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8.3 |
Microorganisms and Viruses |
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- Microorganisms are tiny organisms and not be seen with naked eyes
- Microorganisms can only be seen with the help of light or electron microscope
- Microorganisms consists of bacteria,protozoa,fungi and algae
- Microorganisms are much smaller particles that do not carry out reproduction and only can develop in host cell
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Description |
Bacteria |
Unicellular organisms
Have cell wall, plasma membrane and DNA which is not enclosed by a nuclear membrane
Are heterotrophs or autotrophs
Reproduced by binary fission and conjugation
Form spores under unfavourable condition
Examples: Escherichia sp coli., Lactobacillus sp.
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Protozoa |
Unicellular organisms
Live in aquatic
Have plasma membrane, nucleus and other membranous organelles
Heterotrophs organisms
Use cilia, pseudopodium and flagellum to move around
Reproduce sexually or asexually
Examples: Paramecium sp., Ameoba sp. and Plasmodium sp.
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Algae |
Unicellular organisms, non-fillamentaous and multicellular organisms
Able to carry out photosynthesis as they have chloroplast
The cell wall is made up of glycoprotein
Do not have stems, leaves and roots
Reproduce sexually or asexually
Examples: Chlamydomonas sp. and Spirogyra sp.
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Fungi |
Unicellular organisms and multicellular organisms
Has no chlorophyll
Saprophytic or parasitic organisms
Secrete extracellular enzymes to breakdown organic matter before they are absorbed
Reproduce by binding or formation of spores
Examples: Yeast, Mucor sp.
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Viruses |
Not microorganisms
The smallest size
Can only be seen under an electron microscope
Only consists of DNA or RNA covered by a protein coat
Cannot reproduce outside the host cells
All are parasites
Can be crystallised outside host cells
Examples: Bacteriophage, influenza virus and HIV
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Nitrogen cycle:
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Source:[Text Book Biology KSSM Form 5] |
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The roles of microorganisms:
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Producer |
Examples: Cyanobacteria,phtoplankton (algae)
- Provide nutrients to primary consumers
- Main energy source in a food chain
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Decomposer |
Examples: Saprophytic bacteria,fungi
- Decompose organic materials to reduce pollution by preventing accumulation of the organic waste remains
- Return nutrients to soil
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Symbionts |
Examples: Tryconympha sp. (protozoa) and Lactobacillus sp.
- Tryconympha sp. in a alimentary canal of termites secretes cellulase to digest carbohydrate into glucose to be absorbed by the termites
- Human colon has symbiotic bacteria which syntheis vitamin B and vitamin K
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Parasite |
Examples: Some bacteria & fungi
- As predator to form a balanced food chains
- Also as prey for other consumers
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Definition of pathogen and vector:
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Pathogens |
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- Definition: An organism which causes diseases
- Examples:
- Bacteria
- Viruses
- Protozoa
- Fungi
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Vector |
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- Definition: Organisms which transmit pathogens and cause certain disease
- Examples:
- Mosquito
- Flies
- Cockroaches
- Infected wild animals
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Effects of pathogens on human health:
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Pathogen, disease and symptoms |
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Virus - Human papillomavirus (HPV)
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- Disease: Sexually transmitted disease,cervix cancer and other cancer
- Symptoms:
- Warts on hand,leg,face and genital organ
- Irregular blood spotting after periods
- Prolonged and more menstruation than normal
- Postmenopausal bleeding
- Increased vaginal discharge
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Bacteria - Salmonella sp.
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- Disease: Food poisoning
- Symptoms:
- Vomitting
- Diarrhea
- Abdominal cramps
- Headcahe
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Protozoa- Plasmodium sp.
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- Disease: Malaria
- Symtpoms:
- Shrivel is followed by headache
- Skin becomes yellowish
- Anaemia
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Fungi - Tinea sp.
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- Disease: Ringworm
- Symptoms:
- An erythematous patch with slightly scaly and small erythematous popules present at its periphery
- The patch will enlarge and with the presence of its central clearing, it will appear ring-like or annular
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