4.1.1 - Communicable Disease (set A - Pathogens - Including Types Of Pathogens) Flashcards
What are pathogens?
Infective organisms - include bacteria, viruses, fungi and protoctista
What are communicable diseases?
- caused by pathogens (eg bacteria,fungi, viruses ext)
- can be passed from one organism to another or between species
- spread directly from plant to plant
Vectors (eg water or insects) carry pathogens from one organism to another
Outline the type of pathogen - bacteria?
- small portion of bacteria, cause communicable diseases
- prokaryotic cells (no membrane-bound organelles or nucleus)
- classified by basic shape or cell wall
Outline the 2 main types of classification of bacteria?
- basic shape - might be rod shaped (bacilli), spherical (cocci) or spiralled (spiralla)
- cell wall - after staining, gram positive bacteria look purple-blue where as gram negative bacteria appear red
Why is classifying bacteria by their cell wall useful?
The type of cell wall affects how bacteria reacts to different antibiotics (compounds that kill or inhibit the growth of bacteria)
Outline the type of pathogen - viruses?
- non-living infectious agents which invade and take other biochemistry of host cells
- 0.03-0.3 micrometers in length (50 times smaller than bacteria)
- basic structure involves genetic material surrounded by protein
- reproduce rapidly and evolve
Outline the pathogen - Protista?
- group of eukaryotic organisms
- protist which cause disease are parasitic (use people or animals as host organism)
- pathogenic protists may need vector to transfer them to host
- eg - malaria
Outline the pathogen - fungi?
- eukaryotic organisms that are often multicellular
- yeast causes human disease and are single-celled
- fungi are saprophytes (feed on dead, decaying matter) and do no photosynthesise
- can spread rapidly through production of tiny spores
- affect plants by infecting leaves, preventing photosynthesis
Outline how viruses affect the host tissue?
- take over cell metabolism
- viral genetic material gets into host cell and is inserted into the host DNA
- viruses uses host cell to make new viruses which then burst out of the cell , destroying it and infecting others
Outline how protoctista affect the host tissue?
- take over cells and break them open - as new generation emerge (do not take over genetic material of the cell)
- digest and use the cell contents as they reproduce
Explain how toxins damage host tissues?
- most bacteria produce toxins that poison or damage host cells - causing disease
- do this by breaking down the cell membranes, damaging/inactivating enzymes or interfering with host cell genetic material (preventing them dividing
- fungi can produce toxins which affect host cells and cause disease
Outline the plant disease - ring rot?
- bacterial disease of potatoes, tomatoes and aubergines
- caused by gram positive bacterium
- damages leaves, tubers and fruit
- no cure - once bacterial ring rot infects a field it cannot be used to grow potatoes again for 2 years
Outline the plant disease - tobacco mosaic virus (TMV)?
- infects tobacco plants and tomatoes, peppers, cucumbers ext
- damages leaves, flowers and fruit - stunting growth and reducing yield
- resistant crop strands available but no cure
Outline the plant disease - potato blight?
- caused by fungus-like protoctist
- penetrates host cells, destroying leaves, tubers and fruit
- no cure but resistant strains and chemical treatments available
Outline the plant disease - black Sigatoka?
- banana disease
- caused by fungus, which attacks and destroys the leaves - turning them black
- can cause 50% reduction in yield
- treatments can control the spread - no cure
