Animal and plant pathogens Flashcards Preview

Chapter 12 Communicable Disease > Animal and plant pathogens > Flashcards

Flashcards in Animal and plant pathogens Deck (18):

What is a communicable disease?

-Disease passed from one organism to another.
-Caused by pathogens.


What are pathogens?

-Microorganisms that cause disease.
-4 types; bacteria, virus, protocista and fungi.


What are vectors?

-Carry pathogens from one organisms to another.
-E.g. insects and water.


What are the characteristics of bacteria?

-Prokaryotic cells.
-No membrane-bound nucleus or organelles.
-Only a small proportion of bacteria cause disease.


How can bacteria be classified?

-By their shape; e.g. rod shaped (bacilli), spiralled (spirila), spherical (cocci).
-By cell walls; Gram positive bacteria look purple/blue under light microscope, and Gram negative bacteria look red.


Why is gram staining useful?

-Shows how type of cell wall affects how bacteria react to different antibiotics.


What are antibiotics?

-Compound that kills or inhibits the growth of bacteria.


What are the characteristics of viruses?

-Non-living infectious agent.
-50 times smaller that average bacterium.
-Basic structure is genetic material surrounded by protein.


How do viruses cause disease?

-Invade living cells and reproduce.
-Take over bacterial cells and use them to replicate.


What else can viruses destroy?

-Bacteria, and they are known as bacteriophages.


What are the characteristics of protoctista?

-Eukaryotic organisms.
-Wide variety of feeding methods.
-Include single-celled and cells grouped in colonies.


How do protoctista cause disease?

-Use people or animals as their host organisms.


What is a host?

-Organism or cell that carries the pathogen.


What are the characteristics of fungi?

-Eukaryotic organism.
-Major problem in plants rather than animals.
-Cannot photosynthesise or digest food extracellulary.
-They are saprophytes so feed on dead matter.


How do fungi cause disease?

-Affect plant leaves so stop them photosynthesising and kill the plant.
-Produce millions of spores.


What are the two modes of pathogen action?

-Damaging the host tissue directly.
-Producing toxins which damage host tissues.


How do pathogens damage host tissue directly?

-Viruses take over cell metabolism, viral genetic material inserted into hosts DNA, new viruses are made and burst out of cell which destroys it and spreads to infect other cells.
-Protoctista break open cells and digest cell contents and reproduce.
-Fungi digest and destroy living cells.


How do pathogen produce toxins which damage host tissue?

-Bacteria produce toxins which break down host cell membrane and interfere with genetic material so cells cannot divide.
-Fungi produce toxins which affect host cell and cause disease.