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Summary Grade 11 Life Sciences - Life Sciences (Biology)
Well written summary of Grade 11 Life Sciences: Module 2 on Microorganisms and immunity.
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Biodiversity of MicroorganismsMicroorganisms
Viruses
Bacteria
Protists
Fungi
Viruses are pathogens (cause harm)
Viruses
Viruses consist of a central nucleic acid surrounded by a protein capsule
Viruses can infect plant, animal, bacterial cells
Viruses contain DNA or RNA (never both)
Some viruses (HIV or Flu) are enclosed by a sheath of lipid and protein molecules
Viruses are acellular and have no nucleus, cytoplasm, organelles
Viroid: Virus made of RNA with no protein capsule
Bacteriophage: Virus that infects a bacterial cell
Viruses can only reproduce inside a living cell
Viruses are obligate intracellular parasites
(compulsory, within a cell, lives on cell material and causes harm)
Viruses are host specific or tissue-specific (poliovirus only infects nerve tissue)
Tobacco mosaic virus (TMV) infects plants
AIDS, colds, flu, rabies, measles, polio infects humans
,Reproduction of viruses by entering the host cell:
- Virus sticks to cell membrane of host cell (spikes, knobs match with receptors)
- Host cell engulfs virus as natural defence response and is digested and
destroyed through endocytosis
- Host cell breaks down protein coat (capsid) of virus
- Virus uses material of the cell (DNA or RNA) to replicate its nucleic acids to make
new viruses (viruses prevents cell from making its own proteins)
- When mature, new viruses burst out of the cell and infect more cells
- Host cell is either destroyed, functions are disrupted or host cell chromosomes
mutate
Bacteria
Smallest and simplest living organism
Classified under the Kingdom Monera
Occur in every habitat on earth
Aerobic bacteria live in the presence of oxygen
Anaerobic bacteria live in the absence of oxygen
Some bacteria are pathogenic and cause diseases like cholera, tuberculosis
Bacteria are unicellular and occur as single cells, filaments or colonies
Bacterium cell is surrounded by a cell wall that consists of polysaccharides
(carbohydrates), proteins, lipids
Some bacteria (pathogenic) are surrounded by a slime layer which protects the cell
from drying out and enemies (immune cells)
Cell membrane encloses the cytoplasm
Ribosomes can occur
True nucleus is absent
DNA is in a chromatin body known as the nucleoid
Some bacteria move in liquid by using a flagellum
, Bacteria has various shapes:
- Rod-shaped (bacillus)
- Spherical/round (coccus)
- Spiral-shaped (spirillum)
- Comma-shaped (vibrio)
Bacteria are unicellular, prokaryotic, some autotrophic (photosynthesis/chemosynthesis),
reproduce asexually by binary fission
Most are heterotrophic
Parasitic Bacteria - obtain food from living organisms
Saprophytic Bacteria - obtain food from dead matter
Mutualistic Bacteria - obtain food from another organism (both benefit)
Protista
Under the Kingdom Protista
Three main groups:
Protozoa - animal-like, unicellular, heterotrophic organisms
Algae - plant-like, uni/multicellular, autotrophic organisms
Slime and water moulds - fungus-like, multicellular, heterotrophic organisms
Algae can photosynthesise
Protozoa ingest their food by phagocytosis
Plant-like protists have varied cell walls, green algae has a cell wall of cellulose
Reproduce mostly asexually by binary fission
Some algae reproduce sexually
Protists are aquatic and live in watery environments
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