12.1 Animal and Plant Pathogens

Question 1

What causes communicable diseases?

Answer 1

Pathogens

Question 2

Define what a ‘pathogen’ is

Answer 2

A bacterium, virus or another microorganism that can cause disease

Question 3

What are the 4 types of pathogens?

Answer 3

Bacteria, Viruses, Protoctista and Fungi

Each has particular characteristic that affects how it spreads and how it’s treated

Question 4

What is a communicable disease?

Answer 4

A disease which can spread from one organism to another

Question 5

How do communicable diseases spread in animals?

Answer 5

From one individual to another.

They can also spread between species.

Question 6

How do communicable diseases spread in plants?

Answer 6

From direct contact

Question 7

What is a vector?

Answer 7

Something that doesn’t cause a disease, but spreads the disease - usually an organism

Question 8

What does a vector do?

Answer 8

Carry pathogens from one organism to another

Question 9

What are the 2 common vectors?

Answer 9

Water and insects

Question 10

reserved

Answer 10

.

Question 11

reserved.

Answer 11

.

Question 12

reserve.

Answer 12

.

Question 13

What 2 things can be looked at to classify a bacteria?

Answer 13

1. Their shape

2. Their cell wall

Question 14

Why can bacteria be classified by looking at their basic shape?

Answer 14

Bacteria have different shapes. They can be:

1. Rod shaped (bacili)
2. Spherical (cocci)
3. Comma shaped (vibrios)
4. Spiralled (spirilla)
5. Corkscrew shaped (spirochaetes)

Question 15

Why can bacteria be classified by looking at their cell wall?

Answer 15

The 2 main types of bacterial cell walls have different structures and react differently with gram-staining.

Gram-positive bacteria appear purple/blue after staining under the light microscope, e.g. MRSA
Gram-negative bacteria appear red after staining under the light microscope, e.g. (gut bacteria) E.coli

Question 16

Why is it useful to know the type of bacterial cell wall if you want to eliminate the bacteria?

Answer 16

The type of cell wall affects how bacteria will react to antibiotics

Question 17

What are antibiotics?

Answer 17

Compounds that stunt the growth of/kill bacteria

Question 18

What is a virus?

Answer 18

A non-living infectious agent

Question 19

What is the average size of a virus? How does this compare to the average size of a bacterium?

Answer 19

0.02 - 0.3 microns, 50x smaller than average bacterium

Question 20

What is the basic structure of a virus?

Answer 20

Some genetic material (DNA/RNA) surrounded by protein

Question 21

What do viruses do to their host’s cells?

Answer 21

Invade living cells, where the genetic material of the virus overtakes the host cell, using it to produce more viruses

Question 22

What is the main characteristic of viruses?

Answer 22

They reproduce rapidly.
They evolve by developing adaptations to the host.
This makes them very successful pathogens.

Question 23

What are all naturally occurring viruses called, in terms of what they do?

Answer 23

Pathogenic (cause disease)

Question 24

What are bacteriophages?

Answer 24

Viruses that attack bacteria

Question 25

How do bacteriophages destroy bacteria?

Answer 25

Bacteriophages invade the bacterial cells and use them to replicate, destroying the bacteria in the proces

Question 26

Why are bacteriophages useful for humans?

Answer 26

They can be used to diagnose and treat some diseases

Question 27

What are protoctista (protista)?

Answer 27

A group of eukaryotes with a variety of feeding methods. | A small % are pathogenic.

Question 28

What form can protista take?

Answer 28

Protoctista, also known as protista, include single-celled organisms or cells living in colonies.

Question 29

What are protists called in terms of how they cause diseases?

Answer 29

Parasitic - they use animals or humans as the host

Question 30

Why would pathogenic protists need a vector? Give an example.

Answer 30

To transfer them to their host. | Malaria, sleeping sickness

Question 31

How else can pathogenic protists enter the body? Give an example.

Answer 31

Through polluted water - amoebic dysentery

Question 32

How do fungal diseases affect animals in comparison to plants?

Answer 32

In animals, fungal diseases don't cause a big problem. | In plants, fungal diseases can be devastating.

Question 33

What are fungi in terms of their structure?

Answer 33

Eukaryotes. Often multicellular. Can be single-celled - e.g. yeasts which cause diseases in humans e.g. thrust

Question 34

If fungi can't photosynthesize, how do they obtain energy?

Answer 34

Fungi digest food extracellularly before absorbing the nutrients

Question 35

Many fungi are saprophytes - what does this mean?

Answer 35

They feed on dead and decaying matter.

Question 36

Some fungi are parasitic - what does this mean?

Answer 36

They feed on other living organisms.

Question 37

Why can fungal infections quickly kill plants?

Answer 37

Fungal infections often affect the leaves, stopping them from photosynthesising

Question 38

How are fungi well-adapted to reproduce?

Answer 38

When fungi reproduce, they produce millions of spores which can spread over huge distances. This means they can quickly spread through the crop.

Question 39

In a host, what do most pathogens damage?

Answer 39

The tissues of the organism

Question 40

What makes symptoms of a disease show?

Answer 40

The combination of tissue damage by the pathogen and how the host's body responds to the damage

Question 41

How do viruses attack host tissue?

Answer 41

- Viruses take over the cell's metabolism - Genetic material of the virus enters the host cell and is inserted into the host cell's DNA - The virus then uses the host cell to replicate - The new viruses burst out of the cell, killing the cell - The new viruses spread to infect other cells

Question 42

How do protista attack host tissue?

Answer 42

Some protoctista attack similarly to viruses - they take over cells and burst them open as new protoctista emerge. However, protoctista don't override the host cell's genetic material. Protoctista digest the cell's contents and use it to reproduce

Question 43

How do fungi attack host tissue?

Answer 43

Fungi digest and kill cells. | This, combined with the body's response to the damage, cause symptoms of the disease.

Question 44

What do bacteria produce that causes damage in the host?

Answer 44

Toxins - these damage/poison the host cells and cause disease

Question 45

What are toxins?

Answer 45

By-products of normal functioning in a bacteria

Question 46

How do other toxins damage the host?

Answer 46

Some toxins break down the cell membrane. Some toxins damage/inactivate enzymes. Some toxins interfere with the host cell's genetic material, meaning the host cell can no longer divide

Question 47

How else do fungi damage host cells?

Answer 47

Some fungi release toxins which affect the host cell and cause disease