Biology Revision B6 Beyond the Microscope. 6a Understanding Bacteria Bacteria – smaller than...
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Transcript of Biology Revision B6 Beyond the Microscope. 6a Understanding Bacteria Bacteria – smaller than...
6a Understanding Bacteria Bacteria – smaller than animal or plant
cells, typically a few microns long (1000 of a mm)
Flagellum – for movement Cell wall – for maintainingshape & stop it bursting Bacterial DNA – for cell replication & control of cell
Bacteria lack:1. A ‘true’ nucleus2. Mitochondria3. Chloroplasts4. A vacuole
Main shapes:SphericalRodSpiralCurved rods
6a Understanding Bacteria Food sources – some consume organic
nutrients like carbohydrates & proteins, some make their own using sunlight
Survival – extreme habitats e.g. hot springs, inside humans
Reproduction – by binary fission
Rapid reproductioncauses fast spread ofdisease & foodspoilage, but can be useful
6a Understanding Bacteria Making Yoghurt In large steel fermenters1. Equipment sterilised2. Raw milk pasteurised – heated to 80°C,
then cooled rapildy3. Heated to 40°C4. Live bacterial culture added & incubated5. Bacteria feed on lactose & make lactic
acid6. Manufacturer samples yoghurt7. Flavours & colours added
6b Harmful Microorganisms Pathogens – microbes that cause
diseasePathogen
Illness caused Transmission method
Bacteria
Cholera (Vibrio) Contaminated water
TB Airborne droplets
Food poisoning (salmonella & E. coli)
Contaminated food
Septic wound Contact with wound
Protozoa Dysentery (Entamoeba) Contaminated food/water
Malaria Mosquito bite
Viruses ‘Flu Airborne droplets
Chickenpox/smallpox Direct contact or airborne droplets
Fungi Athlete’s foot Direct contact
6b Harmful Microorganisms Natural DisastersRapid spread of disease because: Sewage systems & water supplies
damaged Electrical supplies damaged -> food decay Disrupted health services
Dysentery, cholera & food poisoning common
6b Harmful Microorganisms History of Disease Treatment
Pasteur – 1860’s – Germ Theory – microbes in the air cause food decay & passed from person to person causing disease
Lister – 1865 – development of antiseptics – use of carbolic acid during surgery
Fleming – 1928 – Penicillin – discovered accidentally that this mould killed bacteria
6c Microorganisms – factories for the future? Yeast – single celled fungus Asexual reproduction – budding Conditions for reproduction:1. Lots of sugar2. Optimum temperature (rate doubles for
every 10°C rise, above 40°C?) & pH3. Removal of waste products e.g. alcohol
6c Microorganisms – factories for the future? Fermentation – anaerobic respiration
in yeast Sugar -> Alcohol + Carbon Dioxide
Uses: Cleaning sugar in water from food
processing factories Making alcohol e.g. beer from barley,
wine from grapes, cider from apples
6c Microorganisms – factories for the future? Brewing Beer1. Mashing – extraction of sugar from
source material2. Hops added for flavour3. Yeast added to ferment (keep warm)4. Tank sealed to cause anaerobic
respiration & prevent unwanted microbes entering
5. Clarifying/clearing to leave a clear liquid6. Pasteurising to kill harmful microbes7. Bottling or casking
6c Microorganisms – factories for the future? Distilling spirits Rum from cane sugar Whisky form malted barley Vodka from potatoes Process:1. Liquid heated to evaporate alcohol2. Concentrated alcohol trapped and
condensed into a liquid Fermentation is limited by increasing
levels of alcohol that eventually kill yeast
6d Biofuels Biogas – contains mainly methane (50%
burns easily 10% is explosive), some carbon dioxide, traces of hydrogen, nitrogen & hydrogen sulphide
Biogas produced by decomposer bacteria in marshes, septic tanks, animal’s digestive systems
Uses: Burned to generate electricity Burned to produce hot water & steam for
central heating Fuel for buses (cleaner than diesel & petrol,
but doesn’t produce as much energy)
6d Biofuels Large scale production of methane Continuous flow method in a digester –
organic material added daily & gas siphoned off
Optimum temperature – too low, little gas produced; above 45°c enzymes denatured, no gas produced
Advantages of biofuels:1. Alternative source to fossil fuels – reduce
greenhouse effect2. No particulates produced3. Cheap4. Renewable/sustainable5. Conservation of resources
6e Life in Soil Composition of soil: Rock particles Humus (dead organic matter) Water Living organisms e.g. fungi, microscopic
protozoans, nematode works, earthworms, bacteria
Importance of worms:1. Burying organic material for decomposition2. Mixing soil layers3. Aerating & draining soil4. Neutralising acid soil
6e Life in Soil Nitrogen Cycle
Nitrogen fixing e.g. Azobacter, Rhizobium & Clostridium
Nitryfying e.g. Nitrosomonas & Nitrobacter convert ammonia to nitrates
Saprophytic bacteria start decomposition & make ammonia
6f Microscopic life in waterAdvantages of living in water
Disadvantages of living in water
No problem of water shortage or dehydration
Water is dense so resists movement
Less variation in temperature Difficult to control the absorption & release of water from living cells
Water gives more support so organisms grow bigger without increases in skeleton size
Waste is easily disposed
Amoeba use active transport to pump water into small vacuoles which join into one contractile vacuole which empties out of the cell
Salmon move from salt to fresh water – they alter their urine concentration to counteract osmosis in or out of cells
6f Microscopic life in water Plankton Phytoplankton – microscopic plants capable of
photosynthesis Zooplankton – microscopic animals
Have limited movement/rely on currents
Seasonal variation in population due to changes in:
Light Temperature Nitrates
Can cause algal blooms
6f Microscopic life in water Water Pollution Sewage - cause eutrophication Oil Fertilisers – cause eutrophication Pesticides e.g. DDT - bioaccumulate Detergents Acid rain PCBs (chemical used to insulate electrical
equipment) – bioaccumulate
Biological Indicators – of pollution/cleanliness