Summary
Summary Chapter 12 4.1.1 - Communicable Diseases
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notes on: 1 - pathogens 2 - transmission 3 - disease 4 - plant defence 5 - animal defence 6 - specific immune response 7 - antibodies and immunity
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12.1 - animal and plant pathogensCommunicable - Caused by pathogens.
diseases - Each pathogen has different ways of spread and cures/preventions to disease they cause.
- Can be spread from one to another including different species.
- Vectors carry pathogen from one to another which helps spread of pathogen and disease.
bacteria - Prokaryotes – no membrane bound organelles.
Classified;
- Shape – rod (bacilli), spherical (cocci), comma (vibrios), spiralled (spirilla), corkscrew (spirochaetes)
- Cell wall – gram positive and negative = shows different cell wall affects how bacteria react to
antibiotics.
- Positive = purple/blue under light microscope (staining)
- Negative = red
virus - Non-living infectious – 0.02/0.3 um.
- Structure - DNA or RNA surrounded by protein.
- Invade living cells where genetic material of virus takes over host cell to reproduce = successful
- Cause disease in every type of organism – all naturally occurring viruses are pathogenic.
- Bacteriophages – viruses that attack bacteria, they take over bacterial cells and use them to
replicate – destroying the bacteria at the same time.
- Bacteriophages can be used to identify and treat diseases – ultimate parasites.
Protoctista - Eukaryotic organisms with range of feeding methods.
- Single celled organisms and cell grouped into colonies.
- Small percentage act as pathogens – causing communicable diseases = parasitic using host.
- May need vector to transfer or through water.
fungi - Mainly in plants, not as problematic in animals
- Eukaryotic and often multicellular apart from yeast (single celled)
- Cannot photosynthesis and digest food extracellularly before absorbing.
- Many are saprophytes (feed from dead and decaying matter) but some are parasitic (feed on living
plants/animals)
- Parasitic fungi cause communicable diseases.
- Infection forms on leaf of the plant and stops plant from photosynthesising which quickly kills the
plant.
- Reproduce millions of tiny spores which can spread rapidly and widely through crop plants.
Pathogens - Damage from pathogen and he body's response = symptoms of disease
damaging host - Viruses take over cell metabolism – viral genetic material gets into host cell and inserted into host
tissues DNA. Virus uses host cell to reproduce which bursts the cell so it can spread to other cells.
directly. - Protoctista - take over cells and break them open as new generation emerged – do not take over
genetic material of the cell. Digest and use cell contents as they reproduce.
- Fungi –digest living cells and destroy them, with the body response to damage = symptoms
Pathogens - Most bacteria produce toxins that poison or damage the host cells – this causes disease.
producing - Bacterial toxins damage the host cells by breaking down the cell membranes, some damage or
toxins which inactive enzymes interfere with host cell genetic material so cells cannot divide.
damage host - Those toxins are a by-product of normal functioning bacteria.
tissues - Some fungi produce toxins which affect host cells and cause disease.
12.2 - animal and plant diseases
Plant diseases - Threaten people;
- Crops fail = people suffer =starvation, no jobs and spreads in ecosystem.
Ring rot - Bacterial disease of potatoes, tomatoes and aubergines – gram positive bacterium.
- Damages leaves, tubers and fruit
- Can destroy 80% of crop – no cure.
- Once a field is infected – field cannot be used for at least 2 years.
TMV - Virus infecting tobacco and 150+ other [lant species.
- Damages leaves, flowers and fruit
- Stunt's growth reducing yield and lead to total crop loss.
- Resistant crop strains are available + No cure.
Potato blight - Fungus-like Protoctista
- Hyphae penetrates host cells, destroys leaves, tubers and fruit = Millions of pounds worth of crop
damage a year
- No cure but resistant strains are there.
- Careful management and chemical treatments can reduce infection risk.
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