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•Only visible under the microscope •Include bacteria, fungi & viruses 1. Nutrient broth poured into flask 2. Neck of flask heated and pulled into an S shape 4. Broth allowed to cool. It stayed clear and fresh for months. 3. Broth boiled for a few minutes to kill any microbes present and drive out air 5. Neck of flask broken off without touching it with hands. Broth went bad within a few days. It became cloudy and was soon teeming with microbes. Microbe VIRUS Disease HIV leading to AIDS Measles Rubella Mumps Colds & Flu Polio BACTERIUM Salmonella food poisoning Gonorrhoea Tuberculosis Chlamydia FUNGUS Athletes Foot AIDS: HIV virus Protein coat Genetic material Stops immune system working. pneumonia cancers Spread & prevention Anti-viral drugs help to control HIV but are expensive Rubella: virus spread coughs & sneezes Rubella rash MMR vaccination If contracted during early pregnancy, rubella may cause, blindness, deafness, low birth weight and heart abnormalities SALMONELLA: bacterium salmonella lives in raw and undercooked meat, eggs, and the gut of chickens. If meat is not thawed or cooked fully, bacteria on the outside will be killed but not those on the inside. They will breed quickly producing a toxin. • The toxin inflames the gut when eaten, causing fever, pain, vomiting, diarrhoea, dehydration and eventually death. • It is a big problem for old and weak people. It can be prevented by the use of antibiotics cooking meat fully. GONORRHOEA: bacterium Play video link TUBERCULOSIS: bacterium The TB bacterium enters the lungs and reproduces forming swellings that burst and bleed. Sufferers cough up blood stained phlegm. TB pustules in cattle lungs Pustules appear as ‘shadows’ in a lung x-ray It is spread through untreated milk, flies and by inhalation. It can be treated with antibiotics. Prevention • immunisation of cattle and humans, • good hygiene and • pasteurisation of milk. Immunisation: 1. Test if you are immune by injecting harmless antigens under the skin (Heaf test). If you carry antibodies a reaction occurs producing red swellings. 2. Vaccine (BCG) contains a weakened form of TB bacterium. Immunity lasts about 10 years. ATHLETES FOOT: fungus Spread: prevention: Dry between toes Don’t share towels Cure: anti-fungal cream & powders The First Line of Defence Mucous membranes – produce mucus which traps dirt & bacteria. Cilia sweep it to the back of the throat where it is swallowed Skin – acts as a barrier to prevent entry of microbes Clotting- seals skin & prevents entry of microbes Occurs when part of the skin is cut. It happens to form a barrier against microbes while new skin is being re-grown. When you become ill through a disease-causing organism you eventually recover as your body's defences defeat the invading pathogen. Antibodies fit over antigens antibodies antigen microorganism lymphocyte phagocyte bacterium nucleus 1. Strands of cytoplasm engulf bacterium 2. Enzymes digest the bacterium • The reactions which take place the FIRST time an antigen enters the body is called the PRIMARY RESPONSE • The reactions which take place the SECOND time an antigen enters the body is called the SECONDARY RESPONSE Number of antibodies Pathogen has time to reproduce and cause symptoms while WBCs make correct antibody against antigen Memory cells recognise antigen and quickly make antibodies before pathogen can reproduce Time 1st exposure to antigen 2nd exposure to antigen VACCINATION NATURAL IMMUNITY ARTIFICIAL IMMUNITY NATURAL IMMUNITY ARTIFICIAL IMMUNITY antibodies slowly produced Antibodies rapidly produced Small numbers of antibodies produced Large numbers of antibodies produced Antibody numbers fall quickly Antibody numbers remain high for longer AQUIRED & ACTIVE IMMUNITY INNATE & PASSIVE IMMUNITY Body makes antibodies Body receives antibodies from somewhere else Memory lymphocyte cells made No memory lymphocyte cells made so disease can’t be fought at a later date Long lasting Short lasting Explain why Jenner waited a period of time between infecting James with cowpox and then small pox. This gave the white blood cells time to identify cowpox antigens and produce antibodies, which would then be able to destroy the smallpox virus when it was injected. Why do you think that most immunisation programmes are aimed at young children and not adults? Most diseases are caught in childhood, so children can be protected before they come across the disease. Why is it important that the micro-organisms used in vaccination are dead or modified in some way? The person can still produce antibodies against the antigens on the microorganism, but it cannot reproduce and cause disease.