grade 12 biology

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137 sahifa grade 12 biology — PDF

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unit 4 genetics grade 12 biology unit 2 microorganisms by ebisa geleta what are microorganisms? microorganisms question: what are micro-organism (also called microbes)?  are microscopic organisms that cannot be seen with the naked eyes.  it needs a tool called microscope most of them are unicellular  some are multicellular ( ex, those which can photosynthesize their food) cont…  the branch of science that used to study about microorganisms know as microbiology.  microbiology study:  what they are  how they work and  what they do. note: microorganisms are everywhere  based on evolutionary lines, there are three main kinds of organisms.  these are: 1. bacteria 2. archaea and 3. eukarea note: archaea have cell walls without peptidoglycan, while bacterial cell walls contain peptidoglycan eubacteria • eubacteria: literally means "true bacteria“ • bacteria are relatively simple in structure. • they are prokaryotic unicellular organisms with …

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t encloses the cell's nucleus, and nucleolus). g) they lack: mitochondria, golgi apparatus, plastid and endoplasmic reticulum. h) both dna and rna are present in the bacterial cell. structure of bacterial cell  as bacterial cells are very minute (very small), they are studied under electron microscope in which it reveals various structures.  some of these are external to the cell wall while  other are internal to the cell wall.  the brief descriptions of the readily evident structures of bacteria is as follows: pili: they initiate contacts between mating pairs; or they facilitate the transfer of genetic material; cytoplasm: transport, biosynthesis nucleoid: regulates the growth, reproduction, and function of the prokaryotic plasmid: communication of genetic information between bacteria  eukaryotic microbes are an extraordinarily diverse group, including species with a wide range of:  life cycles,  morphological specializations, and  nutritional needs. • although more diseases …

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aggregates (a feature of tissue formation that allows the binding of cells of the same), motility, formation of spores, and reaction to the gram stain • in general the way that bacteria can be classified include; 1. shape i. cocci ii. bacilli iii. spirochaetes iv. comma 2. cell wall composition i. gram positive ii. garm negative 3. respiration mode i. aerobic bacteria: require oxygen for respiration. examples: pseudomonas and escherichia coli. ii. anaerobic bacteria: do not require oxygen for respiration. they use alternative electron acceptors such as nitrate, sulfate, or carbon dioxide. • anaerobic bacteria can be further divided into two subcategories: a) facultative anaerobes: these bacteria can switch between aerobic and anaerobic respiration depending on the availability of oxygen. examples: include escherichia coli and staphylococcus aureus. • b) obligate anaerobes: these bacteria are unable to survive in the presence of oxygen, and they rely on anaerobic respiration exclusively. examples: …

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planes and remain in a group of four, 4. sarcinae: those that divide into three planes and remain attached in cube-like groups of eight. 5. staphylococci: when the bacteria's divide into multiple planes to form clusters or broad sheet-like arrangements. 2. bacilli (singular, bacillus) - rod-shaped bacteria  bacilli are not arranged in complex patterns as compared to coccus  most bacilli occur in pairs and are called diplobacilli.  but some species also occur in chain-like forms called streptobacilli, example : subtilis (not a frank human pathogen but can cause toxin to human ) anthracis (anthrax disease) 3. spirochaetes - spiral or corkscrew-shaped bacteria (syphilis)  spirilla are helically spiral-shaped bacteria.  they have one or more twists and are never straight.  they are basically rods with helical curves like a corkscrew and have fairly rigid bodies. 4. comma-vibrio cholera (vibrio cholerae)  vibrio cholerae is a bacterium …

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he gram staining process includes four basic steps, including: 1. heat fix/ attach the bacteria to the silde, 2. applying a primary stain (crystal violet), 3. adding a mordant (gram's iodine), 4. rapid decolorization with ethanol, acetone or a mixture of both, & 5. counterstaining with safranin. note: then observe the color change at each levels. the staining technique includes simple staining (use single dye) or differencial staining (use different dyies) key words a) gram's staining: a test for distinguishing bacteria. named after hans christian gram, who developed the technique in 1884) b) differential staining: is a staining procedure that distinguishes organisms based on their staining properties. peptidoglycan: the rigid layer of the cell walls of bacteria, a thin sheet composed of n-acetylglucosamine, n-acetylmuramic acid, and a few amino acids. endotoxin: the lipopolysaccharide portion of the cell envelope of certain gram-negative bacteria, which is toxin to human when solubilized. nutritional …

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unit 4 genetics grade 12 biology unit 2 microorganisms by ebisa geleta what are microorganisms? microorganisms question: what are micro-organism (also called microbes)?  are microscopic organisms that cannot be seen with the naked eyes.  it needs a tool called microscope most of them are unicellular  some are multicellular ( ex, those which can photosynthesize their food) cont…  the branch of science that used to study about microorganisms know as microbiology.  microbiology study:  what they are  how they work and  what they do. note: microorganisms are everywhere  based on evolutionary lines, there are three main kinds of organisms.  these are: 1. bacteria 2. archaea and 3. eukarea note: archaea have cell …

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