ëpellicleà which makes body flexible.
→ Photosynthetic in presence of sunlight but become heterotrophs if they do not get sunlight. (Mixotrophic nutrition)
→ Example : Euglena
(iv) Slime Moulds
• Saprophytic protists
• Under suitable conditions form an aggregates called plasmodium, grows on decaying twigs and leaves.
• During unfavourable conditions, plasmodium differentiates and forms fruting bodies bearing spores at their tips.
• Spores have true walls which are exrtremely resistant and survive for many years and dispersed by air currents.
(v) Protozoans: Are heterotrops and live as predators or parasites. Have four major groups.
• Amoeboid: Catch prey using pseudopodia. Example: Amoeba. Entamoeba are parasite.
• Flagellated : Have one or more flagella. Cause disease like Sleeping
• Sickness e.g., trypanosoma.
• Ciliated : Have clilia to move food into gullet and help in locomotion. e.g., Paramoecium.
• Sporozoans : Have infective spore like stage in life cycle, e.g., Plasmodium which causes malaria.
Kingdom Fungi
• Heterotrophic organisms
• Non chlorpohyllous hyphae
• Network of hyphae called mycelium
• Hyphae which have multinucleate cytoplasm are called coenocytic hyphae
• Cell wall of chitin and polysaccharides
• Cosmopolitan. Grow in warm and humid places.
• Saprophytic, parasitic, symbiotic (Lichen and Mycorrhiza) e.g., Puccinia, (wheat rust disesae), Penicillium, Yeast is a unicellular fungus.
• Reprouction can take place by vegetative means fragmentation, fission and budding. Asexual reproduction by spores-conidia, sporangiospores or zoospores. Sexual reproduction by Oospores, ascospores and basidiospores produced in fruiting bodies.
• Sexual cycle involves 3 steps:
(i) Plasmogamy (fusion of Protoplasms.)
(ii) Karyagamy (fusion of two nuclei.)
(iii) Meiosis in zygote resulting in haploid spores.
• Dikaryophase is a condition of having dikaryon in an intervening dikaryotic stage (n + n i.e., two nuclei per cell) between plasmogamy and karyogamy in fungi like ascomycetes and basidiomycetes.
Classes of Fungi
(i) Phycomycetes:
→ grow on decaying wood or as obligate parasites on plants.
→ Mycelium aseptate and coenocytic.
→ Spores produced endogenously in sporangium.
→ Asexual repdouction by Zoospores or Aplanospores
→ Zygospores are formed by the fusion of gametes. Example: Rhizopus, Albugo, Mucor
(ii) Ascomycetes:
→ also known as ‘sac fungi’.
→ Are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
→ Mycelium branched and septate.
→ Asexual spores are called conidia produced exogenously on the conidiophores.
→ Sexual spores are called ascospores produced endogenously in ascus, produced inside fruiting body called Ascocarp.
→ Example: Aspergillus, Neurospora, Sacharomyces (Unicellular fungi), Claviceps, morels, trufles.
(iii) Basidiomycetes:
→ Mycelium septate and branched.
→ Generally asexual sprors are not found.
→ Vegetative reproduction by fragmentation.
→ Sexual reproduction by fusion of vegetative or somatic cells to form basidium produced in basidiocarp.
→ Basidium produces four basidiospores exogenously after meiosis.
Example: Agaricus, Ustilago, Puccinia.
(iv) Deuteromycetes:
→ Called as ‘Fungi Imperfecti’ as sexual form (perfect stage) is not known for them.
→ Once sexual form is discovered the member is moved t o Ascomycetes or Basidiomycetes.
→ Mycelium is septate and branched.
→ They are saprophytic parasitic or decomposers.
→ Example: Alternaria, Colletotrichum, Trichoderma.
Viruses:
→ They did not find a place in classification.
→ Not truly living.
→ non-cellular organisms which take over the machinery of host cell on entering it and become living but as such they have inert crystalline structure appear non-living. So, difficult to call them living or non-living.
→ Virus means venom of poisonous fluid. Pastuer gave the term virus.
→ D.J. Ivanowsky found out that certain microbes caused Tobacco Mosaic Disease in tobacco plant.
→ M.W. Beijerinek called fluid as ‘Contagium vivum fluidum’ as extracts of infected plants of tobacco could cause infection in healthy plants.
→ W.M. Stanely showed viruses could be crystallized to form crystatls of protein which are inert outside their specific host.
→ Viruses are obligate parasites.
Structure of Virus:
→ It is a nucleoprotein made up of protein coat called Capsid. Capsid is made up of capsomeres arranged in helical or polyhedral-geometric forms. Have either DNA or RNA as genetic material which may be single or double stranded.
→ Usually plant viruses have single stranded RNA; bacteriophages have double stranded DNA and animal viruses have single or double stranded RNA or double stranded DNA.
Diseases caused in humans:
→ Mumps, Small pox, herpes, influenza and AIDS etc. In plants, symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.
Viroids:
→ Infectious agent, free RNA (lack protein coat)
→ RNA has low molecular weight.
→ Causes potato spindle tuber disease.
→ Discovered by T.O. Diener.
Lichens:
→ Symbiotic association between algal component (Phycobiont) and fungal component (mycobiont). Algae provides food. Fungi provides shelter and absorb nutrients and water for alga.
→ Good pollution indicators as they do not grow in polluted areas.