Title Chapter 2 Microorganisms Friend and Foe.pdf ✅

SCIENCE Chapter 2: Microorganisms: Friend and Foe
(1) 02 MICROORGANISMS: FRIEND AND FOE Microorganisms: Friend and Foe Microorganisms • Organisms too small to be seen with our naked eyes are called microorganisms or microbes. • They can only be seen using a microscope. • Microorganisms are found in a variety of habitats such as air, soil and water. • They can live and survive in extreme environments, from ice cold regions to hot springs, from deserts to marshy lands. • Some microorganisms are useful to us in many ways. They are called beneficial microbes. Example: Bacterium Rhizobium helps in nitrogen fixation. • Some microorganisms cause diseases in plants, animals and human beings. They are called • pathogens. Example: Anthrax bacillus causes anthrax in animals. • Robert Hooke and Anton Van Leeuwenhoek discovered the existence of microbes during the period 1665 - 1683. Major Groups of Microorganisms GROUP DESCRIPTION Algae • Found on walls, in fields and in small puddles. • May be unicellular or multicellular with a size of 1 μ-1 m. • Oscillatoria, Nostoc and Anabaena are examples of this type of algae. • Sexual reproduction occurs by conjugation. Fungi • Grows on stale bread, chapati, pickles, damp clothes and shoes in monsoon. • Respires aerobically or anaerobically. • Lives a saprophytic or parasitic life. • Mucor, Rhizopus and Aspergillus are examples of fungi.
(2) 02 MICROORGANISMS: FRIEND AND FOE Protozoa • Amoeba, Paramoecium and Plasmodium are examples of protozoa. • Amoeba has an irregular shape. • Locomotion occurs through pseudopodia. • Paramoecium is slipper shaped. • It has numerous cilia for locomotion. • Plasmodium is a protozoan living a parasitic life. It is responsible for the spread of malaria. Bacteria • Found in any kind of environment from deserts to Polar Regions. • Range in size is from 0.2 to 10 μ. • Reproduces sexually and asexually. • Respires aerobically or anaerobically. • Main types of bacteria according to their shape are Coccus, Bacillus, Vibrio and Spirillium. • Rhizobium and Lactobacillus are examples of bacteria. Virus • Smallest microorganisms which can grow and develop only inside the host cell. • In free-living form, viruses are like non- living particles. • Viruses are classified into three types based on the type of host they infect. • Examples: Animal viruses: Foot and Mouth Disease Virus (FMDV) Plant viruses: Tobacco Mosaic Virus (TMV) Bacteriophage: Coliphage infecting Escherichia coli
(3) 02 MICROORGANISMS: FRIEND AND FOE Suitable medium Availability of sunlight Supply of oxygen Conditions Necessary for the Growth of Microorganisms Availability of moisture Suitable temperature Availability of food Conditions Necessary for the Growth of Microorganisms