FORM 5 SCIENCE

FORM 5 SCIENCECHAPTER 1 :

MICROORGANISMS AND THEIR EFFECTS ON LIVING THINGS CHAPTER 1 : MICROORGANISMS AND THEIR EFFECTS ON LIVING THINGS

1.1 Classification of microorganisms1.2Factors that affect the growth of microorganisms1.3 Useful microorganisms1.4The harmful effects of microorganisms1.6 How diseases caused by pathogens are treated1.7The profound effects of microorganisms on human beings and the balance of nature1.1CLASSIFICATION OF MICROORGANISMSMicroorganisms or microbes are very tiny organism that cannot be seen with naked eye but can be seen under the microscope.

Type of microorganismsBacteriaFungiVirusesAlgaeProtozoa

Pathogens cause diseases to humans, animals and plants.

BACTERIABacteria are tiny unicellular microorganisms They live in damp placeThere are generally four shapes of bacteria which are Cocci, Bacilli, Vibrio and Spirilla

4BACTERIABacteria obtain food through three waysSaprophytic bacteria obtain food from dead animals and plants

Parasitic bacteria obtain food from living organisms

Autotrophic bacteria photosynthesis / make their own food (have chlorophyll)

Bacteria reproduce by forming spore or binary fissionFUNGIOrganisms without chlorophyll. They cannot produce their own foodBigger size than bacteriaCan be seen with naked eyesExample : mushrooms, mould and yeast

Reproduce by buddingSaprophyteHas a cell wall made of cellulose and has a nucleusFUNGI YEASTFUNGI BREAD MOULD The organism reproduces by spore when the sporangia burstIt is saprophyteUse to made antibiotics

ALGAEA very simple plants with chlorophyll.Can make their own food by photosynthesisDoes not have root, stems or leavesBigger than bacteria and can be seen with naked eyesLive in fresh water, salt water, damp soil or on damp bark of trees

ALGAE (EXAMPLE)

ALGAE REPRODUCTIONReproduce by binary fission, fragmentation, spore and conjugation (sexually).

VIRUSESThe tiniest and simplest organismDoes not respire, excrete waste product, does not have nucleus, cell membrane and cytoplasmHave only protein capsule that covers a simple genetic substancesVirus are parasites and can only active in living medium.Reproduce by injecting DNA into the host cells

VIRUS (EXAMPLES)

PROTOZOAUnicellular animalsExample

PROTOZOAProtozoa obtain food through three waysHeterotrophic bacteria Digest organic food

Parasitic obtain food from living organisms

Autotrophic (Euglena) photosynthesis / make their own food (have chlorophyll)

Reproduce through conjugation and binary fission1.2 Factors that affect the growth of microorganism

Factors LightTemperatureHumidityNutrientspH value

LightUnder bright condition, microorganisms such as bacteria and spores will be destroyed when exposed to sunlight or UV light

Under dark condition, bacteria reproduce and grow rapidlyFactors that affect the growth of microorganism

Temperature

TemperatureCondition of microorganisms0CInactive37CVery active50C or higherKilled or destroyed (microorganisms with spores can be destroyed at 120C or higher)Graph of bacteria growth rate against temperatureFactors that affect the growth of microorganismHumidity

Nutrients (increase the growth rate of microorganisms)Saprophytic microorganismsobtain food from dead animals and plants

Parasitic microorganisms obtain food from living organisms

Autotrophic microorganisms photosynthesis / make their own food (have chlorophyll)Humidity (% of water)Condition of microorganismsLess than 3%Die or produce sporesLess than 20%Inactive25% and aboveMost active and will reproduceFactors that affect the growth of microorganismpH value

Some microorganisms can live actively in alkaline or acidic medium

pH valueCondition of microorganismsAlkaline medium (More than 7)KilledNeutral (7)Most active and will reproduceAcidic medium (Less than 7)Killed1.3 Useful microorganismsDigestion of foodSymbiotic bacteria can be found in stomach of herbivores (rabbit, goat and cow) producing enzyme cellulase which converts cellulose to glucose.

Cellulose Glucosecellulase (enzyme)

Useful microorganismsDecompositionSaprophytic bacteria and fungi decompose dead animals, plants and other organic matter. Prevent them from accumulating and polluting the environmentTurn the organic matter into humus which rich in minerals

Useful microorganismsMedicineAntibiotics To kill bacteria

Vaccines Prepare from dead or very weak bacteria and virusesTo stimulate the body to produce antibodiesExample : BCG injection to prevent Tuberculosis

Useful microorganismsAgricultureMaturing of tobacco leaveBacteria used to make tobacco leaves matureNitrogen cycle

Nitrogen fixing bacteriaBacteria of decayNitrifying bacteriaDenitrifying bacteriaUseful microorganismsIn IndustryMaking breads and cakes (Yeast)Yeast will reacts with sugar to produce alcohol, carbon dioxide and energy. (Fermentation)Yeast + sugar carbon dioxide + ethanol + energy

enzymezymase

A dough will expand is due to the carbon dioxide release by yeast

Useful microorganismsMaking ethanolProduction of vinegar and yogurtVinegar is prepared by using bacteria to change ethanol into ethanoic acid

Yogurt is prepared by the action of bacteria on milk

ethanol + oxygen ethanoic acid (vinegar) + water

bacteria lactose (milk) lactic acid (yogurt)

bacteria