1. MICRO-ORGANISMS ……….. and DISEASE

2. DISEASE IN HUMANS  Types of disease can be categorised in many different ways.  Looking at CAUSE of disease the three main groups are:  Biological agents including micro-orgs eg. viruses  Faulty genes (inheritance) eg. CF  Environmental factors eg. Smoking Note: Generally both inherited and environmental diseases are also classed as ‘NON-INFECTIOUS’  If any disease is to be stopped both prevention and cure must be considered……

3. 1. Prevention Throughout history, particularly since Victorian times, advancements have been made to deal with disease. Prevention:  Sewerage systems (public health)  Refuse collection  Water purification  Hygiene  Nutrition  Education  Standard of living  Immunisation

4. 2. Treatment Throughout history, particularly since WW2, advancements have been made in ways to treat disease. Treatments:  Medical help available to all (NHS)  Anaesthetics  Analgesics  Antiseptics  Antibiotics  Operating techniques eg. Key hole surgery  Development of disease specific treatments eg. chemo and radiotherapy  Genetic engineering

5. Problems continue…… Despite these advance ‘we’ still have major problems with fighting disease.  Antibiotic resistance in bacteria eg.MRSA  Disease caused by social influences: eg.drug abuse, obesity, old age  Viral diseases eg. HIV/AIDS

6. Infectious diseases  Caused by micro-organisms including:  Bacteria (Prokaryotes)  Fungi  Viruses Disease may also be caused by parasitic macro-organisms  The spread of infectious diseases can be (and is) prevented using simple hygiene: Answer Q. e Page 183 (TS bk)

7. Bacteria Bacteria are prokaryotes. These are all single- celled organisms but their cells are very different to the animal and plant cells studied in Year 10:  No cell wall  No distinct nucleus (DNA in long strands and small ‘circles’ or plasmids)  Reproduce by ‘binary fission’  May produce harmful toxins eg. in TETANUS the toxin paralyses the jaw and thoracic muscles eg. Whooping cough, MRSA, pneumonia, septicaemia, cholera, TB

8. Fungi Yeasts, moulds, mushrooms etc were once classified as PLANTS, but now form a separate Kingdom ‘FUNGI’ WHY?......  Do not contain chlorophyll (no photosynthesis) so are…  Heterotrophic feeders, growing directly on ‘food’  Microscopic fungal threads or ‘hyphae’ grow into a ‘mycelium’ (visible mass of hyphae) on the food  Asexual reproduction (spores) eg. Athlete’s foot, thrush (oral, vaginal, systemic)

9. Viruses Viruses are so small that they are only visible using EM. They are considered to be non-living organisms. WHY?  Cannot perform MRS GREN  No cell, just a protein ‘coat’ containing DNA or RNA  Reproduce by taking control of a cell’s DNA eg. common cold, polio, measles, chickenpox, AIDS

10. Parasites  ‘Larger’ organisms (including protoctista) which live on/in a host organism. Note: the host does not benefit in any way from the presence of the parasite eg protoctista: plasmodium (Malaria) worms: tapeworm, toxocara insects: fleas, headlice

11. HIV  Human Immunodeficiency Virus  Contracted by sexual contact or direct transfer of body fluids eg. shared needles of drug users  Infects and destroys the immune system, specifically white blood cells (lymphocytes), preventing the production of antibodies  Body becomes susceptible to invasion from other micro-organisms leading to……..AIDS

12. AIDS  Acquired Immune Deficiency Syndrome  People with HIV eventually die from a collection (syndrome) of diseases that their immune system cannot prevent or fight off eg pneumonia, TB, various cancers

13. Preventing HIV and AIDS  Unless tested a person may be unaware for many years (8+ on average) that they are infected with HIV  During this time they may unknowingly infect others  Precautions should be taken:  fewer sexual partners  safe-sex (condom)  clean needles for drug use/abuse

14. Fighting Disease - Antiseptics  Chemicals used to kill micro-organisms on the SURFACE of the skin  Very useful for pre-surgical cleansing to avoid micro-organisms entering body  Very useful for cleaning surfaces/equipment to be used in surgery  But in some cases can delay healing as may destroy body cells as well as micro- organisms

15. Fighting Disease - Antibiotics  Drugs that kill or slow down the growth of bacteria INSIDE the body (Antibiotics do not affect VIRUSES)  Antibiotics are produced naturally by fungi and plants and were first discovered by Alexander Fleming in 1928. With Chain and Florey the first antibiotic, penicillin, was manufactured for public use  Many strains of bacteria are developing antibiotic RESISTANCE QHow does antibiotic resistance develop?  Infections like MRSA will become more common unless antibiotic resistance is reduced QHow can antibiotic resistance be reduced?

16. Fighting Disease – New Solutions  New antibiotics – expensive and slow and bacteria will soon develop resistance again  Chemically alter existing drugs (antibiotics) – bacteria will soon develop resistance again  Phage technology, using specific viruses to attack and kill bacteria QWhat are the possible advantages and disadvantages of using phage technology

17. Preventing disease - Immunity  Immunity – the means by which the body protects itself from disease  Active Immunity – long lasting immunity acquired as a result of the disease itself or a vaccination against it  Passive Immunity – short lived immunity from introducing antibodies into the body eg for tetanus treatment and through pregnancy and breast feeding

18. Preventing disease - Immunisation Immunisation – where the body is encouraged to make specific antibodies Artificial immunisation uses vaccination HOW DOES IT WORK? 1.A dead or mild form of a pathogen is introduced into the body (often by injection) 2.The body produces specific antibodies in response to the dead/mild form of the pathogen 3.If a virulent form of that pathogen then invades the body the specific antibodies are ready to destroy it Note: Edward Jenner produced the world’s first vaccine against SMALLPOX in 1796 using cowpox virus

19. Artificial Immunisation - Problems  Pathogens may mutate so that antibodies will no longer ‘fit’ to fight the disease eg the common cold  There are very small risks involved in introducing pathogens into the body (even mild or dead ones!) therefore…  Some people chose not to be vaccinated thus increasing the risk of disease spreading (by reducing ‘herd immunity’)  The risks from the disease are much greater than the risks from vaccination

20. Useful pathogens Biological control is the use of living organisms to control pests: - [Predators] - [Parasites] - Disease (pathogens) a pollution-free alternative to using pesticides long lasting and organic pest control eg myxomatosis (myxoma virus) in rabbits Disadvantage– organisms can develop immunity

21. DISEASE IN PLANTS  Plant diseases cause economic problems  Interventions and legislation have been introduced to reduce the problems: Chemical treatments Selectively breeding resistant varieties Crop rotation Change to sowing times Grafting crops onto disease resistant root stock Laws against growing susceptible varieties Laws against transporting infected material  Explain how each of these points may prevent the effect of a disease  Any other suggestions?

22. Example: Potato Blight This disease caused the ‘potato famine’ in Ireland in 1846 resulting in many Irish people moving to America to find work and food  A fungus that attacks potatoes via the leaves  Fungal spores germinate on the leaves and grow into the plant destroying cells  Spores remain in the soil for future crops Current treatments: selectively bred potato varieties resistant to blight fungicides biological control? (organic farming)