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CBSE Class 11 Biology Notes

Biological Classification

 

The process of grouping living organisms into convenient categories based on simple characters is known as Biological Classification.

Two kingdom classification.

  • Plants. (autotrophs, cell wall, do not move)
  • Animals (heterotrophus, no cell wall, can move)
Linnaeus  -  plantae & Animalia

Later found two kingdom classification was not sufficient because in that

  1. Prokaryotes & Eukaryotes   were grouped together.
  2. Heterotrophs & Autotrophs were together.
  3. No difference between unicellular and multicellular
  4. Simple organisms were placed along with higher organism.

Five kingdom classification.  (R.H Whittaker  1959)

Main criteria for classification: 
  • Complexity of cell structure (prokaryotes/ eukaryote )
  • Body organization (unicellular/ multicellular)
  • Mode of nutrition (autotrophic / heterotrophic / holozoic)
  • Life style ( producers / consumers / decomposers)
  • Phylogenic relationships (revolutionary history)

Five kingdoms are

  1. Kingdom Monera (bacteria ) – prokaryotic unicellular
  2. Kingdom  Protista   ( amoeba ) – eukaryotic  unicellular
  3. Kingdom Fungi   - multicellular eukaryotic
  4. Kingdom Plantae  - multicellular eukaryotic
  5. Kingdom  Animalia – multicellular eukaryotic   

1. Kingdom Monera  (eg. Bacteria )

Habitats-  omnipresent

Grouped in to  4 groups based on their shape.

1.   Cocus (spherical) 2. Bacillus (rod) 3. Vibrio (comma) 4. Spirillum (spiral)

Mode of nutrition – autotrophs and heterophs.

Kingdom Monera– includes

  • Archaebacteria
  • Eubacteria (Cyanobacteria,  Chemosynthetic and Heterotrophic)
  • Mycoplasma

Archaebacteria – Harsh habitats ΰ Halophiles (saline)  Thermoacidophiles (hot spring), Methanogens  (gut of ruminants)

Eubacteria  – True bacteria - Rigid cell wall - Motile flagellum

  • Autotrophic bacteria - Cyanobacteria (BGA) have chlorophyll a unicellular, colonial/ filamentous.
    Marine /terrestrial habitat/ gelatinous sheath
    Form blooms - can fix nitrogen in heterocysts. Eg. Nostoc, Anabaena.
  • Chemosynthetic bacteria – Oxidise nitrates , nitrites and ammonia release energy (ATP) help in Recycling of nutrients ( eg. Pseudomonas, nitrobacter )
  • Heterotrophic bacteria – Decomposers – making curd from milk, antibiotics, nitrogen fixing  (Rhizobium )  some are pathogenic ( cause diseases ) cholera, T.B, diarrhea. Reproduction by binary fission, spore / sexual reproduction.

Mycoplasma

No cell wall – smallest living cell.
Anaerobic – pathogenic  in animals and plants.

2. Kingdom protista

Unicellular – Eukaryotic – aquatic
Flagella / cilia  - Reproduce sexually / asexually   

Chrysophyta

  • Planktons diatoms and golden algae ( desmids )
  • Fresh water/ marine
  • Microscopic – photosynthetic
  • In diatoms , cell wall is indestructible (silica )form  diatomaceous earth, its being gritty used for polishing, fitration of oil and syrups.
  • Chief producers in oceans.
1. Dinoflagellates. Marine photosynthetic, yellow, green, blue or red pigments - Cell wall is cellulosic – have 2 flagella - Red dionflagellate (Gonyaulax ) forms red tides and toxins are released.

2. Euglenoid eg. Euglena

Fresh water – stagnant water – no cell wall but protein rich layer is present, called pellicle.

Pellicle is flexible with flagella – they are Myxotrophic, because Photosynthetic (in light) Heterotrophs (when no light).

Myxotrophs – Mixture of both autotrophs and heterotrophs.

3. Slime moulds.

Saprophytic – body moves on decaying twigs and leaves

During suitable conditions from aggregation called plasmodium (mass of slime moulds)

Unfavourable conditions form spores and survive for many years.

4.  Protozoans – Heterotrophs – predators/ parasites

There are 4 major groups;

·   Amoeboid protozoans. Fresh water, sea and moist soil  -pseudopodia – marine forms have silica shells . Entamoeba (parasite) cause Amoebic dysentery

·   Flagellated protozoans  - free living / parasites have flagella – parasites cause diseases – Sleeping sickness (Trypanoroma) is  a parasite of flagellated protozoans.

·   Ciliated protozoans – aquatic cilia, cavity gullet  eg. Paramoecium.

·   Sporozoans – Spore stage in their life cycle. Plasmodium causes malarial fever.

Kingdom Fungi

Multicellular – eukaryotic – heterotrophic - cosmopolitan - grow in warm and humid places.

  • Fungi are filamentous with long, slender thread like Hyphae and the net work of hyphae is known as Mycelium –  They can be septate or non septate (aseptate)
  • Multinucleated cytoplasm (coenocytic hyphae)
  • Cell wall is chitin.
  • Parasitic/ symbionts (Lichens and Mycorrhizae)
  • Symbionts of algae and fungi (Lichens) and Pine trees roots and fungi (Mycorrhizae) on roots to absorb  water.
  • Reproduction by fragmentation, fission, buddin.
  • Asexual reproduction by oospores, ascospores, basidiospores.
  • Sexual reproduction steps.

1. Plasmogamy

2. Karyogamy and

3. Meiosis in zygote result in haploid spores – dikaryon

Dikaryophase ΰ Zygote (2n –diploid) ΰhaploid Spores (n – haploid))

Based on morphology of mycelium mode of spore formation, fruiting bodies , there 4 classes;

1. Phycomycetes

2. Ascomycetes

3. Basidiomycetes

4. Deuteromycetes

Phycomycetes

  • Aquatic decaying wood mycelium is aseptate coenocytic
  • asexual reproduction by zoospores (motile ) / aplanospores ( non motile )
  • Eg. Rhizopus, mucor.

Ascomycetes : (Sac fungi)

  • Multicellular  (penicillium ) / Unicellular ( yeast )
  • Saprophytic – decomposers – parasitic – coprophilous
  • Mycelium is branched and septate –asexual spores are called conidia
  • Sexual spores are called ascospores.
  • Eg. Aspergillus, Neurospora

Basidiomycetes : (Eg. Mushroom/ bracket fungi/ puffballs)

  • Grow in soil, logs, tree stumps, in plant bodies as parasitic (as rust and smuts)
  • Mycelium is branched and septate
  • Reproduction by fragmentation
  • Dikaryon – basidium –karyogamy
  • Eg. Agaricus (mushroom)

Deuteromycetes :

  • Imperfect fungi mycelium is septate and branched.
  • Only asexual reproduction by conidial spores
  • Saprophytes / parasitic / decomposers
  • Help in Mineral cycling
  • Eg. Trichoderma, Alternaria

Kingdom Plantae :

Autotrophs – size varies from herbs to tall trees. There are different groups;

  • Algae 
  • Bryophytes                                                   
  •  Pteridophytes                                                   
  •  Gymnosperms
  • Angiosperms ΰ Monocotyledons and  Dicotyledons

5.Kingdom Animalia

Heterotrophs – locomotory – holozoic / saprophytic / parasitic – cosmopolitans.

It consists of two subkingdom Invertebrata with 9 Phylum and Phylum Vertebrata (Chordata) with 5 Classes.

Virus

Pasteur coined the term virus, which means Venom / poison.  It is made of a outer protein coat and a centre genetic material (RNA / DNA).  A virus is a nucleoprotein and the genetic material is infectious.  Virus that infect plants have single stand RNA and those infect animals have either single or double RNA or double stranded DNA. Bacteriophages are viruses that infect the bacteria.  Viruses cause disease like mumps, small pox, herpes, influenza and AIDS.  In plants the symptoms can be mosaic formation, leaf rolling, and curling, yellowing, dwarfing and stunted growth. 

Viroids

T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. It has only a free RNA and lacked the protein coat, so named as viroid.

Lichens

Symbiotic association between algae and fungi.  Phycobiont is algal component, which prepare food for fungi and  Mycobiont  is a fungal  component, which provide shelter and absorb mineral nutrients and water for its partner.

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