• Life science has many branches like botany, zoology etc
  • Biology is a study of plants and animals
  • Biology can be divided into two main branches
  • Botany- study of plants
  • Zoology- study of animals
  • Some of the sub branches are
  1. Bacteriology- study of bacteria
  2. Virology- study of virus
  3. Phycology- study of algae
  4. Mycology- study of fungi
  5. Cytology- study of cell

Important terms coined by,

  • Biology- Lamarck and Treriranus
  • Cell- Robert Hooke
  • Protoplasm- Purkinjee
  • Genetics- W.Bateson
  • Vaccine- Edward Jenner

Considered as father of

  • Aristotle- Father of biology and zoology
  • Theoprastus- Father of botany
  • Gregor Johann Mandel- Father of Genetics
  • Carl Linnaeus- Father of Modern Taxonomy

Micro Organisms

  • Living organisms show a great degree of diversity in their size.
  • They are measured in microns and milli microns. Example: Virus, bacteria, algae, fungi and protozoan.


  • Virus is a Latin word which means poison. Viruses are the smallest and simplest of all living organisms.
  • The study of viruses is called Virology.
  • Based on their host, viruses are classified in to five types.



(Plant Virus)

Phycophage       (Algal Virus)


Zoophage             (Animal virus)

Mycophage        (Fungal Virus)



  • The curd contains Lacto Bacillus bacteria which helps to change the milk into curd.
  • Bacteria are unicellular and microscopic, belonging to the world microbes. The study of bacteria is called Bacteriology.
  • Bacteria are measured in microns. 1 micron = 1/1000 millimeter.
  • Four types of bacteria are recognized based on shape. They are
  1. Cocci (Spherical shaped)
  2. Bacilli (Rod shaped)
  3. Spirillum (Spiral or cork screw)
  4. Vibrio (Comma Shaped)
  • On the basis of the number and arrangement of the flagella, bacteria are classified as
  1. Monotrichous (Single flagellum at one end)
  2. Amphitrichous (Tuft of flagella arising at both ends)
  3. Atrichous (without any flagella)
  4. Lophotrichous (Tuft of flagella at one ends) –
  5. Peritrichous (Flagella all around)


  • Algae are a unicellular green algae. It is spherical or oval in shape.
  • The cell wall may have a pectic sheath around it. There is a single large cup-shaped Chlamydomonas chloroplast
  • There are narrow end of the cells which helps in locomotion.
  • The study of algae is called phycology.


  • The conversion of sugar solution into alcohol and liberation of carbon dioxide is known as fermentation.
  • Wine, alcohols are prepared from the molasses by the fermentation activity of the yeast. etc.
  • Fungi do not ‘possess chlorophyll. Hence they are incapable of photosynthesis.
  • The study of fungi is called Mycology.


  • Protozoans are unicellular organisms.
  • Protozoan’s show mainly two modes of life, free living and parasitic.
  • Free living organisms inhabit fresh and salt water. Parasitic forms lives as ectoparasites or endoparasites. They cause diseases.

Use of Micro organisms in medicine agriculture, industry and daily living

Micro-organisms are used in the manufacturing of antibiotics, linen, bread, wine ,beer and other industries. Microorganisms are used to enrich the soil fertility

Name of the species



Streptomyces riseus Bacillus subtils

Streptomycin Bacitracin



Penicillium notatum

Penicillium chrysogenum




  • It may be defined as the science or practice of farming.
  • The following bacteria are involved to enrich the soil fertility:
  • Ammonifying bacteria: e. g. Bacillus ramosus
  • Nitrifying bacteria: e.g., Nitrobacter
  • Nitrogen-fixing bacteria: e.g., Azatobactor, Clostridium, Phizobium (Root nodules bacteria)
  • The leaves of tea, tobacco, the beans of coffee and cocoa are fermented by the activity of Bacillus megaterium to impart the characteristic flavor. This is called curing.
  • Streptococcus lactis (lactic acid bacteria) converts milk protein into curd. Vinegar is manufactured from sugar solution employing Acetobacter aceti.
  • Oxalic acid is the fermentation product of fungi Aspergillus Niger. Yeast is the best source of vitamin B complex and vitamin Riboflavin
  • Mushroom is also an edible (e.g.) Agaricus Morchella are edible and are cultivated


Micro Organisms

Name of the species




Xanthomonas citri



Xanthomonas cryae

Citrus Canker

Wilt of potato

Bacterial blight in Rice



Cercospora personata

Cercospora arachidicola


Tikka disease of groundnut

Blast disease of rice



Bunchy top virus

Tobacco Mosaic virus

Cucumber mosaic virus

Bunchy top of banana

Tobacco Mosaic disease

Cucumber Mosaic disease



Mode of Transmission


Common cold,Polio,Hepatitis,Influenza,Jaundice


Air Water,direct contact

Sexual contact






Contaminated water

Cuts and wound

Contact of animal’s urine

(Rat and squirrel)



Athlete’s feet

Spores in water and in ground



Vector example mosquito

Bottling and Canning

  • Pasteurization is used to preserve m.ilk. Milk is heated to 72°C forminutes and then suddenly cooled to 12°C
  • Microbes are killed without causing damage to the taste, quality of milk  for a longer time and packed in polythene pouches

The role of microbes in genetic engine

  • Viruses are used in eradicating harmful pests like insects.
  • Vaccines are produced to prevent serious viral infections.
  • Their ability to move genetic information from one cell to another makes them useful for cloning  DNA and could provide a way to deliver gene therapy(transformation)
  • Viruses are very much used as biological research tools due totheir simplicity of structure and rapid multiplication.
  • The cyclic movements of chemicals of Biospere between the organisms and the environment are referred as Bio – geo cycle.
  • Algal bloom: Under certain conditions, algae produce “blooms” i.e. dense masses of materials that cover the water surface, thereby decrease oxygen content of water.
  • This is followed by the death ofaquatic organisms.
  • Algal bloom leads to loss of speciesdiversity which is known as Eutrophication.
  • Pathology is a science which deals with diseases of plants, animals and human beings caused by viruses, bacteria and fungi.
  • The cyclic movements of chemicals of Biosphere between the organisms and the environment are referred as Bio – geo cycle.

Algal bloom:  

  • Under certain conditions, algae produce “blooms” i.e. densemasses of materials that cover the water surface, thereby decrease the oxygen content of water.
  • This is followed by the death of aquatic organisms. Algal bloom leads toloss of species diversity which is known as Eutrophication.
  • Pathology is a science which deals with diseases of plants, animals and human beings caused by viruses, bacteria and fungi.
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