CHAPTER 2 MICROORGANISMS

INDEX WHAT IS MICROORGANISMS? TYPES OF MICROORGANISMS. VIRUSES. FRIENDLY MICROORGANISMS AND THEIR

USESE. HARMFUL MICROORGANISMS. DISEAS CAUSD BY MICROORGANISMS. FOOD PRESERVATION. NITROGEN CYCLE.

1.WHAT IS MICROORGANISMS Microorganisms are very small organisms

which cannot be seen with the unaided eye. Microorganisms may be unicellular or

multicellular. Microorganisms may exist alone or in

colonies. Microorganisms are found in all kinds of

environment like ice cold climate, hot spings,desert,marshy lands etc. they are also found inside the bodies of other organisms.

TYPES OF MICROORGANISMS.

There are four types of microorganisms they are:-Bacteria , Fungi , Algae , Protozoa

Viruses are also considered as microorganisms. They are different from others microorganisms because the reproduce only in the body of host organisms like bacteria, plants or animals.

E.g. :- algae-chlamydomonas,spirogyra etc. fungi-breadmould,penicillium,aspergilles etc. protozoa-amoeba, paramaecium etc.

VIRUSES Viruses are also considered as

micrroorganisms.the are different from other microorganisms because they reproduce only in the body of host organisms like bacteria, plants or animals.

FRIENDLY MICROORGANISMS AND THEIR USES.

There are some useful microorganisms. Their uses are following:- Making curd from milk. Making bread. Making alcohol. Making medicinesVaccines are dead or weakened microbes introduced

into the body to produce antibodies , these antibodies protect the body from disease causing microbes. Diseases like polio , cholera , typhoid , small pox , hepatitis etc. can be prevented by taking vaccines.

HARMFUL MICROORGANISMS. Some microorganisms cause diseases in

plants and animals. Such disease causing microorganisms are called pathogens.

Some microorganisms grow in food substances and produce toxic substance and makes the food poisonous. Food poisonous causes illness and even death.

Some microorganisms spoil materials like clothing, leather, wood etc.

DISEASES CAUSED BY MICROORGANISMS.

Cold, influenza(flu),cough are cause by viruses.

Polio,ckicken pox,dysentery,malaria are caused by protozoa(protozoans).

Typhoid and tuberculosis (TB) are bacterial diseases.

SOME COMMON HUMAN DISEASES CAUSED BY MICROOGANISMS.

SOME COMMON PLANT DISEASES CAYSED BY MICROORGANISMS.

FOOD PRESERVATION. There are four types of preservation of

food. They are :- Chemical method. Preservation by common salt. preservation by sugar. Preservation by oil and vinegar. By heating and cold treatment.

CHEMICAL METHOD.Food like pickles can be preserved by using

chemicals like salts and edible oils . Jams and squashes can be preserved by using sodium benzoate , sodium meatabisulphite.these chemicals are called preservatives.

PRESERVATION BY COMMON SALT.

Food items like fish , meat amla , raw mangoes , tamarind etc can be preserved by using common salt. It prevents the growth of microorganisms.

PRESERVATION BY SUGAR.

Food items like jams,jellies,squashes etc can be preserved by using sugar solution. It prevents the growth of microbes.

PRESERVATION BY OIL AND VINEGAR

Food items like pickles, vegetables fish, meat etc are preserved by using oil and vinegar. It prevents the growth of microbes.

HEAT AND COLD TREATMENT.

Heating food items kills microbes. Similarly storing food items at low temperatures prevents growth of microbes.

NITROGEN CYCLE .Certain bacteria convert compounds of

nitrogen present in the soil into nitrogen gas which is released to the atmosphere.