12.1 Animal And Plant Pathogens

Question 1

What are communicable diseases?

Answer 1

A disease that can spread between organisms (between individuals within a species or between species. Communicable diseases are caused by pathogens.
Vectors carry pathogens from one organisms to another

Question 2

What are the types of pathogens?

Answer 2

Bacteria, Viruses, Protoctista, Fungi

Question 3

Describe bacteria
What are the two ways they can be classified?

Answer 3

Bacteria are prokaryotes, they do not have a membrane bound nucleus or organelles
Bacteria can be classified in two main ways:
- by their basic shapes (bacilli are rod shaped, cocci are spherical shape, vibrios are comma shapes, spirilla are spiralled shaped)

• by their cell walls: there are two main types of bacterial cell walls that react differently with Gram staining. Gram positive bacteria look purple-blue under the light microscope e.g. MRSA , Gram negative bacteria appear red e.g. E coli
  This is useful as the type of cell wall affects how bacteria react too different antibiotics

Question 4

Describe viruses

Answer 4

Viruses are non-living pathogens
- 50 times smaller in length than the average bacterium (viruses are 0.02-0.3 micrometers in diameter)
- basic structure: a genetic material surrounded by protein
- parasites
- viruses invade living cells
- viruses that attack bacteria are known ac bacteriophages

Question 5

Describe protoctista

Answer 5

• eukaryotic and single-celled organisms
• small percentage of protoctista act as pathogens
• the protoctista that cause disease are parasitic (use animals or mammals as their host organism)

Question 6

Describe Fungi

Answer 6

• fungal diseases are not a major problem in animals but can cause devastation in plants
• fungi are eukaryotic organisms that are often multicellular but yeasts that cause human diseases such as thrush are single celled
• many fungi are saprophytes which means they feed on dead and decaying matter
• some fungi are parasitic (they cause disease) they feed on living plants and animals
• when fungi reproduce they produce millions of spores which can spread huge distances (therefore can widely affect crops = starvation)

Question 7

How do viruses damage host tissues directly?

Answer 7

• viruses take over the cell metabolism
• the viral genetic material gets into the host cell and is inserted into the host DNA. The virus then uses the host cell to make new viruses which then burst out of the cell, destroying it and then spread to infect other cells

Question 8

How to protoctista damage host cells directly?

Answer 8

• the digest and use the cell contents as they reproduce, they do not take over the generic material of the cell

Question 9

How do fungi damage host tissues?

Answer 9

• fungi digest living cells and destroy them
• some fungi produce toxins which affect the host cells and cause disease

Question 10

How do bacteria damage host tissues?

Answer 10

• most bacteria produce toxins that poison or damage the host cells causing disease

e.g. Toxins damage host cells by breaking down the cell membranes